Search Results (2,698)

The Sugars Will Eventually be Exported Transporters (SWEET) family plays a crucial role in the carbohydrate distribution, phloem loading, and stress response of plants, yet the evolutionary characteristics and functional diversification of SWEET genes in the endangered timber species Phoebe bournei (Hemsl.) Yen C. Yang remain largely unexplored. In this study, 21 PbSWEET genes were identified and classified into four subfamilies (A-D). Subfamily A exhibited a unique lineage expansion, mainly driven by tandem and segmental duplications. The nonsynonymous-to-synonymous substitution ratio (Ka/Ks) values of all duplicate gene pairs were all less than 1, indicating a strong selective suppression effect; consistent with this evolutionary constraint, the majority of PbSWEET proteins harbor the conserved Medicago truncatula Nodulin 3/saliva (MtN3_slv) domain, with only a few exceptions lacking a complete version. Promoter and hormone response analyses revealed that under abscisic acid (ABA) stress, PbSWEET4 exhibited an immediate burst, whereas PbSWEET10 showed a delayed burst. Physiological data indicated that soluble sugars may be more dominant osmolytes than proline (Pro), a pattern that points to a potential carbon-centric regulatory strategy. PbSWEET4 showed an early burst before sugar/oxidative peaks, suggesting a possible non-canonical signaling role, whereas PbSWEET10 exhibited a late increase coinciding with sugar/malondialdehyde (MDA) peaks, suggesting potential involvement in sugar redistribution. Under methyl jasmonate (MeJA) treatment, PbSWEET10 was rapidly induced, yet sugar accumulation occurred only at 24 h, a temporal decoupling that suggests a possible transcription–metabolism decoupling. Collectively, these correlative patterns point to a possible dual-wave transcriptional mechanism and nominate PbSWEET10 as a candidate for stress response, though these inferences require functional validation. 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

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. Full article

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. Full article

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. 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

Gallotia simonyi and G. bravoana are large lacertids inhabiting the islands of El Hierro and La Gomera, respectively, in the Canary Archipelago. Both species are critically endangered, but over the last several decades, they have been bred in outdoor terraria (G. simonyi since the 1990s and G. bravoana since 2000). In this study: (1) we describe all procedures carried out in the breeding centres and quantitatively analyse the long-term trajectory of breeding success throughout the study period; (2) we examine whether any parental individuals or specific pairs had a stronger influence on the number of successfully hatched offspring; (3) we report the trials of reintroducing individuals into the wild on each island in different years; (4) we provide information on several predator (cat-control) campaigns conducted on each island; (5) we detail the veterinary protocols and the results obtained when assessing the health status of breeding lizards; and (6) we report several educational activities carried out on each island. Gravid females laid eggs in suitable laying boxes; the eggs were then kept inside incubators with controlled temperature and humidity until hatching. Breeding produced 1267 offspring during the years considered for G. simonyi and 499 for G. bravoana. The mean NEL was 8.8 for G. simonyi and 5.2 for G. bravoana, and the mean HO was 6.4 and 3.54, respectively. Both NEL and HO were significantly higher in G. simonyi than in G. bravoana. NEL was significantly influenced by species and year, and by female snout–vent length (SVL) as a covariate, but not by male SVL. HO was significantly affected by year and by both male and female SVL, but not by species. There were significantly higher or lower values of both variables in specific years, but no clear long-term trend. Some breeding pairs had a greater influence on the dependent variables. Reintroduction into the wild has resulted in a currently stable population of G. simonyi on a small islet off the north-western coast of El Hierro, and some individuals are still present at an inland reintroduction site. For G. bravoana, some live specimens have recently been detected at a new reintroduction site. We conclude that: (1) captive breeding has been successfully carried out over the years in both centres; (2) there have been significant differences between the two species in NEL and HO; (3) female SVL was significantly related to both NEL and HO; and (4) reintroduction attempts have been only partially successful in each species. Veterinary monitoring revealed high dehydration tolerance, seasonal fluctuations in microbial flora, previous mineral imbalances that were corrected by improved nutrition, and effective parasite control that maintained overall lizard health. Except for a few individuals, most lizards were in good health. Full article

