Proceedings doi: 10.3390/proceedings2026146122

Authors: Margarida Vizeu-Pinheiro Sebastião Farias Maria Lourie Saoirse Tak-Yung Macklin Paula Dominguez Rein-Loring Ray van Eeden Rui Rosa

Introduction: As apex and mesopredators, elasmobranchs help maintain marine ecosystem balance by shaping food-web structure and habitat connectivity, yet more than one-third of species are threatened with extinction. Identifying where and when they aggregate within atoll systems is therefore a prerequisite for spatially explicit conservation planning. Lhaviyani Atoll, in the central Maldives, lies within a recognised Indian Ocean elasmobranch hotspot and hosts two Important Shark and Ray Areas (ISRAs), yet fine-scale information on aggregation sites, habitat partitioning and seasonal use remains limited. Objective: To map persistent activity hotspots, characterise habitat partitioning between sharks and batoids, quantify seasonal and inter-annual dynamics, and provide an ecological basis for habitat-focused conservation in Lhaviyani Atoll. Methodology: Using a seven-year (2017–2024) opportunistic dive-log dataset of 12,732 SCUBA surveys and 142,994 elasmobranch records across 94 dive sites, spatial kernel-density estimation was applied separately to sharks and batoids to identify activity hotspots and visualise spatial overlap. Habitat associations were examined across substrate types and reef geomorphic zones. Seasonal and inter-annual dynamics in relative abundance and diversity (Shannon, Pielou’s evenness) were quantified across monsoon phases and the 2017–2024 period. Results: Twenty-eight species (14 sharks, 14 batoids) were recorded, including 23 listed as threatened on the IUCN Red List (4 Critically Endangered, 12 Endangered, 7 Vulnerable). Four persistent activity hotspots were identified along the northern atoll rim, two overlapping with the Fushifaru Kandu and Kuredhu–Huravalhi–Komandoo ISRAs. Sharks were concentrated along more complex exposed and semi-sheltered slopes and high-flow channels, with significantly higher occurrence on reef and sheltered reef slopes and lower occurrence on rubble and sand substrates; batoids were distributed broadly within lagoonal habitats with no strong substrate or geomorphic preferences. Relative abundance and diversity peaked during the late southwest monsoon (August–September) and declined into the northeast monsoon (December–March); after 2021, diversity and evenness increased while overall abundance declined. Conclusions: Persistent hotspots, contrasting habitat use by sharks and batoids, and consistent monsoonal seasonality support the ecological relevance of existing ISRAs in Lhaviyani Atoll, while providing finer-scale information on habitat partitioning and additional priority areas for threatened elasmobranchs, including four Critically Endangered species.

Proceedings doi: 10.3390/proceedings2026146120

Authors: Nati Franch Marc Ventura Carles Alcaraz Víctor Osorio David Mateu Lluís Jornet Helena Fanlo Josep M. Queral Miguel Clavero Núria Cid

Introduction: Mediterranean coastal wetlands are highly dynamic ecosystems that support diverse fish communities and are often of high conservation value. The Ebro Delta is one of the most important coastal wetlands in the Western Mediterranean, and knowledge of fish assemblages is essential for its effective conservation and management. Environmental DNA (eDNA) metabarcoding provides a non-invasive approach that can potentially complement conventional surveys for fish biodiversity monitoring. Objective: This study aimed to evaluate the potential of eDNA metabarcoding as a complementary tool to conventional fyke net surveys for fish biodiversity monitoring in the Mediterranean coastal wetlands. Methodology: In 2022, fish assemblages were surveyed across 12 areas of the Ebro Delta using eDNA metabarcoding (12S MiFish) and conventional fyke net sampling. Results were compared with a 22-year historical dataset. Results: A total of 27 fish taxa were detected, 13 of which were exclusive to eDNA, 11 were shared between methods, and three were recorded only by fyke nets. The reliability of eDNA metabarcoding was supported by the detection of endangered species, such as Anguilla anguilla and Apricaphanius iberus; ubiquitous taxa, such as Atherina boyeri and Pomatoschistus microps; and invasive species, such as Gambusia holbrooki and Cyprinus carpio. Detection of invasive species was maximized using eDNA. While eDNA revealed higher species richness than fyke nets, community composition differed significantly between methods, reflecting distinct detection patterns. eDNA preferentially detected non-benthic species, whereas fyke nets were more robust for benthic taxa detection. eDNA recovered most historically recorded species but failed to detect some taxa, such as Misgurnus anguillicaudatus and Sardina pilchardus. Despite richness differences, the two methods provided complementary views of fish assemblages, highlighting method-specific detection limitations and opportunities. Conclusions: eDNA does not fully replace conventional surveys and their combined use improves the detection of threatened and invasive species, better supporting conservation and management.

Proceedings doi: 10.3390/proceedings2026146121

Authors: José Teixeira Bernardo Pinto Jonathan M. Wilson Pedro M. Guerreiro Filipe Castro

Introduction: The aglomerular kidney, characterised by the absence of functional glomeruli and reliance on tubular secretion alone, has evolved independently across multiple teleost lineages occupying diverse environments, including notothenioids of the Southern Ocean, gadids of cold North Atlantic and Arctic waters, and syngnathids distributed across temperate and tropical seas. Despite sharing this independently derived renal architecture, these groups face markedly distinct osmotic, thermal and chemical challenges in their natural habitats. How aglomerular kidneys cope with environmental stressors, including fluctuations in temperature and salinity, and how they handle the excretion of xenobiotics and other exogenous compounds through exclusively tubular mechanisms, remains poorly understood. The physiological and molecular responses underlying renal function in these lineages have received comparatively little attention relative to their glomerular counterparts. Objective: This study investigates how aglomerular kidneys across phylogenetically distinct teleost lineages respond, at molecular and physiological levels, to contrasting environmental conditions, namely temperature and salinity challenges predicted to alter the functional demands on renal osmoregulation. Methodology: Adult and juvenile specimens from target lineages were subjected to controlled exposure experiments combining different temperature and salinity regimes. Blood and urine samples were collected to assess osmolality and ionic composition. Renal tissues were processed for gene expression analysis of key transport and structural genes, histology, immunohistochemistry and enzymatic activity assays, providing an integrated picture of renal function under each condition. Results: Molecular analyses are currently underway. Preliminary work has established protocols for RNA extraction and quantitative PCR across target species, enabling comparative gene expression profiling to proceed across the full dataset. Conclusions: A comparative physiological and molecular approach across aglomerular teleost lineages will clarify whether shared renal architecture translates into shared functional responses to environmental challenge and identify lineage-specific mechanisms of renal adaptation, with broader relevance for predicting how these fishes may respond to ongoing environmental change.

Proceedings doi: 10.3390/proceedings2026146116

Authors: Wilfred Boa Morte Zacarias Bupebe Júlio Sanca Mirian Gorett Gomes Cravid Bocar Sabaly Baldé

Small pelagic fishes are essential for artisanal fisheries and food security in São Tomé and Príncipe, yet biological information required for stock assessment remains scarce. This study examined the population dynamics and life-history traits of Caranx crysos, Euthynnus alletteratus, Hemiramphus balao, and Cheilopogon melanurus using 9052 specimens collected from artisanal landings between 2023 and 2025. C. melanurus (35.2%) and H. balao (34.0%) dominated the sampled catches, followed by C. crysos (18.1%) and E. alletteratus (12.7%). Standardized CPUE series modelled using GAMs revealed significant temporal and seasonal variation in relative abundance, with contrasting species-specific trends. Length–weight relationships revealed negative allometric growth in three of the four species examined (75%), with b values ranging from 2.50 to 3.19, while Fulton’s condition factor differed significantly among species (Kruskal–Wallis χ2 = 6702.7, p < 0.001). Sex-ratio analyses showed significant deviations from parity in C. crysos and C. melanurus, whereas E. alletteratus and H. balao remained balanced. Gonadosomatic index and maturity-stage distributions indicated year-round reproductive activity with distinct spawning peaks. Length at first maturity (L50) ranged from 30.2 cm to 38.8 cm among species. Growth parameters estimated from length-frequency data using the von Bertalanffy Growth Function fitted through ELEFAN_GA in TropFishR yielded L∞ values of 43.9–68.4 cm and K values of 0.065–0.336 yr⁻1. Growth performance index (φ′) ranged from 2.48 to 2.99, corresponding to theoretical longevities of 8.9–46.3 years. Length-based cohort analysis indicated biomass concentration in intermediate size classes and increasing fishing mortality towards larger individuals. Exploitation rates revealed contrasting fishing pressures among species, while sensitivity analyses identified growth and mortality parameters as the main sources of uncertainty. These findings provide the first integrated biological baseline for the assessment and management of small pelagic resources in São Tomé and Príncipe.

Proceedings doi: 10.3390/proceedings2026146119

Authors: Quim Pou-Rovira Jordi Delgado Eloi Cruset Teresa Buchaca Víctor Osorio Danilo Buñay Nerina Gilbert Claudia Riera Barend Vandrooge Raimon Prats Pilar Fernández Joan O. Grimalt Rocco Tiberti Marc Ventura

Currently, more than half of Pyrenean high mountain lakes are occupied by fish as a result of historical introductions that date back centuries and which have accelerated during the last 70 years. In the southern slope of these mountains, the main fish that have been introduced are Brown trout (Salmo trutta), Brook trout (Salvelinus fontinalis), Rainbow trout (Oncorhynchus mykiss), and European minnow (Phoxinus sp). The specific impacts of the introduction of fish include, among others, the transformation of the ecosystem structure and trophic relationships, and the reduction and extirpation of native species. The project LIFE RESQUE ALPYR (LIFE20 NAT/ES/000369), started in 2022 and ending in 2026, includes among its main objectives the restoration of ten high mountain lakes with fish (trout or minnow) and the recovery of native species of European interest by the eradication of introduced fish. We planned and executed continuous and sustained campaigns to achieve the complete removal of fish. From 2022, we began with operations in seven objective lakes by means of several capture techniques, mainly gill nets for trout and a combination of gill nets, fyke-nets, and electrofishing for minnows. In 2024 and 2025, in three other lakes, chemical treatments with rotenone were carried out to achieve rapid eradication of fish. Currently, we have already achieved the complete removal of fish in four lakes, either with sustained capture or chemical treatments. In the other three lakes, this objective is also expected to be achieved in 2026, and only few individuals persist in actuality. In the other two lakes, the European minnow has been removed, and trout are now the focus of a two-stage strategy. In the remaining lake, we have only achieved a reduction in the European minnow (>50% reduction), with trout still remaining. We present, in detail, the methodologies applied and the results obtained.

Proceedings doi: 10.3390/proceedings2026146114

Authors: Bianca Neves Felippe Alexandre Daros Rafael Schroeder Rafael Gaio Kulzer Marcus Rodrigues da Costa Rodolfo Miguel Silva Alberto Teodorico Correia

Introduction: Understanding population structure is essential for effective fishery management, and otolith shape analysis provides a robust framework for detecting spatial variation in marine fish populations. The bluefish (Pomatomus saltatrix), a commercially important and widely distributed species along the southeastern and southern Brazilian coast, may exhibit subtle population structuring that is still not fully resolved. Methodology: Otolith contour variation was analyzed using two complementary approaches: Elliptical Fourier Descriptors (EFD) and Wavelet Transformed Descriptors (WTD). A total of 75 individuals (25/site) were sampled from Rio de Janeiro, São Paulo, and Santa Catarina, with total lengths ranging from 33.2 to 45.5 cm. Multivariate analyses included Permutational Multivariate Analysis of Variance (PERMANOVA), pairwise Hotelling’s t-tests (HT2), Flexible Discriminant Analysis (FDA), and jackknife reclassification matrices (JKC). Results: For the EFD approach, PERMANOVA showed no significant differences among localities, while FDA revealed partial overlap among groups and a JKC overall reclassification accuracy of 46%. In contrast, the WTD approach detected significant spatial differences, with PERMANOVA indicating overall variation among localities and HT2 identifying significant differences between Santa Catarina and the other regions. FDA improved visual separation of Rio de Janeiro samples, although the JCK accuracy decreased to 35%. Conclusion: The combined results suggest the presence of weak to moderate spatial structuring in P. saltatrix along the studied coastline. However, inconsistencies among analytical approaches and relatively low reclassification success rate to the original site indicate that the observed differentiation is insufficient to conclusively define distinct population units, remaining compatible with either a single stock exhibiting spatial heterogeneity or weakly differentiated subpopulations.

Proceedings doi: 10.3390/proceedings2026146113

Authors: Yáiza F. Jorreto Victor Gallego Luz Pérez Thales S. França Juan F. Asturiano

Introduction: Elasmobranchs play a crucial role in ecosystem regulation, but they are highly vulnerable to rapid environmental changes, particularly those driven by anthropogenic activities. Therefore, elasmobranchs are among the most threatened vertebrate groups worldwide, with overfishing and habitat degradation representing the primary threats to their survival. To address these challenges, in situ and ex situ conservation programs are complementary approaches. Objective: The implementation of assisted reproductive technologies, still poorly developed for elasmobranchs, represents a critical component of these ex situ strategies. Focused on that aspect, the main goal of this work was to get a better understanding of the sperm cells morphologies of different Mediterranean elasmobranch species. Results: The Elasmobranchii spermatozoa possesses a long and he-lical head, an elongated midpiece, and a flagellum supplemented with additional ultrastructural components to its axoneme. The comparative analysis of sperm head morphology revealed substantial interspecific variation among the studied elasmobranchs. Head length was relatively conserved, ranging from 48.5 to 62.0 μm, whereas helical parameters showed much greater variability. S. canicula and M. mobular exhibited the most compact head morphology, characterized by short helical wavelengths, low amplitudes, and the highest numbers of helices. In contrast, the batoids R. rhinobatos, R. radula, and R. clavata displayed broader, more widely spaced helices and fewer turns. Phylogenetic patterns were partially evident, as the closely related rajids shared very similar sperm morphology, while R. rhinobatos showed a comparable batoid morphotype. However, similarities between the distantly related M. mobular and S. canicula, and differences between the scyliorhinids S. canicula and G. melastomus, suggest that ecological and reproductive factors, in addition to phylogeny, have influenced the evolution of sperm head morphology in elasmobranchs. Conclusion: Elasmobranchii species possess big spermatozoa (compared to bony fishes) with an elongated helical head and tail similar to one currently existing (but later diverged) in birds, reptiles, and amphibians, which can be considered an evolutionary ancient. Sperm head morphology varies markedly among elasmobranchs, mainly regarding helical traits rather than head length. While phylogeny explains similarities among rajids, convergent patterns in distantly related species suggest that additional ecological and reproductive factors influence sperm evolution and structural design.

Proceedings doi: 10.3390/proceedings2026146117

Authors: Hugo Lopes André Oliveira António Martinho João Soares Carrola

Introduction: Biological invasions constitute one of the main threats to freshwater ecosystems, causing significant ecological changes through the introduction of exotic species that compete with or prey upon native species. In Portugal, the introduction and spread of exotic species in lotic and lentic ecosystems, such as pike (Esox lucius), European catfish (Silurus glanis), and largemouth bass (Micropterus salmoides), all top predators, may have a big impact on autochthonous species. In contrast, bleak (Alburnus alburnus), European perch (Perca fluviatilis), and common carp (Cyprinus carpio) compete aggressively for food resources. In the Sousa River basin, gudgeon (Gobio lozanoi) is considered an exotic species with potential ecological impact, with the minnow (Phoxinus phoxinus) stand having been recently identified in Portugal and, so far, recorded only in this river basin, and not yet being classified as an invasive species in Portugal. Public knowledge regarding invasive aquatic biodiversity remains a significant bottleneck for conservation. Because recreational angling is a prominent dispersal vector, initiatives that directly target this community are relevant. Objective: The aim is to carry out a bibliographic review on the exotic ichthyofauna species present in the Sousa River, with special focus on the invasion potential of the minnow (P. phoxinus). Methodology: The literature review was conducted based on the ScienceDirect, Springer Nature Link, and Fauna Norvegica databases, selecting publications between 2006 and 2025 concerning relevant studies on the potentially invasive characteristics of the minnow (P. phoxinus). The methodology is based on the analysis of studies regarding the impacts caused on riparian ecosystems. Results: The species P. phoxinus presents a generalist diet and high adaptive capacity, allowing it to colonise new habitats and compete aggressively with native species for trophic resources. Its presence is associated with negative impacts on brown trout populations (Salmo trutta), reducing growth and productivity, especially in mountain ecosystems. Increased species density also causes a significant decrease in benthic macroinvertebrate biodiversity. Studies conducted in the Douro basin indicate that the arrival of minnow in Portugal resulted from human action, probably associated with its use as live bait in recreational fishing. Conservation programmes use diverse tactics to bridge the awareness gap. Recent initiatives feature electrofishing demonstrations to visually differentiate species, theatrical performances, and even culinary show-cooking events using invasive predators like the European catfish to promote harvesting. Conclusions: The potential transition of P. phoxinus into an exotic and invasive species may be associated with the ecological pressure exerted on native communities, particularly through competition for trophic resources, highlighting the need to assess its dispersion in the Sousa basin and its impacts on fish fauna and benthic macroinvertebrates. It is important to do more sampling to understand its real distribution in the Sousa Basin. Additionally is important to explain to recreational anglers and the general population the impacts of fish transfer and the adverse effects of invasive species on freshwater Portuguese ecosystems.

Proceedings doi: 10.3390/proceedings2026146115

Authors: David J. Nachón Marta Cousido-Rocha Anxo Paz M. Grazia Pennino Santiago Cerviño Francisco Izquierdo Patricia Verísimo Pablo Caballero Estíbaliz Díaz

Diadromous fishes support culturally important small-scale fisheries in Galicia (NW Spain), but their assessment is constrained by scarce biological and effort data. We evaluated nine data-poor fishery units using first-sale records for Alosa alosa, Anguilla anguilla, Petromyzon marinus and Platichthys flesus from six Galician ports (A Guarda, Arcade, Carril, Ferrol, Vigo and Rianxo) over the period 1997–2026. The workflow combined data cleaning and ecological classification, Mann–Kendall and Theil–Sen trend analyses, actual catch over maximum catch, and catch-only CMSY models with species-specific resilience priors. Results revealed widespread signals of depletion in both anadromous and catadromous groups. Six of the nine units were classified as collapsed or critical by CMSY, three as overexploited, and none as sustainable. The most severe cases were sea lamprey (P. marinus) in A Guarda and Carril (B/BMSY = 0.10 and 0.11, critical). A. alosa in A Guarda and European eel (A. anguilla) in Arcade, Carril and A Guarda (glass eel) were classified as collapsed (B/BMSY = 0.35–0.50). Trend analyses detected significant declines in lamprey at A Guarda and Carril and in adult eel at Ferrol, whereas P. flesus in Rianxo showed a significant positive slope but remained under alert status. Overall, three stocks showed increasing trends (although only one was statistically significant), while six showed declining trends (of which only three were significant). These findings showed that public landing time series can support precautionary assessment in data-limited migratory fisheries, and justify adaptive harvest restrictions, intensified monitoring, and routine screening to support recovery and management prioritization.

Proceedings doi: 10.3390/proceedings2026146104

Authors: Miguel Encarnado Carlos M. Alexandre Bernardo Quintella Esmeralda Pereira Ana F. Belo Ana Filipa Silva João P. Marques António Faro Pedro R. Almeida

Fish Aggregating Devices (FADs), traditionally used to attract and concentrate fish, can also serve as effective environmental enrichment tools in reservoirs, particularly in those with homogeneous characteristics and scarce refuge habitat, enhancing structural complexity and promoting recreational fishing opportunities. This study aimed to evaluate patterns in the use of prototype fish aggregation devices (FADs) in small size reservoirs. It was conducted at the Nascentes Reservoir (Crato), a small Mediterranean reservoir (ca. 10 ha) located in southern Portugal. These FADs were installed to enhance refuge habitat for fish species of interest to recreational fisheries, particularly largemouth bass (Micropterus salmoides Lacepède, 1802), thereby promoting the occurrence of trophy specimens. Two types of FADs were deployed and tested: (1) bank FADs (TREES), used in shallow waters near the margins; and (2) pelagic FADs (DAPs), suspended in the water column in deeper areas at the center of the reservoir. To monitor movement patterns and habitat use, an acoustic telemetry receiver array was deployed with a design to secure a three-dimensional fine-scale positioning with high accuracy. A total of 20 largemouth bass were tagged with acoustic transmitters equipped with pressure (i.e., depth) sensors. A before–after approach was used with 10 fish tracked before FAD deployment and 10 after. Results of fish behavior analysis provide strong evidence of fish using DAPs, but not TREES. In the presence of FADs, fish reduced their home ranges and movement amplitudes, becoming closely associated with these artificial habitats. Several environmental predictors explained fish behavior in the presence of artificial refuges, namely, diel period, moonlight intensity, and fish depth. The findings of this study are expected to contribute to the development of guidelines for refuge habitat enhancement in small- to medium-sized Mediterranean reservoirs, thereby increasing their recreational fishing attractiveness.

Proceedings doi: 10.3390/proceedings2026146108

Authors: Karim Erzini

Transitional waters—such as estuaries, lagoons, deltas, and coastal wetlands—are dynamic environments where freshwater and seawater interact, forming highly productive and biologically diverse ecosystems. Shaped by temperature and salinity gradients, tidal influence, sediment transport, and nutrient-rich conditions, these habitats support diverse ecological functions. Their structural complexity—including seagrass beds, salt marshes, mudflats, and mangroves—provides essential habitats for many fish species. These areas are crucial for fish life cycles, serving as nurseries, spawning grounds, feeding zones, and refuges from predators. Many commercially important species depend on them during early life stages before moving offshore, making them vital for both commercial and recreational fisheries. Beyond food provision, they deliver key ecosystem services, including water purification, coastal protection, and carbon storage. Research on the fish community of the Ria Formosa lagoon in Portugal since the 1980s highlights long-term changes in the fish community and the dominant role of habitat structure and temporal dynamics. Subtidal seagrass beds support higher fish abundance and diversity than unvegetated areas, acting as key nursery habitats and provide important fish provisioning services. Seasonal variation is also central, driven by recruitment pulses of marine migrants in late winter–spring. Recent pressures on this system have been driven by human activity and environmental change. Seagrass loss reduces nursery and feeding areas, while pollution degrades water quality. Overfishing (including illegal fishing), recreational activities, and aquaculture expansion add stress. Climate warming and invasive species such as Caulerpa prolifera, further disrupt ecosystem balance and threaten biodiversity. Sustainable management—such as habitat restoration, protected areas, and integrated policies—is essential to preserve the ecological and economic value of this unique lagoon. Ongoing research, monitoring, habitat restoration, and stakeholder engagement remain critical for ensuring resilience.

Proceedings doi: 10.3390/proceedings2026146112

Authors: Francisco Javier Sanz-Ronda Juan Francisco Fuentes-Pérez Ana García-Vega Marina Martínez-Miguel Juan de María-Arnaiz Francisco Javier Bravo-Córdoba

Introduction: River connectivity is a fundamental component of lotic ecosystems, frequently disrupted by anthropogenic barriers. Fishways are critical mitigation tools for restoring this connectivity; however, their temporal use by fish is often assumed to be restricted to specific seasonal windows (mainly spawning season). Understanding the fine-scale temporal dynamics of fishway use by native species such as the common barbel (Luciobarbus bocagei) is essential for effective, long-term river management and the conservation of Iberian freshwater biodiversity. Objective: This study aims to evaluate the daily and seasonal patterns of use of pool-type fishways by L. bocagei, in order to improve the determination of their temporal period of use and provide data-driven recommendations for their management. Methodology: The study was conducted in the middle reach of the Duero River (Burgos province). Over a multi-year period, more than 1000 individual barbels were captured, tagged with Passive Integrated Transponder (PIT) tags, and released. Movements were continuously monitored across two pool-type fishways. Telemetry detection data were analyzed to evaluate daily rhythms and seasonal use, as well as to estimate the start and end dates of the movement periods. Results: Our analysis revealed a highly marked daily pattern in fishway use, showing a clear increase during daylight hours, with more pronounced peaks at dawn and dusk. This daily activity dynamically adjusts throughout the year in response to the solar cycle. Furthermore, we successfully determined that the seasonal activity extends from March to November, a pattern that remained consistent throughout the different study years. Crucially, the telemetry data empirically demonstrated that L. bocagei utilizes fishways for a substantial portion of the year, indicating relevant non-reproductive movements. Conclusions: The extended temporal use of these fishways indicates their potential ecological functions throughout much of the year. This must be reflected in management and maintenance protocols that ensure sufficient flow conditions, cleaning, and active vigilance during most of the year. Additionally, this predictability reinforces the value of fishways as strategic biological monitoring stations for endemic populations.

