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Swimming performance is a key feature that mediates fitness and survival in aquatic animals. Dispersal, habitat selection, predator–prey interactions and reproduction are processes that depend on swimming capabilities. Testing the critical swimming speed (Ucrit) of fish is the most straightforward method to assess their prolonged swimming performance. We analysed the contribution of several predictor variables (total body length, experimental water temperature, time step interval between velocity increments, species identity, taxonomic affiliation, native status, body shape and form factor) in explaining the variation of Ucrit, using linear models and random forests. We compiled in total 204 studies testing Ucrit of 35 inland fishes of the Iberian Peninsula, including 17 alien species that are non-native to that region. We found that body length is largely the most important predictor of Ucrit out of the eight tested variables, followed by family, time step interval and species identity. By contrast, form factor, temperature, body shape and native status were less important. Results showed a generally positive relationship between Ucrit and total body length, but regression slopes varied markedly among families and species. By contrast, linear models did not show significant differences between native and alien species. In conclusion, the present study provides a first comprehensive database of Ucrit in Iberian freshwater fish, which can be thus of considerable interest for habitat management and restoration plans. The resulting data represents a sound foundation to assess fish responses to hydrological alteration (e.g. water flow tolerance and dispersal capacities), or to categorize their habitat preferences.

We provide a unique fish individual body size dataset collected from our own sampling and public sources in north-eastern Spain. The dataset includes individual body size measures (fork length and mass) of 12,288 individuals of 24 fish species within 10 families collected at 118 locations in large rivers and small streams. Fish were caught by one-pass electrofishing following European standard protocols. The fish dataset has information on the local instream conditions including climatic variables (i.e., temperature and precipitation), topography (i.e., altitude), nutrient concentration (i.e., total phosphorus and nitrates), and the IMPRESS values (a measure of cumulative human impacts in lotic ecosystems). The potential uses of this new fish dataset are manifold, including developing size-based indices to further estimate the ecological status of freshwater ecosystems, allometric models, and analysis of variation in body size structure along environmental gradients We thank all people who participated in the fish sampling and the agencies Agència Catalana de l'Aigua (ACA) and Confederación Hidrográfica del Ebro (CHE) for their help. The original sampling and this study were financially supported by ACA, CHE, and the Spanish Ministry of Science and Innovation [grants ref. RTI2018-095363-B-I00, PID2019-103936GB-C21]

Neotropical Ichthyology promotes the Special Issue (SI) “Human impacts and the loss of Neotropical freshwater fish diversity” with the purpose of publishing relevant scientific articles on the current biodiversity crisis and the loss of Neotropical freshwater fishes in the Anthropocene. The SI is composed of 22 publications, being two review articles and 20 original articles. A total of 107 researchers contributed to these papers, involving 44 institutions based in Brazil and six other countries. Published articles investigated main anthropic activities and their impacts on fish diversity, with special focus on river regulation, mining, land use changes, aquaculture, and fisheries. Studies provided evidence about the loss of fish diversity in the Neotropics, including fish kill events, demographic changes, contamination, changes in assemblage structure, loss of taxonomic and functional diversity, besides the degradation of ecosystem functions and services, and the lack of effective protection and conservation. Studies were conducted in rivers, streams, lakes, and reservoirs from different Neotropical systems. The studies published in this SI represent a relevant sample of the current worrisome situation of freshwater fishes in the Neotropical region and call for urgent revision in environmental policies, management and conservation initiatives, and socioeconomic priorities. Resumo A revista Neotropical Ichthyology lança o Volume Especial (SI) “Human impacts and the loss of Neotropical freshwater fish diversity” com o objetivo de publicar artigos científicos relevantes sobre a atual crise da biodiversidade e a perda de diversidade de peixes de água doce Neotropicais no Antropoceno. O SI é composto por 22 publicações, sendo dois artigos de revisão e 20 artigos originais. Um total de 107 pesquisadores contribuíram com esses artigos, envolvendo 44 instituições sediadas no Brasil e em seis outros países. Os artigos publicados investigaram as principais atividades antrópicas e seus impactos sobre a diversidade de peixes, com foco especial na regulação dos rios, mineração, mudanças no uso do solo, aquicultura e pesca. Os estudos forneceram evidências sobre a perda de diversidade de peixes na região Neotropical, incluindo eventos de mortandade, alterações demográficas, contaminação, mudanças na estrutura das assembleias, perda de diversidade taxonômica e funcional, além da degradação de funções e serviços ecossistêmicos, e falta de ações efetivas de proteção e conservação. Os estudos foram conduzidos em rios, riachos, lagos e reservatórios de diferentes sistemas Neotropicais. Os estudos publicados neste SI representam uma amostra relevante da atual situação dos peixes de água doce na região Neotropical, reforçando a necessidade de revisão das políticas ambientais, ações de manejo e conservação, e prioridades socioeconômicas.

[spa] El objetivo general de esta tesis ha sido evaluar los efectos de determinados contaminantes sobre la reproducción, el estrés fisiológico y el comportamiento dos especies de ciprínidos autóctonas del NE de Cataluña y el SE de Francia. Esta es una tesis que ha buscado analizar, desde un punto de vista multidisciplinar, y combinando trabajos de campo con experimentos de laboratorio, los efectos de la contaminación sobre las poblaciones de peces. Con este propósito general se establecieron los siguientes objetivos específicos: • Evaluar, en un ambiente natural, los posibles efectos de la contaminación de origen industrial, frecuente en los ríos mediterráneos, sobre la biología reproductiva del bagre (Squalius laietanus). A tal efecto se planteó describir el ciclo gonadal, calcular la fecundidad y analizar la posible presencia de histopatologías en ovarios y testículos para determinar cómo la presencia de contaminantes considerados disruptores endocrinos podía alterar la biología reproductiva de este ciprínido autóctono. El estudio fue complementado mediante un análisis por biomarcadores. • Analizar el efecto de la contaminación urbana sobre el estrés fisiológico de S. laietanus mediante el análisis de cortisol en moco epidérmico. El objetivo fue validar una técnica de análisis del cortisol por métodos no invasivos (moco epidérmico) y utilizarla como método para determinar el grado de bienestar de esta especie bajo los efectos de la mencionada contaminación. • Evaluar el efecto de la contaminación por amonio sobre el comportamiento en el barbo de montaña (Barbus meridionalis) en condiciones experimentales de laboratorio. En particular, se analizaría también si la exposición previa de los peces a este contaminante en un ambiente natural podría predisponerlos a una mejor tolerancia después de haber sido detoxificados en el laboratorio. Los peces serían sometidos a diferentes concentraciones subletales de amonio y se analizaría tanto su comportamiento alimentario (voracidad y saciedad) como su actividad de natación. • Determinar el efecto de la contaminación por amonio sobre la personalidad de B. meridionalis en condiciones experimentales de laboratorio. En particular, se investigó sobre su capacidad de retención de memoria tras haber pasado por una experiencia de aprendizaje apetitivo basada en un test de osadía (en ausencia de amonio) y tras haber sido expuesto a diferentes concentraciones subletales de este contaminante en posteriores test., [eng] Mediterranean rivers are subject to intense pollution of anthropic origin. Among the most frequent pollutants are ammonia and emerging compounds such as endocrine system disruptors (EDCs). This thesis has analyzed the effects of some of these pollutants on the reproduction and physiological stress of the Catalan chub (Squalius laietanus) and on the behavior of the Mediterranean barbel (Barbus meridionalis), two cyprinids native to the Iberian Peninsula. In field studies carried out in S. laietanus (Besòs river basin), EDCs such as benzotriazole and benzothiazole (coming from a textile industry) could be responsible for both a decrease in the gonadosomatic index (in both sexes) and a lower fecundity and spawn desynchronization (in females), as well as a smaller diameter in the seminiferous tubules of males. Higher levels of stress (cortisol) found in both blood and epidermal mucus, as well as the abnormalities detected in red and white blood cells of S. laietanus, were attributable to urban pollution from sewage treatment plants. In B. meridionalis, through experimental laboratory studies, it was shown that ammonia (at sublethal concentrations) altered feeding behavior (voracity and satiety), but not swimming activity. However, in fish that had been pre-exposed to ammonia (in the natural environment), these alterations occurred in absence of this compound. In another experiment, also carried out in B. meridionalis and aimed at investigating the effect of ammonia on the cognition, exposed fish were found to have poorer memory retention than non exposed ones. After a learning experience, individuals of this species were able to retain memory for at least 16 days, which is considered long-term memory.

