Search Results (1,440)

This study evaluates the ecological impacts of seawater desalination discharge on coastal marine ecosystems through a sequential analytical framework linking systematic literature synthesis, field-monitoring evidence, spatial analysis, and predictive ecological modeling. The novelty of the study lies in combining multi-regional evidence from Mediterranean coastal zones, Persian Gulf waters, and Pacific coastal environments with threshold-based ecological risk assessment, thereby linking discharge-related environmental stressors with biological responses and ecosystem-function alterations. The systematic review first retained 750 studies published between 2004 and 2024 for qualitative synthesis. On this basis, 59 high-quality references with sufficient numerical information were selected for the main quantitative meta-analysis, while field-monitoring data were used to support the interpretation of distance-based discharge gradients. Spatial interpolation and hierarchical modeling were then applied to evaluate exposure–response patterns and ecological threshold behavior. The results showed that desalination facilities generated measurable ecological impacts mainly within 50–200 m of discharge points, with a critical transition distance of approximately 127 m where hypersaline conditions, typically 1.5–2.0 times ambient seawater levels, were associated with marked changes in marine community structure. Benthic assemblages showed taxon-specific responses, with mollusks and echinoderms exhibiting greater sensitivity than polychaetes and small crustaceans. Marine vegetation declined strongly under combined salinity, thermal, and chemical stress, while phosphonate-based antiscalants accumulated in filter-feeding organisms and produced bioaccumulation factors up to 42.1 times ambient levels. Ecosystem-function indicators, including microbial community composition and sediment organic matter processing, remained altered up to 300 m from discharge points, indicating that functional impacts may extend beyond the primary hypersaline plume. The predictive modeling framework further demonstrated that ecological risk decreased nonlinearly with distance and varied according to discharge intensity, local hydrodynamics, and biological sensitivity. These findings indicate that conventional uniform buffer-based assessment may underestimate the ecological footprint of desalination discharge. Sustainable desalination management should therefore adopt site-specific monitoring, species-sensitive protection thresholds, improved brine-management technologies, and adaptive mitigation strategies based on real-time environmental feedback. Full article

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. Full article

Aquatic and semi-aquatic plant assemblages, water quality, riparian habitat, and landscape conditions were assessed for 140 ponds located in the Ozarks region in Arkansas and Missouri in order to better describe their occurrences and distributional patterns. Local environmental and landscape-level determinants that shape their diversity and influence their respective distributions, particularly in light of urbanization, were also assessed. Ozark ponds are highly variable in terms of physical structure, habitat quality, and plant diversity. Urban ponds were generally of lower quality in terms of environmental attributes compared to those in non-urban areas, but they had similar plant taxa richness as well as numbers of non-native species compared to their non-urban counterparts. Ponds had high plant diversity (N = 204 taxa, $\overline{\mathrm{x}}$ = 9.89, range = 0–33). Taxa richness increased with increasing pond size, and urban ponds had slightly more species on average compared to non-urban ponds (10.38 vs. 9.58, respectively). Spatial beta diversity of plants showed a high dissimilarity among ponds, with turnover being the dominant fraction. Beta diversity also followed a significant distance-decay model. These findings show that urban Ozark ponds serve as important habitats for a broad variety of aquatic plants. Full article

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. Full article

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. Full article

This study evaluates the multi-year taxonomic diversity and functional structure of beetle assemblages (Coleoptera) within Sub Arini Park, a historic urban green space in Sibiu, Romania. Following a preliminary baseline and methodological calibration phase in 2023, systematic monitoring was conducted during the 2024 and 2025 seasonal cycles utilizing standardized pitfall trapping across diverse park zones. We explicitly tested two hypotheses: (H1) that long-standing historic park management preserves a resilient and functional insect community structure, and (H2) that local spatial heterogeneity and microhabitat variations significantly drive species distribution. A total of 14,843 individuals belonging to 39 species were analyzed. While total abundance exhibited a slight decrease from 2024 (N = 7112) to 2025 (N = 6551), true diversity metrics (Hill numbers) revealed a significant increase in raw species richness (q = 0) from 30 to 39 species, alongside an enhanced equity of frequent species (Shannon diversity, q = 1, increased from 4.26 to 5.12). Functional guild analysis and multivariate PCA demonstrated a highly structured biocenotic distribution; specialist and hygrophilous species (e.g., Carabus variolosus Fabricius, 1787) were strictly constrained to high-humidity riparian corridors, whereas thermophilous generalists dominated open lawns under high anthropogenic stress. Our spatial analysis identified critical degradation within these heavily managed zones, specifically driven by intensive mowing, soil compaction, and organic debris removal. These findings confirm both hypotheses, revealing that the park operates as a heterogeneous mosaic of ecological refugia rather than a uniform habitat block. Crucially, this study provides a concrete, quantitative basis—derived from empirical thresholds of species richness, abundance shifts, and mapped microhabitat preferences—for implementing nature-based management strategies (such as establishing buffer zones with reduced mowing frequencies, limiting trampling, and retaining coarse woody debris) aimed at mitigating urban biodiversity loss and maintaining vital biological pest control services in Central–Eastern Europe. Full article