Proceedings doi: 10.3390/proceedings2026146097

Authors: Alexandre Carreira Sara Lourenço Manuel J. Rodrigues Filipe Costa Ana Lígia Primo Milene Guerreiro Miguel A. Pardal Szymon Smoliński Filipe Martinho

Introduction: Long-term ecological changes in estuarine communities are primarily driven by anthropogenic and environmental pressures. While abundance-based indicators are commonly used to assess these shifts, they often mask underlying ecological aspects related to age and/or size dynamics that may not necessarily be reflected in the abundance-based approach. Objective: This work tested a size-based indicator approach to examine the long-term changes in the size structure of the Mondego estuarine fish community (Portugal), using a 22-year dataset (2003 to 2025). Methodology: To capture the whole size structure, eight size-based indicators were applied, including mean length (MeanL), length at the 10th percentile (L10), median length (MedianL), length at the 90th percentile (L90), mean length of the 90th percentile (Lmax), size spectrum, the Large Fish index, and the Shannon index of length classes, at community and species levels and subsequently considered these in relation with with local and large-scale environmental factors. Results: Linear models identified a sharp, consistent decline in the overall size of the community, significantly correlated with the North Atlantic Oscillation index (NAO) and increasing estuarine water temperatures. A dynamic factor analysis (DFA) further identified one common trend across species for all indicators, corroborating the decrease in the overall size of the community while also acknowledging contrasting responses from different species, suggesting a heterogenous response across the fish community. Conclusions: These results highlight the importance of size-based indicators when assessing long-term ecological changes in marine ecosystems, allowing us to better understand how size structures shift, their relationship with a changing environment, and the long-term ecological outcomes in terms of community stability, resilience, recruitment, and ecosystem functioning.

Proceedings doi: 10.3390/proceedings2026146111

Authors: Martin Čech Lukáš Vejřík Luboš Kočvara Vladislav Draštík Zuzana Sajdlová Diogo Dias Rui Rivaes Diogo Ribeiro Beatriz Castro Filipe Ribeiro Carlos Fernández-Delgado Agustín P. Monteoliva Pietro Volta

Introduction: Longlines are traditional fishing gear and are widely used in marine systems for both quantitative and qualitative sampling of large predators like tuna, swordfish, sailfish, marlin or sharks. This highly selective method has been applied for the sampling of European catfish (Silurus glanis), the largest freshwater fish in Europe. This apex predator is a highly valuable fish species in its native localities of Central and Eastern Europe (commercial fishing, anglers’ trophy fishing, biomanipulation purposes) but a dangerous alien invasive species in South and Western Europe. Objective: The efficiency and selectivity of longlines for European catfish sampling were compared with more traditional fishing methods like gillnets and electrofishing. Methodology: European catfish were sampled in native areas (Římov, Žlutice, Vrchlice, Hubenov, Lipno, Želivka reservoirs; Czech Republic) and areas of invasion (Lakes Campagna, Avigliana Grande, Maggiore; Italy; Belver, Meimoa, Cedillo reservoirs; Portugal; Iznajar, Mequinenza reservoirs; Spain) following the protocols of best catfish (Silurus glanis) capture methodologies in small and large lakes and reservoirs established for the current needs of the European Commission within the LIFE PREDATOR project. Results: The longline efficiency expressed as the proportion of individual hooks catching catfish (live baits exposed overnight) was from low to medium (5–25%; Czech reservoirs, Italian lakes, Meimoa reservoir) to very high (up to over 50%; Portuguese and Spanish reservoirs). In many water bodies, specifically in areas of invasion, catfish represented 100% of the longline catch (Campagna, Maggiore, Cedillo, Iznajar, Mequinenza). In the rest of the water bodies, the by-catch ranged from 2 to 20% with the highest values occurring in its native localities (due to the presence of large individuals of Northern pike, Esox lucius, another predatory fish in these systems). In areas of invasion, the inconsiderable by-catch was composed of other non-native predatory fish species like pikeperch (Sander lucioperca), European perch (Perca fluviatilis) or channel catfish (Ictalurus punctatus). Both the efficiency and selectivity of longlines were higher compared to gillnets and electrofishing, and longlines also caught larger catfish individuals. Conclusions: Longlines represent an efficient and extremely selective method for European catfish sampling, reduction and even eradication, especially in areas of invasion. Their usage, however, requires specific equipment, skills and also baits.

Proceedings doi: 10.3390/proceedings2026146096

Authors: Carlos Cano-Barbacil Emili García-Berthou Filipe Ribeiro Marko Ćaleta Jesús Pedreño Francisco José Oliva-Paterna

Introduction: The circum-Mediterranean region is a global biodiversity hotspot, hosting a highly distinctive freshwater fauna with a high degree of endemism and conservation concern. However, these ecosystems are increasingly threatened by biological invasions, particularly by non-native fish species, which represent a major driver of biodiversity loss. Objective: This study aims to compile a comprehensive and updated inventory of non-native inland fish species across the circum-Mediterranean region and to identify the main taxonomic, biogeographical, and socio-environmental drivers shaping their distribution. Methodology: We conducted an extensive review of the scientific literature, online databases (including EASIN, GISD, and CABI), and technical reports to compile records of non-native fish species across inland and transitional waters of Mediterranean-climate basins. Analyses focused on species composition, taxonomic representativeness, introduction pathways, native regions, and the relationship between species richness and selected environmental and socio-economic variables. Results: A total of 151 non-native fish species were recorded across the study area. Italy, Spain, Bosnia and Herzegovina, France, and Croatia exhibited the highest numbers of established species. Taxonomic representation was uneven, with Salmoniformes and Esociformes overrepresented among established non-native species, while Siluriformes and Characiformes were underrepresented. Most introductions originated from Europe, Asia, and North America, primarily through intentional releases and escape events. Non-native species richness was positively correlated with gross domestic product, precipitation, and the number of dams, highlighting the role of economic development and habitat modification in facilitating invasions. Conclusions: Biological invasions by non-native fishes are widespread across the Mediterranean basin and are strongly driven by human activities and environmental conditions. The high invasion levels observed in this biodiversity hotspot pose a significant threat to endemic freshwater faunas. These findings underscore the need for coordinated transnational management strategies, stricter regulation of introduction pathways, and prioritization of high-risk species to mitigate further impacts.

Proceedings doi: 10.3390/proceedings2026146110

Authors: Samira Nuñez-Velazquez Pedro M. Guerreiro Gonçalo Jacinto Pedro Veiga Mafalda Rangel

Introduction: Marine recreational fishing (MRF) is a socially, economically, and ecologically important activity. However, the absence of systematic monitoring and research in Portugal has limited a comprehensive understanding of the sector and its broader implications. Addressing these gaps is essential to support evidence-based and adaptive recreational fisheries management. Objective: This work aimed to improve understanding of marine recreational fishing in Portugal by integrating social and biological perspectives across national, regional, and local scales. Methodology: A multidisciplinary approach was applied. At the national scale, online questionnaire data were combined with licencing information and regional effort estimates to quantify fishing effort, catches, release rates, catch composition, and direct trip expenditures. The same survey framework was also used to identify recreational fisher profiles based on motivations, behaviours, fishing practices, and attitudes toward management. At the local scale, shore angling surveys conducted before the implementation of the Natural Marine Park of the Algarve Reef were used to estimate fishing activity and establish a baseline for future monitoring. From a biological perspective, field-based catch-and-release experiments were conducted to assess post-release mortality and physiological disturbance, using indicators such as mortality, condition, capture and handling variables, and blood biomarkers of stress and recovery. Results: The national estimates documented substantial fishing effort, catches, and direct expenditure, confirming the relevance of MRF in Portugal at both ecological and socio-economic levels. Portuguese recreational fishers were also shown to be heterogeneous in their motivations, behaviours, and practices, reinforcing the need for management approaches that reflect this diversity. At the local scale, shore angling estimates from the Natural Marine Park of the Algarve Reef provided an important pre-protection baseline for the now established Marine Protected Area, enabling future comparisons and long-term assessment of management effects. Biological experiments showed that recreational fishing can generate measurable physiological disturbance in fish, with post-release condition influenced by capture and handling factors. Among the variables examined, hook location emerged as particularly important, with deep-hooked fish showing greater impairment and higher mortality risk. Conclusions: Together, these findings show that improving recreational fisheries management in Portugal requires integrating social patterns, fishery magnitude, and biological responses to capture and release. Long-term monitoring programmes, combined with management approaches adapted to different fisher profiles and fishing contexts, are essential to support more effective and sustainable recreational fisheries governance.

Proceedings doi: 10.3390/proceedings2026146109

Authors: Quim Pou-Rovira Neus Mairal Elena Farré Bernat Dalmau Llorenç Ferrer Maria Spotti Eloi Cruset

Currently, in Catalonia, Spanish toothcarp (Apricaphanius iberus) has a discontinuous distribution, with its main populations located in the Ebro Delta and the Empordà wetlands. Along the Catalan coast, there are some small, isolated populations, most of which have been recently introduced. In the Empordà area, this species still maintains three isolated populations within two natural parks, where it currently occupies the northernmost site of its global distribution. Between 2017 and 2025, several fish sampling campaigns were carried out in the Empordà wetlands (Northeast Catalonia), gradually covering the entire area of potential distribution of this species in the area. In total, 228 points have been sampled, at least in one occasion, in all types of water bodies (rivers, canals, lagoons, marshes). In 106 points, more than two sampling events have been performed. Furthermore, in 2025, a specific diagnosis was carried out to better understand the current situation of the species in these protected spaces after a prolonged and severe drought. Sampling was carried out everywhere with fykenets, adding the use of nets and electrofishing in some stations located in large bodies of water. The known historical evolution of Spanish toothcarp distribution in the Empordà has been presented since the first data was made available at the beginning of the 1980s of the 20th century until now. Today, this fish only occupies approximately 10% of its potential distribution in the area. Over the last five decades, its distribution has expanded and contracted several times, but in 2025, it was once again in the worst possible situation of the analysis period. Therefore, the implementation of protected areas, or the execution of several large ecological restoration projects, have only succeeded in maintaining existing populations, but not in the expansion of its potential distribution to unoccupied areas. The main factors that explain this general situation are mainly (1) the proliferation of exotic species, (2) the loss of ecological status, and (3) hydrological alterations and increasingly severe droughts. Thus, the recovery and long-term conservation of Spanish toothcarp in the Empordà area inevitably requires the implementation of more extensive and decisive measures to reverse the incidence of these factors.

Proceedings doi: 10.3390/proceedings2026146106

Authors: Bianca Neves Felippe Alexandre Daros Rafael Schroeder Rafael Gaio Kulzer Marcus Rodrigues da Costa Rodolfo Miguel Silva Alberto Teodorico Correia

Introduction: Understanding population structure is essential for the effective management of marine resources. The bluefish (Pomatomus saltatrix) is a widely distributed and commercially important species along the Brazilian coast, yet its population structure in the South–Southeastern region remains unclear. Objectives: This study aimed to assess the body morphological variation and to infer the population structure of P. saltatrix along the South and Southeastern coasts of Brazil using a landmark-based geometric morphometrics method. Methodology: Individuals were collected between August and October 2024 from artisanal fisheries in Rio de Janeiro (n = 46), São Paulo (n = 37), and Santa Catarina (n = 29). A total of 12 landmarks were used to derive a truss network and extract 25 transformed distances (DTs). Data were analyzed using univariate (one-way ANOVA, followed by Tukey’s test if needed, or Kruskal–Wallis followed by Dunn’s test if needed) and multivariate statistics (PERMANOVA and Flexible Discriminant Analysis (FDA)). Results: Significant regional differences were detected for most DTs, except DT3, DT4, DT6, DT9, DT13, DT24, and DT25. PERMANOVA revealed significant differences among all sampling locations, including pairwise comparisons (p < 0.05). FDA achieved an overall reclassification success of 93% of individuals to their original location. Conclusion: Despite the high reclassification accuracy, the results support the existence of a single stock with spatial structuring rather than completely distinct population units, indicating that P. saltatrix in this region is not homogeneous.

Proceedings doi: 10.3390/proceedings2026146105

Authors: João Leça Bruna Henriques Filipe Soares Cláudia Magalhães Rui Rocha Paulo Rema

Introduction: Fish skin is the first line of defense against the aquatic environment, acting as a physical, chemical, and immunological barrier. In addition to preventing pathogen entry, the skin and its mucus contribute to osmoregulation, innate immunity, and redox balance. Skin lesions—caused by mechanical damage, parasites, environmental stress, or handling—disrupt this barrier, increasing susceptibility to infections, inflammation, and production losses. Thus, efficient skin regeneration is essential for fish welfare and performance. Nutrition plays a key role in this process by providing substrates for epithelial repair, immune function, and antioxidant defense. Among dietary factors, zinc (Zn) is particularly important due to its involvement in cell proliferation, enzymatic activity, and maintenance of skin integrity. Objective: Our objective is to assess the effectiveness of image-based analysis in quantifying the skin healing process in Atlantic salmon fed diets supplemented with zinc. Methodology: The trial comprised three dietary treatments: a control diet with 42 mg Zn per kg (D1), and two diets supplemented up to 120 mg/kg of zinc, derived from inorganic (D2) or organic (D3) forms. Pit-tagged fish with an initial body weight (78 ± 0.1 g) were fed the diets for 75 days. After 15 days of experimental feeding, a standardized wound lesion (2.5 mm diameter × 0.5 mm depth) was inflicted in deeply anesthetized fish, with a disposable biopsy punch, in the dorsal area. After wound infliction, the fish resumed their normal feeding regime for the rest of the trial days. The progression of skin wound healing was assessed using standardized digital image analysis. High-resolution photographs of individual wounds were collected 8, 16, 24 and 32 days post-wounding. All images were acquired under standardized conditions with the inclusion of ArUco identifiers to enable a subsequent computer-assisted comparison. Morphometric parameters (wound width, diameter, perimeter and area) were used to assess wound contraction and closure over time. In parallel, a semi-quantitative visual scoring system was applied to each wound image to capture qualitative aspects of healing that are not fully described by morphometric data alone. Results: Full data analysis is currently underway, but the first results show beneficial effects of dietary zinc supplementation on the skin regenerative process. Conclusions: The combined use of objective digital measurements and standardized visual scoring enabled a comprehensive evaluation of wound healing progress, bridging quantitative tissue remodeling with biologically relevant phenotypic outcomes. This image-based framework provides a sensitive and reproducible approach for assessing dietary interventions targeting skin regeneration and barrier restoration in Atlantic salmon.

Proceedings doi: 10.3390/proceedings2026146099

Authors: Silvia Perea Miriam Casal-López Hamid Reza Ghanavi Ignacio Doadrio

Introduction: Squalius palaciosi (Doadrio, 1980; Leuciscidae) is a highly threatened freshwater fish species with an extremely restricted distribution, currently confined to a few tributaries on the right bank of the Guadalquivir River basin. During the 1980s, its populations were abundant and constituted a dominant component of local fish communities. However, multiple threats led to a drastic population decline, bringing the species to the brink of extinction. From an evolutionary perspective, S. palaciosi is particularly remarkable due to its polyploid condition and its potential involvement in hybridogenetic complexes, a rare phenomenon in the Iberian Peninsula. Hybridogenetic systems are well documented in its congeners Squalius alburnoides, widely distributed across Iberian river basins, and Squalius sp., restricted to the Guadiana basin. In these systems, the maternal lineage is shared (Squalius pyrenaicus), whereas the paternal lineage varies and remains unknown in S. palaciosi. Objective: This study aims to generate the first genomic data for S. palaciosi and to elucidate its evolutionary origin, as well as its mitochondrial and nuclear phylogenetic relationships within hybridogenetic complexes. Methodology: Genomic DNA was extracted from skeletal remains of preserved specimens housed in the fish collection of the National Museum of Natural Sciences (MNCN-CSIC) and subjected to Illumina short-read sequencing. After quality filtering, potential contaminant reads were removed. The complete mitochondrial genome and several nuclear gene fragments were assembled. Mitochondrial phylogenetic analyses were conducted using publicly available whole-genome sequencing data from Iberian freshwater fish species. Nuclear gene fragments were taxonomically assigned using BLAST analyses. Results: Phylogenetic analyses revealed that S. palaciosi is closely related at the mitochondrial level to S. alburnoides and S. tartessicus, with strong statistical support. BLAST-based taxonomic assignments of nuclear markers suggest the involvement of multiple Iberian freshwater fish species in the hybridogenetic origin of S. palaciosi. Conclusions: Our results provide novel insights into the evolutionary history of S. palaciosi and support a complex hybridogenetic origin involving multiple parental lineages. This study contributes to a better understanding of hybridogenetic speciation in freshwater fishes, a rare but evolutionarily significant process.

Proceedings doi: 10.3390/proceedings2026146102

Authors: Luísa Sousa Carla Silva Pedro Anastácio Filipe Ribeiro

Introduction: The global ornamental fish trade is a rapidly expanding sector and a major pathway for the introduction of non-native species, particularly in freshwater ecosystems in developed countries. The introduction of non-native species can result in a range of ecological impacts, including predation, competition, hybridization, and disease transmission, often leading to ecosystem degradation and biotic homogenization. Therefore, it represents a clear ecological risk, especially serious in freshwater systems with a high endemism rate, such as the Iberian Peninsula. The occurrence of ornamental non-native species in the Iberian Peninsula has been common, yet little has been done to describe the overall ornamental fish trade as a first step to evaluate invasion risk. Objective: This study characterizes the import dynamics of ornamental freshwater fish in Portugal between 2020 and 2024 and evaluates its potential role as a pathway for species introductions. Methodology: Data were obtained from the Institute for Nature Conservation and Forests database, including information on species composition, quantities, sizes, prices, and countries of origin. A total of 431 records were analyzed, resulting in 27,689 validated entries of imported freshwater fish, which were taxonomically verified and filtered to retain only freshwater species. Results: A total of 666 species from 88 families were identified, with an average of 380 species imported annually, reflecting high taxonomic diversity. Import volumes increased from approximately 1.25 million individuals in 2020 to 1.75 million in 2024, while total import value nearly doubled from €300,000 to €600,000. Imports were predominantly from five Southeast Asian countries, particularly Indonesia and Vietnam, and largely supported by aquaculture production (88%). A stable core of highly traded species, including Carassius auratus, Poecilia reticulata, and Paracheirodon innesi, suggests a sustained and very high propagule pressure, while some species variability was observed on yearly basis, suggesting the importance of monitoring programs on actual imports. Conclusions: Overall, the ornamental fish trade represents a significant and growing pathway for biological invasions in Portugal. The combination of increasing trade volume, high species diversity, and persistent dominance of key taxa highlights the need for improved monitoring, regulatory frameworks, and public awareness to mitigate ecological risks.

Proceedings doi: 10.3390/proceedings2026146107

Authors: Monica Torres-Ruiz María Muñoz-Palencia Laura Sánchez-Ramos Ana I. Cañas-Portilla Antonio de la Vieja

Introduction: Aquatic contaminants can alter fish behavior before overt toxicity becomes evident, making neurobehavioral endpoints relevant for ecosystem protection and for hazard prioritization within a One Health framework. We recently developed a high-throughput visual-acoustic zebrafish larval thigmotaxis assay in which edge preference is interpreted as an anxiety-like behavioral endpoint, thereby adding spatial phenotyping beyond conventional locomotion metrics. Objective: To evaluate assay performance in a multisubstance screening challenge and determine whether it can discriminate distinct behavioral fingerprints without prior knowledge of chemical identity. Methodology: Zebrafish larvae were exposed for 1 h at 120 hpf. For each substance, 24 larvae were tested per condition, with six concentrations per substance, plus positive and negative controls. Larvae were challenged using alternating light/dark and tapping/quiet paradigms. The primary endpoint was the percentage of time spent at the edge as a proxy for anxiety-like behavior, while total distance and mean total velocity when moving were used as contextual locomotor metrics; edge distance and edge velocity were used as supportive spatial metrics. Data from 37 substances were analyzed through a standardized automated workflow. Results: Controls performed as expected and supported assay stability across runs. The chemical screening revealed heterogeneous but reproducible behavioral fingerprints. Seven substances produced weak/minimal acute responses, ten showed predominantly suppressive profiles, three predominantly activating profiles, nine showed prominent thigmotaxis-specific anxiety-like signals not explained by locomotion alone, and eight displayed mixed or stimulus-dependent patterns, including non-monotonic responses. Several substances altered edge preference while distance and velocity changed less, differently, or in the opposite direction, indicating behavioral reorganization rather than simple hypo- or hyperactivity. The multi-stimulus design was critical because some effects were evident only under specific sensory contexts. Conclusions: The multisubstance challenge supports the discriminatory capacity, robustness, and added value of the assay for high-throughput neurobehavioral screening. By capturing anxiety-like behavior through thigmotaxis and complementing it with locomotor context, the method improves phenotypic resolution for aquatic pollution assessment and offers a sensitive fish-based NAM to prioritize chemicals of concern for both environmental and human health-oriented testing strategies.

Proceedings doi: 10.3390/proceedings2026146098

Authors: Inês Amaral Rita A. Costa Antonio Zamora-López Wim Zimmermann Adrián Guerrero-Gómez Sílvia F. Gregório Pedro M. Guerreiro

Introduction: Marine heatwaves are increasing in frequency and intensity, posing major challenges for fishes inhabiting shallow coastal ecosystems. Short-term exposure to extreme warming can alter metabolic performance and thermal tolerance, with potential consequences for species persistence and school composition in thermally variable habitats. Understanding the capacity of coastal fishes to withstand acute warming events is therefore essential for predicting ecological responses to climate change. Objective: We aimed to determine the effects of simulated marine heatwaves on thermal tolerance and metabolic performance in juvenile grey mullets, Chelon labrosus and Chelon aurata, two abundant sympatric species inhabiting the Ria Formosa lagoon (southern Portugal). Methodology: Juvenile mullets acclimated at 17 °C were exposed to simulated heatwave treatments of 23, 27, or 33 °C and sampled either at peak temperature or after 48 h and 1-week recovery at 17 °C. Critical thermal maximum (CTmax, using a 1 °C/min thermal ramp), static oxygen consumption (MO2), and intermittent respirometry parameters were measured. Standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic scope (AS) were derived from intermittent respirometry. A complementary temperature-ramp (>3 h at each temperature step 17, 23, 27 and 33 °C) was performed to evaluate routine metabolic rate and estimate Q10 values across increasing temperatures. Additional plasma and tissue analyses are being conducted to assess energetic substrate mobilization and cellular responses to thermal and oxidative stress. Results: CTmax increased significantly with warming in both treatment modes, demonstrating rapid heat hardening in juvenile mullets. Fish exposed to 27 and 33 °C exhibited higher CTmax than control fish, and this elevated tolerance persisted after recovery. Chelon labrosus showed slightly higher CTmax values than C. aurata. Oxygen consumption increased with temperature, with the strongest responses occurring at 33 °C. SMR increased markedly with warming, particularly in heatwave-exposed fish, while MMR increased mainly at the highest temperature treatment. In contrast, AS showed no clear thermal optimum or decline across treatments. Routine metabolic rate increased non-linearly with temperature in the complementary ramp experiment, with a mean Q10 of 2.28, confirming strong thermal dependence of metabolism. Conclusions: Juvenile mullets possess substantial short-term thermal plasticity and can rapidly increase heat tolerance during marine heatwaves but this enhanced tolerance is accompanied by elevated metabolic costs under extreme warming, indicating potential energetic trade-offs near upper thermal limits. Differential physiological responses between species may influence school composition and ecological performance across thermal landscapes. Ongoing plasma and tissue analyses will further clarify the energetic and cellular mechanisms underlying thermal and oxidative stress resilience in coastal fishes.

Proceedings doi: 10.3390/proceedings2026146103

Authors: Juan Carlos Arronte Jose Manuel González-Irusta Francisco Velasco Alberto Serrano

Introduction: The tub gurnard (Trigla lyra) is a demersal species of commercial interest whose long-term distributional dynamics remain poorly understood. Understanding spatial and temporal changes is essential for fisheries management and for assessing biogeographic shifts. Objective: To characterise the spatio-temporal distribution and persistence of T. lyra across Galician and Cantabrian Sea waters over a 33-year period (1993–2025) and to identify environmental and fishing drivers associated with observed changes. Methodology: We analysed data from the DEMERSALES bottom trawl survey series (1993–2025), for which the sampling design remained consistent throughout. Species distribution was modelled using a delta–GAM framework (presence–absence and positive values), complemented by a presence-only GAM fitted to Vessel Monitoring System (VMS) data; because these data were only available for 2009–2023, this model was restricted to that period for biological coherence. Environmental predictors included bathymetry, slope, sediment composition (organic matter, mud, fine and coarse sand), bottom temperature, and salinity. Spatial structure was assessed using aggregation curves, occupied area, centre of gravity, a Space Selectivity Index, and an Index of Persistence. Results: The occupied area increased from 45 to 963 km2 (+2040%), accompanied by a sustained decline in the Space Selectivity Index and a westward shift of the distributional centroid (~20 km), indicating progressive range broadening. The frequency of occurrence rose from 4.5% in 1993 to 87.7% in 2025, reflecting a marked increase in spatial occupancy and encounter probability. Abundance increased sharply after 2015 (+47%), consistent with strong positive year effects in the GAM. Higher occurrence and densities were associated with muddy substrates, intermediate to high organic content, and depths of 100–300 m, matching the stable aggregation cores found along the shelf break. A reduction in trawling effort (−38% in mean intensity, −17% in swept area over 14 years) likely facilitated these trends. Conclusions: T. lyra expanded its distribution and shifted westward between 1993 and 2025, with persistent aggregation cores on the shelf break. No significant effect of temperature was found, suggesting that climate warming is not the primary driver; the expansion appears most plausibly to have been favoured by the decline in fishing pressure.