The extreme body sizes of megafishes associated with their high commercial values and recreational interests have made them highly threatened in their native range worldwide by human-induced impacts such as overexploitation. Meanwhile, some megafishes have been introduced outside of their native range. A notable example is the European catfish (Silurus glanis), one of the few siluriforms native to Eastern Europe. It is among the 20 largest freshwater fish worldwide, attaining a total length over 2.7 m and a documented mass of 130 kg. Its distinct phylogeny and extreme size imply many features that are rare among other European fish, including novel behaviours (massive aggregations, beaching), consumption of large bodied prey, fast growth rates, long lifespan, high fecundity, nest guarding and large egg sizes. The spread of the species is likely to continue due to illegal introductions, primarily for recreational angling, coupled with natural range extension associated with climate change. Here, the most recent knowledge on the current distribution and the ecology of the species are reviewed. A series of key research questions are identified that should stimulate new rese arch on this intriguing, yet largely unknown, species and, more generally, on the ecology of freshwater invaders This work was produced as part of the ‘‘European Catfish Working Group’’ that was financially supported by the University of Toulouse. Individual members of the group were supported by the Spanish Ministry of Economy and Competitiveness (Project CGL2013-43822-R), the Government of Catalonia (ref. 2014 SGR 484), the European Commission (COST Action TD1209), Czech Science Foundation (Project 16-06498S) and the French Laboratory of Excellence Project ‘‘TULIP’’ (ANR-10-LABX-41; ANR-11-IDEX-0002-02)

This paper is based on a workshop funded by the Spanish Ministry of Science, Innovation and Universities (project CGL2015‐69311‐REDT). Additional financial support was provided by the same ministry (projects: ODYSSEUS, BiodivERsA3‐2015‐26, PCIN‐2016‐168; and CGL2016‐80820‐R) and the Government of Catalonia (ref. 2014 SGR 484 and 2017 SGR 548). Freshwater ecosystems constitute only a small fraction of the planet's water resources, yet support much of its diversity, with freshwater fish accounting for more species than birds, mammals, amphibians or reptiles. Fresh waters are, however, particularly vulnerable to anthropogenic impacts, including habitat loss, climate and land use change, pollution and biological invasions. This environmental degradation, combined with unprecedented rates of biodiversity change, highlights the importance of robust and replicable programmes to monitor freshwater fish. Such monitoring programmes can have diverse aims, including confirming the presence of a single species (e.g., early detection of alien species), tracking changes in the abundance of threatened species, or documenting long‐term temporal changes in entire communities. Irrespective of their motivation, monitoring programmes are only fit for purpose if they have clearly articulated aims and collect data that can meet those aims. This review, therefore, highlights the importance of identifying the key aims in monitoring programmes and outlines the different methods of sampling freshwater fish that can be used to meet these aims. We emphasize that investigators must address issues around sampling design, statistical power, species’ detectability, taxonomy and ethics in their monitoring programmes. Additionally, programmes must ensure that high‐quality monitoring data are properly curated and deposited in repositories that will endure. Through fostering improved practice in freshwater fish monitoring, this review aims to help programmes improve understanding of the processes that shape the Earth's freshwater ecosystems and help protect these systems in face of rapid environmental change. Postprint

Biological invasions rank among the main global threats for biodiversity. The Eastern mosquitofish (Gambusia holbrooki) is considered one of the 100 world worst invasive species due to its high adaptation capability to new environments. Using the restriction-site-associated DNA tags (RADtags), introduced European locations were compared against native US mosquitofish populations to analyse genomic changes that occurred during invasive process of European locations. After filtering, 7724 RADtags containing only one SNP were retained for population studies. Comparative genomics indicated that 186 of these RADtags matched sequences in the transcriptome of Xyphophorus maculatus, the most closely related genome available. Genomic analyses showed that invasive populations show high reductions in diversity. Further, analyses of population structuring based on these data are concordant with previous analyses based on microsatellites. It is concluded that during the invasion process genetic drift was the main evolutionary force affecting patterns of diversity and population structure. While recognizing that positive selection could be masked by the strong drift during founder events, adaptive processes were evidenced in a reduced number of RADtags (

The flow regime is a determinant of the ecological function and natural dynamics of a river system with a prominent effect on freshwater fish. Here, we introduce a number of contributions to the Special Session, “Ecohydraulics of river flow alterations and impacts on freshwater fish,” that occurred at the XIX Conference of the Iberian Association of Limnology. The multidisciplinary contributions illustrate the impacts of river flow alteration on aquatic biota, describe mitigation measures and restoration actions to address river flow regulation, and present innovative tools for research in the ecohydraulics field. The research topics debated included environmental flows, river restoration, hydropeaking impacts on aquatic organisms, innovative methods and devices, and hydropeaking mitigation strategies. The importance of ecohydraulics as an emerging science was debated. The bridge between the disciplines of limnology and ecohydraulics was highlighted to understand flow alteration impacts and provide solutions to mitigate those impacts. This Special Session provided an opportunity to embrace ecohydraulic scientists in limnology research., This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 727830 (www.fithydro.eu); Journal article DOI: 10.23818/limn.39.14

In freshwater ecosystems, abiotic factors such as flow regime and water quality are considered important predictors of ecosystem invasibility. The aim of this study was to investigate the critical swimming capacity and metabolism of the eastern mosquitofish, Gambusia holbrooki, focusing on sex and size effects, to evaluate the influence of water flow on its invasive success. Specimens of mosquitofish were captured from the Ter Vell lagoon (L'Estartit, north-eastern Spain) in July 2014, and we measured the critical swimming speed (Ucrit) and oxygen consumption of individual fish (30 females and 30 males) using a mini swim tunnel. The mean Ucrit of this poeciliid fish was estimated at 14.11 cm·s-1 (range = 4.85-22.26), which is lower than that of many other fishes of similar size and confirms that this species is limnophilic and its invasive success might be partially explained by hydrologic alterations. However, the Ucrit and maximal metabolic rate vary markedly with fish size and sex, with males having much higher values for the same body mass, and thus probably being more resistant to strong water flows. Multiple regression models illustrate that multivariate analyses might increase the predictive power and understanding of swimming performance and metabolic traits, compared to results from conventional simple regressions This research was supported by the Spanish Ministry of Economy and Competitiveness (project CGL2013-43822-R), the Government of Catalonia (ref. 2014 SGR 484), the European Commission (COST Action TD1209) and the Brazilian Ministry of Education (CAPES, ref. 88881.068352/2014-01). P.S. and Y.L. benefitted from fellowships from the European Commission (Erasmus Mundus Partnership ‘Techno’, 204323-1-2011-1-FR-EMA21)