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. Full article

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. Full article

The Jabal Ali Marine Sanctuary, Dubai, is one of the most important marine protected areas (MPAs) in the UAE. The Arabian Gulf is characterised by extreme environmental conditions, including high temperatures and hypersaline waters. These conditions, combined with increasing anthropogenic pressures from coastal development projects such as desalination plants, energy plants and the Palm Jebel Ali development, may influence the pelagic ecosystems of MPAs. This study examined seasonal variability in phytoplankton communities and environmental conditions between summer (June 2017) and winter (December 2017), with particular emphasis on the interactions between temperature-driven stratification, hypersaline conditions, and phytoplankton community structure, abundance, and diversity. The AZTI (AZTI Tecnalia Marine Research Centre) Marine Biotic Index indicated predominantly “Good” to “High” ecological status of the pelagic ecosystem, indicating favourable environmental conditions. Potentially harmful algal bloom taxa, including Pseudo-nitzschia and Dinophysis, were detected at low abundances. Summer surveys recorded higher total species richness (44 vs. 34 species) and greater phytoplankton abundance (mean 68.6 vs. 49.8 cells/L) compared to those in winter. Diatoms dominated the assemblages in both seasons, accounting for 62–69% of the recorded species, while distinct spatial zonation patterns reflected habitat heterogeneity. The observed seasonal and spatial variability highlight the importance of incorporating temporal and spatial dimensions into management strategies. As the first pelagic phytoplankton assessment conducted in an MPA, this study provides important baseline data for understanding phytoplankton ecology in one of the world’s most environmentally extreme marine ecosystems. The findings contribute to evidence-based management under increasing climate change and anthropogenic pressures. However, because sampling was limited to the two principal climatic seasons, the study characterises inter-seasonal variability rather than a complete annual succession cycle. Additional surveys during spring and autumn are recommended to fully resolve seasonal succession dynamics. Overall, the findings support the continued protection of the sanctuary as an important biodiversity reservoir and a potential reference site for assessing marine ecosystem responses to environmental conditions. These findings are directly relevant to the environmental sustainability agenda of the Dubai 2040 Urban Master Plan, which prioritises the protection and expansion of the emirate’s nature reserves and the safeguarding of marine and coastal biodiversity. By establishing the first pelagic phytoplankton baseline for the sanctuary, this study provides an evidence base for monitoring and managing marine protected areas in line with this long-term framework. Full article

Temperate broadleaved forests support diverse arthropod communities, but canopy-dwelling insects in European lime (Tilia cordata Mill.) stands are still poorly known. We surveyed light-attracted canopy insects in six T. cordata Genetic Conservation Units and related protected stands across Lithuania. One modified, solar-powered UV light trap was installed in the canopy (10–15 m) at each site and operated twice per month from June to August in 2023 and 2024. We used diversity metrics, similarity indices, multiple regression, and non-metric multidimensional scaling (NMDS) together with PERMANOVA to examine the structure of insect communities and assess the influence of environmental factors. In total, 6031 individuals representing 295 insect species were recorded, with higher abundance, species richness and Shannon diversity in 2024 than in 2023. Across both years and all sites, Shannon H diversity index ranged from 3.21 to 3.92. Sørensen indices indicated moderate species similarity among sites and distinct species composition at the Ukmergė genetic reserve. The 20 most abundant taxa comprised over 60% of all individuals, and dominance structure changed markedly between years: Serica brunnea dominated in 2023 but was nearly absent in 2024. Regression revealed a significant positive effect of air temperature on insect abundance (about a 31% increase per 1 °C), while precipitation had no significant effect on insect abundance. NMDS and PERMANOVA showed strong spatial structuring, with sites explaining most of the variation, and weaker but significant temporal and site-by-year effects. Overall, insect diversity metrics showed non-significant correlations with T. cordata genetic diversity parameters. Results demonstrate that mature T. cordata forest stands are important reservoirs of canopy insect diversity and highlight pronounced spatial heterogeneity, interannual dynamics, and temperature sensitivity of canopy assemblages in Lithuanian forests. Full article