Proceedings doi: 10.3390/proceedings2026146091

Authors: Víctor Manuel Álvarez-Navarro Adrián Guerrero-Gómez Antonio Zamora-López Antonio Andrés Herrero-Reyes Elena Parra-Espín Mar Torralva José Manuel Zamora-Marín José Manuel Vidal-Gil Francisco José Oliva-Paterna

Introduction: The Iberian killifish (Apricaphanius iberus), an endemic cyprinodontid of the Spanish Mediterranean coast, is a key conservation species due to its restricted distribution, high sensitivity to habitat alteration and invasive fish, and ecological role in saline wetlands. Classified as Endangered by national administration and listed in Annex II of the EU Habitats Directive, its populations have undergone severe declines across its native range. Coastal salt pans have become critical refuges for the persistence of this species, often supporting some of the highest population densities recorded. However, the conservation value of these anthropogenic systems strongly depends on hydrological management, which directly influences habitat stability and suitability. Objectives: This study aims to assess the long-term population responses of A. iberus under contrasting hydrological management regimes in coastal salt pans. Methodology: We analysed ten years of monitoring data across five salt pan circuits in the perimeter area of the Mar Menor coastal lagoon (SE Spain), covering a salinity gradient and three management regimes: economic exploitation (EE), preventive management (PM), and non-management (NM). Population metrics (occurrence, abundance and breeder proportion) were evaluated. Results: Population performance differed markedly among management regimes. EE circuits showed consistently high occurrence and abundance, including in hypersaline ponds, high breeder proportions, low interannual variability, and weak dependence on meteorological conditions and ephemeral prey. PM circuits displayed intermediate patterns. In contrast, NM circuits exhibited low occurrence and abundance, low breeder proportions, high temporal fluctuations, and strong dependence on meteorological variability. Conclusions: Hydrological management is a key determinant of A. iberus population stability in coastal salt pans. Maintaining or restoring traditional management practices enhances habitat suitability, buffers environmental variability, and supports conservation actions such as reintroduction. These findings highlight the critical role of managed anthropogenic wetlands as refuges for endangered fishes and provide a transferable framework for conservation under global change.

Proceedings doi: 10.3390/proceedings2026146095

Authors: Ana S. Rato Carlos M. Alexandre Ana F. Silva João P. Marques Sara S. Silva Maria J. Lança Bernardo R. Quintella Pedro R. Almeida

The Iberian barbel (Luciobarbus bocagei Steindachner, 1864) is a potamodromous species that displays migratory movements, with adults moving upstream during spring to spawn, followed by downstream migration in autumn by both adults and juveniles to feed and inhabit more productive river stretches. Increasing river fragmentation due to dam construction and operation causes a loss of connectivity and suitable habitat, which can affect this natural behaviour. In a tributary of River Douro, River Tua, a 108 m high dam, was recently built (i.e., Foz Tua dam in 2017) at only 1.1 km from the river mouth, leaving the upstream spawning area inaccessible. To evaluate the species behavioural response to this impact, a passive acoustic telemetry array was deployed in the study area, and between 2018 and 2023, 120 tagged fish had their movements tracked. The results showed two different behavioural profiles in the same population with migratory (42.5%) and resident (54.0%) individuals. During this period, a specific experimental study was developed to evaluate the response of a subset of 90 fish, captured upstream of the Foz Tua dam and translocated to an alternative downstream Douro tributary (River Pinhão, ~20 km downstream from River Tua). From these, 66.7% remained at the release site, whilst 23.3% returned to the river of origin, i.e., River Tua. From the returned fraction, 28.6% of the tagged fish maintained this migratory behaviour between both rivers in the following years. Generalized Additive Models were used for each of the two behavioural profiles observed in this study, to identify which environmental variables were associated with the presence of the tagged barbels downstream the Foz Tua dam. Ecological flow, temperature and day-period were some of the predictors explaining the use of this river stretch downstream of Foz Tua dam. This study substantially updates the available information regarding this species’ movement patterns at large spatial and temporal scales, contributing to enhancement of management and conservation programs for potamodromous species, in highly impounded and fragmented rivers.

Proceedings doi: 10.3390/proceedings2026146082

Authors: Lide Izeta-Zalduendo Rafael Miranda José Barquín Alexia M. González-Ferreras Maria Moran-Luis Francisco J. Peñas Amaia A. Rodeles Ana Sánchez-Alcázar Ana Villarroya David Galicia

Introduction: Artificial infrastructure interrupts river longitudinal connectivity, preventing the free flow of water, matter, energy, and organisms through the system, altering the habitat and impacting freshwater biodiversity. Freshwater fishes are especially sensitive to this threat, since they are constrained to the limits of the river network. Transversal obstacles, such as dams and weirs, hinder their movements upstream and downstream and fragment populations. Longitudinal connectivity can be simply measured as the proportion of connected river length in a basin. However, other indices have been suggested more recently, measuring connectivity as the proportion of connected elements of interest (e.g., populations of a species) in a river basin. Objective: The aim of this work was to study (1) the degree of connectivity of native freshwater fish species populations in eleven Spanish river basins and (2) the impact of artificial river fragmentation in these basins on population connectivity. Methodology: Fish populations’ location and size were estimated through sampling presence data, and completed using the predicted occurrence of each species in a river basin, calculated through Species Distribution Models (SDMs). To estimate the degree of connectivity between populations of each species, the Population Connectivity Index (PCI) was calculated under two scenarios: the “current” scenario, considering all the artificial obstacles fragmenting the river network and their specific passabilities, and the “natural” scenario, considering that all the artificial obstacles in the river network were completely passable. Results: Native freshwater fish populations are severely fragmented in Spanish rivers, with a mean current PCI of 9.8% across species and river basins. The impact of artificial fragmentation is high, causing a mean decrease in PCI of 52 percentage points across species and river basins. Moreover, although the impact of artificial river fragmentation is high in all river basins, it is important to point out that there are significant differences between river basins attributed to their size and the specific traits of the ichthyofauna inhabiting them. Conclusions: The degree of connectivity in a river basin varies depending on the elements of interest considered. Therefore, incorporating ichthyofauna into the decision-making process is essential to improve the effectiveness of river restoration actions.

Proceedings doi: 10.3390/proceedings2026146093

Authors: Elena Parra-Espín José Manuel Zamora-Marín José Manuel Vidal-Gil Antonio Zamora-López Antonio Guillén-Beltrán Miguel Ángel Richarte Adrián Guerrero-Gómez Antonio Andrés Herrero-Reyes Víctor Manuel Álvarez-Navarro Jorge Madrid-Ruiz Rocío Peñalver Mar Torralva Francisco José Oliva-Paterna

Introduction: Freshwater fish communities in Mediterranean basins have undergone profound changes over recent decades due to biological invasions, habitat alteration, and hydrological regulation. The Segura River basin (SE Spain), particularly in the Region of Murcia, represents a paradigmatic case of these transformations, with increasing pressures on native ichthyofauna and growing relevance for recreational fisheries. Objective: This study aims to provide an updated inventory of fish communities in the rivers and reservoirs of the Region of Murcia, assessing current composition, relative abundance, and conservation status. Methodology: Fish assemblages were surveyed during sampling campaigns conducted in autumn 2023, 2024 and 2025. Sampling sites included representative reservoirs and river reaches within the middle sector of the Segura River basin, focusing on areas of interest for recreational fishing. Passive fishing gears were used in reservoirs, while electrofishing was conducted in riverine habitats. Presence and relative abundance data were recorded for all detected taxa. Results: A total of 15 taxa were identified (8 in reservoirs and 15 in river reaches). Reservoir communities were almost entirely dominated by non-native invasive species, including Cyprinus carpio, Alburnus alburnus, Sander lucioperca, Micropterus salmoides, Lepomis gibbosus, and Gambusia holbrooki, with Luciobarbus sclateri as the only native species. Riverine sections of the main channel also showed a strong dominance of exotic taxa, with additional species such as Esox lucius, Oncorhynchus mykiss, Gobio lozanoi, and Pseudochondrostoma polylepis. Native species detected included L. sclateri (dominant), Anguilla anguilla, and Salariopsis fluviatilis, the latter showing a recent expansion likely linked to human-mediated introduction. Isolated tributaries hosted the most valuable assemblages, including populations of L. sclateri, Squalius tartessicus, and the endangered Valencia hispanica (recently unauthorized translocations into the Segura river basin). Conclusions: Current fish communities in the Region of Murcia reflect a marked ecological degradation compared to historical conditions, driven by the proliferation of non-native species and habitat alteration. Changes over the last 30 years have been particularly pronounced in reservoirs and regulated sections of the main river channel, where local extinction of the native S. tartessicus has also been detected. Only the headwaters of certain tributaries retain fish assemblages of notable conservation interest, highlighting their priority for management and protection.

Proceedings doi: 10.3390/proceedings2026146085

Authors: Raquel Abad Antía Alonso Alexandre M. Schönemann Humberto Quesada Ricardo Beiras

Introduction: The discharge of treated wastewater into coastal and marine environments represents a continuous source of pollutants, including pharmaceuticals and plastic additives with endocrine-disrupting (ED) potential. These compounds are of increasing concern for the European Union due to their capacity to interfere with hormonal systems and their inclusion in current environmental monitoring priorities. ED compounds may induce sublethal effects in aquatic organisms, particularly in vertebrates, where endocrine pathways are highly conserved. In this context, the use of Cyprinodon variegatus, a euryhaline fish species, provides a suitable model to assess potential risks in marine ecosystems. Despite advances in wastewater treatment technologies, the persistence of biologically active substances in treated effluents remains a concern. Objective: This study aims to evaluate whether treated effluent water still contains compounds with endocrine-disrupting activity and to assess their potential effects on marine organisms. Methodology: Larvae of C. variegatus from a laboratory stock maintained at ECIMAT (University of Vigo), one of the few available stocks of this species in Europe, were exposed for 48 h to environmentally relevant dilutions (1:10, 1:30, and 1:100) of wastewater treatment plant effluent collected after UV disinfection as the final treatment step. Pools of 10 larvae were used for each condition. Sublethal effects were assessed through gene expression analysis using quantitative PCR (qPCR), targeting biomarkers involved in endocrine regulation. Two housekeeping genes (tbp and hprt) were used for normalization. Estrogenic responses were evaluated through vtgab and zp2, while androgenic responses were assessed using 17hsd and 11hsd. Results: Preliminary results indicate significant alterations in estrogen-related gene expression, particularly in vitellogenin (vtgab) and zona pellucida (zp2), highlighting the activation of estrogenic pathways and supporting the presence of endocrine-disrupting activity in treated effluent water. Conclusions: This study highlights the relevance of assessing endocrine disrupting activity in treated effluents and supports the use of molecular biomarkers as sensitive tools for evaluating their potential impact on marine ecosystems, contributing to the improvement of wastewater monitoring and management strategies.

Proceedings doi: 10.3390/proceedings2026146083

Authors: Marta Ramalho Catarina Caldeira-Santos Melanie Court Jaquelino Varela Bernardo Duarte Rui Rosa

Introduction: Establishing baseline descriptions of inorganic elements in the early life stages of sharks and in their respective nursery areas is essential for assessing anthropogenic impacts and supporting conservation strategies. Objectives: This study presents the first baseline of plasma trace element concentrations (Al, Zn, As, Cu, Cr, Cd, Co, Mn, Ti, Ni, Hg, Pb) for four juvenile shark species (Carcharhinus limbatus, Paragaleus pectoralis, Rhizoprionodon acutus, and Sphyrna lewini) from Sal Rei Bay, Boa Vista Island, Cabo Verde—the first multi-species shark nursery area described in Atlantic Africa. Methodology: Seawater and sediment samples were collected from eight sites and analyzed along with plasma samples using total reflection X-ray fluorescence spectroscopy (TXRF). Sediment granulometry and pollution indices, including the enrichment factor (EF), ecological risk index (RI), and metal pollution index (MPI), were used to characterize habitat contamination. Data were analyzed using statistical models to explore spatial and element-specific patterns. Results: Overall, environmental contamination was low, with slight increases in Cd, Co, and Hg at sites 1 and 2, near the fishing port, and at site 5, likely reflecting natural transport, sediment redistribution, and enhanced nearshore deposition. Juvenile sharks exhibited generally low plasma trace element concentrations, although species-specific elemental signatures were evident: elevated levels of Al and Cu in C. limbatus, Zn in S. lewini, and As in R. acutus and P. pectoralis. Conclusions: These findings establish critical baseline reference values for trace elements in juvenile sharks from a key Atlantic nursery area. The results provide an essential framework for future biomonitoring efforts and contribute to the management and conservation of Cabo Verdean shark nursery habitats.

Proceedings doi: 10.3390/proceedings2026146094

Authors: Álvaro Pita Manuel Vera Sandra Heras Jordi Morata Raúl Tonda David -Diez-del-Molino Dorte Bekkevold Adrián Casanova Alba Abras Maria Inés Roldán Jose-Luis García-Marin

Introduction: Brown trout (Salmo trutta L.) is a salmonid fish considered a genetically and geographically highly structured species. The species is catalogued as vulnerable in the Spanish Red List since 1992. Based on morphological differentiation, some authors have proposed splitting Salmo trutta into many taxa and in recent years, several binomials involving morphologically differentiated Western Mediterranean brown trout morphs have regained relevance as distinct species and are now assessed in the IUCN Red List. However, Spanish legislation still considers a single species, S. trutta, inhabiting Atlantic and Mediterranean rivers. Analyses of mitochondrial DNA variation across the species’ native range have revealed numerous matrilineal lineages and helped disentangle the phylogenetic relationships and biogeographic history of brown trout. Four largely distant evolutionary lineages defined by sequencing the mitochondrial control region (Adriatic, AD, Mediterranean, ME, Atlantic, AT and Duero, DU) are native among the Iberian brown trout populations. Stocking activities have resulted in introgressive hybridization of these native populations with non-native northern Atlantic stocks throughout the Iberian rivers and compromise the evolutionary singularities of brown trout in the Iberian Peninsula. Methodology: In this study, we compare complete mitogenomes from Iberian brown trout specimens with those from other regions, using both newly sequenced samples and whole mitogenomes from the GenBank database and estimate their divergence times relative to those observed among species of other Salmoninae genera, such as Oncorhynchus and Salvelinus, to assess patterns of species-specific divergence among Iberian brown trout populations. Results: The evolutionary relationships of the specimens using their mitogenomes fitted with previous analyses using partial mitochondrial sequences and confirmed the strong differentiation among the Iberian lineages. All the branches involving distant Iberian mitogenomes are sister branches with taxa historically described under different binomials (such as Salmo macrostigma, S. multipunctatus, S. pallaryi). Conclusions: The results provide evidence supporting the existence of potentially distinct and undescribed native Salmo species in the Iberian rivers.

Proceedings doi: 10.3390/proceedings2026146092

Authors: Margarida Vizeu-Pinheiro Sebastião Farias Maria Lourie Saoirse Tak-Yung Macklin Paula Dominguez Rein-Loring Ray van Eeden Rui Rosa

Introduction: Elasmobranchs play a vital role in marine food webs through top-down control and the structuring of ecosystem stability, yet more than one-third of species face extinction. The Maldives, a recognised Indian Ocean hotspot for shark and batoid diversity, designated its EEZ as a shark sanctuary in 2010, but multispecies elasmobranch occurrence patterns and environmental drivers remain poorly characterised in Lhaviyani Atoll in the central Maldives, which hosts two Important Shark and Ray Areas (ISRAs). Recreational SCUBA networks can turn routine dive activity into long-term conservation evidence, already informing nearly 10% of the western Indian Ocean ISRAs. Objective: To characterise spatiotemporal patterns of elasmobranch assemblages in Lhaviyani Atoll (2017–2024), quantify how environmental and geomorphic drivers shape relative abundance, diversity, and hotspots, and provide evidence for targeted elasmobranch conservation. Methodology: A seven-year opportunistic dive-log dataset of 12,732 SCUBA surveys and 142,994 elasmobranch records across 94 dive sites was analysed. Effort-standardised relative abundance and community metrics (Shannon diversity, Pielou’s evenness) were modelled against sea surface temperature (SST), salinity, dissolved oxygen, chlorophyll-a, zonal current velocity, substrate type, and reef geomorphology using generalised additive models (GAMs). Spatial analyses identified persistent northern-rim aggregation areas aligned with ISRAs. Results: Twenty-eight species (14 sharks, 14 batoids) were recorded, including 23 threatened on the IUCN Red List (4 Critically Endangered, 12 Endangered, 7 Vulnerable). Relative abundance and diversity peaked during the late southwest monsoon (August–September) and declined during the northeast monsoon (December–March). After 2021, diversity and evenness increased while overall abundance declined. Relative abundance was primarily driven by SST, salinity, and current velocity; for sharks, dissolved oxygen and chlorophyll-a were additionally significant, whereas batoid abundance was driven mainly by temperature, oxygen, and current velocity. Four persistent hotspots along the northern atoll rim were identified, with sharks concentrated along exposed slopes and channels, and batoids distributed broadly within lagoonal habitats. Conclusions: Long-term citizen science dive-log monitoring is cost-effective for elasmobranch conservation in remote tropical seascapes. These results show how dive-industry partnerships can inform conservation governance over a decade after sanctuary designation, supporting targeted, habitat-focused management as shark and batoid conservation frameworks continue to evolve.

Proceedings doi: 10.3390/proceedings2026146088

Authors: Laura Guimarães Luís Oliva-Teles Raquel Pinto Cláudia Teixeira Pedro Rodrigues Matilde Moreira-Santos António Paulo Carvalho

Introduction: Aquatic chemical pollution is among the most worrying threats to ecosystem health. There is an ever-increasing variety of pollutant substances detected across the source-to-sea continuum, causing loss of biodiversity and ecological disequilibrium. Achieving cleaner and healthier systems relies on carrying out sustained, cost-effective, diagnosis and aquatic effects monitoring, within the adaptive management cycle. The available methods are, however, cumbersome, which creates a clear need for innovative expeditious approaches for low-cost surveillance monitoring. In the last decade, Raman Spectroscopy (RS) has gained wide recognition for application to biological questions, for its ability to uncover the complexity of molecules and their interactions. Various fields, from pharmacology to disease diagnosis and prognosis, have suffered an innovation revolution through the application of RS. In this technique inelastic light scattering of a small part of photons of an incident electromagnetic monochromatic light beam (ranging from near-infrared to visible or ultraviolet) is caused by the molecular vibration of chemical bonds. This results in shifts in energy, which indicate discrete vibrational modes of polarisable molecules, providing qualitative and quantitative assessments of the chemical composition and molecular structure of the sample. The technique shows high sensitivity, no need for sample preparation and the possibility of use in non-invasive and label-free analysis. Objective: The aim of this work is to present and discuss evidence about the application of Raman Spectroscopy (RS) to environmental diagnosis and aquatic effect monitoring of pollution. Methodology: The technique was applied to different biological models, i.e., diatoms, zebrafish embryos and larvae and freshwater snails. Quality assessments with diatoms were tested in environmental monitoring, while assessments with other models were done upon exposure to metals and organic contaminants. Results and conclusions: The Raman spectra obtained from the samples analysed comprised bands detected within the 800 to 2000 cm−1 wavenumber range. These were related to bond vibrations of carbohydrates, DNA phosphate groups, proteins or CH, NH and OH stretching in lipids and proteins. Data analysis using chemometric methods clearly distinguished pollutant exposure from control sites or treatments, pointing out the potential for surveyance monitoring. The next steps include the comparison with other sensitive methods (e.g., locomotion and avoidance behaviours, omics methods) to assess efficiency and bring further mechanistic understanding.

Proceedings doi: 10.3390/proceedings2026146089

Authors: Eduardo López-Segovia Juan J. Schmitter-Soto Jesús Alvarado-Ortega Luis Fernando Del Moral-Flores

Introduction: The genus Thorichthys comprises nine species of Central American freshwater cichlids, which are distributed along the eastern slopes of Mexico and Honduras. These species are grouped into two subgroups: “helleri” and “meeki”. While some analyses of the group’s ecomorphology and character evolution have been conducted, the skeletal structures of this genus remain to be described. Objective: This study provides an osteological description of the species in the genus Thorichthys. Methodology: The specimens were sectioned and stained with alizarin red, and the bone structures were analyzed and described. Results: The genus Thorichthys possesses 12 abdominal vertebrae and 12–13 caudal vertebrae. Species of “helleri” group are characterized by the following points: (1) there is a urohyal bone with a sharply concave dorsal margin and a spiniform, inclined process; (2) typically, there are a total of 14–15 gill rakers in the first gill arch; (3) the opercular bone bears a dorsally displaced, posterior protuberance; (4) a total of 12–13 anal pterygiophores; and (5) a slightly recurved cephalic profile. Meanwhile species of the “meeki” group exhibit the following characteristics: (1) a urohyal with a broad, unsharpened dorsal concavity and a small, blunt, nearly straight process; (2) a total of 15–21 gill spines; (3) a dorsally positioned protuberance in the middle of the opercular bone; (4) a total of 14–16 proximal anal pterygiophores; and (5) a straight cephalic profile. Conclusions: These bony elements are proposed as a complement to the taxonomic differentiation of the species in Thorichthys, and to contribute new morphological characteristics to the study of other cichlid genera.

Proceedings doi: 10.3390/proceedings2026146090

Authors: Marta Ramalho Ana S. Rato Carlos M. Alexandre Bernardo R. Quintella Pedro R. Almeida

Introduction: Restoring riverine connectivity is a cornerstone of ecological restoration for migratory fish populations. When physical barriers like dams lack effective fishways, translocation to more suitable sites becomes an alternative. Objectives: This study aims to present a decision-support methodology based on the Fragmentation Index (FI), designed to prioritize release sites in alternative river stretches that maximize the likelihood of survival of translocated diadromous fish. Methodology: The method integrates field-based obstacle characterization and transposability classification, together with a weighted penalty for restrictive obstacles located closer to the confluence with the main stem. The methodology was applied to six tributaries of the Douro River, targeting the European eel (Anguilla anguilla). Results: The FI successfully distinguished between functional reaches and severely fragmented systems. Results revealed high heterogeneity among the studied tributaries, with the Távora (FI = 1.07) and Ceira (FI = 1.12) Rivers identified as top priorities due to low fragmentation and stable hydrology. In contrast, the Tedo River (FI = 5.18) illustrates index’s sensitivity. Despite a high barrier density, its downstream stretch of ~14 km remains functionally connected because the first restrictive obstacles are located far upstream from the confluence. Conversely, the Torto River (FI = 0) was excluded due to severe drought conditions, underscoring the need to pair connectivity metrics with hydrologic viability. Conclusions: For large-scale translocations, this framework enables distributing fish across multiple systems to safeguard the ecological integrity of recipient communities while ensuring individuals can successfully complete their life cycles. Overall, this approach provides a quantitative and replicable framework for managing endangered species by prioritizing release sites with high longitudinal connectivity.

Proceedings doi: 10.3390/proceedings2026146084

Authors: Ana Beatriz Oliveira Ana Sofia Rato Carlos M. Alexandre Rita Almeida Maria João Lança Bernardo R. Quintella Pedro R. Almeida

The Tua River is a tributary of the Douro River in the North of Portugal used as a spawning ground for potamodromous fish, namely the Iberian barbel (Luciobarbus bocagei, Steindachner, 1864). Although access to this tributary became severely constrained after the construction of the Foz Tua Hydroelectric Facility (AHFT), fish continued to use the remaining accessible 1.1 km stretch of the Tua River below the dam, especially during their spawning season. Therefore, this study presents the monitoring of migratory fish influx downstream of the AHFT and associated mitigation measures. Fixed and mobile surveys, using an ARIS 1800 sonar, and focused on Iberian barbel were conducted between March and July, from 2023 to 2025. In 2023, fixed sonar monitoring recorded 100,289 individuals, showing a progressive increase over the sampling period, while mobile surveys confirmed high local concentrations (2083 individuals) and temporal fluctuations. In 2024, total counts rose substantially to 182,216 individuals (fixed surveys) and 2656 individuals (mobile surveys), with a peak in early May followed by a gradual reduction in these numbers. In 2025, the highest abundance was observed, with 196,935 individuals (fixed surveys) and 5441 individuals (mobile surveys), alongside higher variability between monitoring campaigns. Overall, these results suggest an intensifying pattern of fish accumulation downstream of the AHFT during the sampled periods, with recurring seasonal peaks. As a method to mitigate massive accumulation of fish downstream of this dam, in 2024 and 2025, a near real-time detection and mitigation protocol was implemented. This protocol identifies an initial “trigger” and a sequential methodology that recognizes possible massive accumulation scenarios, followed by the application of an adaptive operational management measure (e.g., ecological flow regulation) by the AHFT. The application of these measures effectively contributed to reducing fish accumulation during the critical periods. In conclusion, the results highlight a consistent increase in migratory fish accumulation, over the study period, downstream of the AHFT. The successful application of adaptive measures demonstrates that the implemented strategy seems to be effective so far and provides a strong basis for future management actions.