7 pages, 2 figures, 3 tables, supplementary data https://doi.org/10.1016/j.ygcen.2019.01.015, A significant body of literature suggests that aquatic pollutants can interfere with the physiological function of the fish hypothalamic-pituitary-interrenal (HPI) axis, and eventually impair the ability to cope with subsequent stressors. For this reason, development of accurate techniques to assess fish stress responses have become of growing interest. Fish scales have been recently recognized as a biomaterial that accumulates cortisol, hence it can be potentially used to assess chronic stress in laboratory conditions. We, therefore, aimed to evaluate the applicability of this novel method for cortisol assessment in fish within their natural environment. Catalan chub (Squalius laietanus) were sampled from two sites; a highly polluted and a less polluted (reference) site, in order to examine if habitat quality could potentially influence the cortisol deposition in scales. We also evaluated the seasonal variation in scale cortisol levels by sampling fish at three different time points during spring-summer 2014. In each sampling, blood was collected to complement the information provided by the scales. Our results demonstrated that blood and scale cortisol levels from individuals inhabiting the reference site were significantly correlated, therefore increasing the applicability of the method as a sensitive-individual measure of fish HPI axis activity, at least in non-polluted habitats. Since different environmental conditions could potentially alter the usefulness of the technique, results highlight that further validation is required to better interpret hormone fluctuations in fish scales. Scale cortisol concentrations were unaffected by habitat quality although fish from the polluted environment presented lower circulating cortisol levels. We detected a seasonal increase in scale cortisol values concurring with an energetically costly period for the species, supporting the idea that the analysis of cortisol in scales reveals changes in the HPI axis activity. Taken together, the present study suggests that cortisol levels in scales are more likely to be influenced by mid-term, intense energetically demanding periods rather than by long-term stressors. Measurement of cortisol in fish scales can open the possibility to study novel spatio-temporal contexts of interest, yet further research is required to better understand its biological relevance

The temporal components of genetic diversity and geographical structure of invasive mosquitofish populations are poorly known. Through the genetic monitoring of four consecutive cohorts of Gambusia holbrooki from three different river basins we aimed to determine temporal patterns of regional genetic variation and dispersal rates within invasive populations. Despite showing evidence of strong population size fluctuations, genetic diversity levels were maintained among local cohorts. We only detected temporal allele frequency changes associated with seasonal flooding that did not modify major trends on population structure among cohorts. Downstream gene flow coupled with increased connectivity at lowland locations to increase genetic diversity levels in these areas. A large proportion of local fish (up to 50 %) were dispersers, often originated from locations within the same river basin. High dispersal capability, ecological tolerance, and reproductive traits likely promote river colonization. Finally, our results also confirmed that human-assisted translocations promote within and among basin gene flow and maintained levels of genetic diversity, particularly in upstream locations This work has been possible thank to the financial support of the former Spanish Ministry of Economy and Competitiveness (MINECO, CGL2009-12877-C02-02). DDM held a Ph.D. scholarship from the University of Girona (UdG, BR10/12)

Gold mining activities in fluvial systems may cause arsenic (As) pollution, as is the case at the Anllóns River (Galicia, NW Spain), where high concentrations of arsenate (AsV) in surface sediments (up to 270 mg kg−1) were found. A 51 day-long biofilm-translocation experiment was performed in this river, moving some biofilm-colonized substrata from upstream (less As-polluted) to downstream the mine area (more As-polluted site), to explore the effect of As on benthic biofilms, as well as their role on As retention and speciation in the water-sediment interface. Eutrophic conditions (range: 0.07–0.38 mg L−1 total phosphorus, TP) were detected in water in both sites, while sediments were not considered P-polluted (below 600 mg kg−1). Dimethylarsenate (DMAV) was found intracellularly and in the river water, suggesting a detoxification process by biofilms. Since most As in sediments and water was AsV, the high amount of arsenite (AsIII) detected extracellularly may also confirm AsV reduction by biofilms. Furthermore, translocated biofilms accumulated more As and showed higher potential toxicity (higher As/P ratio). In concordance, their growth was reduced to half that observed in those non-translocated, became less nutritive (less nitrogen content), and with higher bacterial and dead diatom densities. Besides the high As exposure, other environmental conditions such as the higher riparian cover at the more As-polluted site could contribute to those effects. Our study provides new arguments to understand the contribution of microorganisms to the As biogeochemistry in freshwater environments This work was supported by the Spanish Ministry of Economy and Competitiveness (Project Ref. CGL2010-22059, CGL2013-46003-P and CGL2013-43822-R), the University of Girona (Project Ref. SING12/09 and MPCUdG2016/120) and the Government of Catalonia (Project Ref. 2014 SGR 484). Laura Barral Fraga benefited from a doctoral fellowship from the University of Girona (BR 2013/06) and a mobility grant from the Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA, at Bordeaux, France) SI

Understanding the variation of fish assemblages in reservoirs is crucial for precise interpretations of ecological processes. However, representative samples in such environments are subjected both to spatial zonation (longitudinal and transversal gradients) and limitations of fishing gears. We used a large zoned reservoir (Itaipu, Brazil) to perform a quasi-experiment that assessed the relative role of spatial gradients and fishing methods on fish diversity and composition. Active (cast nets, electrofishing and seines) and passive (gillnets and longlines) fishing gears were employed in lotic, transitional and lentic habitats of the reservoir and three large tributaries. In total 6281 individuals of 101 species were captured. Sampling methods and spatial gradients had an influence on species composition, with significant interactions between these factors. In addition, results produced by a variation partitioning analysis suggested that 21 % of the species richness was explained by the sampling methods and 7 % by the longitudinal gradient; whereas for species composition, 12 and 3 % corresponded to sampling methods and transversal gradients, respectively. Overall, our results suggest that variations among fishing gears is greater than across strong spatial gradients, emphasizing the importance of using multiple and complementary fishing methods in reservoirs for characterization of fish assemblages. The interactions between spatial gradients and sampling methods were higher with transversal than with longitudinal gradients, suggesting that substantial differences in species richness and composition among sampling gears depend to some extent on habitat. The approach used here would be applicable to any large zoned inland waterscape Financial support was provided by the Spanish Ministry of Economy and Competitiveness (project CGL2013-43822-R), the Government of Catalonia (ref. 2014 SGR 484), and CAPES (Programa Pesquisador Visitante Especial, ref. 88881.068352/2014-01).

The aquarium trade has been identified as an important vector of aquatic invasive species but this question has mostly been investigated in North America. We investigated the variation in diversity and species composition in different trade types in southwestern Europe (three major international wholesalers, different retail store types, and local internet forums), mostly in Spain and Portugal. As in previous studies, the diversity of fishes in the aquarium trade was vast, with a total of 20 orders, 79 families, and 1,133 fish species detected in the trade types analyzed. 248 species were observed in a single metropolitan area (Barcelona), with estimates of about 294 species being present. International wholesalers had higher species richness and evenness, with a single one having over 700 species. General pet stores had much lower evenness but due to high turnover had a total richness of over 200 species. Internet forums had the lowest evenness but similar richness. The different commerce types varied significantly in relative species abundance with about a dozen of popular fish species (e.g., goldfish, Siamese fighting fish, common carp, guppy, swordtails) dominating the retail stores, particularly the general pet stores. Our results imply that frequency in the trade varies strongly among species and commerce types and although general pet stores have usually low diversity, this is compensated with a higher species turnover. Many of the most popular species are well known invasive species and some of the species available are temperate species that might establish in Europe, reinforcing the need for more careful implementation of education programs, regulation and monitoring of trade, and internalization of environmental costs by the industry We thank the aquarium websites mentioned in the methods for the valuable information provided, the Spanish Ministry of Science for financial support (CGL2009-12877-C02-01 and Consolider-Ingenio 2010 CSD2009-00065), and Julian D. Olden, the associate editor, and anonymous reviewers for insightful comments on the manuscript