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. Full article

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). Full article

Mitochondrial genomes are widely used in insect taxonomy and phylogenetics, but their signals may conflict with morphology and nuclear genomic evidence because the mitochondrial genome represents a single maternally inherited locus. Here, we assembled complete mitochondrial genomes of four pygmy grasshoppers, Zhengitettix transpicula, Formosatettix sp., Gibbotettix parvipulvillus, and Bolivaritettix sp., using PacBio HiFi reads. The four mitogenomes ranged from 15,152 to 17,976 bp and contained the typical 37 mitochondrial genes. Mitochondrial phylogenies inferred by maximum likelihood and Bayesian methods were topologically identical and recovered several well-supported tetrigid relationships, including a close relationship between Formosatettix sp. and Bolivaritettix sp. However, Z. transpicula was unexpectedly placed near Macromotettixoides rather than close to other Zhengitettix representatives. In contrast, a morphology-based tree recovered Z. transpicula with Z. triangularis, and comparison with a published nuclear single-copy ortholog tree based on 1962 loci supported a non-mitochondrial placement of Zhengitettix inconsistent with the anomalous mitochondrial position of Z. transpicula. Independent assembly from the original HiFi reads, read-depth inspection, protein-coding gene checks, and nuclear-genome screening for NUMT-like sequences supported the authenticity of the assembled Z. transpicula mitogenome. These results document mito–nuclear and cyto-morphological discordance in Tetrigidae and highlight the need for integrative interpretation of mitochondrial phylogenies in taxonomically complex insect groups. Full article

Introduction: Otoliths have been widely used in recent years as tracers of fish life history, ranging from visual aging to chemical analyses that reconstruct environmental conditions, migration patterns, and metabolic changes. Yet, Iberian endemic or endangered species are understudied. This study focuses on Andalusian barbel (Luciobarbus sclateri), endemic to the southern half of the Iberian Peninsula. Objective: The aim was to evaluate whether otolith chemical profiles can simultaneously support age estimation and reveal the impact of environmental variations, particularly hypoxia. Methodology: Fish were caught in two sites with different environmental properties, including strong hypoxia: the Guadalquivir estuary and the dock of Seville (which is isolated from the main river channel by a ship lock and could, therefore, be used as a control). Otolith chemical composition was analyzed from core-to-edge transects with a laser-inductively coupled plasma mass spectrometer (LA ICP-MS). Results: Patterns of variation in Mg and Mn in relation to hypoxia and environmental conditions are discussed. We visually counted growth rings in the sections, and we found a strong correlation (R² = 0.904) in Mg:Ca peaks with growth rings. Body condition, assessed using Fulton’s condition factor (K), differed between sites, with fish from the estuary exhibiting a lower condition than those from the dock. Conclusions: The strong correlation between counter growth rings and Mg:Ca peaks suggests that chemical analysis could be used as a valid method for supporting aging. The pattern of lower condition in fish from the estuary is consistent with persistent hypoxic events documented in the estuary but not within the dock environment. This whole approach provides a powerful framework to assess habitat quality and support conservation of L. sclateri in the Guadalquivir estuary. Full article

Gongolaria barbata has undergone a major decline along the Romanian Black Sea coast due to historical winter events of the 1970s and ongoing anthropogenic pressures and is currently listed as Critically Endangered in the Romanian List of Endangered Marine Species, highlighting the need for ex situ culture to support restoration and long-term preservation of this habitat-forming species. This study evaluates how different substrate types (travertine, shale and ceramic) influence early thallus development in G. barbata, and attachment and growth dynamics, and establishes an ex situ culture procedure tailored to Black Sea conditions. Germling-based culture was carried out under controlled conditions, with salinity maintained at 17.1 ± 0.5 PSU and seawater temperature at 19.0 ± 0.8 °C. After 216 days of ex situ culture, thalli reached comparable sizes across all substrates, with mean heights between 5 and 7 cm and maximum values ranging from 12 to over 20 cm. Thallus development progressed steadily across all substrates, each supporting comparable growth, a finding relevant for restoration, aquaculture, and large-scale cultivation. All tested hard substrates sustained early development, with travertine producing slightly more robust thalli and stronger holdfasts, highlighting its potential for future restoration initiatives along the Romanian Black Sea coast. Full article

Climate change and habitat loss pose severe threats to the survival of alpine butterflies worldwide. Parnassius imperator is a rare, endemic, and endangered butterfly in China, yet the spatiotemporal dynamics of its suitable habitats under climate change remain largely unknown. In this study, we applied ensemble species distribution models to simulate the shifts of its current and future suitable habitats, incorporating bioclimatic variables, elevation, normalized difference vegetation index, and human footprint. Results showed that the current suitable habitats cover 185.87 × 10⁴ km² and are concentrated in western China, mainly regulated by elevation, temperature seasonality (BIO4), precipitation of the wettest month (BIO13), precipitation of the warmest quarter (BIO18), and precipitation of the driest month (BIO14). Under future climate change scenarios, suitable habitats will shrink drastically, even to only 82.16 × 10⁴ km² under SSP585 in the 2070s, with nearly a complete loss of highly suitable habitats. In addition, centroid shift analyses reveal that the distribution centroid will shift eastward. Our findings indicate that suitable habitats will contract significantly, and P. imperator will face a sharply increasing risk of extinction in the future. Considering the overlap between suitable habitats and existing nature reserves, we recommend implementing integrated conservation strategies, including expanding protected areas, establishing long-term monitoring programs, restoring habitats, and strengthening law enforcement and public education. This study provides a scientific basis for the climate-adaptive conservation of P. imperator and other vulnerable alpine insects. Full article