Proceedings doi: 10.3390/proceedings2026146087

Authors: Ignacio Pons Imanol Miqueleiz Marta Rodríguez Rey Rafael Miranda

Introduction: Freshwater habitats underpin global biodiversity and provide an array of essential ecosystem services to humans. However, threat hotspots like the Iberian Peninsula combine severe anthropogenic impacts (habitat degradation, climate change, and biological invasions, among others) with a high number of endemic range-restricted freshwater species. Despite the urgency, current conservation actions fall short of providing adequate protection. The irreplaceability index has been proposed as a useful assessment tool to focus limited efforts on areas that provide the highest benefit for threatened species. However, the transboundary nature of many rivers in the Iberian Peninsula can be a source of inefficiencies in protection if prioritisation efforts are conducted at a national rather than a peninsular scale. Objective: The aim of this study is to identify priority conservation basins for threatened native freshwater fish in the Iberian Peninsula and to evaluate the impact of national versus transboundary management strategies on the spatial protection afforded to these species. Methodology: The irreplaceability index was calculated for each basin by integrating basin richness, species rarity and their IUCN Red List conservation status. First, we modelled the species’ probability of presence using field observations recorded since 2000. Rarity was then calculated as the ratio between the modelled probability and the total number of basins within the species’ theoretical natural distribution. We then weighted each species’ rarity by its IUCN Red List conservation status, with higher weights to threatened species. We then calculated the basin irreplaceability index as the sum across all the species present in the basin of their conservation status-weighted rarity and ranked them according to this index. We replicated this approach considering Spain and Portugal independently, and both countries as one conservation planning unit. Results and Conclusions: The most irreplaceable basins were those harbouring a high density of threatened, narrow-range endemics. The priorities in each country differ depending on whether management strategies adopt a national or a broader geographical approach. Therefore, effective conservation requires transboundary planification to safeguard the shared biodiversity across countries.

Proceedings doi: 10.3390/proceedings2026146086

Authors: Álvaro Checa Felipe Morcillo Paloma Alcorlo Anabel Perdices

In the Iberian Peninsula, the rapid expansion of the invasive species Alburnus alburnus (bleak) has intensified its contact with several endemic cyprinid species, raising concerns about hybridization, introgression, and the loss of genetic diversity. Despite increasing evidence of hybridization, data remain limited for many Iberian River basins, where endemic species persist in fragmented and vulnerable habitats. The aim of this study is to assess the extent and spatial distribution of hybridization between the bleak and the following native cyprinid species, Anaecypris hispanica (jarabugo), Iberochondrostoma lemmingii (pardilla), Pseudochondrostoma willkommii (Guadiana nase), and Squalius alburnoides (calandino), across several rivers within the Guadalquivir Basin. To this end, Sanger sequencing will be performed on the mitochondrial cytochrome b gene (maternal lineage; approximately 1000 base pairs (bp)) and the nuclear β-actin gene (paternal lineage; approximately 950 bp) from individuals of all endemic species and the bleak. Parental species and putative hybrids were initially identified in the field using diagnostic morphological and meristic characters, including number of rays in the anal fin morphology, mouth position, and the number of lateral line scales. Molecular analyses will include haplotype network reconstruction and phylogenetic tree inference to evaluate relationships among individuals from different species and to assess lineage divergence. The results will allow us to: (1) detect hybrids between the bleak and endemic cyprinids, (2) identify hybridization events among endemic cyprinid species, and (3) evaluate the correspondence between diagnostic morphological and meristic traits and the molecular identification of hybrid individuals. Overall, these findings will provide key information for the conservation management of endangered Iberian freshwater fishes in the context of invasive species expansion and global change.

Proceedings doi: 10.3390/proceedings2026146081

Authors: Eduardo López-Segovia Luis Fernando Del Moral-Flores Juan J. Schmitter-Soto Eduardo López-Urrutia Verónica García-Castillo Carlos Pérez-Plasencia Omar Domínguez-Domínguez Eloísa Torres-Hernández Jorge Ciros-Pérez

Introduction: The fish fauna in the Yucatan Peninsula exhibit a unique composition, shaped by the region’s complex geological and hydrological history. Thorichthys meeki is a widely distributed cichlid species that has been the subject of morphological, behavioral, and phylogenetic studies. Nevertheless, the historical and biogeographical processes that have shaped its diversification and genetic structure remain unexplored. Objective: The objective of this study was to identify phylogeographic patterns and assess the genetic diversity of T. meeki in southeastern Mexico. Methodology: Genomic DNA was extracted from the muscle tissue of specimens preserved in 90% ethanol. DNA was amplified using a polymerase chain reaction (PCR) and sequences were obtained from two molecular markers: cytochrome oxidase 1 (CO1) and S7 intron 1. Phylogeographic analyses included genetic diversity indices molecular variance analyses to assess population structure and haplotype networks. Results: A total of 60 CO1 and 40 S7 intron 1 sequences were obtained from 26 sampling sites. For CO1, 14 haplotypes were identified, with high haplotype diversity (Hd = 0.84), and low nucleotide diversity (π = 0.0048). For S7 intron 1, 16 haplotypes were recovered with lower haplotype diversity (Hd = 0.543) and π = 0.021. A hierarchical AMOVA (2 groups) showed the greatest variation; 72.3% in CO1 and 79.8% in S7 within population groups with significant ΦST values. Haplotype networks identified three haplogroups for each gene. A single CO1 haplotype was found in 26 sequences from 13 sampling sites. For S7 intron 1, one haplotype was identified in 22 sequences and was shered from all populations. Conclusions: A widely distributed haplotype for CO1 and S7 reflects historical connectivity among hydrological systems. These preliminary results provide an interesting insights into the processesthat have influenced the distribution of T. meeki on the Yucatán Peninsula.

Proceedings doi: 10.3390/proceedings2026146080

Authors: César Vilas Ray Czaja Arnaud Grüss Stefenia van Bergeijk Enrique González-Ortegón J. Pedro Cañavate

Introduction: Climate change is reducing freshwater availability worldwide, making it essential to understand how freshwater inflow influences estuarine ecosystem functioning and marine fisheries productivity. In the Gulf of Cádiz (SW Spain), one of the most important fishing areas in Spain, the Guadalquivir Estuary serves as a key nursery habitat for commercially important fish and crustacean species. Objective: The aim of this study is to evaluate the effects of droughts and floods on estuarine functioning and coastal fisheries. Methodology: We analyzed 25 years of monthly data (1997–2022) from the Guadalquivir Long-Term Ecological Research Program (GUADALQUIVIR-LTER), using time-series analyses and dynamic structural equation modelling. Environmental variables, zooplankton and mysid biomass, and juvenile biomass of anchovy, sardine, and meagre were examined to assess trophic relationships and recruitment dynamics. Results: Our findings show that positive North Atlantic Oscillation (NAO) phases, associated with drought conditions in southern Europe, reduced freshwater inflow from the Alcalá del Río Dam into the estuary. Freshwater input increased organic matter and turbidity, which positively affected the mysid Rhopalophthalmus tartessicus, an important prey species for anchovy recruits. The mysid Mesopodopsis slabberi showed the strongest positive effect on anchovy recruitment (0.39). Although turbidity initially had a negative effect on M. slabberi, a significant positive effect appeared after monthly lag = 4. Conclusions: These findings demonstrate that spring freshwater inflow is essential for maintaining estuarine productivity, enhancing mysid abundance, and supporting anchovy recruitment, ultimately benefiting adult fish stocks after juveniles migrate from the estuary to coastal waters.

Proceedings doi: 10.3390/proceedings2026146079

Authors: Sara Lourenço Catarina N. S. Silva Miguel A. Pardal Paolo Momigliano André S. Afonso Filipe Martinho

Introduction: Skates (Rajidae) are cornerstone elasmobranchs, yet their intrinsic biological constraints, like slow growth, late maturation, and low fecundity, render them exceptionally susceptible to anthropogenic pressure. Despite their ecological and economic importance, tracking their population trajectories is historically hindered by “taxonomic blurring” and aggregated reporting in commercial fisheries. Objective: This study evaluates long-term conservation trends and exploitation dynamics of Rajidae species in the Northeast Atlantic and the Mediterranean Sea. Methodology: We analyzed 31 Rajidae species across the Northeast Atlantic and the Mediterranean Sea (FAO Areas 27 and 37) by integrating IUCN Red List assessments, species-specific life-history traits (maximum body size and depth distribution), and FAO fisheries landing data from 1992 to 2023. Descriptive analyses and Spearman correlations were used to assess temporal trends in conservation status and exploitation patterns. Results: Our synthesis reveals that some species show improvements in IUCN Red List category assessments, likely driven by recent management interventions such as species-specific reporting, catch quotas, and targeted retention bans. However, we also identify a critical mismatch between policy and biology: current Total Allowable Catches (TACs) and minimum landing sizes often do not explicitly incorporate species-specific life-history traits, inadvertently favoring smaller, less-marketable taxa while leaving larger, vulnerable species at risk. While FAO landings offer a valuable broad-scale overview of exploitation, the results highlight the limitations of aggregated fisheries statistics for species-level conservation assessments. Conclusions: These findings underline the need to adopt more precise and species-specific fisheries management approaches for Rajidae, including expanded regional monitoring programs, the use of data collected by on-board observers or electronic monitoring tools, and improved control of data reporting procedures, to prevent continued aggregation of species-level data.

Proceedings doi: 10.3390/proceedings2026146077

Authors: José Maria Santos Paulo Branco Maria João Costa Ana Filipa Filipe

Introduction: The Guadiana basin harbours one of the most threatened freshwater fish faunas in Europe, concentrating a high number of Iberian endemisms and species of high conservation interest. Among these, the Iberian minnowcarp (Anaecypris hispanica) and the Iberian Arched-Mouth Nase (Iberochondrostoma lemmingii) stand out as threatened species whose populations are in serious decline. Methodology: In March 2023, an obsolete river barrier, the Galaches weir, was removed from the Odeleite River (Guadiana basin), releasing an 8 km lotic stretch previously inaccessible to downstream fish fauna. This study aimed to evaluate the effects of weir removal on the composition and structure of the fish community, using a Before-After design with fish sampling conducted before (2022) and after (2024) weir removal. Fish sampling took place in early summer by means of electrofishing in two 150 m long river sites, one upstream and one downstream of the weir. Results: Before removal, both upstream and downstream sites were dominated by native leuciscids (A. hispanica, I. lemmingii, Squalius pyrenaicus, and Pseudochondrostoma willkommii) and cyprinids (Luciobarbus spp.), with non-natives Lepomis gibbosus and Australoheros facetus occurring in lower abundance. After removal, native species remained clearly dominant at both sites, while A. facetus was no longer detected and L. gibbosus did not increase in abundance, suggesting that barrier removal did not favour the spread of non-native fish. Species size–structure revealed the presence of multiple size classes, possibly supporting a regular recruitment of key native taxa: A. hispanica occurred almost exclusively with total lengths of 4 to 6 cm, whereas I. lemmingii and other native leuciscids displayed broader size ranges, spanning juveniles to adults, consistent with sustained reproduction and growth in the restored river stretch. Conclusions: These findings support the hypothesis that weir removal has improved the sustainability of native fish populations such as A. hispanica by improving habitat connectivity and increasing recruitment. The results highlight the importance of weir removal for the conservation of threatened species in Mediterranean river systems.

Proceedings doi: 10.3390/proceedings2026146075

Authors: Amílcar Teixeira Ryan Alves da Silva Douglas Santos Fernando Miranda Fernando Teixeira

Mediterranean rivers experience various pressures that cause native fish populations to decline. This is the case of Achondrostoma asturicense, a threatened endemic species recently classified as "endangered" (EN) by the Portuguese Red Book. In northeastern Portugal, the main populations occur in the Carvalhais (Tua basin), Maçãs, and Angueira (Sabor basin) rivers. This study aimed to evaluate the effect of small weirs on the distribution, abundance, and habitat use of A. asturicense populations along the longitudinal gradient of River Angueira. Three river zones (Z1 to Z3) affected by small weirs were selected along the watercourse. In each zone, four sampling sites were distributed relative to the weir, as follows: A1—200 m downstream; A2—immediately downstream; A3—under the influence of the reservoir; and A4—200 m upstream (reference). Sampling was carried out in three seasons: winter, spring, and summer 2025. Physical–chemical (water), hydromorphological (habitats), and biological (fish) elements were assessed in accordance with the protocols of the Water Framework Directive. The results revealed the worst water quality in the summer season due to flow reduction, dissolved oxygen depletion, elevated conductivity, and high nutrient (N, P) concentrations, leading to eutrophication phenomena. The distribution and abundance of A. asturicense were negatively influenced by the presence of small weirs, which were dominated by the non-native species Lepomis gibbosus. PERMANOVA analysis (two-way, p < 0.05) identified significant differences (Pseudo-F = 28.349, p < 0.05) between sampling sites and river zones, and paired similarity analysis tests (ANOSIM; one-way, p < 0.05) confirmed that these differences occur only between the weir reservoir (A3) and the remaining sampling sites. A. asturicense showed a maximum length (Lmax) of 135 mm, isometric growth only in the upstream zone (Z1), and significant differences in body condition (0.75 < K < 0.84). This species showed a preference for rheophilic habitats, with coarse substrate and diversity of currents and distinct cover mainly guaranteed by submerged aquatic macrophytes. A. asturicense populations are severely affected in the River Angueira by habitat fragmentation, riparian degradation, pollution, invasive alien species (e.g., L. gibbosus, P. clarkii, N. vison), and climate change, justifying the development of mitigation and restoration measures for the conservation of natural habitats and native threatened species.

Proceedings doi: 10.3390/proceedings2026146101

Authors: Mafalda Moncada Diogo Ribeiro Beatriz Castro Diogo Dias Rui Rivaes Filipe Ribeiro

Introduction: Knowledge of Iberian freshwater fish fauna among the general public is scarce and generally limited to a handful of species. Moreover, this knowledge gap increases as time goes by, particularly in younger generations, due to the lack of content on native fish fauna in school programmes. Nevertheless, schools across the country are proving increasingly receptive to innovative approaches that engage students in meaningful, real-world learning. Objectives: The LIFE PREDATOR programme leverages this opportunity to educate young people about freshwater fish communities. It aims to prevent the spread of the largest invasive fish in Portugal, the European catfish (Silurus glanis), by engaging students as active conservation ambassadors. Methodology: In inland Portugal, fishing is a cultural practice, and children frequently participate in angling activities alongside friends and family members. By reaching children, the programme simultaneously targets future anglers, potential decision-makers, and a channel for intergenerational knowledge transfer. Results: Thus far, the programme has reached over 5000 students and almost 60 schools, mostly throughout the Tagus basin. Preliminary assessments revealed improvements in students’ ability to name emblematic native fish species like the Iberian nase (Pseudochondrostoma spp.), European eel (Anguilla anguilla) and Iberian barbel (Luciobarbus spp.), and recognise the threats posed by invasives like the European catfish. To ensure national scalability, we have developed learning materials designed for use by teachers across Portugal, which are to be made available for free online. Beyond the dissemination directed to adult fishermen, which is often more demanding, Conclusions: LIFE PREDATOR ensures that knowledge about native river fauna, invasive species, and responsible fishing practices is conveyed through trusted, familiar voices. This intergenerational transmission model has the potential to embed long-lasting behavioural change within future fishing communities.

Proceedings doi: 10.3390/proceedings2026146100

Authors: Amílcar Teixeira Fernando Miranda Fernando Teixeira

Brown trout (Salmo trutta L.) is a bioindicator species of ecological integrity in mountain rivers of northern Portugal. Habitat loss and recreational fishing justify sustainable management to balance the conservation and exploitation of these fish populations. In fact, salmonid streams in NE Portugal are low productive watercourses and fish stocking has been continuously demanded by fishermen. However, this most common management action must be analyzed carefully and determined the effective increase for local fisheries, taking into consideration the potential dispersal of stocked fish. The objective of the present study, developed in River Sabor, was to determine short- and medium-term movement and dispersal patterns and habitat preferences of wild and stocked Brown trout, using radio telemetry, during a weekly monitoring 4-month period (October to February 2026; n = 18). Fish was sampled by electrofishing at beginning and the end of the experiment. Twenty-four adult Brown trout, equally distributed by two salmonid sections, and three groups, (1) wild resident (River Sabor) (213–270 mm TL); (2) wild non-resident (from contiguous basin, River Baceiro) (200–375 mm TL) and (3) rear-captivity (Castrelos Fishfarms, ICNF) (227–365 mm TL) fish, were surgically implanted with radio transmitters. Significant differences (KW-H (2;24) = 4.67; p = 0.09) were observed for the dispersal distances, considering fish detected at least in five sampling events, ranging from 120–1437 m for the wild resident stationary group to 192–14,150 m for the stocked mobile group. Moreover, wild non-resident fish displayed higher movement in the upstream direction, in opposition to the downstream movement of stocked individuals. Wild resident and non-resident trout tended to display increased movements during November and December, probably related to spawning activity, showing preferences by riffle and run habitats. Stocked fish were detected in pool habitats (mainly weir reservoirs), exhibiting significantly lower growth rates, and increased movement during January and February, particularly during flood events. These findings are valuable information for managers related to movement patterns, habitat use and stocking management.

Proceedings doi: 10.3390/proceedings2026146078

Authors: Zoé Lemoine André Gomes-dos-Santos David Barros-García

Elopomorpha is one of the most primitive teleost lineages and is characterised by a unique trait, the leptocephalus larva. Its leaf-like and transparent body is largely composed of glycosaminoglycan (GAG), which makes it distinctive from other fish larvae. Hyaluronic acid (HA) has been identified as the principal GAG present in these larvae and is thought to play several physiological roles, such as floatability, osmoregulation, and energy storage. During the larval stage, HA reaches a concentration of up to 40 to 50% of the body composition due to a HA synthesis peak. Later in metamorphosis, HA concentration decreases and, after this, adults show a normal HA metabolism. These observations could be explained if the larva has an alternative HA metabolism compared to the adult. It is known that HA synthesis is done by three hyaluronan synthase (HAS) enzymes, which differ in the length of HA synthetized, codified by three genes: HAS1, HAS2 and HAS3. Therefore, to test the hypothesis of a larval-specific metabolism, the genomic basis of these genes in Elopomorpha will be analysed. To this end, HAS coding and protein sequences from nine Elopomorpha, four Osteoglossomorpha and 21 Clupeocephala species were mined from the NCBI database to ensure a broad phylogenetic coverage. To guarantee a complete retrieval of HAS genes, the BLAST tool (https://blast.ncbi.nlm.nih.gov/Blast.cgi, accessed on 1 March 2026) and synteny analysis were performed. Then, Pseudochecker was used to confirm the functionality of the candidate genes obtained. Functional genes were used for phylogenetic analyses, maximum likelihood and Bayesian inference to test orthology. Both lineage and species duplications of HAS1 and HAS2 were found in Elopomorpha, which would be responsible for the synthesis of HA during the larval stage. These new genetic patterns provide the first evidence of a possible alternative metabolism of HA during the larval stage of Elopomorpha.

Proceedings doi: 10.3390/proceedings2026146076

Authors: Marina Martínez-Miguel Ana García-Vega Francisco Javier Bravo-Córdoba Francisco J. Sanz-Ronda Juan Francisco Fuentes-Pérez

Introduction: River fragmentation caused by hydropower infrastructure remains a primary threat to aquatic biodiversity, creating a critical need for fish passage solutions that can adapt to high environmental variability. Although adaptive management (AM) has the potential to significantly improve longitudinal connectivity and ecological resilience, its application in real-world fishway operations is currently limited. Objective: This study aims to present and validate a flexible AM framework designed to optimize fish passage by integrating low-cost monitoring systems with automated data processing and predictive modeling. Methodology: The proposed system combines a sensor network for real-time water-level and environmental monitoring with biological performance data obtained through Passive Integrated Transponder (PIT) technology. These data were processed locally using edge computing. Over a two-year period, weekly aggregated data were used to develop Random Forest models to identify the primary drivers of fish movement. Results: The final model successfully identified five key drivers: luminosity, water temperature, and three nested hydraulic parameters at the fishway’s upstream section. Validation at a vertical-slot fishway in Vadocondes (Duero River, Spain) showed that retrospective optimization—specifically adjusting sluice-gate regulation—could increase downstream water levels and reduce drops at the first cross wall. This adjustment demonstrated a substantial increase in predicted fish passage without requiring changes to the hydropower plant’s core operation. Conclusions: The framework is highly flexible and transferable to other regulated river systems. However, its success is contingent upon the definition of clear ecological objectives and the seamless integration of monitoring results into the day-to-day operation of river infrastructure.

Proceedings doi: 10.3390/proceedings2026146074

Authors: David Barros-García André Gomes-dos-Santos André M. Machado Francisco Baldó

The vertebrate mitochondrial genome (mitogenome) is a small, circular DNA molecule typically ~16–17 kb in length, encoding 37 genes that are essential for the electron transport chain, the mechanism that drives mostly all the ATP synthesis in cells. Owing to its central role in energy metabolism, its structure is highly conserved across vertebrate lineages in both the number and relative position of each gene in the genome. Nevertheless, different variations have been found in several teleost lineages, including antarctic fishes (Nototheniidae), gadiforms, hatchetfishes (Sternoptychidae), and Batrachoidiformes. The explanation for these phenomena remains unknown yet may reflect shifts in functional constraints and can provide insights into lineage-specific and/or coevolutionary processes. This raises the possibility that mitogenome structure is related to habitat selection, potentially reflecting environmental influences on energetic regulation. To further test this hypothesis, we studied more than 400 teleost species across all major teleost lineages. The mitogenome sequences were downloaded from NCBI and annotated using two independent algorithms (MITOZ and MITOS) and then compared with a reference (Danio rerio) to find any deviation from the standard structure. Similarly, ecological data was downloaded from FishBase using the R Package “rfishbase” 5.0.3. Two independent ancestral reconstruction analyses were carried out for both traits, “Mitogenome” and “Habitat”, using a reference evolutionary tree for teleosts to unravel both evolutionary histories. The possible association between mitogenome and habitat was then assessed using a suite of phylogenetic comparative methods, including Pagel’s correlation test (corHMM) to evaluate whether both traits evolved in a correlated fashion, branch-level co-transition analysis to identify lineages where structural changes and habitat shifts co-occurred, and node-by-node comparisons of ancestral state probabilities across the phylogeny. Preliminary results suggest a correlation between some deep-sea environments and a modified mitogenome structure, with structural deviations tending to cluster in lineages inhabiting greater depths. These exploratory findings raise the possibility that changes in mitogenome architecture may be linked to adaptations in energetic metabolism required for life in extreme low-energy environments. Further analyses are underway to clarify the functional significance of these genomic changes and their relationship to ecological and metabolic pressures in teleost evolution.

Proceedings doi: 10.3390/proceedings2026146073

Authors: Ana Filipa Filipe Janine da Silva Virgilio Hermoso

Introduction: Species Distribution Models (SDMs) are widely used to infer environmental drivers of freshwater fish distributions and to project biodiversity responses to climate and land-use change. However, freshwater ecosystems present specific conceptual and methodological challenges, including dendritic network structure, strong spatial autocorrelation, dispersal constraints, and scale mismatches between biological processes and environmental predictors that remain insufficiently addressed. At the same time, emerging data sources such as environmental DNA (eDNA) and high-resolution remote sensing offer new opportunities to improve data coverage and ecological realism in SDMs. Methodology: Focusing on Iberian systems as illustrative case studies, here, we synthesize the following recent advances and challenges in SDM applications to freshwater fishes: (i) the implications of using presence–absence versus abundance data; (ii) the integration of hydrological and connectivity metrics as predictors; (iii) approaches to explicitly account for spatial structure and biotic interactions; and (iv) the contribution of novel datasets, including eDNA and remote sensing. Furthermore, we examine the performance and transferability of correlative models under analogue and non-analogue climate conditions. Results: Our synthesis highlights the importance of incorporating network topology, seasonality, dispersal constraints, and novel data sources to improve ecological realism and predictive performance. The integration of emerging biodiversity and environmental data can substantially reduce data gaps and improve model calibration and validation, particularly in poorly sampled systems. Nonetheless, model transferability remains a challenge, particularly for endemic and range-restricted species. Advancing freshwater SDMs through the integration of hydrologically explicit frameworks and novel data sources will strengthen their capacity to support evidence-based management of freshwater fish assemblages facing accelerating environmental changes.