L'objectiu d'aquesta tesi és de'explorar alguns aspectes de l'impacte humà sobre les poblacions de peixos i altres components dels ecosistemes fluvials Mediterranis de Catalunya. Es va mostrar com els peixos del Riu Llobregat acumulen quantitats significatives de metalls pesants, amb concentracions en el múscul que varien al llarg del riu i segons l'espècie i la talla dels peixos. En el Riu Tordera, afectat per l'extracció d'aigua, el règim de temperatures es veu alterat en correspondència dels trams intermitents, en els quals la probabilitat de supervivència i l'abundancia dels peixos , i en menor mesura el creixement i la condició corpòria, també pateixen les conseqüencies de l'alteració hidrològica, The goal of this thesis is to explore some aspects of anthropogenic impact on the fish populations and other components of two Mediterranean stream ecosystems in Catalonia NE Spain). It was shown how Llobregat River's fish accumulate significant trace metal quantities, with muscle concentrations varying across sampling sites along the river, fish species and size. In the Tordera Stream, affected by water abstraction, the temperature regime was disrupted in correspondence of the intermittent reaches, where fish abundance and survival probability and, at a lower extent, growth and body condition, also suffered the consequences of hydrologic alteration

The knowledge of capture efficiency and side effects of electrofishing is essential for research and monitoring of stream fish populations. Differences amongst electrofishing crews have hardly been investigated and are particularly important given the on-going implementation of the Water Framework Directive and wide-ranging exchange of data worldwide. We aimed to assess fish catchability in Mediterranean streams and to compare four electrofishing crews (with minor differences in gears used) and their short-term effects on fish populations. In eight different sites, we compared two adjacent stations, one sampled with conventional single-pass catch-effort data and the other closed with block nets and with four-pass removal estimates. We used a Williams' cross-over design to estimate the independent effects of repeated sampling in four consecutive days, site and crew and also to assess a potential carry-over effect. We modelled capture probability and estimated population size using program MARK and an information-theoretic framework. Our results show that electrofishing was generally efficient in these reaches, with 50-100% of the species and of 40-60% of the individuals captured in a single pass. The CPUE was significantly higher at sites blocked with nets than at open sites, but observed richness was not significantly different. Capture probability was generally not constant along removal passes and increased with fish size. Observed fish richness and species composition did not depend on electrofishing crew and fishing day and there was no significant carryover effect. There were, however, significant differences in single-pass CPUE estimates amongst electrofishing crews, after accounting for other sources of variation. There was also a significant carry-over effect, surprisingly with increasing fish captured after fishing by specific crews. Overall, our results suggest that although capture probability depends heavily on a number of factors (such as species, size, and sampling site) and needs careful consideration, the effect of electrofishing crew is negligible for assessment of species richness and composition but considerable for fish abundance This study was financially supported by the Catalan Water Agency (project Ibicat2) and the Spanish Ministry of Science (projects CGL2009-12877-C02-01 and Consolider-Ingenio 2010 CSD2009-00065)

A popular species for food and sport, the European catfish (Silurus glanis) is well-studied in its native range, but little studied in its introduced range. Silurus glanis is the largest-bodied freshwater fish of Europe and is historically known to take a wide range of food items including human remains. As a result of its piscivorous diet, S. glanis is assumed to be an invasive fish species presenting a risk to native species and ecosystems. To assess the potential risks of S. glanis introductions, published and 'grey' literature on the species' environmental biology (but not aquaculture) was extensively reviewed. Silurus glanis appears well adapted to, and sufficiently robust for, translocation and introduction outside its native range. A nest-guarding species, S. glanis is long-lived, rather sedentary and produces relatively fewer eggs per body mass than many fish species. It appears to establish relatively easily, although more so in warmer (i.e. Mediterranean) than in northern countries (e.g. Belgium, UK). Telemetry data suggest that dispersal is linked to flooding/spates and human translation of the species. Potential impacts in its introduced European range include disease transmission, hybridization (in Greece with native endemic Aristotle's catfish [Silurus aristotelis]), predation on native species and possibly the modification of food web structure in some regions. However, S. glanis has also been reported (France, Spain, Turkmenistan) to prey intensively on other non-native species and in its native Germany to be a poor biomanipulation tool for top-down predation of zooplanktivorous fishes. As such, S. glanis is unlikely to exert trophic pressure on native fishes except in circumstances where other human impacts are already in force. In summary, virtually all aspects of the environmental biology of introduced S. glanis require further study to determine the potential risks of its introduction to novel environment This investigation was supported in part through research grants from the Environment Agency (Sussex Area) and the UK Department of Environment, Food and Rural Affairs, the Spanish Ministry of Education and Science (REN2003-00477), the Government of Catalonia (Distinction Award for University Research 2004 to EGB) and the EC Marie Curie programme

We provide mitochondrial sequence variation of the invasive fish Gambusiaholbrooki from 24 European populations, from Portugal to Greece. Phylogeographic structure in Europe was compared with genetic data from native samples (USA) and historical records were reviewed to identify introduction routes. Overall, data agree with records of historical introductions and translocations, and indicate that the most abundant haplotype throughout Europe originated from North Carolina and corresponded to the first introduction in 1921 to Spain, being transferred to Italy in 1922 and to many countries afterwards. Our results also show that at least another independent introduction occurred first in France and subsequently from France to Greece. Haplotypes of G. affinis were not detected in our European sampling effort but historical records and other data suggest that this species was introduced to Italy in 1927 and it might be present. At the continental scale, there is less diversity in Europe than in North America, in agreement with the low number of introduced fish. At the local scale, some European populations gained diversity from multiple introductions and from "de novo" mutations This study was financially supported by the Spanish Ministry of Education (CGL2006-11652-C02-02/BOS) and the Government of Catalonia (Catalan Government Distinction Award for University Research 2004 to EGB)

Human activity has spread trace amounts of chemically stable endocrine-disrupting pollutants throughout the biosphere. These compounds have generated a background level of estrogenic activity that needs to be assessed. Fish are adequate sentinels for feminization effects as male specimens are more sensitive than humans to exogenous estrogenic compounds. High mountain lakes, the most distant environments of continental areas, only receive semi-volatile compounds from atmospheric deposition. We analyzed the expression levels of estrogen-regulated genes in male fish from these mountain lakes in Europe. Incipient feminization involving expression of estrogen receptor and zona radiata genes revealed a widespread diffuse estrogenic impact. This effect was correlated with the concentrations of some organochlorine compounds in fish and was consistent with the persistent occurrence of these tropospheric pollutants in the most remote planet regions. These results should be of general concern given the increasing endocrine disruption effects in human populations. © 2015, Nature Publishing Group. All rights reserved., We acknowledge financial support from the EU projects, EUROLIMPACS, CROME-LIFE, HEALS, and the Spanish project, Consolider-Ingenio GRACCIE.

The Water Framework Directive includes fish fauna as one of the biological elements, jointly with aquatic flora and benthic invertebrates, to assess and monitor water and habitat quality. Successful implementation of the Directive depends in part on the development of reliable, science-based tools to directly assess biological conditions. Although fish have been used as ecological indicators for more than 30 years around the world, mainly in North America and more recently in Europe, few studies have been done in Mediterranean streams. Fish assemblages of the Mediterranean basin, similarly to other Mediterranean areas such as California, have particular characteristics that hamper IBI’s development: few native species, poor knowledge of their ecological requirements, high number of endemisms with a wide range of tolerance to environmental variations and many exotic species. This chapter summarizes our experience in developing fish-based tools in Catalonia. We discuss the challenges and difficulties to develop these approaches in Mediterranean streams. We show the IBICAT2010 as a fish-based assessment method suitable for the evaluation of the ecological status of Catalan rivers. Moreover, we assess size-related variables as a bioassessment tool because population size structure can provide insights into species-specific applications and management. Finally, we analyse the longitudinal connectivity throughout Catalan rivers and fish passes by using the index of river connectivity (ICF) specially designed to Catalan rivers.