Introduction: The upper Arlanza River (Duero Basin, Burgos, Spain) hosts a genetically distinct local lineage of brown trout (Salmo trutta fario), the “Arlanza strain”, largely free from hatchery-derived introgression, alongside other native cyprinids of conservation concern, including the Iberian chub (Achondrostoma arcasii, Vulnerable—IUCN). The river also supports the Iberian desman (Galemys pyrenaicus, Endangered—IUCN) and Eurasian otter (Lutra lutra). Despite these values, the study reach presents multiple transverse obstacles limiting longitudinal connectivity and degraded riparian cover in critical sections due to livestock erosion, compromising habitat quality for all species. Objective: This study aimed to design engineering interventions to improve fluvial and riparian habitat in a 4 km reach of the upper Arlanza River, restoring longitudinal connectivity and thermal refuge availability while strictly preserving the genetic integrity of the native Arlanza trout strain. Methodology: The reach was characterised through electrofishing surveys, riparian quality assessment (modified RQI index), hydraulic refuge evaluation (IR index), and hydrological analysis based on a 30-year flow record. Brown trout population dynamics were modelled using dimP 1.0 software, with a comparative analysis between upstream (Quintanar de la Sierra village) and downstream (Vilviestre del Pinar village) sampling points to identify connectivity bottlenecks. Engineering works were scheduled to avoid reproductive periods of all target species. Results: The upstream population showed a rejuvenated age structure (density: ~1.40 ind/m; mean length: 12.0 cm), consistent with good spawning conditions but limited growth capacity due to cold temperatures and low summer flows. The downstream point exhibited a severely reduced population (~0.10 ind/m), indicating marked loss of connectivity and habitat degradation. Priority intervention zones were identified in the Camping and lower Prado Mayor sub-reaches. Proposed measures included weir notching to restore fish passage, livestock watering points to reduce bank erosion, and riparian restoration by planting native species (Populus tremula, Betula alba, Salix spp.) protected with fences. Conclusions: Restoring longitudinal connectivity and riparian cover in the upper Arlanza River are essential to protect the genetically valuable Arlanza trout strain, the endangered G. pyrenaicus, and other native fish species, providing a transferable framework for headwater fluvial restoration that jointly addresses biodiversity conservation and genetic resource protection. Full article

Introduction: Biological invasions are a major driver of biodiversity loss, particularly in freshwater ecosystems. The Iberian Peninsula, a hotspot of endemic diversity, is increasingly threatened by invasive predatory fish, which may exert higher predatory rates under warmer environmental conditions, disrupting/endangering native fish communities. One such species is the European catfish (Silurus glanis), a large and voracious apex predator. Despite growing research, most telemetry studies have focused on lentic systems, limiting our understanding of its behaviour in lotic environments. Moreover, high-resolution biologging approaches remain largely unexplored. Objective: This study aims to characterize the habitat use and activity patterns of European catfish in a non-native lotic section of the lower Tagus River, and to identify key environmental drivers shaping its predatory behaviour. Methodology: Adult individuals were tagged with radio telemetry transmitters equipped with temperature, pressure (depth), and 3D-accelerometer archival sensors. A preliminary controlled experiment established activity thresholds to classify behaviours. Ten adult fish were then actively tracked over one year, combining spatial data with high-resolution biologging. Habitat use and activity patterns were analyzed across seasonal and circadian scales. Generalized Additive Models (GAMs) were used to assess the effects of environmental variables on activity levels and depth use, while Hurdle models were applied to identify the environmental drivers influencing the occurrence and frequency of burst activity events (predatory behaviour proxies). Results: Fish displayed strong site fidelity, frequently using structured habitats near riverbanks. European catfish also showed clear seasonal and circadian patterns in habitat use and activity, occupying deeper habitats in winter and shallower areas in warmer seasons. Activity occurred year-round, increasing in spring and summer and peaking at dusk, being influenced by temperature, river flow, season, and time of day. Burst activity occurred more often in spring and at dusk. Conclusions: This study unveils insights on European catfish behaviour in invaded lotic systems, highlighting consistent patterns linked to environmental conditions. These findings can support more targeted and effective management strategies for controlling this invasive species. Full article