Proceedings doi: 10.3390/proceedings2026146064

Authors: Ana Filipa Filipe Maria João Costa Arthur Cupertino Maria Teresa Ferreira Daniel Mameri Patricia María Rodríguez-González José M. Santos Catarina Grilo José Pedro Ramião João Oliveira

Introduction: AQUArestore is a three-year project focused on promoting adaptive ecological restoration strategies for river ecosystems in the vulnerable cross-border region of Portugal. The project responds to pressing environmental challenges across the territory, including severe habitat degradation, climate vulnerability, declining water security, and biodiversity loss, with particular concern for freshwater fish communities, making river restoration essential to preserve native species and freshwater ecosystem services. Objective: The project aims to develop a replicable framework for restoration of Mediterranean transboundary riverine habitats, supporting the objectives of the EU Nature Restoration Law (NRL, Regulation 2024/1991). The consortium AQUArestore will develop (1) robust restoration indicators, (2) implement living labs for restoration experimentation, and (3) establish capacity-building and training programs for technicians and citizens. Methodology: The project kick-off meeting was used to operationalize project tasks, detail the implementation calendar and milestones, and clarify responsibilities of each project member and partner institutions within the different work tasks. The meeting gathered consortium members from the coordinating institution CEF-ISA (researchers at the Instituto Superior de Agronomia) and partners WWF Portugal (an environmental NGO) and Mushmore Cooperative, each one contributing according to their respective expertise and institutional objectives. Results: The AQUArestore project kick-off meeting took place in January 2026 at ISA, Lisbon, and included a presentation of the NRL and a detailed discussion of project task development. In detail, the activities will begin with the compilation of information on previously restored sites (Task 1). This will support the development and validation of environmental and biodiversity indicators of restoration outcomes, including those linked to freshwater fish assemblages and riparian vegetation (Task 2). The project will then establish two living labs as platforms to test nature-based solutions in collaboration with stakeholders and local communities (Task 3). In parallel, AQUArestore will strengthen technical capacity through training for practitioners and public authorities (Task 4). Finally, dissemination will be supported through citizen science, communication activities, and stakeholder engagement, fostering a broader impact (Task 5). Together, these tasks provide an integrated, science-based, and participatory framework aiming to support adaptive river restoration under climate and environmental changes. Conclusions: By integrating ecological restoration, biodiversity and environmental monitoring, and stakeholder engagement, AQUArestore is expected to contribute to the recovery of Mediterranean freshwater ecosystems and improve habitat quality and connectivity for native fish communities, enhancing resilience to climate change and other anthropogenic pressures.

Proceedings doi: 10.3390/proceedings2026146067

Authors: Amândio de Barros Diana Santos Tiago Lourenço Célia Lopes Tânia Vieira Madureira Eduardo Rocha

Introduction: The liver is a central metabolic regulator responsible not only for energy storage and allocation but also for the production of essential egg proteins. In seasonal breeders such as brown trout, physiological demands increase during spawning, requiring strong metabolic and structural adaptations. Understanding the cellular mechanisms underlying these fluctuations is essential for clarifying how liver function is regulated during reproduction. Objective: The aim of this study was to investigate cellular mechanisms underlying liver remodelling during the reproductive cycle of male and female brown trout by examining proliferation and apoptosis markers at both molecular and protein levels during four distinct reproductive stages: spawning capable, regressing, regenerating, and developing. Methodology: Adult male and female brown trout were sampled at four reproductive stages. Liver gene expression of proliferating cell nuclear antigen (PCNA) and caspase-3 was analysed using qRT-PCR. At the protein level, liver tissue sections were immunolabelled with antibodies against PCNA and caspase-3. Caspase-3 staining intensity was quantified using ImageJ, while PCNA expression was assessed by counting positively stained nuclei. Results: PCNA gene expression was upregulated during the regressing stage, while PCNA-positive nuclei immunolabelling increased during the regressing and spawning-capable stages. Caspase-3 transcript levels showed no significant differences among stages, whereas immunostaining increased during regenerating and developing stages. Conclusions: Overall, the liver undergoes dynamic cellular remodelling throughout the reproductive cycle, balancing proliferation and apoptosis to meet reproductive demands. The results suggest that proliferation is more evident during regenerating stages, while apoptotic activity may be regulated post-transcriptionally. PCNA also indicates that proliferative activity may persist during spawning capable stages, reflecting ongoing mitotic readiness despite reduced overall proliferation.

Proceedings doi: 10.3390/proceedings2026146063

Authors: Rodrigo Alves Célia Lopes Rosária Seabra Sofia Esquível Maria J. Rocha Eduardo Rocha Tânia Vieira Madureira

Introduction: Temperature is a key environmental factor influencing the physiological and biochemical processes of aquatic organisms, including xenobiotic metabolism. Understanding how temperature modulates the toxicological effects of pollutants such as polycyclic aromatic hydrocarbons (PAHs) is crucial in the context of climate change. Among these compounds, benzo[a]pyrene (BaP) and benzo[a]anthracene (BaA) are priority pollutants in aquatic environments, resulting from incomplete combustion. Their relevance is attributed to persistence and metabolic bioactivation potential. Fish primary hepatocyte cultures represent a relevant in vitro model for studying combined effects of thermal stress and chemical exposures, while supporting the 3Rs principles (Replacement, Reduction, and Refinement). Objective: This study aims to assess temperature-dependent effects of BaP and BaA, and their mixtures in brown trout hepatocytes using cytochrome P450 1A (CYP1A) immunohistochemistry as an indicator of xenobiotic metabolism. Methodology: Primary hepatocytes were isolated using a two-step collagenase perfusion method and cultured in 24-well plates at 18 °C and 22 °C. Cells were exposed for 72 h to supplemented L-15 medium (control) or to 0.1% dimethyl sulfoxide in supplemented L-15 medium (solvent control), as well as to single exposures of 1 and 10 µM of BaP and BaA and to equimolar mixtures of both compounds (1 and 10 µM). Viability was assessed using the lactate dehydrogenase (LDH) assay. CYP1A immunostaining was quantified based on cytoplasmic staining intensity relative to background area. Results: No significant effects on cell viability were observed under any condition. Temperature significantly reduced CYP1A expression in single exposures at 22 °C compared to 18 °C. BaP induced a significant dose-dependent increase, while BaA differed from controls only at 10 µM. In mixtures, only treatment- and dose-dependent effects were observed, with no temperature influence detected. Conclusions: Overall, the data highlight temperature as a key modulator of biochemical responses to PAHs, with single and mixed exposures eliciting distinct effects and suggesting potential synergism in mixtures.

Proceedings doi: 10.3390/proceedings2026146071

Authors: Ariana Pérez-Pereira Ondina Ribeiro Luís Félix Maria Tiritan Cláudia Ribeiro João Carrola

Introduction: Synthetic cathinones (SC) are an emerging class of neuroactive contaminants increasingly detected in aquatic systems due to their widespread recreational use. Their continuous release at ng–µg L−1 levels is particularly concerning, as these compounds are specifically designed to alter neural function, raising the likelihood of subtle yet ecologically relevant effects in non-target organisms. Among them, 3,4-methylenedioxypyrovalerone (MDPV) is one of the most-reported SC in wastewater and surface waters. Nevertheless, its chiral nature has been largely overlooked in ecotoxicological studies, despite growing evidence that enantiomers can differ markedly in biological activity, potentially leading to underestimated environmental risks. Objective: The ecotoxicological impact of racemic MDPV ((R,S)-MDPV) and its separate enantiomers ((R)-MDPV and (S)-MDPV) were examined using zebrafish (Danio rerio) as a model, focusing on survival and embryonic development. Methodology: Zebrafish embryos, at approximately 3-hours post-fertilization (hpf), were exposed over 96 h to environmentally relevant concentrations of MDPV forms (0.18−2.8 μg L−1). Each treatment and control group included 50 animals distributed across 5 replicates. Mortality was assessed at multiple developmental stages (7, 24, 48, 72, and 96 h), along with cumulative mortality. Developmental endpoints included spontaneous movements (24 h), heartbeat (48 h), and hatching rate (48 and 72 h), quantified using stereomicroscopy and video analysis. Results: MDPV showed concentration and enantioselective effects, with (S)-MDPV being the most toxic. Behavioral and cardiac responses varied across forms, while hatching depended on concentration and time without a clear enantioselective pattern. Conclusions: MDPV disrupts early zebrafish development, impairing survival and embryonic development in a concentration-dependent and enantioselective manner, with (S)-MDPV demonstrating greater toxicity. These findings emphasize the importance of considering chirality in the environmental risk assessment of psychoactive contaminants such as SC, as enantiomer-specific effects may influence organism fitness, survival, and broader ecological outcomes.

Proceedings doi: 10.3390/proceedings2026146072

Authors: Ana Marcelino Catarina Caldeira-Santos Melanie Court Joana Raimundo Rui Rosa

Environmental contamination by rare earth elements (REEs) is increasing globally due to their extensive use in modern technologies, medicine, agriculture, and aquaculture. Their release into aquatic systems via wastewater discharge, industrial emissions, surface runoff, and atmospheric deposition has raised concerns regarding their environmental fate and potential ecotoxicological effects. Despite this, information on REE accumulation in marine predators remains limited. This study provides a multi-species assessment of REE bioaccumulation in elasmobranchs. Concentrations of 14 REEs (Ce, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sm, Tb, Tm, and Yb) were quantified in liver and muscle tissues of six elasmobranch species collected from demersal and deep-sea habitats along the Portuguese continental shelf. Generalized linear models (GLMs) were used to evaluate differences in REE concentrations among species and tissues, and to explore potential patterns associated with ecological traits. Results indicated that REE concentrations varied significantly across tissues and species, with muscle generally exhibiting higher accumulation than liver. Overall, this study provides the first comprehensive baseline of REE bioaccumulation in elasmobranchs from the Portuguese coast, contributing to a better understanding of emerging contaminants in marine food webs. These findings have important implications for environmental biomonitoring and highlight potential risks associated with seafood consumption.

Proceedings doi: 10.3390/proceedings2026146068

Authors: Stefano Brignone Bernardo Quintella Rui Rivaes Ana Filipa Silva Pietro Volta Filipe Ribeiro

Introduction: Understanding the movement ecology of invasive species such as the European catfish Silurus glanis, with documented strong impacts on freshwater fish communities, is essential to improve the effectiveness of management and containment actions, as detailed knowledge of species spatio-temporal habitat use strongly influences the success of control strategies. Objective: This study aimed to investigate the spatial and temporal behaviour of the S. glanis in a river–reservoir system in Portugal, including the Ponsul River and part of the Tagus River within the Cedillo reservoir, and to provide ecologically relevant insights to support targeted management strategies. Methodology: Acoustic telemetry was used to monitor 27 tagged individuals equipped with depth sensors. Fish movements were tracked using an array of 17 acoustic receivers over one and a half years. Results: Three behavioural profiles were identified: a resident group in the lower Ponsul (n = 4), a group moving between the Tagus River and the lower Ponsul (n = 6), and a larger group primarily migrating within the Ponsul River (n = 12). The remaining five individuals were considered dead, due to illegal fishing in this protected area. Migratory individuals showed a clear seasonal pattern, moving downstream to deeper waters during early winter and returning upstream to shallower areas as temperatures increased in early spring, likely in response to thermal gradients. Distance-based analyses confirmed this trend, with minimum inter-individual distances occurring in winter and early summer. Vertical behaviour supported this pattern, with individuals occupying shallow waters (≤7 m) for most of the year and reaching depths of up to 30 m in winter. Conclusions: The observed preference for shallow habitats during warmer periods and downstream migration in winter indicates that eradication efforts should be spatially and temporally targeted. Control actions should prioritize upstream sections during warm seasons and downstream areas of the Ponsul during winter migration, focusing efforts on traditional methods such as large-mesh multimesh gillnets or new longline techniques. Overall, this study highlights the value of telemetry in supporting targeted, evidence-based management of invasive species.

Proceedings doi: 10.3390/proceedings2026146065

Authors: Margarida Vilaça Rosária Seabra Maria João Rocha Eduardo Rocha Célia Lopes

Introduction: The temperature of rivers in the Iberian Peninsula has increased due to global warming. In addition, these rivers are polluted by contaminants of emerging concern, such as polycyclic aromatic hydrocarbons (PAHs). Higher temperatures and pollution concurrently impose threats to the Iberian Peninsula’s endemic species, including the brown trout (Salmo trutta), a cold-water species widely used in ecotoxicological studies. Because the liver is the main biotransformation organ, and is particularly sensitive to both chemical and temperature changes, in vitro liver models may represent valuable alternatives for assessing combined stressor effects, complying with the 3Rs principle. Objective: In line with the above, the present study aimed to evaluate the combined effects of a 4 °C temperature increase and the model PAH benzo[k]fluoranthene (B[k]F) on fish liver cells using a primary brown trout hepatocyte culture as a model. Methodology: Primary hepatocytes were seeded in 6-well plates at a density of 1.0 × 106 cells/mL and exposed for 48 h to 1, 10, and 20 µM B[k]F at 18 °C (normothermia) and 22 °C (warming scenario). Cell viability was assessed using trypan blue, alamarBlue, and lactate dehydrogenase (LDH) assays. Cytochrome P450 (CYP)1A was evaluated in terms of its gene expression by RT-qPCR and its protein expression through immunocytochemistry (ICC). The immunostaining was quantified using a score system which considered five intensity staining levels. Results: Exposure to B[k]F and to the higher temperature increased LDH leakage without interaction effects. In contrast, the other viability assays did not show significant differences across conditions. Regarding CYP1A, both gene and protein expression increased with all B[k]F concentrations in relation to the controls, but were not influenced by temperature. Notably, the lowest B[k]F concentration (1 µM) elicited the highest CYP1A gene expression, suggesting a non-monotonic response. Conclusions: Overall, the model was responsive to both temperature (4 °C) increase and to B[k]F, validating its usefulness for assessing liver pollutant effects in the context of global warming. These findings support the application of fish primary hepatocyte models as relevant tools in ecotoxicology under environmentally realistic multi-stressor scenarios.

Proceedings doi: 10.3390/proceedings2026146062

Authors: Sabrina M. Rodrigues Francisco Lopes Cristina Marisa R. Almeida Sandra Ramos

Introduction: The early stages of fish represent a critical phase for survival and recruitment, as they are highly vulnerable to both biotic and abiotic factors, as well as anthropogenic pressures. To enhance survival, many marine species use estuaries as nursery areas. However, these ecosystems are increasingly exposed to contaminants such as microplastics (MPs; plastic particles < 5 mm) that can cause several direct or indirect negative impacts on fish larvae, namely impairing their development or survival. Objective: This study aimed to quantify and compare temporal changes in the ratio of microplastics (MPs) to fish larvae (FL) (MP:FL) in the Douro estuary (NW Portugal), assessing how exposure to MPs varies across years and seasons. Methodology: Seasonal sampling campaigns were conducted in the Douro estuary during 2021/2022 and 2025. Multiple stations along the estuary were sampled using plankton tows with a 0.5 mm mesh size. In the laboratory, fish larvae were sorted and identified, and the remaining material was processed to isolate and quantify MPs. The recovered MPs were subsequently characterized according to type, size, and color. Results: Data from 2022 indicated that Clupeidae, Gobiidae, and Gadidae were the most abundant fish families, while colorless and blue fibers between 2 and 3 mm were the dominant MP types. Data from 2025 showed that Gobiidae, Labridae, and Atherinidae were the most abundant families, with similar MP types observed in water in 2022. The ratio of MPs:FL in summer and autumn of 2021/2022 was 36 and 65 MPs:1 FL, respectively, whereas in 2025 it was 0.26 and 3.80 MPs:1 FL, respectively. Conclusions: These preliminary results indicate a decreasing trend in the ratio of MP:fish larvae over time. Although further data analysis is ongoing, the observed interannual differences highlight the importance of long-term monitoring of estuarine nursery areas to better understand contamination dynamics and their potential effects on early fish life stages.

Proceedings doi: 10.3390/proceedings2026146069

Authors: Sabrina M. Rodrigues Francisca Espincho Michael Elliott Cristina Marisa R. Almeida Sandra Ramos

Introduction: The physical characteristics of microplastics (MPs), particularly their size and color, closely resemble natural food prey for several marine organisms, leading to active or accidental ingestion by marine species, including fish larvae. Despite growing concern, the occurrence of MPs in wild fish during early developmental stages remains insufficiently documented, and laboratory studies report inconsistent results. Given their key ecological role in marine food webs and their economic relevance, the health and survival of fish larvae are critical for maintaining fish populations. Objective: This study aimed to investigate MPs’ presence throughout the larval developmental stages and assess whether MP contamination profiles (concentration, color, type, and size) differ between species. Methodology: MPs were analyzed in the larval stages of two fish species with distinct ecological niches: the European sardine (Sardina pilchardus), a marine migratory species, and the common goby (Pomatoschistus microps), an estuarine resident species. Samples were collected from the Douro Estuary (NW Portugal) over one year, covering different developmental stages. Results: MPs were detected in both species at all developmental stages observed, including the yolk-sac stage (where the feeding of larvae is endogenous), indicating contamination at a stage when the mouth is not yet functional. Sardina pilchardus showed a higher abundance of transparent nylon fibers of 0.5 mm, and Pomatoschistus microps transparent polypropylene fibers of size 0.4 mm. Moreover, MP contamination did not vary between species or throughout the developmental stages, showing similar levels and profiles of MPs contamination. Conclusions: These findings provide new evidence that MP contamination begins at the earliest developmental stages of the fish, from hatching onwards. The results further suggest that MP uptake in fish larvae is primarily driven by environmental availability rather than fish larvae’s preferences or ecological guild, physical characteristics, or even the ontogenetic developmental stage.

Proceedings doi: 10.3390/proceedings2026146070

Authors: Francisco José Oliva-Paterna Antonio Zamora-López Adrián Guerrero-Gómez Víctor Manuel Alvaréz-Navarro Antonio Andrés Herrero-Reyes Elena Parra-Espín José Manuel Zamora-Marín Mar Torralva

Introduction: Long-term ecological monitoring is essential to understand the responses of fish communities to global change in transitional ecosystems. Coastal lagoons are particularly vulnerable to eutrophication, which can trigger abrupt regime shifts, mass mortality events, and loss of ecological functions. The Mar Menor coastal lagoon (SE Spain) represents one of the most impacted Mediterranean systems, providing a unique opportunity to assess long-term ecological responses of fish assemblages to sustained anthropogenic pressure. Objetives: This study aims to synthesize long-term monitoring data to evaluate structural, functional, and population-level responses of fish assemblages to eutrophication processes, and to identify critical habitats and mechanisms supporting resilience. Methodology: We integrated multiple datasets derived from long-term monitoring programs (2002–2004 as and 2018–2025), including community structure, functional diversity, population dynamics of resident species, and habitat-based indicators. Analyses encompassed pre-impact, eutrophication, and post-disturbance phases, allowing for a multi-scale assessment of ecological responses. Results: Eutrophication-driven disturbances caused major shifts in fish assemblages, including declines in biomass and abundance, species-specific responses, and increased dominance of opportunistic trophic groups. Functional diversity analyses revealed strong homogenization processes and loss of specialist traits, indicating reduced ecosystem functionality. Population dynamics of resident species reflected habitat degradation, highlighting their value as ecological indicators. Despite these impacts, shallow coastal habitats acted as critical refuges, buffering hypoxic conditions and enabling partial persistence and recovery of fish communities. Conclusions: Our results demonstrate that long-term monitoring provides essential insights into the mechanisms driving fish community responses to eutrophication. The identification of functional changes and refuge habitats is key for adaptive management. Protecting and restoring critical habitats, particularly shallow areas, is crucial to enhance resilience and guide conservation strategies in Mediterranean coastal lagoons under global change.

Proceedings doi: 10.3390/proceedings2026146066

Authors: Sofia Esquível Rodrigo Alves Eduardo Rocha Tânia Vieira Madureira

Introduction: Glucagon-like peptide-1 receptor agonists (GLP-1 RAs), such as liraglutide (LIR), are widely used in humans to treat type 2 diabetes mellitus, obesity, and non-alcoholic fatty liver disease. In mammals, GLP-1 RAs have been shown to influence hepatic lipid metabolism, although the underlying mechanisms remain unclear. In fish, GLP-1 also plays an important role in regulating hepatic processes, including glycogenolysis, gluconeogenesis, and lipolysis. However, the effects of GLP-1 RAs on liver lipid metabolism in fish remain largely unexplored. Objective: This study aimed to evaluate the effects of LIR on lipid target genes using primary hepatocytes from brown trout as an in vitro model. Methodology: After 24 h, a hepatocyte monolayer culture was established, and cells were exposed for 24 and 48 h to supplemented L-15 medium (control), 0.1% dimethyl sulfoxide in supplemented L-15 medium (solvent control), and five single exposures to LIR at 1, 10, 100, 500, and 1000 nM. After 24 and 48 h, cell viability was assessed using the trypan blue exclusion assay. Gene expression was analysed by real-time qPCR, targeting genes involved in lipogenesis, lipid transport, and cholesterol efflux. Results: No concentration-dependent effects on cell viability were observed. Gene expression analysis showed that LIR exposure modulated the mRNA levels of lipid-related genes, including acetyl-CoA carboxylase (ACC), acyl-CoA long-chain synthetase 1 (Acsl1), and fatty acid synthase (FAS), with time being the main influencing factor. Overall, expression levels were higher at 48 h compared to 24 h. Additionally, dose-dependent effects were observed for ACC expression, with higher LIR concentrations showing significant differences compared to controls. Conclusions: These findings indicate that LIR modulates lipid-related gene expression in primary hepatocytes of brown trout without affecting cell viability. The results suggest that GLP-1 receptor activation may influence key pathways involved in hepatic lipid metabolism, with time-dependent effects playing a predominant role. Overall, this study supports the use of brown trout primary hepatocytes as a suitable in vitro model for investigating hepatic lipid responses to LIR and other GLP-1 receptor agonists, while providing initial insight into their potential effects in fish.

Proceedings doi: 10.3390/proceedings2026146059

Authors: Paloma Moreno-Rendón César Esteban Simón-Talero Guadalupe de la Cruz Ortiz César Fallola Sánchez-Herrera Miguel Angel Cotallo de Cáceres

European catfish, an invasive alien species (IAS) that inhabits the Tagus River in Extremadura, is a threat to freshwater biodiversity and the local economy. As a freshwater mega-predator, it eats all kinds of fish, impacting local ichthyofauna as well as sport-recreational angling, a major economic driver in Extremadura, with 100,000 angling licenses issued by the Extremadura local government and more than 1000 annual bank fishing competitions. The introduction of Silurus glanis into Tagus basin is recent, dating to the 20th century, but it has rapidly spread. Although this expansion is driven by anglers, boat anglers account for only two per thousand anglers in the region, and even among them European catfish anglers are scarce, as fishing for this species is prohibited in the region and local anglers and anglers associations are against European catfish expansion. Efforts to control catfish in Extremadura have been based on studies of selective capture methods, such as trammel nets, gill nets, long lines, fish traps, and electrofishing combined with nets in areas where barbel congregate during their spawning migration. The most effective and selective methods for European catfish, avoiding bycatch, are trammel nets and electrofishing. Therefore, a combination of these methods and collaboration between local government and anglers are proposed for its control in reservoirs. In cases of recent introductions into standing water, rapid actions have been taken, involving complete drainage of the water body, rescue of native fish and removal of European catfish. These measures are feasible in reservoirs up to 10 hectares and can be combined with sediment management to improve water quality. Deterrence and control measures have been implemented in response to the promotion of catfish angling in regional media and on social media. To control European catfish expansion, collaborative actions involving public agencies, local government, angler associations and public awareness are essential.

Proceedings doi: 10.3390/proceedings2026146060

Authors: Tiago Lourenço Maria João Rocha Eduardo Rocha Tânia Vieira Madureira

Introduction: Fish and humans share evolutionarily conserved pathways regulating lipid metabolism. However, the effects of pharmaceuticals on lipid homeostasis in fish remain poorly understood, particularly regarding mechanistic lipid dysregulation and its implications for fish physiology and environmental toxicology. While hypolipidemic drugs such as statins have been shown to modulate lipid metabolism in teleosts, other lipid-lowering agents, including cholesterol absorption inhibitors, remain largely unexplored. Additionally, synthetic hormones have been shown to interfere with lipid regulation, although their effects—particularly those of progestins—remain poorly characterized. Objective: This study aimed to explore the mechanistic lipid disruptions induced by potential hypo- and hyperlipidemic modulating pharmaceuticals in brown trout juveniles exposed to subchronic pharmacological conditions. Methodology: Juvenile brown trout were exposed via intramuscular injection every 72 h for 28 days and allocated into six experimental groups (n = 12 per group): control (C; 0.7% NaCl), solvent control (SC; 0.7% NaCl, 0.9% ethanol, 0.1% dimethyl sulfoxide), atorvastatin (ATV; 0.3 µg·g−1), ezetimibe (EZB; 0.3 µg·g−1), 17α-ethinylestradiol (EE2; 2 µg·g−1), and levonorgestrel (LNG; 0.1 µg·g−1). All concentrations represented pharmacological doses. On day 28, the fish were euthanized and sampled. Endpoints included biometric measurements, blood lipid profiling, serum biochemistry, and hepatic lipid accumulation. Results: ATV fish displayed greater body length, whereas EE2 increased liver weight and hepatosomatic index. EE2 reduced high-density lipoproteins and increased low-density lipoproteins, while atorvastatin reduced low-density lipoproteins. EE2 exposure also increased albumin levels and decreased glucose concentrations. Furthermore, EE2 significantly enhanced hepatic lipid deposition. Conclusions: The hyperlipidemic effects of EE2 were the most pronounced, whereas ATV produced the strongest hypolipidemic responses, consistent with its known effects in humans, and also influenced biometry. These findings provide a robust foundation for understanding how pharmaceuticals influence lipid metabolism and related physiological processes such as growth in fish, with relevance for both fish physiology research and environmental toxicology.