[spa] El blenio de río (Salaria fluviatilis) es un pez de agua dulce de distribución circum-mediterránea que se encuentra amenazado en muchos de los países en los que se ha descrito. Con tal de aportar información útil para su conservación, en la presente tesis, se abordaron diferentes aspectos de comportamiento como: las estrategias reproductivas, el desarrollo embrionario en función del cuidado parental, la personalidad y la capacidad de aprendizaje. En cuanto a la estrategia reproductiva, los resultados obtenidos revelan que la ausencia de machos dominantes más grandes promueve el desarrollo en caracteres sexuales secundarios (CSSs) y la adopción de la táctica parental en los machos jóvenes, mientras que su presencia inhibe estos procesos. La escasez de nidos, por su parte, estimula el crecimiento de la cresta cefálica. El estudio de desarrollo embrionario muestra que los embriones mantenidos con los progenitores presentan un mayor volumen de saco vitelino, una menor altura de cabeza y una menor longitud de mandíbula al nacer que los embriones mantenidos sin los progenitores. Ello sugiere que la presencia de ambos padres (especialmente del macho, quién tiene un contacto próximo con las puestas y presenta cuidado parental) podría afectar el desarrollo de los embriones y por tanto debería mantenerse en los programas en cautividad. En el estudio de personalidad se investiga si el tiempo que tardan los machos en emerger de un refugio al estar expuestos a un entorno nuevo se relaciona con el desarrollo en CSSs. Se observa que los machos que tardan menos en asomarse del refugio presentan más tarde, durante la época reproductora, un mayor desarrollo de la cresta cefálica y que los que salen completamente del refugio crecen más en longitud. Por último, en el estudio de aprendizaje espacial, se observa que los machos aprenden el ejercicio antes que las hembras y se relaciona la rapidez de aprender de dichos machos con el desarrollo de su cresta cefálica. Todas estas observaciones permiten comprender mejor cómo se adapta la especie a su entorno y pueden aportar información relevante para la conservación in situ así como en el ámbito de la cría en cautividad y de las reintroducciones., [eng] The river blenny (Salaria fluviatilis) is a freshwater fish inhabiting the circum-Mediterranean region that has been described as threatened in many of the countries where it occurs. In order to provide useful information for its conservation, in the present thesis, different aspects related to behaviour were approached: reproductive strategies, embryo development related to parental care, personality and learning capacity. Results concerning reproductive strategies show that the absence of larger dominant males promotes the secondary sexual characteristics (SSCs) development and the parental status acquisition in young males, while their presence inhibits these processes. Nest limitation, meanwhile, stimulates the cephalic crest growth. Embryo development study reveals that embryos maintained with progenitors have a major yolk sac volume, a minor head height and a minor jaw length at birth than the embryos maintained without progenitors. This suggests that the presence of both parents (specially the male, who has a close contact with clutches and exhibit parental care) could affect embryo development and therefore should be maintained in captivity programs. In the study about personality, it is explored if the time to emerge from a refuge when exposed to a novel environment is related to SSCs development. Males that emerge faster from the refuge present later, during reproductive period, a major development of the cephalic crest, and those who exit completely the refuge grow more in body length. Finally, in the spatial learning study, it is observed that males learn faster the task than females and their rapidity to learn is associated to the cephalic crest development. All these observations allow us to understand better how this species adapts to the environment and might provide relevant information for the conservation in situ, captive breeding and reintroduction programs

Genetic analyses contribute to studies of biological invasions by mapping the origin and dispersal patterns of invasive species occupying new territories. Using microsatellite loci, we assessed the genetic diversity and spatial population structure of mosquitofish (Gambusia holbrooki) that had invaded Spanish watersheds, along with the American locations close to the suspected potential source populations. Mosquitofish populations from the Spanish streams that were studied had similar levels of genetic diversity to the American samples; therefore, these populations did not appear to have undergone substantial losses of genetic diversity during the invasion process. Population structure analyses indicated that the Spanish populations fell into four main clusters, which were primarily associated with hydrography. Dispersal patterns indicated that local populations were highly connected upstream and downstream through active dispersal, with an average of 21.5% fish from other locations in each population. After initially introducing fish to one location in a given basin, such dispersal potential might contribute to the spread and colonization of suitable habitats throughout the entire river basin. The two-dimension isolation-by-distance pattern here obtained, indicated that the human-mediated translocation of mosquitofish among the three study basins is a regular occurrence. Overall, both phenomena, high natural dispersal and human translocation, favor gene flow among river basins and the retention of high genetic diversity, which might help retain the invasive potential of mosquitofish populations.

Condition-specific competition is widespread in nature. Species inhabiting heterogeneous environments tend to differ in competitive abilities depending on environmental stressors. Interactions between these factors can allow coexistence of competing species, which may be particularly important between invasive and native species. Here, we examine the effects of temperature on competitive interactions between invasive mosquitofish, Gambusia holbrooki, and an endemic Iberian toothcarp, Aphanius iberus. We compare the tendency to approach heterospecifics and food capture rates between these two species, and examine differences between sexes and species in aggressive interactions, at three different temperatures (19, 24 and 29°C) in three laboratory experiments. Mosquitofish exhibit much more aggression than toothcarp. We show that mosquitofish have the capacity to competitively displace toothcarp through interference competition and this outcome is more likely at higher temperatures. We also show a reversal in the competitive hierarchy through reduced food capture rate by mosquitofish at lower temperatures and suggest that these two types of competition may act synergistically to deprive toothcarp of food at higher temperatures. Males of both species carry out more overtly aggressive acts than females, which is probably related to the marked sexual dimorphism and associated mating systems of these two species. Mosquitofish may thus impact heavily on toothcarp, and competition from mosquitofish, especially in warmer summer months, may lead to changes in abundance of the native species and displacement to non-preferred habitats. Globally increasing temperatures mean that highly invasive, warm-water mosquitofish may be able to colonize environments from which they are currently excluded through reduced physiological tolerance to low temperatures. Research into the effects of temperature on interactions between native and invasive species is thus of fundamental importance.

Biological invasions are considered one of the main anthropogenic factors that reduce the abundance of native species. Understanding the patterns of population structure and behavior of introduced species is important to determine invasion sources and pathways, in addition to improving the protective management of native species. Thus, we set out to advance our knowledge about the mosquitofish Gambusia spp., which is an invasive species that was introduced to southern Europe in 1921 to control mosquito populations. We assessed the genetic diversity and population structure of this species at 13 European locations, by screening variation at six microsatellite loci. We also evaluated six American samples (four of G. holbrooki and two of G. affinis) to identify the most likely source of the populations that established in Europe, and to determine whether G. affinis is also present. The results showed that, while there was evidence of recent bottleneck events in a few isolated locations, most introduced populations harbored a considerable amount of gene diversity, probably because of multiple introductions and secondary contacts. Populations displayed strong genetic differentiation that was mainly associated with geographical distance. At least two main routes of colonization of G. holbrooki seem to have occurred in Europe. The first, and more ancient colonization, was consistent with historical records, with the species invading the Iberian Peninsula. A second and more recent colonization probably occurred in Greece and, from there, France. The presence of G. affinis was not detected in any of the European samples The work was funded by the Spanish Ministry of Education and Science (MEC) research projects CGL2006-11652-C02-02/BOS and CGL2009-12877-C02-02