Marine biological invasions are rapidly reshaping Mediterranean ecosystems, with growing consequences for biodiversity and fisheries. This study investigates recent changes in the composition of commercially important crustacean assemblages along the south-eastern coast of Sicily (central Mediterranean), focusing on penaeid shrimps (Penaeus aztecus and Penaeus kerathurus) and stomatopods (Erugosquilla massavensis and Squilla mantis). Field surveys were conducted during the fishing seasons of 2021 and 2025 at major landing sites and markets (Portopalo di Capo Passero, Syracuse and Catania), using standardized subsampling protocols applied to catches obtained by trammel nets and bottom trawls. Species composition was quantified through repeated sampling events, and temporal differences were analyzed using non-parametric tests and binomial generalized linear models, incorporating year and fishing gear as explanatory variables. Quantitative data were complemented by local ecological knowledge derived from structured interviews with professional fishers. Across the four-year interval, both taxonomic groups exhibited a pronounced shift in species dominance. The proportion of the invasive shrimp P. aztecus increased from approximately 20% in 2021 to over 80% in 2025, while the invasive stomatopod E. massavensis rose from about 2% to nearly 90% of total landings. These changes were statistically significant and independent of fishing gear. Fishers’ perceptions closely mirrored the quantitative trends, confirming the rapid replacement of native species by non-indigenous taxa and highlighting emerging socio-economic implications for local fisheries. Our findings document a rapid shift in the composition of commercial crustacean landings in Sicilian coastal waters, with invasive species becoming the dominant component of catches within a few years. This study underscores the need for adaptive fisheries management and integrated monitoring frameworks capable of responding to accelerating biological invasions in Mediterranean marine ecosystems. Full article

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. Full article

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. Full article

Introduction: A diverse ichthyofauna is supported by the Lima River in northern Portugal. Despite its ecological significance, Ramsar-protected wetlands status and Natura 2000 site, the system remains among the least studied in the Iberian Peninsula. Objective: This study characterises the fish assemblage of the Lima River and some of its tributaries. It examines the composition and abundance of species, as well as key biological parameters, across the river’s freshwater and estuarine sections. Particular attention is given to the balance between native and exotic taxa, and to the threats facing the native ichthyofauna. Methodology: Between 2021 and 2023, 3242 individuals belonging to 15 species were sampled using fyke nets, trammel nets, and electrofishing at 13 sites along the river system. Results: Native species accounted for 51.1% of the total catch. This comprised resident freshwater taxa, such as Pseudochondrostoma duriense, Achondrostoma oligolepis, Luciobarbus bocagei, Squalius carolitertii, Cobitis atlantica, Gasterosteus aculeatus, and resident Salmo trutta, alongside diadromous species, namely Chelon ramada, Petromyzon marinus, Alosa spp., migrant Salmo trutta and Anguilla anguilla. Exotic species accounted for 48.9% of the total catch, with four non-native taxa being recorded: Lepomis gibbosus, Micropterus salmoides, Carassius auratus and Gobio lozanoi. This reflects the extent of the biological invasion pressure on this system. Analysis of the stomach contents of Salmo trutta revealed active predation of non-native species. Plastic debris was detected in 1.1% of Salmo trutta stomachs, which evidences that anthropogenic pollution has reached freshwater feeding habitats. The first recorded instance of the invasive nematode Anguillicola crassus in the Lima River, where 84.8% of the eels sampled exhibited moderate-to-severe swim bladder damage, highlights the vulnerability of native species to biological invasions. Conclusions: Biometric analyses and condition factors suggest that the fish community is under cumulative anthropogenic stress, caused by factors including river fragmentation due to three dams and traditional fishing weirs. The near-equal representation of native and exotic species in catches indicates that the freshwater fish community is under significant invasion pressure, which has direct consequences for the conservation of the native ichthyofauna. These findings establish a crucial baseline for the evidence-based management of an Iberian river system that is ecologically important but data-poor. Full article

Introduction: Elasmobranchs are key components of marine ecosystems but are particularly vulnerable to fishing pressure due to their life-history traits, including slow growth, late maturity, and low fecundity. The Gulf of Cádiz supports a diverse assemblage of coastal and deep-water elasmobranch species, many of which are subject to incidental capture in demersal fisheries. Reliable fishery-independent information on their distribution, relative abundance, and biomass is essential to assess population status and to inform ecosystem-based fisheries management in the northeastern Atlantic. This study aims to provide an updated overview of the composition, relative abundance, biomass, and occurrence of elasmobranch species in the Gulf of Cádiz, contributing baseline information for monitoring and conservation purposes. Methodology: Data were obtained from the ARSA bottom trawl survey carried out in March 2026 using a stratified random sampling design by depth. A total of 45 valid hauls were performed. Results: A total of 29 elasmobranch species belonging to Rajiformes, Carcharhiniformes, Squaliformes, Myliobatiformes, Hexanchiformes, and Torpediniformes were identified. Small demersal sharks and skates dominated the assemblage. Scyliorhinus canicula was the most frequent and abundant species, occurring in 37 hauls and showing the highest mean abundance and biomass. Other recurrent taxa included Torpedo marmorata, Etmopterus spinax, Leucoraja naevus, and Raja clavata. Several species of conservation concern, such as Rostroraja alba, Centrophorus uyato, and Galeorhinus galeus, were recorded at low frequencies and abundances, highlighting their rarity in survey catches. The assemblage reflected a clear dominance of shelf and upper-slope species with occasional captures of deep-water taxa. Conclusions: The ARSA survey provides a valuable snapshot of the current elasmobranch community in the Gulf of Cádiz, confirming the prevalence of small-bodied, benthic species and the low occurrence of large or vulnerable taxa. These results underscore the importance of continued standardized surveys to detect temporal trends and support management strategies aimed at the conservation of elasmobranch diversity in the gulf. Full article