Proceedings doi: 10.3390/proceedings2026146057

Authors: Ondina Ribeiro Luís Félix Antonio De la Vieja Monica Torres-Ruiz João Soares Carrola

Introduction: Chemical pollution of water bodies constitutes a global problem with huge impacts on fish populations. Consequently, the assessment of the effects of contaminants, especially on the nervous system, has become essential. The zebrafish (Danio rerio) has emerged as a prominent vertebrate model in ecotoxicology and neuroscience, in large part owing to the availability of genetic resources, including a high level of genome sequencing and annotation, plus the similarity of its neuron types and neurotransmitters to other vertebrates, including humans, and its stereotyped behaviour. Objective: The main objective of this mini-review is to present a synthesis of the key behavioural assays used in zebrafish larvae to assess neurotoxicity, focusing on developmental neurotoxicity. Methodology: A literature review was conducted based on the ScienceDirect and PubMed databases, covering publications between 2000 and 2025, selecting relevant studies on larval (up to 120 hpf) behaviour and contaminant exposure. The methodology was based on the analysis of behavioural tests applied to larvae, which evaluate responses to various stimuli, including visual, acoustic, tactile, and social stimuli. Results: Established, commonly used key assays include the light/dark test and locomotor, touch, photomotor, acoustic, and social response tests. The literature results confirm that zebrafish larvae exhibit complex behavioural patterns comparable to those of higher vertebrates, making them suitable for neurobehavioural studies. Changes in locomotor behaviour, responses to stimuli, or social patterns are extremely sensitive indicators of early neurotoxic effects, often before morphological changes are observed. Furthermore, the developing nervous system is particularly sensitive to chemicals, with high potential for irreversible effects, even with short-term exposures. Conclusions: Overall, our findings demonstrate that behavioural assays in zebrafish larvae constitute an effective, sensitive, and economically viable tool for assessing the neurotoxicity of compounds, contributing to a better understanding of the mechanisms of action and advancing environmental protection and public health strategies, considering also the “one health” approach.

Proceedings doi: 10.3390/proceedings2026146118

Authors: Patrícia Carneiro Cláudia A. Rocha Sandra M. Monteiro Carlos Venâncio Luís M. Félix

Fish are continuously exposed to stress factors throughout their life cycle, making the use of anaesthetics essential for a wide range of experimental procedures. Currently, the most commonly used and FDA approved anaesthetic for fish research is Tricaine Methanesulfonate (MS-222). However, its use has been associated with several undesirable effects, including hypoxemia, hypercapnia and hypoglycaemia, as well as environmental concerns due to its release through aquaculture effluents. These limitations highlight the need for alternative anaesthetic strategies. Natural compounds such as clove oil, menthol and thymol have been investigated as potential alternatives, demonstrating effective anaesthetic properties. However, their low aqueous solubility, represents a significant challenge, which may be overcome through nanoencapsulation. This approach can enhance solubility, enable controlled release, and reduce the effective dose required. Accordingly, the present study aims to provide an overview of the recent advances in nanoparticle-based encapsulation strategies for anaesthetic delivery in fish, with a focus on their efficacy, safety and environmental impact. Some studies have demonstrated the benefits of nanoencapsulation. In adult zebrafish (Danio rerio), lower concentrations of benzocaine were required when encapsulated in chitosan-PLGA nanoparticles, while lidocaine-loaded lipid NPs reduced bradycardia. In Nile Tilapia (Oreochromis niloticus), clove oil encapsulated in lipid-based nanocapsules enabled effective anaesthesia and prolonged release of the active compound eugenol. Similarly, mucoadhesive zein NPs, reduced the effective concentration of Eugenol by up to 50%. Monoterpenes such as menthol and thymol also show promise for zebrafish anaesthesia, demonstrating efficacy at 50 mg/L. These findings suggest that nanoparticle-based delivery systems can improve the efficacy and safety of fish anaesthetics while reducing required doses and potential environmental impact. Future research should focus on optimizing nanoparticle-anaesthetic systems by combining natural compounds with biocompatible and biodegradable nanocarriers (e.g., zein, chitosan or PLGA) to achieve controlled release, targeted delivery and minimization of side effects.

Proceedings doi: 10.3390/proceedings2026146061

Authors: Francisco Baldó Miguel Ángel Cortes-Pujol David Barros-García Juan Manuel Martínez-Vázquez Rafael Bañón

Introduction: Elasmobranchs are an important component of deep-water and slope ecosystems, playing a key role in benthic and demersal food webs. Many species inhabiting offshore banks of the northeastern Atlantic are characterized by low productivity and high sensitivity to fishing pressure, which makes fishery-independent assessments particularly relevant. The Porcupine Bank supports a diverse assemblage of deep-water sharks and skates, yet quantitative information derived from standardized trawl surveys remains essential to characterize community structure and support ecosystem-based management. This study aims to provide an updated overview of the composition, relative abundance, biomass, and occurrence of elasmobranch species on the Porcupine Bank. Methodology: Data were collected during the Porcupine bottom trawl survey carried out in September–October 2023. The survey used a stratified random sampling design by depth and comprised a total of 88 valid demersal trawl hauls. Results: A total of 23 elasmobranch species belonging to four orders (Carcharhiniformes, Squaliformes, Rajiformes, and Hexanchiformes) were recorded. The assemblage was dominated by deep-water sharks, particularly squaliforms and carcharhiniforms. Galeus melastomus was the most dominant species, showing the highest stratified mean biomass and abundance and occurring in the majority of hauls. Other abundant and recurrent species included Etmopterus spinax, Scyliorhinus canicula, and Deania calceus. Skates of the genera Dipturus and Leucoraja were less abundant but showed consistent occurrences across depth strata. Several deep-water species, such as Apristurus spp. and Rajella fyllae, were recorded only sporadically, with very low abundances and limited occurrence. Conclusions: The results highlight the predominance of small- to medium-sized deep-water sharks on the Porcupine Bank and the comparatively lower contribution of rajid skates. This study provides a robust description of elasmobranch assemblage structure based on standardized sampling and constitutes a valuable baseline for future monitoring and comparative assessments in offshore Atlantic ecosystems.

Proceedings doi: 10.3390/proceedings2026146056

Authors: António Tovar Faro João Manuel Oliveira Pedro Segurado Verónica Pinto Lia Barros Felisbina Quadrado Tamara Leite Gonçalo Duarte Paulo Branco Teresa Ferreira

Introduction: Despite more than two decades of implementation, the European Water Framework Directive (WFD) still faces major challenges in achieving good ecological status across European water bodies. Key limitations persist in connectivity restoration, transboundary harmonization, monitoring network design, and biological assessment of complex systems such as large rivers, reducing the Directive’s capacity to provide consistent ecological diagnoses and support effective river basin management. Objective: This work had four objectives: (I) incorporate ecological status into connectivity assessments; (II) evaluate harmonization in Iberian transboundary basins; (III) optimize the national fish monitoring network through co-creation; (IV) develop a fish-based multimetric index for Portuguese large rivers. Methodology: The work combined four approaches: (1) graph-based connectivity analysis integrating the probability of achieving good ecological status to evaluate functional connectivity across European river networks; (2) cross-border comparison of ecological classifications between Portugal and Spain in shared Iberian basins; (3) optimization of the Portuguese fish monitoring network through a co-creation approach involving the national authority; (4) development of a fish-based multimetric index designed for Portuguese large rivers. Results: Integrating ecological status into connectivity analyses reduced estimated connectivity and highlighted the combined effects of fragmentation and degradation. Cross-border comparisons showed that formal harmonization does not ensure consistent ecological classification. The optimized monitoring networks improved ecological representativeness without increasing sampling effort, while co-creation ensured operational feasibility. The new fish index for large rivers captures spatial variation in ecological quality and responds to pressure gradients, addressing a recognized methodological gap. Conclusions: Improving WFD implementation requires progress across multiple complementary components rather than isolated advances. More effective river management depends on integrating ecological processes, comparable assessment outputs, representative monitoring networks, and system-specific tools. These approaches provide transferable pathways for strengthening freshwater assessment and supporting more coherent river restoration and management across Europe.

Proceedings doi: 10.3390/proceedings2026142010

Authors: Shah Asim Azhar Malik Shafaq Mahmood Ayesha Iftikhar

Universities increasingly rely on digital self-service channels to manage high volumes of time-sensitive admissions enquiries. AI enabled chatbots represent a prominent solution because they can provide round-the-clock responses, standardize guidance, and potentially reduce uncertainty for applicants. Yet evidence on whether such chatbots meaningfully assist students and improve their satisfaction with admissions support remains limited in many developing higher education contexts. This quantitative study evaluates the perceived effectiveness of AI chatbots used for university admissions in Pakistan, with a focus on student assistance and satisfaction as key outcomes. Using a cross-sectional survey design, data were collected from students who had recently engaged with university admissions information services (e.g., website chat widgets, messaging-based virtual assistants, and admissions enquiry portals) across private universities in Pakistan. Admissions chatbot effectiveness was measured through established information systems and service quality constructs system quality (ease of use, responsiveness, accessibility), information quality (accuracy, clarity, completeness), and service quality and trust cues (assurance, privacy confidence, and appropriateness of conversational support). Student assistance captured the extent to which chatbot interactions helped participants complete admissions related tasks and navigate application procedures. Student satisfaction reflected overall evaluation of the admissions support experience. The results indicate a positive association between perceived chatbot quality and perceived student assistance, and a further positive association between student assistance and student satisfaction with admissions support. The overall pattern suggests that student assistance functions as a key mechanism through which chatbot effectiveness translates into satisfaction. At the same time, respondents highlighted limitations in resolving complex or exception based queries, emphasizing the importance of transparent escalation to human admissions staff. The study contributes context specific evidence from Pakistan and offers an empirically grounded framework that university administrators can use to evaluate and improve admissions chatbots. Practical implications emphasize maintaining accurate knowledge bases, designing clear handoff pathways, and implementing governance practices that strengthen students’ confidence in information reliability and data privacy.

Proceedings doi: 10.3390/proceedings2026146058

Authors: Diogo Ribeiro Christos Gkenas Diogo Dias Mafalda Moncada Beatriz Castro Rui Rivaes Filipe Ribeiro

Introduction: The colossal European catfish (Silurus glanis) is the largest invasive freshwater fish on the Iberian Peninsula, reaching up to 2.8 metres and 130 kg in weight. Its large size makes it a highly valued target for recreational anglers, leading to repeated illegal introductions across several Iberian watersheds. Despite its appeal to anglers, this species is recognised as a high-impact invasive predator with substantial ecological consequences for European freshwater ecosystems. Recently, large catfish aggregations have been reported by anglers and environmentalists in several areas of Portugal and Spain. These impressive aggregations are frequently documented on videos and posted on social media networks (Facebook, WhatsApp groups, etc) or shared directly with our team members. Objective: Such records provide a valuable source of information for identifying the habitats and seasonal periods associated with aggregation behaviours and may therefore support more efficient management and population control actions. Methodology: We compiled information on European catfish aggregation events in Southern Iberia, namely date and location. The catfish aggregations were mapped, and their general habitat characteristics were described. Results: We recorded 10 catfish aggregation events, most of which occurred between May and June. These were generally located in transitional areas between lentic and lotic habitats, especially in narrower river sections. Possible explanations include hydromorphological constraints, seasonal environmental conditions, and species-specific behavioural responses, although these mechanisms require further investigation. Conclusions: Within the LIFE PREDATOR project, which focuses on the management of European catfish in the Tagus watershed, knowledge of aggregation locations is important to direct population control efforts aimed at reducing the abundance of this invasive fish. Moreover, the identification of common habitat characteristics may help predict other potential aggregation sites and improve the planning of future management actions.

Proceedings doi: 10.3390/proceedings2026146055

Authors: João Oliveira Miguel Macário Vanda Andrade Paula Ruivo Maria Oliveira João Gago Filipe Ribeiro Abigail Lynch

Introduction: Inland fisheries in their diverse forms are an important activity in Portugal, currently involving about 100,000 fishers. Despite their relevance, there is still limited knowledge regarding the economic multiplier effect associated with this activity, including its contribution to local and regional economies, its broader socio-economic impacts, and its role in promoting nature-based tourism. Objective: The INFISHERIES.PT project aims to characterize the socio-economic value of inland fisheries in Portugal. Methodology: The three main fishing activities in Portugal (professional, sport, and recreational fisheries) were considered to assess inland fisheries’ economic value. Data on annual expenditures of competitive sport anglers were collected through an online questionnaire distributed by the Portuguese Federation of Sport Fishing, while data on recreational fishers were obtained through face-to-face surveys. The analysis of professional fisheries was based on official catch declarations submitted to the national licensing authority (ICNF) between 2012 and 2024. Interim Results: Results for sport fisheries indicate an estimated mean annual direct expenditure of €6.7 million, with fishing equipment accounting for the largest share, followed by travel, meals, and accommodation. Social interaction was identified as the main motivation for recreational fishing, followed by contact with nature, as well as motivations related to peace, relaxation, and entertainment. Respondents most frequently reported annual expenditures between €100 and €499 on fishing equipment, travel, and food during fishing trips. Regarding professional fisheries, results highlight the increasing importance of non-native species in total catches, particularly the red swamp crayfish, in recent years. Native migratory species, such as the European eel, sea lamprey, and allis shad, despite lower catch volumes, maintain high market value and make a significant contribution to total revenue. Conclusions: The results obtained to date in this project indicate that freshwater fishing in Portugal is a relevant activity, both in its commercial and non-commercial forms, and plays an important economic role at local and regional levels. Moreover, sport and recreational angling, in particular, also serve as drivers of nature-based tourism, potentially contributing to increased environmental awareness among the population and pressuring authorities to maintain freshwater ecosystems in good ecological condition.

Proceedings doi: 10.3390/proceedings2026146054

Authors: Roberto Rocha Tavares Rafael Gaio Kulzer Rodolfo Miguel Silva Régis Vinícius Souza Santos Alberto Teodorico Correia

Introduction: Understanding population structure is essential for fisheries management and stock identification. In marine species, spatial differentiation may arise from environmental conditions and biological factors, even when populations appear continuous. Otolith shape and body analyses have been widely used as effective tools to detect such differences, as they reflect both genetic and environmental influences. Objectives: The main objective of this study was to assess the population structure of Sarpa salpa in three fishing grounds in the Northeast Atlantic using two geometric morphometric approaches. Methodology: A total of 133 individuals collected between November 2025 and March 2026 from Santa Maria (n = 48), Peniche (n = 36), and Olhão (n = 49) were analyzed using two geometric morphometric approaches. The first involved otolith contour analysis using Elliptical Fourier Descriptors (EFD), with 12 descriptors explaining 90% of the cumulative variance. The second approach used truss network analysis based on 11 body landmarks, corresponding to 22 transformed distances (TD). Statistical analyses included multivariate analysis of variance (MANOVA), Hotelling’s T-square tests (HT2) for multiple comparisons, and linear discriminant function analysis (LDFA), with reclassification success assessed using a jackknifed (leave-one-out) classification matrix (JKM). Results: EFD analysis showed significant differences for MANOVA, with significant HT2 between all locations, but LDFA indicated considerable overlap, with a global JKM reclassification rate of 60%. In contrast, TD also showed significant MANOVA results, with significant HT2 across all comparisons. However, LDFA demonstrated clear separation among the three groups, achieving a JKM overall reclassification success of 98%. Conclusions: The results indicate that geometric morphometrics based on body landmarks provides greater discriminatory power than otolith contour analysis for identifying population structure. These results suggest the existence of distinct population units of Sarpa salpa in the Northeast Atlantic, highlighting the importance of spatially explicit approaches for fisheries assessment and management.

Proceedings doi: 10.3390/proceedings2026146052

Authors: Xavi Giménez-Borrás Carolina Ayelén Ángela Brotons Pilar Risueño Victor Gallego

Introduction: The fartet (Apricaphanius iberus) and the samaruc (Valencia hispanica) are two endemic fish species from the Valencian Community that have experienced significant population declines due to habitat degradation, competition with invasive species, and the impacts of climate change. Despite their critical conservation status, key aspects of their population dynamics and reproductive biology remain poorly understood. Objective: This study aimed to assess the resilience of their embryos to water stress through diapause-like mechanisms. Methodology: For studying the embryonic arrestment, eggs were collected from captive populations and subjected to different incubation periods (1, 3, 7, 10 and 14 days) on different substrates (commercial sand and filter paper). Hatching rates were analyzed in relation to the duration of exposure to stress water conditions and the type of substrate used. Results: The experiments conducted demonstrated that the embryos of both species were able to withstand water stress conditions (eggs out of the water). In the case of the samaruc, the results showed that eggs collected in both May and June could resist water-stress conditions for at least 10 days, exhibiting hatching rates of 100% during this period, which decreased to 50% by day 14. Regarding the fartet, embryos from eggs collected in May were able to survive up to 3 days under water-stress conditions, with hatching rates of 100%. In contrast, embryos from eggs collected in June showed greater resilience to water stress, with high hatching rates of 60–100% at days 7 and 10. Conclusions: These results suggest that, although a mechanism like embryonic diapause may be present in these species, its effectiveness as an adaptive strategy may depend on multiple environmental factors not controlled in this study, such as temperature, oxygen availability, and water salinity. The absence of hatching after prolonged incubation periods indicates that, if a diapause mechanism exists in these species, it may not be as efficient as in other annual cyprinodontiforms adapted to extremely fluctuating environments. These results highlight the importance of adaptive management measures to mitigate the effects of climate change and ensure the long-term persistence of both species.

Proceedings doi: 10.3390/proceedings2026146051

Authors: João Gago Miguel Macário Vanda Andrade Paula Ruivo Maria Oliveira João Oliveira Filipe Ribeiro Abigail Lynch

Introduction: Competitive sport angling is a specialized form of recreational fishing in which participants compete in tournaments throughout the year to obtain annual rankings. In Portugal, competitive anglers may exhibit high levels of engagement and expenditure, yet the economic relevance of this activity remains poorly documented. Objective: This study aimed to assess the economic value of inland competitive angling competitions in Portugal. Methodology: Data on anglers’ annual expenditures were collected through a web-based questionnaire distributed in April 2025 by the Portuguese Federation of Sport Angling to 1,230 registered federated anglers. A total of 193 valid responses were obtained, including information on socio-demographic characteristics, angling modalities, and fishing locations, as well as expenditures on fishing equipment, travel, meals, accommodation, and willingness to pay (WTP) to ensure fish availability during competitions. Results: Extrapolation of the results to the national federated inland angler population suggests an estimated annual direct expenditure of approximately €6.7 million, ranging from €4.2 million to €9.2 million. Fishing equipment (e.g., rods, reels, boats, kayaks, and paniers) accounted for the largest share of expenditures, followed by travel, meals, and accommodation. Expenditure patterns varied according to age, angling modality, years of competitive experience, and participation in both inland and marine competitions. Most respondents (62.7%) reported being unwilling to pay additional amounts to guarantee fish availability, arguing that this responsibility should fall on the state and competition organizers given the fees already paid. Conclusions: Inland competitive sport angling appears to make a relevant contribution to economic activity associated with tourism and leisure services in Portugal and should therefore be considered in the management of inland water resources.

Proceedings doi: 10.3390/proceedings2026146043

Authors: Cláudia A. Rocha Tânia Martins Patrícia Carneiro Luís M. Félix Sandra M. Monteiro Carlos Venâncio

Introduction: Aquatic ecosystems are major reservoirs for both legacy and emerging contaminants, facilitating their distribution throughout the environment and bioaccumulation across different trophic levels. As such, wildlife acts as a valuable tool for biomonitoring these contaminants and serves as a key indicator of environmental pollution within the One Health framework. Despite this, knowledge regarding the application of this framework alongside the assessment of aquatic contaminants using wildlife species remains fragmented. Objective: This study aims to synthesize current evidence on aquatic contaminants using wildlife as sentinels of environmental pollution and to explore how the One Health concept is applied in this field. Methodology: A systematic database search was conducted in SCOPUS, and the retrieved studies were screened according to predefined inclusion and exclusion criteria, as well as their relevance to the One Health concept. Results: Despite its timely relevance, only fourteen studies have adopted the One Health approach to assess contaminants in aquatic species. The selected studies focused mainly on plastic particles (53.33%), such as macro- and microplastics; heavy metals (26.67%), such as mercury (Hg), cadmium (Cd), Nickel (Ni), lead (Pb), and selenium (Se); persistent organic pollutants (13.33%), such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), per- and polyfluoroalkyl substances (PFAS), and dioxin/furans; and metalloid (6.67%) arsenic (As). These contaminants were evaluated across four different taxonomic groups: fishes (61.54%), waterbirds (23.08%), mollusks (7.69%) and crustaceans (7.69%). Most studies were conducted in Portugal (37.5%) and the United States of America (18.75%), whereas other countries, including Canada, Australia, Ecuador, Mexico, Indonesia, and Turkey, were mentioned in only one study each (6.25%). Conclusions: Monitoring levels of contaminants in wildlife is essential not only to understand the dynamics of environmental pollution, but also to preserve the integrity of ecosystems while safeguarding animal and human health. However, the limited number of studies adopting a One Health perspective results in an incomplete representation of contaminant classes and affected taxa. These findings highlight the urgent need to expand wildlife-based monitoring strategies within a One Health framework, aiming to improve environmental risk assessment and deepen our understanding of the impacts of pollution across ecosystems, animals and humans.

Proceedings doi: 10.3390/proceedings2026146032

Authors: Ricardo Estevens Telma Luís Samuel Ramos Pereira Vera M. Mendes Bruno Manadas Carolina Madeira Pedro M. Costa

Fish venom biology reaches far beyond addressing risks of human envenomation. The critical understanding of venom composition and the drivers that modulate it will enable scientists to deliver a span of novel bioresources with multiple potential biotechnological applications. The lesser weever fish (Echiichtys vipera), common in the surf of sandy beaches in Portugal, is a noteworthy case study due to frequent envenomation episodes during summer, albeit the lack of information regarding its venom system and the composition of its venom. We collected about one hundred animals from Costa da Caparica (W Portugal) as beach trawl (arte xávega) by-catch. Histology showed a similar essential microanatomical structure of glands in both venomous spines (dorsal and opercular) and no obvious gender differences. Transversal sections across the spines showed a T-shaped supportive bone structure that harbor masses of large, glandular cells that bear large sacculi. The structure is surrounded by a retractable layer of skin, thicker in the opercular spines comparatively to dorsal. The lack of muscular tissue near the glands and missing venom delivery ducts in the spines suggest that venom secretion in this species is holocrine, i.e., that venom is delivered through rupture of the skin and underlying glandular tissue upon mechanical pressure. Proteomics of the venomous spines (dorsal and opercular) showed a different proteomic signature between males and females, pointing to intersexual variation and suggesting that other biotic and abiotic factors might influence venom composition (maturation stage or geographic distribution). Additionally, protein homology matches performed against known toxins from marine venomous fishes indicated the presence of novel unexplored toxins in this species besides expected cytolysins. Our focus in the future is to identify, isolate and characterize the individual components of this venom. We anticipate new insights on the intraspecific adaptation of fish venom systems to specific ecological needs and advocate for sustainable bioprospecting for novel proteins with high biotechnological potential.

Proceedings doi: 10.3390/proceedings2026146041

Authors: Beatriz Castro Ivana Vejříková Filipe Ribeiro Diogo Dias Mafalda Moncada Diogo Ribeiro Rui Rivaes Jan Kubečka Mojmír Vašek Martin Čech Carlos Fernandez-Delgado Agustín P. Monteoliva Jaroslav Semerád Pietro Volta Lukáš Vejřík

Freshwater ecosystems in southern Europe are increasingly impacted by fish invasions from central and northern regions, often facilitated by warmer climates and reduced natural-enemy pressure. The European catfish (Silurus glanis), the largest freshwater fish in Europe, is now widely established across various southern European basins, where its high fecundity, ecological plasticity, and predatory behaviour pose significant risks to native communities. Despite its rapid spread, growth dynamics across native and non-native populations remains scatteredly described in studies with different approaches. Objective: This study compares growth rates between native populations in the Czech Republic and non-native populations in Portugal, Spain, and Italy, and assesses whether growth rates are influenced by introduction timelines, reflecting differences in population age and invasion stage. Methodology: Nine populations spanning the native range (central Europe) and non-native range (southern Europe) were analysed. A total of 427 different vertebrae were used to age the fish and growth was modelled using the von Bertalanffy growth function. Generalised linear models were used to identify environmental and demographic predictors of variation in the growth coefficient (K). Moreover, mark-recapture data from the native populatations was also analysed. Results: Preliminary results indicate substantial variation in growth among populations, with higher growth rates exhibited in non-native populations (Iberian), while native populations showed consistently lower growth rates. Growth was primarily associated with population age and minimum temperature, decreasing with increasing population age and increasing under warmer thermal conditions. These patterns suggest faster growth in recently established and warmer populations. Conclusions: Growth dynamics of European catfish vary markedly across native and non-native ranges, driven mainly by thermal conditions and invasion history. Faster growth in warmer and recently established populations may enhance invasion success by accelerating size-at-age and reproductive potential. This study highlights the importance of integrating environmental and demographic factors to improve predictions of invasion dynamics and ecological impacts in freshwater ecosystems.