0000-0001-8628-0514 WOS: 000325182400014 Mediterranean-climate regions (med-regions) are global hotspots of endemism facing mounting environmental threats associated with human-related activities, including the ecological impacts associated with non-native species introductions. We review freshwater fish introductions across med-regions to evaluate the influences of non-native fishes on the biogeography of taxonomic and functional diversity. Our synthesis revealed that 136 freshwater fish species (26 families, 13 orders) have been introduced into med-regions globally. These introductions, and local extirpations, have increased taxonomic and functional faunal similarity among regions by an average of 7.5% (4.6-11.4%; Jaccard) and 7.2% (1.4-14.0%; Bray-Curtis), respectively. Faunal homogenisation was highest in Chile and the western Med Basin, whereas sw Cape and the Aegean Sea drainages showed slight differentiation (decrease in faunal similarity) over time. At present, fish faunas of different med-regions have widespread species in common (e.g. Gambusia holbrooki, Cyprinus carpio, Oncorhynchus mykiss, Carassius auratus, and Micropterus salmoides) which are typically large-bodied, non-migratory, have higher physiological tolerance, and display fast population growth rates. Our findings suggest that intentional and accidental introductions of freshwater fish have dissolved dispersal barriers and significantly changed the present-day biogeography of med-regions across the globe. Conservation challenges in med-regions include understanding the ecosystem consequences of non-native species introductions at macro-ecological scales. DST/NRF Centre of Excellence for Invasion BiologyDepartment of Science & Technology (India); David and Elaine Potter Foundation; Spanish Ministry of ScienceSpanish Government [CGL2009-12877-C02-01, Consolider-Ingenio 2010 CSD2009-00065]; Czech Ministry of Culture [DKRVO2012, DKRVO 2013/14, 00023272]; Czech Ministry of Culture (National Museum) SMM acknowledges the financial support of the DST/NRF Centre of Excellence for Invasion Biology and the David and Elaine Potter Foundation during his PhD studies. EGB acknowledges funding support from the Spanish Ministry of Science (projects CGL2009-12877-C02-01 and Consolider-Ingenio 2010 CSD2009-00065). DLM acknowledges Dr Stephen Beatty (Murdoch University) for his work on the fishes of south-western Australia. RS. acknowledges support from the Czech Ministry of Culture (DKRVO2012 and DKRVO 2013/14, National Museum, 00023272). The authors thank Nicolas Poulet (ONEMA) for providing data on French Mediterranean river systems, Meta Povz and Predag Simonovic for providing data on Adriatic river systems, and Sergio Zerunian and Massimo Lorenzoni for providing data on Italian river systems.

This chapter reviews the diversity and composition of algal, invertebrate and fish communities in the Llobregat basin and analyses the factors affecting their distribution. Phytoplankton develops only during short periods and in particular areas where the hydraulic residence time is high. Diatoms are by far the most diverse and abundant in autotrophic benthic biofilms. The invertebrate community is highly rich taxonomically, whereas the native fish richness is relatively low, with about eight freshwater species and some others of marine origin. Some of the fish native species are threatened and two have been extirpated. Many exotic fish species have been introduced into the basin and are suspected to have contributed to the decline of native fish. Salt inputs, organic pollution and hydrological conditions lead to further alterations in water quality in the middle part of the river and downstream, thus reducing ecological quality. Multiple pressures on fluvial biodiversity severely compromise the integrity of this river’s ecosystem. To recover the structure and functioning of the biological communities, it is important to maintain the integrity of headwater ecosystems to ensure a species pool for colonisation downstream and reduce water abstraction, regulation and nutrient and pollutant inputs This research was funded by the Spanish Ministry of Science and Innovation, projects SCARCE (Consolider-Ingenio 2010 program, CSD2009-00065), CGL2009-12877-C02-01 and CGL2011-30474-C02

The aim of the present report is to describe the establishment of viable populations of Cobitis paludica (de Buen, 1930) in the Segura River Basin. We found two isolated populations: one located in the upper part of the Segura River and the mouth of its tributary, the Zumeta River, and another in the Mundo River, between the Talave and Camarillas reservoirs. We hypothesised that the introduction of this species may be attributable to the deliberate or accidental introduction by anglers or fish translocation from the Tajo-Segura interbasin water transfer system. C. paludica is a threatened endemic fish species from the Iberian Peninsula, and it exhibits sharply declining populations. Therefore, further investigation is needed to assess the genetic origin of the populations reported in this report and to monitor the population trends to determine the population status and the appropriate management plan in the Segura River Basin. El presente trabajo constituye la primera referencia al establecimiento de poblaciones viables de Cobitis paludica (de Buen, 1930) en la cuenca del río Segura. Se han detectado dos poblaciones separadas geográficamente: una localizada en la zona alta del río Segura y la desembocadura del río Zumeta, y otra en el río Mundo, entre los embalses de Talave y Camarillas. Su presencia puede ser debida a la introducción deliberada o accidental por parte de los pescadores, o a la translocación de ejemplares a través del trasvase Tajo-Segura. C. paludica es una especie amenazada endémica de la Península Ibérica cuyas poblaciones se encuentran actualmente en declive. En este sentido, es necesario realizar estudios genéticos que confirmen el origen de estas poblaciones y desarrollar protocolos de seguimiento para establecer su estado poblacional y el plan de gestión de esta especie en la cuenca del río Segura.

Heavy metal concentrations were determined in 43 perches (Perca fluviatilis) and in two of its most common parasites, the acanthocephalan Acanthocephalus lucii and the cestode Proteocephalus percae, collected in the period 2009–2010 from Ružín, a seriously polluted water reservoir in Slovakia. Samples of muscle, liver, kidney, brain, male and female reproductive organs and adipose tissue of fish and both parasites were analyzed for As, Cd, Cr, Cu, Hg, Mn, Ni, Pb and Zn, by ICP-MS. Mean concentrations of individual heavy metals in all fish samples decreased in the order zinc > copper > manganese > mercury > arsenic > chromium > cadmium > nickel > lead. Zinc was found to be the dominant element and its antagonistic interaction with copper was confirmed. The kidney was a key target organ receiving the highest mean concentrations of all analyzed metals, but some metals showed specific affinity for particular tissues. In terms of human health, concentration of Hg in fish muscle, which exceeded more than two-times its maximum level admitted in foodstuffs in European countries, is of great importance and should be taken into account. Bioaccumulation factors (C[parasite]/C[fish tissue]) calculated for all elements indicated much higher detection skills of A. lucii and P. percae parasites than fish organs and hence, present results allow proposing both parasite models as useful tools to monitor aquatic environmental quality. Acanthocephalans, however, seem to be superior for heavy metal monitoring, also demonstrated under experimental conditions. Present results also indicate the decreasing heavy metal burden of the reservoir and its gradual recovery in the course of time.