Proceedings doi: 10.3390/proceedings2026145001

Authors: Ana M. Vernia-Carrasco

The Active Music Programme (MAP) is an interdisciplinary initiative designed to foster inclusion, communication, and emotional well-being through participatory music-making. Integrating active music education, guided improvisation, and creative interaction, MAP seeks to enhance quality of life for individuals with diverse abilities. This pilot project, implemented in a special education centre with adolescents and adults with Autism Spectrum Disorder (ASD), combines weekly collaborative sessions led by music and education professionals. Using a qualitative, participatory framework, the study aims to examine how musical engagement is expected to support shared attention, emotional regulation, and social connection, positioning MAP as a replicable model for inclusive education and community practice.

Proceedings doi: 10.3390/proceedings2026146036

Authors: Susana D. Amaral Ricardo Branca Ulisses Cabral João Pádua José M. Santos

Introduction: The Touvedo hydropower plant, located on the Lima River 47 km from its mouth, is equipped with a fish lift (2.14 m long × 1.29 m wide × 2.85 m high) on the left bank designed to facilitate fish migration past the dam. This mechanical system attracts fish by means of a guide current, traps them in a water-filled cage, and then lifts and releases them upstream, enabling passage over the dam. Within the framework of the Sustainability Policies from the EDP Group, particularly those related to Environment and Biodiversity, and under the Eel Management Plan, a long-term video-monitoring program has been implemented since 2011 to collect data on the species using the device and to evaluate its effectiveness. Objective: This study aims to present and analyze nine years of video-monitoring data collected across three programs—the “Action Plan for the Optimization of the Fish Lift at the Touvedo Hydroelectric Facility (2011/2014)”, which aimed to diagnose and assess the effectiveness of the fish lift and to define and implement measures needed to optimize its operation; “Video Monitoring of the Touvedo Fish Lift (2017/2020)”, that was carried out as a follow-up to the Action Plan; and more recently, a new video-monitoring project (2021–2024) which was implemented to expand the dataset and validate the patterns observed in the previous studies. Methodology: The fish lift was continuously monitored using an automatic video-recording system, which consists of a video camera installed at the top of the lift to capture images of the trapping cage during the final stage of its ascent, and a server for video storage. The trapping cage is lined with 20 cm × 20 cm white tiles to increase contrast and allow estimation of fish body length. Collected data included the timing of fish passage (day and hour), the number of fish per cycle, species-level identification and the estimated total length of each individual. Results: The European eel (Anguilla anguilla) has remained the dominant species using the lift, and, consistent with observations from Video-Monitoring 1, the Iberian barbel (Luciobarbus bocagei) has become the second most representative species, replacing the northern straight-mouth nase (Pseudochondrostoma duriense), whose proportion has declined. Brown trout (Salmo trutta) showed a slight but continued increase in Video-Monitoring 2, following the decrease recorded in Video-Monitoring 1 compared to the Action Plan. Conclusions: These results highlight the importance of continuing video monitoring of the Touvedo fish lift to assess its operability, confirm the observed passage patterns, determine the success of the implemented improvements, and evaluate the possible need for additional measures.

Proceedings doi: 10.3390/proceedings2026146038

Authors: Alejandra Cruz Raquel Merino-Aguirre Esther Lantero Belén Méndez-Cea Juan A. Ardura Josué García Yagüe Ana Clara Sampaio Franco Emili García-Berthou David H. Fletcher David Almeida

Habitat alteration and biological invasions are two main drivers of biodiversity loss at the global scale. Eutrophication and invasive fish greatly disturb freshwater native communities. This is of particular conservation concern in the Iberian Peninsula (Portugal and Spain), where fish fauna display a high level of endemism. For this eco-region, there is a dearth of information on the interactions among water quality, physical condition and parasites of invasive fishes. Consequently, the aim of this study was to assess the effect of nutrient enrichment on health status and parasitological traits in the invasive mosquitofish Gambusia holbrooki inhabiting an Iberian river. Water (n = 18 replicates, three per site) and fish (n = 400 individuals, 33–34 ind. per site and year) samples were collected in September 2024 and 2025 along the River Bullaque (central Spain). Sampling effort was standardised among sites, with the following parameters consistent: seine and pond nets were used, deployed by wading; 10:00 solar time; 1.5 h duration; personnel (the same seven trained researchers); and weather/environmental conditions; ensuring methodological consistency and data comparability. Laboratory procedures were carried out near the sampling sites to minimise both fish stress and distortions to parasite communities. Morphological and parasitological parameters were compared between mesotrophic and eutrophic reaches (six sampling sites, three per reach). Body condition and health assessment index* were greater under eutrophic conditions. Fluctuating asymmetry (a measure of developmental instability) was significantly higher for eye diameter in the mesotrophic reach. Parasite taxonomic composition differed between reaches, with more digeneans and cestodes in the mesotrophic sites, whereas ciliates and monogeneans were more abundant in mosquitofish from the eutrophic reach. Parasite prevalence, abundance and index of life-cycle complexity (heteroxenous species) were lower in the eutrophic reach. These results strongly suggest that eutrophication can facilitate mosquitofish invasiveness. This is reflected in a variety of morphological and parasitological traits, such as better body condition, health status, developmental stability, parasite resistance and tolerance. Overall, these parameters indicate that mosquitofish is taking advantage of anthropogenic impacts to improve their level of establishment and subsequent spread throughout Iberian fresh waters.

Proceedings doi: 10.3390/proceedings2026146046

Authors: Christos Gkenas Nicholas Koutsikos Katelyn Lawson Filipe Ribeiro Leonidas Vardakas

Introduction: Freshwater ecosystems are global biodiversity hotspots, yet they remain highly vulnerable to biological invasions. Non-native freshwater fish species (NNFS) have established self-sustaining populations across nearly all biogeographic realms, reshaping regional ichthyofaunas and driving community-level impacts through predation, competition, hybridisation and ecosystem disruption. Critically, both foreign introductions and within-country translocations (extralimital species) contribute to this process, yet the latter remain more weakly regulated and consistently under-studied in invasion risk frameworks. Objective: We developed a stage-structured profiling framework to jointly evaluate foreign and extralimital NNFS in Greece and predict three sequential invasion outcomes, establishment, spread and integration, with the goal of identifying the ecological traits and pathway variables that best explain invasion success at each stage and informing management policy. Methodology: We compiled a dataset of 63 NNFS recorded in Greek freshwaters (36 foreign, 27 extralimital), characterised by eleven ecological, biogeographic and anthropogenic attributes. Logistic and multiple regression models and classification and regression trees (CART) were fitted independently for each invasion stage, with cross-validated predictor screening to limit multicollinearity and a taxonomy-based covariate to account for phylogenetic non-independence. Results: All 27 extralimital translocations established successfully, compared with only 11 of 36 foreign introductions, underscoring the disproportionate establishment success of within-country movements. Establishment probability was positively associated with high physiological tolerance and proximity to the nearest native source, and negatively associated with maximum adult size; propagule pressure provided only weak additional support. Spread across drainage basins was driven primarily by introduction effort and physiological tolerance. Integration increased with introduction effort, while the CART identified distance from the nearest native source as the primary partition of widespread, high-abundance outcomes, with trophic level further structuring outcomes among extralimital taxa. Conclusions: Our results indicate that management frameworks focused solely on foreign NNFS substantially underestimate invasion risk from within-country translocations. A compact set of predictors, biogeographic proximity, physiological tolerance and introduction effort, offers a practical, pathway-inclusive screening tool to guide prevention, surveillance and early detection in Mediterranean river networks, addressing a recognised European policy gap where extralimital movements remain more weakly regulated than foreign introductions.

Proceedings doi: 10.3390/proceedings2026146053

Authors: Nuria Perez-Bielsa Lilith Weimer Helena Mas Sandra Heras Jose-Luis Garcia-Marin Alba Abras

Introduction: The Catalan chub (Squalius laietanus) is a freshwater cyprinid endemic to Catalonia, from the lower course of the Ebro River to the Tech, Tet, Agly, and Massane rivers in France. Classified as Vulnerable in the IUCN Red List (2024), its populations face significant threats due to anthropogenic pressures and the potential hybridization with the European chub (Squalius cephalus). Objective: This study aimed to characterize the genetic variation of the mitochondrial control region (CR) of S. laietanus across the main Catalan river basins to determine the population genetic structure of this species in the core of its distribution range. Methodology: A 789 bp fragment of the CR was sequenced in 334 chubs from 24 sampling sites collected by electrofishing between 2021 and 2025. The S. laietanus specific matrilineage of all these specimens had been previously detected by sequencing the Cytochrome c oxidase subunit I (COI) but this marker did not detect clear genetic structuring among basins. Results: In contrast to the low diversity within and among locations reported by COI, the CR showed a population structure distinguishing between northern (Muga, Fluvià, Daró, Ter, and Tordera rivers) and southern basins (Besòs, Llobregat, Gaià, Francolí, and Ebro rivers). In the southern rivers, a single haplotype, (H1), was present. This haplotype declined in abundance towards the north, being replaced with H2. In the Muga River, native Catalan chub populations showed the fixed H3 haplotype, suggesting strong isolation, while populations from the Daró River contained a private haplotype (H4). In contrast, the presence of a common and single haplotype in southern basins possibly resulted from genetic drift under strong summer droughts. Conclusions: Overall, these results reveal population structuring in S. laietanus and highlight the importance of considering regional differentiation in conservation and management strategies.

Proceedings doi: 10.3390/proceedings2026146048

Authors: Marina Paixão Gil Mario Vinicius Condini Maurício Hostim-Silva Felippe Alexandre Daros

Introduction: Estuaries are dynamic environments that structure fish populations and can be investigated through geochemical signatures recorded in otoliths throughout the lives of individuals. Objective: This study aimed to assess the spatial geochemical differentiation of Genidens genidens, Guri sea catfish, across estuaries in southeastern Brazil using otolith elemental ratios and both univariate and multivariate approaches. Methodology: A total of 68 individuals were sampled from three estuaries (Rio Doce, Ipiranga, and São Mateus), with a subset of 53 individuals (aged 3–5 years) used for ontogenetic comparisons. Otolith microchemistry was analyzed using LA-ICP-MS, generating elemental profiles along the growth axis. Core, edge, and full transect signatures were defined. Data were analyzed using univariate and multivariate approaches, including PERMANOVA and Random Forest for spatial discrimination. Results: Geochemical signatures revealed spatial differentiation among estuaries, with a distinct separation of Rio Doce from Ipiranga and São Mateus (PERMANOVA: Pseudo-F = 20.23; p = 0.001). For individuals aged 3–5 years, no spatial differentiation was detected in the core (p = 0.184), whereas the edge showed significant separation among estuaries (p = 0.001; R2 = 0.434). Random Forest achieved an overall classification accuracy of 82.35%, with the highest accuracy for Rio Doce (95.65%), and identified Ba:Ca as the most important variable (56.0%). Conclusions: The observed spatial differentiation indicates that otolith geochemical signatures reflect regional environmental contrasts among estuaries, with Ba:Ca acting as the main discriminant. The lack of differentiation in the core, in contrast to the edge, suggests that spatial signals are primarily associated with more recent life stages. The high classification performance further supports the ability of multi-elemental signatures to discriminate estuarine systems, although lower accuracy between Ipiranga and São Mateus highlights the influence of environmental similarity. Overall, otolith microchemistry proved effective in detecting spatial structure at a regional scale.

Proceedings doi: 10.3390/proceedings2026146049

Authors: Gabriel de la Hucha Felipe Morcillo Anabel Perdices

Our objective is to assess the potential of ichthyological material from scientific collections for contemporary trophic studies by determining whether stomach contents of freshwater fish preserved in museum collections are well conserved and therefore comparable to those of present-day specimens. Specifically, we examined whether stomach contents from four native species—Squalius alburnoides, Iberochondrostoma lemmingii, Pseudochondrostoma willkommii, and Anaecypris hispanica—housed in the Museo Nacional de Ciencias Naturales (MNCN, CSIC) are suitable for quantitative dietary analyses. Museum specimens were collected in the Guadiana and Guadalquivir basins during spring–summer prior to 1980. Contemporary specimens were captured by electrofishing during spring–summer 2025 in the Bembézar River (Guadalquivir basin). Stomach content from the anterior third of the stomach was identified under a stereomicroscope, and all prey items were categorized. To analyze diet composition and characterize interspecific trophic structure, we assessed multivariate homogeneity of dispersion (PERMDISP) and performed permutational multivariate analyses of variance (PERMANOVA) based on Bray–Curtis distances. SIMPER analyses were used to identify the dietary items contributing most to dissimilarities between historical and contemporary samples for each species. Potential preservation-related biases were further evaluated by comparing the frequency of larval prey categories in museum specimens versus contemporary specimens. Our results indicate: (i) the overall suitability of museum specimens for dietary studies in all species examined; (ii) no evidence of a systematic loss of larval prey items in collection material, suggesting the absence of a generalized degradation bias; (iii) significant dietary differences between contemporary (2025) specimens and historical specimens (pre-1980), which in P. willkommii and I. lemmingii may be attributable to data dispersion, whereas in S. alburnoides these differences may reflect changes in trophic ecology, potentially associated with the introduction of invasive exotic species; and (iv) no significant differences in diet between historical and contemporary specimens of Anaecypris hispanica.

Proceedings doi: 10.3390/proceedings2026146044

Authors: Filipe Ribeiro Rui Rivaes Diogo Ribeiro Mafalda Moncada Diogo Dias Beatriz Castro Christos Gkenas Bernardo Quintella Maria Filomena Magalhães Rui Rebelo Alexandra Marçal Cristina Catita José Lino Costa Martin Čech Lukáš Vejřík Stefano Brignone Pietro Volta

Introduction: The invasive European catfish (Silurus glanis) is actively spreading across Iberian freshwaters, with no effective management measures in place to control its growing abundance or prevent its establishment in new localities. It poses a severe threat to endemic and already endangered species, and is simultaneously a preferred target by few anglers who continuously promote its spread. The LIFE-PREDATOR project aims to stop the spread of European catfish in lentic systems in Portugal and Italy, particularly in protected areas. Objectives: This talk will present the mid-term results of the LIFE-PREDATOR in Portugal, and discuss the difficulties and future challenges to reduce the size of local populations of European catfish. Methodology: The LIFE-PREDATOR team developed several tasks in Portugal: (1) established the reference situation of fish communities in six reservoirs in the Tagus Basin, using scientific fishing, fish telemetry and eDNA-based tools; (2) determined the optimal protocols for sampling catfish; (3) implemented an early detection programme based on warning teams, data-mining and eDNA tools; (4) developed population control actions in four reservoirs; and (5) organised dissemination events for the general public, anglers, and students from kindergarten to university levels. Results: Overall, there is a grim view about recipient communities in the studied lentic systems, which tend to be dominated by invasive fish species, including common carp (Cyprinus carpio), gibel carp (Carassius gibelio), European catfish, pikeperch (Sander lucioperca), European perch (Perca fluviatilis) and largemouth bass (Micropterus nigricans). At least three new localities harbouring catfish were identified from online data-mining and warning teams. A total of 8 tons of catfish were removed by mid-June of 2025, mostly from the Natural Park of International Tagus. Outreach activities were conducted in nearly 60 schools, reaching more than 5000 students. Moreover, 67 general public events have reached more than 4500 people since the project started (September 2023). Conclusions: Despite its positive outcomes, the LIFE-PREDATOR team has encountered challenges in engaging key stakeholders such as anglers, involving local municipalities, and implementing catfish removal actions in remote areas. Difficulties and challenges in catfish management must therefore be debated in order to assure the after-LIFE implementation across Portuguese protected areas.

Proceedings doi: 10.3390/proceedings2026146050

Authors: Xavi Giménez-Borrás Hugo Expósito Roselló Ángela Brotons Eduardo Belda Pilar Risueño Victor Gallego

Introduction: The vulnerable status of endemic Iberian fish like A. iberus and V. hispanica, together with limited knowledge of their reproductive biology, makes understanding temperature effects on hatching essential for defining their thermal limits and guiding conservation in a warming climate. Objectives: The main goals of this study were (i) to describe the embryonic development from fertilization to hatching in both species, and (ii) to evaluate the effect of temperature (20, 25, and 30 °C) on the embryonic development of both species, analyzing their future viability in the face of future climate scenarios. Methodology: Eggs at the earliest embryonic stage were evenly distributed among Petri dishes under controlled laboratory conditions. All dishes contained pH-controlled water with methylene blue to reduce fungal development. The hatching success of A. iberus and V. hispanica eggs was assessed across three temperature treatments (T20, T25, T30). Results: At 20 °C and 25 °C, A. iberus embryos achieved 100% hatching, with no failed eclosions. At 30 °C, however, hatching success declined to 33%, largely due to embryo mortality associated with fungal growth favored by higher temperatures. V. hispanica showed an even stronger temperature-dependent response: hatching was 100% at 20 °C, decreasing to 50% at 25 °C, and only 14% at 30 °C. These results indicate that V. hispanica embryos exhibit lower thermal tolerance compared to A. iberus. Conclusion: The data obtained in this study have helped to improve the limited knowledge available on the reproductive biology of these species, complementing existing information on their reproductive cycle. The experiments conducted at different temperatures have also provided valuable insights into how future climate change scenarios may affect their early stages, particularly during sensitive developmental periods. This information is essential for predicting potential impacts of climate change and can be used to guide the development of new conservation and management measures aimed at reducing threats and improving the long-term conservation prospects of these species, especially in vulnerable or changing habitats.

Proceedings doi: 10.3390/proceedings2026146039

Authors: Xavi Giménez-Borrás Adrián Pérez Ángela Brotons Eduardo Belda Pilar Risueño Victor Gallego

Introduction: Studying the structure and dynamics of living communities is essential from both ecological and wildlife management perspectives. Objective: The main objective of this study was to analyze the fish community structure inhabiting different river sections across several basins in the Mediterranean area. The data collected here contributed to: (i) creating a regional and national reference inventory to assess ichthyological biodiversity; (ii) generating digital cartographic information on species distribution and potential habitats; and (iii) providing scientific data to update national legal protection for governments. Methodology: Fish assemblages were monitored using electrofishing, which ensures reproducible data and long-term comparability. The study period extended until autumn 2025, with intensive sampling at 30 sites across major water bodies in the Valencian Community and selected rivers in Mijares, Turia, Jucar and Palancia basins. Results: The results reveal notable ichthyological richness in the studied basins (Turia, Júcar, Palancia, Mijares), with 12 native species identified. Cyprinidae and Leuciscidae were the most representative families, both in species number and spatial distribution, consistent with their dominance in Mediterranean river systems. Areas with the highest species richness corresponded to the middle and lower river sections and to ecologically valuable coastal wetlands. However, the study also detected 10 invasive alien species, representing 45% of the total fish fauna recorded. This high proportion reflects the significant ecological alteration affecting rivers and wetlands in these basins and underscores the urgent need for management actions to limit the spread of invasive species and reduce their impact on native biodiversity. The most widespread IAS were the bleak (A. alburnus), mainly in the Júcar basin, and the mosquitofish (G. holbrooki), predominantly in coastal wetlands. Conclusions: This study contributes directly to updating the Atlas of Ichthyofauna of the Valencian Community, providing a robust and current information base to support environmental decision-making at regional and national levels. The findings highlight the importance of strengthening proactive conservation measures, particularly in areas where biodiversity is most vulnerable.

Proceedings doi: 10.3390/proceedings2026146045

Authors: Rafael Miranda Javier Oscoz Felipe Morcillo Frederic Casals Andrea Pino-del-Carpio Silvia Perea

The Iberian Peninsula hosts one of the world’s most endemic fish faunas. Its extensive evolutionary, palaeogeographic, and geological history has produced a distinctive freshwater fish fauna. Many of these species have very limited distributions, making them especially vulnerable to habitat disturbance. Past monitoring of this biodiversity has revealed alarming results, indicating that most native Spanish species are at risk. The causes of this serious situation are varied and reflect the ongoing deterioration of freshwater ecosystems. The main pressures faced by populations include pollution, loss of river connectivity caused by hydraulic infrastructure, regulation of watercourses, water extraction, fishing, and the presence of invasive species. Additionally, the effects of climate change worsen the risk of extinction for these populations, particularly through the increased frequency and intensity of droughts and heatwaves. It is evident that current planning models and investments are inadequate to conserve freshwater fish. To prevent the extinction of many populations in Spain, especially Iberian endemics, it is crucial to change the management of aquatic ecosystems and adopt integrated solutions that halt population declines and promote the sustainable use of aquatic resources. The IUCN Red Lists of Threatened Species are vital indicators of biodiversity health and are widely used to guide and structure conservation efforts. These lists, published in the Red Books, result from a thorough evaluation process that employs specific categories and criteria to assess the extinction risk of species, both globally and regionally. This report presents preliminary findings from a monitoring study on the current state of freshwater fish in Spain. The monitoring results reveal that, based on IUCN assessment criteria, two species are classified as extinct (EX), four as critically endangered (CR), eighteen as endangered (EN), and twenty-one as vulnerable (VU). Of fifty-seven species documented, 79% are considered threatened. The project’s final outcome is the development of the Atlas and Red Book of Freshwater Fish of Spain. This resource includes the main native and invasive freshwater and diadromous fish species, offers detailed information on their biological and ecological traits, and provides an up-to-date inventory of records along with an assessment of their conservation status.

Proceedings doi: 10.3390/proceedings2026146040

Authors: Matilde Moreira-Santos Laura Guimarães Cristiano V. M. Araújo

Introduction: The rationale of traditional toxicity assessments, such as fish lethality tests (e.g., OECD TG 203), is to use forced exposure tests to characterise the ecotoxicity of chemicals by deriving concentration–response relationships based on observed physiological effects to estimate environmental risks. This approach assumes that physiological mechanisms, such as detoxification, are the main means that organisms use to minimise contamination effects. However, non-forced exposure approaches, where organisms can freely move along a contamination gradient, show that mobile species like fish can avoid adverse contaminant levels and escape to favourable areas. As populations are exposed to disturbed habitats, direct ecosystem-level effects may occur through population downsizing, even in the absence of individual suffering. Contaminants may thus act as habitat disturbers, regulating fish dispersion patterns by provoking emigration from contaminated areas at concentrations well below lethal levels. Spatial avoidance responses therefore align with a key priority in environmental risk assessment (ERA): progressing beyond standard tests to gain ecological realism when assessing impacts on biodiversity, habitats, ecological processes and recovery. Objective: To increase ecological relevance in ERA while halting animal distress, pain and suffering. This study reviews existing data on fish avoidance tests, with the ultimate goal of discussing their value and fostering their implementation as an ecologically relevant and more humane alternative to fish lethal testing in chemical ERA. Methodology: This review analyses results from studies using two main non-forced multi-compartment exposure systems: linear systems and the bi-dimensional HeMHAS (Heterogeneous Multi-Habitat Assay System), compared with traditional forced exposure tests. Conclusions: Spatial avoidance is generally triggered after short exposure periods (5 min to 48 h) at concentrations causing no mortality. Fish populations may therefore become locally extinct before any deaths occur, as individuals promptly emigrate without physiological impairment. The simplicity of experimental design provides strong potential for standardisation and routine implementation in ERA. Fish avoidance tests represent a key ecologically relevant tool at ecosystem and landscape levels and support the 3Rs (replacement, reduction and refinement) as well as the new 3Rs (reproducibility, relevance and regulatory applicability), helping reduce uncertainty in chemical assessment, as urged by many EU legislations.