Informe sobre l'ajust de l’Índex d’Integritat Biòtica (IBICAT) basat en l’ús dels peixos com a indicadors de la qualitat ambiental als rius de Catalunya

The eastern mosquitofish (Gambusia holbrooki) is among the most invasive fish worldwide and yet, while very abundant in most Mediterranean countries, it is unable to tolerate the colder winters of northern and central Europe. Understanding the effects of latitude on its life-history traits is essential to predict the potential for its invasion of central Europe in current scenarios of climate change. We studied the variation of life-history traits and parasite load in the eastern mosquitofish along a latitudinal gradient from southern France to southern Spain, sampling mosquitofish populations in eight Mediterranean river mouths ranging 5° in latitude. Southern mosquitofish populations displayed higher catch rates, allocated more energy to reproduction (gonadosomatic index and gonadal weight after accounting for fish size) and had a lower condition (total weight and eviscerated weight after accounting for fish size) than in northern populations. Despite variability among populations, size-at-maturity (L50) significantly varied with latitude and northern individuals matured at smaller size (lower L50). Parasite prevalence ranged from 0.0 to 26.7% but parasite richness was very low; all the parasites identified were larvae of pleurocercoid cestodes belonging to the order Pseudophyllidea. The abundance of mosquitofish parasites decreased with latitude and the presence and number of parasites infecting the mosquitofish had a significant negative effect on fish condition. The significant effects of latitude on the catch rates, life history and parasites of mosquitofish highlight the importance of latitudinal studies of invasive species to understand the interactive mechanisms of climate change and biological invasions This study was financially supported by the Government of Catalonia (AIRE 2003 and Catalan Government Distinction Award for university research 2004 to EGB) and the Spanish Ministry of Education (REN2003-00477 and CGL2006-11652-C02-01/BOS)

Since its first record in a tributary of the Ebro basin in 1992, the bleak Alburnus alburnus has spread to almost the whole Iberian Peninsula. In this paper (based on electrofishing surveys in 598 localities), we provide information on the expansion of the bleak. We detail current distribution in the Ebro basin and the rivers of the Eastern Pyrenees and we report its presence in three other major Iberian drainages. Currently, the bleak is sympatric with 15 Iberian endemic species (58% of total Iberian endemic fish). The possible threats to the rich Iberian ichthyofauna caused by the presence of the bleak are discussed. The factors that promoted the extremely rapid expansion of this exotic cyprinid are examined, focusing on the role of reservoirs, which seem to favour its dispersal. Desde su aparición en un afluente de la cuenca del Ebro en 1992, el alburno Alburnus alburnus se ha expandido en gran parte de la península Ibérica. El presente trabajo aporta nueva información sobre su expansión (basada en el muestreo de 598 localidades mediante pesca eléctrica). Se facilita información detallada sobre su actual distribución en la cuenca del Ebro y en cuencas al este de los Pirineos, así como nuevas citas de tres grandes cuencas hidrográficas. De acuerdo a su actual distribución en la península Ibérica, el alburno habita en simpatría con 15 especies endémicas (el 58% del total de endemismos ibéricos). Se analiza la posible amenaza que el alburno representa para la ictiofauna ibérica, examinando los factores causantes de su rápida expansión, en especial el papel de los embalses.

The interplay of abiotic factors and competition has a long history in ecology, although there are very few studies on the interaction of salinity and competition in fish. Mosquitofish (Gambusia holbrooki) are among the most invasive fish worldwide, with well documented ecological impacts on several taxa such as amphibians and small native fish. It has been previously hypothesized, based on field observations, that salinity limits the invasive success of mosquitofish and provides a competitive refuge for Mediterranean cyprinodonts. We experimentally tested this hypothesis by examining the agonistic behaviour and food competition between mosquitofish and an endangered native cyprinodont (Aphanius fasciatus) at three salinities (0, 15, 25‰). Intraspecific aggressive behaviour for both species was not significantly affected by salinity. As salinity increased, mosquitofish decreased their aggressive behaviour towards cyprinodonts and captured less prey. In contrast, the cyprinodonts did not change their behaviour with different salinity treatments, with the possible exception of increased defensive acts in higher salinities, but captured more prey with increasing salinity because of the reduced efficiency of mosquitofish. Our study confirms previous field observations that salinity limits the invasive success of mosquitofish and provides one of the few experimental demonstrations that it may mediate behavioural and competitive interactions between fish species. Condition-specific competition of mosquitofish might be expected with other species and ecosystems worldwide and illustrates the importance of integrating biotic and abiotic factors in the study of interspecific interactions Financial support was provided by the Spanish Ministry of Education (REN2003-00477) and the Government of Catalonia (Catalan Government Distinction Award for university research 2004)

En aquesta tesi es pretén aconseguir dos dels aspectes necessaris en relació a la recerca per la conservació de la ictiofauna dels rius mediterranis: - Millorar el coneixement de la biologia de les espècies més comuns de ciprínids amb l'aportació d'aspectes sobre el creixement i la reproducció del barb comú ( Barbus graellsii), el barb cua-roig ( B. Haasi), el barb de muntanya ( B. Meridionalis), la madrilla ( Chondrostoma miegii) i la bagra ( Squalius cephalus). - Analitzar els canvis que es produeixin en el temps i en el espai de les comunitats de peixos de l'Aigua d'Ora (conca del Llobregat), el Llobregat (conca de la Muga), el Matarranya (conca de l'Ebre) i el Ripoll (conca del Besòs) en relació a la variabilitat de les condicions ambientals. Aquest estudi es va plantejar en base a campanyes estacionals (primavera, estiu, tardor i hivern), de freqüència trimestral, que es va mantenir sempre que va ser possible. Al Matarranya es van realitzar un total de 13 campanyes de camp, des de l'estiu de l'any 85 fins l'estiu de l'any 88. A l'Aigua d'Ora, al Llobregat i al Ripoll, el període mostrejat va des de l'hivern de 1987 fins a l'hivern de 1990, amb un total de 11 campanyes. En cadascuna de les campanyes es van agafar mostres per biologia i es van fer mostrejos quantitatius per a l'estudi de la comunitat. Les cinc espècies de ciprínids estudiades ( B. graellsii, B. haasi, B. meridionalis, S. Cephalus, i C. Miegii) presenten dos tipus d'estratègies biològiques: - Les poblacions de les espècies que viuen en els rius mediterranis estacionals tenen una estratègia periòdica caracteritzada per una talla elevada, amb un creixement lent, i un esforç reproductiu moderat, amb una maduració tardana, una fecunditat mitjana i ous de gran diàmetre. - Les poblacions de les espècies que es troben en els rius mediterranis permanents tenen una estratègia oportunista caracteritzada per una talla mitjana, amb un creixement ràpid, i un esforç reproductiu elevat, amb una maduració primerenca, una fecunditat baixa i ous de petit diàmetre. Les comunitats de peixos dels rius mediterranis presenten un elevat grau de persistència, en tant que la estabilitat varia des de moderadament estable en els rius mediterranis permanents fins a molt fluctuant en els rius mediterranis estacionals. En tots els casos, la persistència de les espècies al·lòctones és molt baixa i les seves poblacions són molt fluctuants. Les comunitats de peixos en els rius mediterranis estacionals són regulades per factors estocàstics o abiòtics, en tant que en els rius mediterranis permanents sembla que els factors determinístics o biòtics són els que tenen un paper més important. La producció secundària de les comunitat íctiques dels rius mediterranis és molt elevada, essent les registrades en el Matarranya les més altes de tota la literatura científica. La taxa de renovació es troba directament correlacionada amb la reducció del cabal anual respecte al cabal mitjà característic de cada riu., [eng] Two essential aspects of Mediterranean freshwater fish conservation research are addressed in this dissertation: - First, the biology (growth and reproduction) of the more common cyprinids species, Barbus graellsii, B. haasi, B. meridionalis, Chondrostoma miegii and Squalius cephalus was studied. - Second, temporal and spatial changes in fish community structure related to variability of environmental conditions were monitored in several Catalonian river basins: Aigua d'Ora river (Llobregat basin), Llobregat river (Muga basin), Matarranya river (Ebro basin) and Ripoll river (Besòs basin). Field work was done four times a year, in the spring, summer, autumn, and winter, with a total of 13 sampling periods in the Matarranya river (from the summer of 1985 to the summer of 1988), and 11 in the Aigua d'Ora, Llobregat and Ripoll rivers (from the winter of 1987 to the summer of 1990), and it consisted of sampling for biological study and quantitative estimates of fish communities. The five studied cyprinid species (B. graellsii, B. haasi, B. meridionalis, S. cephalus, and C. miegii) fell into one of two possible life history patterns: - Fish populations inhabiting temporal Mediterranean rivers present a periodic strategy characterized by large size, slow growth, and moderate reproductive effort. - Fish populations inhabiting permanent Mediterranean rivers present an opportunistic strategy characterized by middle size, fast growth and high reproductive effort. Mediterranean fish communities are highly persistent and their stability varies from moderately stable, in permanent Mediterranean rivers, to highly fluctuant in temporal Mediterranean rivers. In all cases, persistence of introduced species is very small and the populations of these species fluctuate widely. Secondary production of Mediterranean river fish communities is very high (the one in the Matarranya river is the highest recorded in scientific literature) and P/B ratios are directly correlated with the reduced amount of the annual discharge in relation to the mean annual discharge characteristic of each river.

The entrances of nests established under small stones by male river blennies Salaria fluviatilis in two rivers of the Ebro Basin in eastern Spain were randomly oriented in slow-flowing sites. In fast-flowing stretches or under large stones, however, nest entrances tended to open at an angle of c. 30° relative to current flow direction, i.e. near a south-east direction. As current velocity increased, males positioned their nest entrance closer and closer to the direction of flow. Selective nest entrance orientation reduced significantly the speed of current reaching the nest entrance such that current velocity was similar (5-7 cm s−1) for all nests, regardless of stone size, prevailing current speed, or study site. Male mating success, measured as egg clutch area, however, was not related to current speed at the nest entrance but instead, it increased with nest stone size and decreased with deviations from a south-east direction. The reasons for female river blenny preference for this specific nest orientation are unknown but may be related to patterns of water flow, and hence oxygenation of the eggs, in the nest.

Most ecosystems undergo substantial variation over the seasons, ranging from changes in abiotic features, such as temperature, light and precipitation, to changes in species abundance and composition. How seasonality varies along latitudinal gradients is not well known in freshwater ecosystems, despite being very important in predicting the effects of climate change and in helping to advance ecological understanding. Stream temperature is often well correlated with air temperature and influences many ecosystem features such as growth and metabolism of most aquatic organisms. We evaluated the degree of seasonality in ten river mouths along a latitudinal gradient for a set of variables, ranging from air and water temperatures, to physical and chemical properties of water and growth of an invasive fish species (eastern mosquitofish, Gambusia holbrooki ). Our results show that although most of the variation in air temperature was explained by latitude and season, this was not the case for water features, including temperature, in lowland Mediterranean streams, which depended less on season and much more on local factors. Similarly, although there was evidence of latitude-dependent seasonality in fish growth, the relationship was nonlinear and weak and the significant latitudinal differences in growth rates observed during winter were compensated later in the year and did not result in overall differences in size and growth. Our results suggest that although latitudinal differences in air temperature cascade through properties of freshwater ecosystems, local factors and complex interactions often override the water temperature variation with latitude and might therefore hinder projections of species distribution models and effects of climate change Financial support was provided by the Spanish Ministry of Economy and Competitiveness (projects CGL2009-12877-C02-01, CGL2013-43822-R and CSD2009-00065) and the University of Girona (project SING12/09)

Top predator loss is a major global problem, with a current trend in biodiversity loss towards high trophic levels that modifies most ecosystems worldwide. Most research in this area is focused on large-bodied predators, despite the high extinction risk of small-bodied freshwater fish that often act as apex consumers. Consequently, it remains unknown if intermittent streams are affected by the consequences of top-predators' extirpations. The aim of our research was to determine how this global problem affects intermittent streams and, in particular, if the loss of a small-bodied top predator (1) leads to a 'mesopredator release', affects primary consumers and changes whole community structures, and (2) triggers a cascade effect modifying the ecosystem function. To address these questions, we studied the top-down effects of a small endangered fish species, Barbus meridionalis (the Mediterranean barbel), conducting an enclosure/exclosure mesocosm experiment in an intermittent stream where B. meridionalis became locally extinct following a wildfire. We found that top predator absence led to 'mesopredator release', and also to 'prey release' despite intraguild predation, which contrasts with traditional food web theory. In addition, B. meridionalis extirpation changed whole macroinvertebrate community composition and increased total macroinvertebrate density. Regarding ecosystem function, periphyton primary production decreased in apex consumer absence. In this study, the apex consumer was functionally irreplaceable; its local extinction led to the loss of an important functional role that resulted in major changes to the ecosystem's structure and function. This study evidences that intermittent streams can be affected by the consequences of apex consumers' extinctions, and that the loss of small-bodied top predators can lead to large ecosystem changes. We recommend the reintroduction of small-bodied apex consumers to systems where they have been extirpated, to restore ecosystem structure and function.

Mediterranean endemic freshwater fish are among the most threatened biota in the world. Distinguishing the role of different extinction drivers and their potential interactions is crucial for achieving conservation goals. While some authors argue that invasive species are a main driver of native species declines, others see their proliferation as a co-occurring process to biodiversity loss driven by habitat degradation. It is difficult to discern between the two potential causes given that few invaded ecosystems are free from habitat degradation, and that both factors may interact in different ways. Here we analyze the relative importance of habitat degradation and invasive species in the decline of native fish assemblages in the Guadiana River basin (southwestern Iberian Peninsula) using an information theoretic approach to evaluate interaction pathways between invasive species and habitat degradation (structural equation modeling, SEM). We also tested the possible changes in the functional relationships between invasive and native species, measured as the per capita effect of invasive species, using ANCOVA. We found that the abundance of invasive species was the best single predictor of natives' decline and had the highest Akaike weight among the set of predictor variables examined. Habitat degradation neither played an active role nor influenced the per capita effect of invasive species on natives. Our analyses indicated that downstream reaches and areas close to reservoirs had the most invaded fish assemblages, independently of their habitat degradation status. The proliferation of invasive species poses a strong threat to the persistence of native assemblages in highly fluctuating environments. Therefore, conservation efforts to reduce native freshwater fish diversity loss in Mediterranean rivers should focus on mitigating the effect of invasive species and preventing future invasions.

This work updates the spatial distribution of the exotic fish species in the Guadiana river basin. To this effect, 241 river stretches and 37 reservoirs and lakes were sampled, corresponding to 261 UTM 10 × 10 Km squares. A total of 12 exotic species were found, including two new species that had not been previously cited in the area, the channel cat-fish (Ictalurus punctatus) and the roach (Rutilus rutilus). These two species, related to lentic systems, had a very restricted distribution in the basin, probably as a consequence of its recent introduction. The expansion of the remaining exotic species was also confirmed. Some species as the pumpkinseed sunfish (Lepomis gibbosus), the mosquitofish (Gambusia holbrooki) or the largemouth bass (Micropterus salmoides) have become common components of the fish community, not only in reservoirs but also in lotic systems., Este trabajo actualiza la distribución espacial de las especies de peces exóticas presentes en la cuenca del río Guadiana. Para ello se han muestreado 241 tramos fluviales y 37 embalses y lagos que se corresponden con 261 cuadrículas UTM 10 × 10 Km. Se encontró un total de 12 especies de peces exóticos, incluyendo dos nuevas especies no citadas hasta el momento en la cuenca: el pez gato punteado (Ictalurus punctatus) y el rutilo (Rutilus rutilus). Estas dos especies, relacionadas con medios leníticos, tuvieron un área de distribución muy restringida en la cuenca, consecuencia probable de su reciente introducción. Además se confirmó la expansión del resto de especies exóticas. Algunas de ellas como el pez sol (Lepomis gibbosus), la gambusia (Gambusia holbrooki) o el black-bass (Micropterus salmoides) se han convertido en componentes habituales de las comunidades de peces, no sólo en embalses, sino también en medios lóticos.