Proceedings doi: 10.3390/proceedings2026146037

Authors: Ana Hernández Felipe Martínez-Pastor Fátima Gil Carla Sousa-Santos Elsa Cabrita Victor Gallego

Introduction: Populations of freshwater fish species of the Iberian Peninsula have been declining since the mid-20th century, and several types of actions (from in situ to ex situ actions) have been applied over the past decades. However, limited knowledge about their reproductive biology makes it necessary to investigate different aspects of the reproductive cycle for improving breeding programs. Objective: The main objective of this work was to advance knowledge in the sperm biology of two endemic fish from Portugal rivers, trying to check whether breeding in captivity is a factor able to modulate sperm subpopulations. Methodology: Populations of different endangered leuciscid species (Iberochondrostoma lusitanicum, IL, and Achondrostoma occidentale, AO) were sampled during the spring of 2022 both in captive populations kept at Aquário Vasco da Gama (AVG) and in wild populations (WILD) from different Portuguese rivers. Sperm samples were collected, and sperm motion parameters were assessed by using a CASA system (VSL, VAP, STR, LIN, WOB, ALH and BCF). Results: The application of a two-step cluster analysis yielded four sperm subpopulations (SP1, SP2, SP3 and SP4) in both species. SP1 comprised fast, linear spermatozoa (high VCL, LIN, STR). SP2 contained slow linear cells (low VCL, high LIN, STR). SP3 included fast nonlinear spermatozoa (high VCL, low LIN, STR). SP4 represented slow nonlinear cells, with low values for all three kinematic parameters. Regarding the origin of fish (wild and captive), and for both species, WILD leuciscids showed higher values of linear and fast sperm subpopulation (SP1) than captive fish (AVG), which showed a higher percentage of non-linear subpopulations (SP3 and SP4). Conclusions: In this context, and given that fast and linear spermatozoa (SP1) have traditionally been correlated with high fertilization success in many fish species, these results may indicate that breeding in captivity over a long period of time may affect gamete quality, making it necessary to renew the broodstock from time to time to avoid reproductive problems (i.e., loss of sperm quality and cases of inbreeding).

Proceedings doi: 10.3390/proceedings2026146035

Authors: Mafalda Fernandes Nuno Gomes Carlos Antunes

Introduction: Estuaries are among the most productive ecosystems in the world, holding great ecological and economic importance. As transitional zones between rivers and the sea, they experience abrupt abiotic changes linked to the tidal cycle, as well as seasonal changes related to greater river discharge during periods of higher rainfall. Therefore, salinity and temperature are key factors in structuring communities. These estuarine areas are recognized as nursery grounds, offering an abundance of food and shelter from predators, which creates ideal conditions for juvenile growth. Objective: Intense heatwaves were recorded in northern Spain during 2021 and 2022. This study aimed to understand how environmental factors influence the daily and seasonal dynamics of epibenthic communities and to compare these results with those obtained 40 years ago. Methodology: The epibenthic community in the Minho River estuary was assessed between September 2021 and August 2022 during spring tides at both low tide and high tide. Five trawls were carried out at each tide using a 2-meter-wide beam trawl. Several physical and chemical parameters were evaluated during the sampling process. Results: A total of 10,527 demersal fish and epibenthic crustaceans belonging to 21 species were caught in the sampling area. The structure of epibenthic assemblages was heavily influenced by tidal regimes. Assemblages at low tide had a greater number of taxa. In contrast, high-tide assemblages exhibited significantly higher diversity and evenness. Significant differences were observed between the spring/summer and winter assemblages. A SIMPER analysis revealed that Carcinus maenas contributed most to assemblage dissimilarity, both seasonally and by tide. Furthermore, Echiichthys vipera and Platichthys flesus were the species that contributed most to assemblage dissimilarity in both 1982 and 2021–2022. Conclusions: Compared with historical data, the rise in temperature and salinity, coupled with reduced water flow, has caused a profound restructuring of benthopelagic communities. This is driven by a significant increase in the marine character of the habitat. Substantial taxonomic turnover is evident, characterized by reductions in abundance and increases in the number of taxa sampled, as well as in diversity and evenness.

Proceedings doi: 10.3390/proceedings2026146034

Authors: Miguel Macário João Gago Vanda Andrade Paula Ruivo Maria Oliveira João Oliveira Filipe Ribeiro Abigail Lynch

Introduction: Professional inland fisheries in Portugal remain poorly characterized despite their ecological, social, and territorial relevance. Objective: The objective of this study is to examine the evolution of the biomass catched by inland professional fisheries and determine its economic value. Methodology: This study examines the evolution of declared biomass between 2012 and 2024 and estimates the market relevance of this activity using official catch declarations submitted to the national licensing authority (ICNF). Records were harmonized by species and water body and subsequently aggregated at hydrographic basin level to identify long-term temporal and spatial patterns. Economic estimation was based on a gross production approach combining declared biomass with species-specific price information collected from retail channels and reports from professional fishermen. Changes in species composition were also analyzed to assess whether the observed trends reflect a broader restructuring of freshwater exploitation. Results: The results show a marked interannual variability and a strong spatial concentration of catches, with a limited number of basins (international rivers) accounting for most reported biomass. They also reveal the increasing prominence of non-native taxa in total catches; particularly, the red swamp crayfish, while native migratory species, although represented by lower volumes, maintain high unit prices and make a relevant contribution to total revenue. This contrast suggests that recent changes in freshwater catches are not merely quantitative, but also structural, with implications for ecological status, the growing dependence of the fishery on invasive species, and the territorial distribution of economic returns. Conclusions: By combining official catch declarations with market-based valuation, this study provides an updated overview of the recent evolution of professional freshwater exploitation in Portugal and offers a useful basis for fishery governance, monitoring programmes, and future discussions on conservation, licensing, and basin-scale management.

Proceedings doi: 10.3390/proceedings2026146031

Authors: Rafael Schroeder Esteban Avigliano Alejandra V. Volpedo Roberta Callico Fortunato Rodrigo Sant’Ana Martin C. Dias Felippe A. Daros Pedro M. Barrulas José A. Mirão Alberto T. Correia

Introduction: The Lebranche mullet (Mugil liza) is a commercially important fish species in southeastern and southern Brazil, which serves as the primary spawning ground for the Southern stock that supports the Brazilian industrial seine fleet. However, this stock’s distribution extends into Argentine waters (northern Patagonian shelf), and the connectivity between mullets caught in Brazil and their breeding areas across South America remains poorly understood. The authors hypothesized that adult mullets landed by the Brazilian fleet consist of two distinct groups: A local group originating in Brazilian waters (BR1) and a migratory group (BR2) that uses nursery areas in Argentina (AR). BR2 presumably returns to its original nursery grounds after spawning, to recover reproductive tissues, following a different migratory pattern than BR1. Objectives: To test this, the study analyzed the micro-chemical life history of 134 otoliths from mullets aged 0+ to 11 years using LA-ICP-MS. Methodology: Two elemental ratios (Ba/Ca and Sr/Ca) were measured from the otolith core to the edge and modelled using a generalized additive model for scale and shape (GAMLSS). Life history transitions were evaluated by pairwise comparisons of fitted values among ages. Results: GAMLSS showed that Ba/Ca ratios differed significantly among groups (AR ≠ BR1 ≠ BR2). In contrast, Sr/Ca ratios were similar between AR and BR2 during the first four years of life, significantly differing from those of BR1. Using empirically established thresholds for estuarine vs. marine habitats, the study determined that BR2 individuals leave nursery areas between ages 5 and 6, migrate back around age 8, and live there one last time after age 10 (the species’ maximum age). BR1 leaves nurseries after age 4 and returns between ages 5 and 6, exhibiting a shorter reproductive cycle. Importantly, the analysis of reproductive tissue mass showed that the weight after age 7 approximately matched the weight at age 3. After recovery, reproductive tissues doubled in weight before the second migration to spawn at sea. Conclusions: These findings provide crucial insights into M. liza’s life cycle, highlighting the need for shared stock management not only with neighboring nations (Argentina and Brazil) but also on a regional scale.

Proceedings doi: 10.3390/proceedings2026146029

Authors: Juan M. Molina Andreas Kunzmann Rita A. Costa Teresa Modesto Alexandra Alves Pedro M. Guerreiro

Introduction: Coastal fishes can adapt to water warming and hypoxia; however, acute tolerance does not necessarily predict longer-term performance and survival. This may be especially important in sedentary, site-faithful species with limited escape to escape increasingly unfavorable habitats. We assessed the climate-related stress responses of the Lusitanian toadfish, Halobatrachus didactylus, a benthic estuarine fish from the Northeast Atlantic, to water warming and hypoxia. Objectives: We aimed to determine the aerobic energy budget, thermal limits (CTmax), and critical oxygen tension (Pcrit), as well as blood indicators of metabolism, altered physiology and systemic stress, as proxies for whole-organism homeostatic state, thereby informing future ecophysiological assessments and bioindicator development in a context of environmental change. Methodology: We determined standard, routine, and maximum metabolic rates; aerobic scope; and critical thermal maximum (CTmax) and critical oxygen (Pcrit) thresholds on a set of 134 individuals ranging from 12 to 160 g in weight. On a different set of individuals (n = 48; 76.3 ± 2.6 g; 16.1 ± 0.18 cm), we simulated 30 days of seasonal scenarios combining low and high temperature with normoxia or hypoxia, followed by integrated metabolic, hematological, biochemical, and multivariate analyses. Results: Acute trials showed high short-term resilience: H. didactylus had an exceptionally low standard metabolic rate and routine metabolic rate, high CTmax (34.82 ± 0.66 °C), and strong hypoxia tolerance (Pcrit 0.59–1.97 mg O2 L−1), although smaller individuals were more sensitive. After 30 days, however, warming more than doubled standard and routine metabolic rates, while warm hypoxia reduced metabolic output relative to warm normoxia, consistent with metabolic depression under compounded stressors. This treatment also showed shifts in glucose, liver mass, red blood cell count, and hematocrit, identifying warm, oxygen-poor water as the most physiologically costly scenario for this species. Conclusions: Together, these results show that high acute tolerance does not guarantee resilience to climate change. In sedentary fishes, survival may depend less on surviving extremes than on maintaining energetic balance, oxygen transport capacity, and physiological homeostasis in increasingly warm, oxygen-poor coastal habitats.

Proceedings doi: 10.3390/proceedings2026146042

Authors: Renan Leite Filipe Romão Isabel Boavida José Maria Santos Paulo Branco Ana Quaresma

Introduction: Freshwater ecosystems are among the most threatened worldwide, with river fragmentation, primarily caused by dams and weirs, identified as a major driver of biodiversity loss. This issue is particularly acute in Europe, where more than one million instream barriers disrupt longitudinal connectivity and compromise the movement of migratory fish. Fishways are widely implemented to mitigate these impacts, yet attraction efficiency at fishway entrances remains poorly understood, especially for Iberian potamodromous cyprinids, a group facing severe conservation pressures. Objective: This study aims to investigate how hydraulic conditions and social context influence the attraction and passage behavior of Luciobarbus bocagei, a rheophilic potamodromous cyprinid endemic to the Iberian Peninsula, in an experimental Vertical slot fishway (VSF) entrance. Methodology: Experiments were conducted in a controlled flume equipped with a VSF entrance design. Two hydraulic scenarios were tested, a Low Head Drop (LD) and a High Head Drop (HD), under a constant discharge of 34 L/s. A computational fluid dynamics (CFD) model was used to characterize and compare the flow field hydrodynamics. Fish were tested individually and in groups of three to assess the role of social dynamics. The metrics collected included time to first approach, first attempt, time to first successful passage, attraction efficiency, and passage efficiency. Cox proportional hazards models were applied to evaluate treatment effects. Results: Preliminary results showed that social context influenced fish attraction behavior. In the two hydraulic scenarios, individuals tested alone tend to exhibit lower likelihoods of approaching, attempting, and successfully negotiating the fishway compared to fish in schools. Delays were also evident for attempts and successful passages, with LD_Ind performing the worst. Conclusions: These findings highlight the importance of hydraulic conditions and social behavior in shaping attraction efficiency. They underscore the need to integrate species-specific behavioral ecology into fishway design, operation, and attraction assessment, acknowledging that fish attractivity is influenced by environmental and ecological factors beyond fishway structure, particularly in Mediterranean river systems where fragmentation pressures are high and potamodromous cyprinids are at risk.

Proceedings doi: 10.3390/proceedings2026146027

Authors: Sandra Barca Rufino Vieira-Lanero Fernando Cobo Carlos M. Alexandre Pedro R. Almeida Esmeralda Pereira Silvia Pedro Gonçalo Rodrigues Luís Macedo Luís Silveirinha Gonçalo Brás Beatriz Mendes Célia Laranjeira Luísa Sousa Pedro Marques Isabel Pragana

LIFE REVIVE aims to restore ecological status and ecosystem services in the Lima and Vouga river basins (NW Iberian Peninsula), where hydromorphological alteration and hydropower-driven flow regulation are major causes of water bodies failing to reach Good Ecological Status under the EU WFD. The project targets key pressures such as longitudinal fragmentation by weirs and dams, artificial flow regimes, degradation of spawning substrates, and the spread of invasive aquatic plants, which strongly affect fish communities, including sea lamprey, salmonids, and other diadromous species. Technically, the project combines barrier removal or eco-adaptation, nature-like fish passes, and spawning-habitat renaturalisation with optimized environmental flow regimes (EFR) downstream of important hydropower systems, explicitly accounting for present and future hydroclimatic scenarios. Multi-scale ecohydrological modelling (species distribution models, habitat suitability models, GLM/GAM approaches) will quantify fish–flow–habitat relationships and support the definition of operational EFR guidelines that balance ecological requirements with hydropower and agricultural constraints through joint work with the main Portuguese hydropower operator, EDP. Impact evaluation is structured around a rigorous BACI monitoring design in intervention and control tributaries, using standard WFD biological indices for fish and aquatic/riparian vegetation, hydromorphological indices (HQA, HMS, RHS), and project-specific Key Performance Indicators for water quality, biodiversity, and habitat. Expected outcomes include the restoration of at least 51 km of rivers towards free-flowing conditions, reduced hydromorphological pressure in more than 20 km of heavily modified river stretches, and measurable increases in the distribution and abundance of fish species and native vegetation. A strong communication and capacity-building programme underpins public engagement, while a decision matrix for barrier prioritization, technical workshops, and pilot replications in additional basins (e.g., Alva, Mouro, Deva, and Tea in Galicia) are designed to maximize transferability, policy uptake, and long-term sustainability of the solutions beyond the project lifetime.

Proceedings doi: 10.3390/proceedings2026146047

Authors: Felippe A. Daros Kauan F. Xavier Estella R. S. Santos Priscila Capizani Arthur Q. Diniz Wanilton P. Batista Marina Paixão Gil Julia P. Altafin

Introduction: The Cananéia–Iguape Lagoon Complex, part of the Lagamar Mosaic of Conservation Units, comprises interconnected ecosystems that facilitate the dispersal and exchange of larvae, juveniles, and adults across habitats. This connectivity is a vital ecological process, driving the demographic linkage of local populations. Due to its commercial importance and abundance, the fat snook (Centropomus parallelus) serves as an ideal model for connectivity studies in this region. This study evaluated the otolith fingerprints of fat snook nursery areas within an estuarine complex using elemental chemical signatures. Methodology: Otoliths from 24 juveniles (n = 6 per site) were sampled across four nurseries: Ariri (AR), Itapanhapima (IT), Subauma (SU), and Iguape (IG). Multi-elemental signatures (Na, Mg, P, K, Ca, Mn, Sr, Ba, and Pb) at the otolith edge were measured via Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Results: Multivariate analysis (PERMANOVA, p < 0.05) revealed significant chemical differences between nurseries, corroborated by pairwise tests. Canonical Analysis of Principal Coordinates (CAP) with leave-one-out cross-validation successfully assigned individuals to their collection sites with accuracies of 55% (AR), 72% (IT), 94% (SU), and 88% (IG), achieving a 78% global reclassification rate. CAP results distinguished two primary groups: the southern nurseries (AR/IT) and northern nurseries (SU/IG). This spatial separation was primarily driven by Sr:Ca and Ba:Ca ratios, reflecting the higher marine influence in the south versus freshwater input from the Ribeira de Iguape River in the north. Conclusions: These findings provide critical data to support public policies for the conservation of coastal ecosystems and the management of associated fish stocks.

Proceedings doi: 10.3390/proceedings2026146022

Authors: Paulo Branco Pedro Segurado José Maria Santos Maria Teresa Ferreira Daniel Mameri Tamara Leite António Tovar Faro Gonçalo Duarte

Introduction: Freshwater systems are increasingly being impacted by a plethora of pressures. Freshwater fish are thus periled, urging the need to investigate the drivers of population decrease to better counteract them, in order to provide some conservation relief to these pressured species. Methodology: To facilitate freshwater research, the Dammed Fish Project developed a series of free tools that simplify procedures and facilitate the access of correct data. Results: RivTool+ is a free software that evolved from RivTool (used in over 75 countries) and that integrates new functions and acts as a tool hub to host additional software apps. The computing engine of RivTool, that allows along the river network calculations and summarizations, is now able to be used by new tools. RivConnect—River network connectivity app that allows graph-based quantification of structural and functional connectivity, using several metrics and understanding network directionality. RivFish—App that contains the corrected, spatially and taxonomically, occurrence, at the basin and sub-basin level, of more than 600 native freshwater fish species of Europe. RivOpt—Optimization tool that allows for river network connectivity restoration optimization. RivOpt accounts for conflicting multiple objectives and is able to deal with different restoration actions for each barrier (removal, partial removal, fishway construction and retrofitting or no action). Conclusions: Dammed Fish tools facilitate research procedures and access to verified data, improving the information baseline, increasing the accuracy of results and accelerating research. Thus, it contributes to an improved understanding of the mechanisms controlling species vulnerability and contributes to their conservation.

Proceedings doi: 10.3390/proceedings2026146028

Authors: Filipe Romão Ana L. Quaresma Susana D. Amaral Renan Leite Isabel Boavida Francisco J. Bravo-Córdoba Francisco J. Sanz-Ronda António Pinheiro José M. Santos

Introduction: The restoration of river connectivity through fishways is essential for the conservation of native freshwater fish, yet it may inadvertently facilitate the upstream spread of non-native invasive species. This trade-off is particularly relevant in Iberian river systems, where invasive cyprinids pose a growing ecological threat. Objective: In this study, we evaluated the potential for selective fish passage in a full-scale vertical slot fishway (VSF), aiming to promote native species movement while limiting invasive taxa. Methodology: Experimental trials were conducted with the common carp (Cyprinus carpio), a widespread invasive species, and the results were compared with those of the native Iberian barbel (Luciobarbus bocagei). Two fishway configurations were tested, both with high slope (15.2%) and high turbulence (volumetric power dissipation >150 W m−3), differing in water depth (0.55 m and 0.80 m). Fish passage performance was assessed through behavioural metrics, including motivation to attempt passage, ascent success, and transit time, using a time-to-event framework. Hydrodynamic conditions were characterised through computational fluid dynamics modelling. Results: The results revealed marked interspecific differences. Common carp exhibited significantly lower motivation to initiate passage and extremely limited success: no individuals ascended the shallower configuration, and only one ascended the deeper configuration. In contrast, Iberian barbel demonstrated high motivation and passage success under both configurations, particularly in more turbulent conditions. Conclusions: These findings suggest that manipulating key hydraulic parameters can create selective passage conditions that favour rheophilic native species while hindering limnophilic invasive taxa. This ecohydraulic approach offers a promising strategy to reconcile the restoration of longitudinal connectivity with the control of biological invasions. Nevertheless, further research under field conditions and across a broader range of species is required to validate and generalise these findings.

Proceedings doi: 10.3390/proceedings2026146021

Authors: Ana Quaresma Susana D. Amaral Rui Rivaes Diogo Dias Diogo Ribeiro Filipe Ribeiro Isabel Boavida Filipe Romão

Introduction: Freshwater ecosystems are increasingly threatened by river fragmentation caused by the accumulation of small barriers such as weirs. These structures disrupt longitudinal connectivity and hinder fish movements, restricting access to essential habitats (e.g., spawning) and affecting biodiversity and ecological river functions. Though many of these structures are obsolete and their removal is increasingly promoted as a river restoration measure under the EU Biodiversity Strategy and the Nature Restoration Law, the ecological implications of barrier removal are not totally positive. One of the most pressing concerns is the unintended spread of Invasive Alien Species (IAS), which may expand upstream once a barrier is eliminated. In this context, selective barriers are gaining attention as a promising management tool to balance ecological restoration goals with IAS control. By carefully designing or adjusting hydraulic features such as head drops, it may be possible to allow passage for native species while restricting the movement of invasive fish. However, despite its potential, selective barrier design remains underexplored. Objective: This research aims to address this gap by testing how head drops influence the upstream movement of Iberian straight-mouth nase (Pseudochondrostoma polylepis), a native leuciscid, and the European perch (Perca fluviatilis), an IAS rapidly expanding across the Iberian Peninsula. Methodology: Laboratory experiments were conducted in an indoor ecohydraulic flume (6.5 × 0.7 × 0.7 m) at the Hydraulics Laboratory of IST. A single weir structure whose downstream water level was adjusted to create three distinct head drops—11, 18, and 25 cm (configurations A, B, and C, respectively)—was tested. Tests were performed using one specimen of each species that were allowed 15 min acclimation to the flume conditions followed by a 60 min trial. The number of approaches, attempts and successful upstream passages were recorded. Additionally, the flow-field characterization was performed using an Acoustic Doppler Velocimeter (ADV; Nortek-AS Vectrino 10 MHz). Results: Preliminary results indicate a strong capability of the native nase to overcome two of the tested head drops, with four and two successful passages recorded for configurations A and B, respectively. In contrast, the invasive species showed no successful passages under these conditions. For configuration C, no successful passages were observed for either species. Conclusions: These results highlight the potential of selective weir designs to promote river connectivity for native species while helping prevent the upstream expansion of invasive fish.

Proceedings doi: 10.3390/proceedings2026146033

Authors: Emanuel Santos Sílvia F. Gregório Rita A. Costa Juan M. Molina Pedro M. Guerreiro

Introduction: Climate warming and drought are intensifying thermal stress in Mediterranean freshwater systems, potentially favoring invasive fish with broad physiological tolerance. Extended environmental tolerance and increased aerobic scope are indicative of the potential to sustain, perform and disseminate in challenging conditions. Objective: We aimed to determine the thermal scope of the invasive Australoheros facetus inhabiting southern Portuguese drainages using an array of physiological proxies. Methodology: We evaluated the thermal biology of the species across a wide temperature gradient to test how warming affects metabolic performance, thermal tolerance, and biochemical status. Fish collected from Algarve watercourses were exposed to 5, 10, 15, 20, 25 and 35 °C (n = 15 per condition, 10–60 g) for at least a week, and intermittent respirometry was used to determine standard metabolic rate (SMR), maximum metabolic rate (MMR) and aerobic scope (AS). Group Q10 was derived from metabolic rates. Plasma and tissue biomarkers of energy metabolism and oxidative stress were analyzed. Critical thermal maximum (CTmax) was assessed in fish acclimated for a week at 10, 20 and 30 °C (n = 10) using a 1 °C/min thermal ramp. Results: Intermediate temperatures (15–25 °C) supported the best overall physiological performance, combining stronger aerobic capacity with higher antioxidant protection. In contrast, 30–35 °C imposed clear physiological costs: maintenance metabolism increased disproportionately, aerobic scope declined, and cellular protection weakened, indicating the onset of heat stress. Despite this, A. facetus showed marked thermal plasticity, with CTmax increasing significantly with acclimation temperature. Fish acclimated to 30 °C had higher CTmax than fish acclimated to 20 °C and 10 °C, although the thermal safety margin decreased progressively as the acclimation temperature rose. Liver antioxidant activity also peaked at intermediate temperatures and declined at the warmest treatments, reinforcing the mismatch between acute tolerance and sustained performance. Conclusions: These results show that A. facetus is highly heat tolerant but that tolerance comes with energetic and cellular trade-offs near upper thermal limits. Despite this limitation at extreme conditions, the combination of broad tolerance and functional performance under warm intermediate conditions may help to explain its invasion success and stand as a competitive advantage in increasingly hot low-flow Iberian freshwater ecosystems.

Proceedings doi: 10.3390/proceedings2026146020

Authors: Cristina Igartua Francisco Baldó Ignacio Ruiz-Jarabo

Introduction: Sharks are key species in marine ecosystems, and their conservation is a priority across European waters. However, several fisheries unintentionally capture sharks as bycatch, raising concerns about their post-capture survival. In the Gulf of Cadiz, demersal trawl fisheries frequently capture the catsharks Galeus atlanticus and G. melastomus. Objective: This study aimed to assess the short-term survival rates of these two species following trawl capture and to identify potential blood biochemical markers predictive of survival. Methodology: Fieldwork was conducted aboard an oceanographic research vessel over two spring seasons. Standarized demersal trawl hauls of 1-h duration were performed. Immediately after capture, individuals were transferred to onboard seawater tanks, where their recovery was monitored for 24 h. Blood samples were collected at two time points: immediately after capture and after the 24-h recovery period. Biochemical parameters associated with secondary stress responses were analyzed. Results: Survival rates were high for both species, reaching 88 ± 8% for G. atlanticus and 90 ± 4% for G. melastomus. Blood analyses indicated a clear physiological recovery in all surviving individuals after 24 h, evidenced by the normalization of stress-related parameters. Notably, interspecific differences were observed in certain biochemical markers after capture, including amino acids and lactate concentrations, suggesting species-specific responses to capture stress. Conclusions: These findings provide valuable insights into the resilience of demersal catsharks to trawl-induced stress and highlight the potential of blood biomarkers as a tool for predicting post-capture survival. The results support the development of evidence-based onboard handling protocols aimed at maximizing the survival of incidentally captured sharks. Such measures can contribute to more sustainable fisheries management and the conservation of vulnerable elasmobranch species in European waters.