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The Mediterranean brown trout (Salmo trutta complex) is native to basins draining to the Western Mediterranean Sea, and natural populations are currently declining in abundance and distribution due to habitat degradation and introgression with stocked trout of the Atlantic lineage. Data on its life history traits are limited, although is an essential first step in developing effective conservation and management strategies. We studied age, growth and reproduction of Mediterranean brown trout from three headwater streams in northeast Iberian Peninsula. The maximum observed fork length was 382 mm in males and 322 mm in females, and six age groups (from 1+ to 6+) were identified. There was large variation in the back-calculated lengths for individual fish within ages. The von Bertalanffy growth curves were similar among streams and comparable to other European populations from small streams, but growth rate was lower when compared to larger and more productive rivers. Overall, sexual maturation began at age 1+, and the estimated L50 was 136 mm for males and 150 mm for females. Monthly variations in the gonadosomatic index showed that spawning occurred between late autumn and early winter, mainly in November and December. Mean fecundity and egg diameter were positively correlated with fish length, and values were within the typical range reported in other brown trout populations. Most of the differences among streams can be explained by differences in water temperature. These results constitute a contribution to better understanding of key aspects of Mediterranean brown trout biology, and to develop conservation and management strategies for preserving their populations. info:eu-repo/semantics/acceptedVersion

Dinoflagellates of the genera Gambierdiscus and Fukuyoa are known to produce several bioactive compounds including the potent neurotoxic ciguatoxins (CTXs) which are able to accumulate in fish and through the food web. When humans ingest fish contaminated with CTXs, it can result in an intoxication named ciguatera. Although not all the currently recognized species are able to produce toxins, G. australes and G. excentricus have been highlighted to be the most abundant and toxic among the species present in the Atlantic. Even though the genera Gambierdiscus and Fukuyoa are endemic to tropical areas, recently their presence was recorded in subtropical and temperate regions. In this work, the development of three molecular assays for the detection of the Gambierdiscus and Fukuyoa genera and for G. australes and G. excentricus species, based on the combination of recombinase polymerase amplification with detection via hybridization, is successfully described. Furthermore, a remarkable limit of detection of a single cell was achieved. Additionally, six different species have been used to check the ability of each primer set to give an amplified product, even in presence of potentially interfering non-target DNAs. Therefore, these developments provide a rapid and cost-effective strategy for detection of both genera and two of the most toxic species, which will undoubtedly contribute to reliable screening of samples and ciguatera risk assessment, guaranteeing seafood safety and protection of human health. info:eu-repo/semantics/acceptedVersion

Dwarf oysters in the Ebro Delta are only observed growing on local pen shells, Pinna nobilis L., currently under extinction risk. The species identification of these populations is uncertain, given recent genetic classifications of dwarf oysters of Ostrea stentina species complex. Hence, the first objective of this study was to confirm the identity of dwarf oysters associated to P. nobilis in the Ebro Delta. Then, we aimed to assess the viability of hatchery and nursery production of O. stentina for potential conservation programs using diets based on a mix of live microalgae species or the commercial Shellfish Diet 1800®. Our results showed that COI sequences obtained were specific to O. stentina. Significant differences in the growth and survival of larvae between diet treatments were observed in 3 days. For the live diet, the larval period lasted from 15 to 22 days (299.2 ± 4 µm) whereas it took up to 36 days using the Shellfish Diet 1800® (280 ± 7.2 µm), with an overall mortality of 72.3 vs. 99.3%, respectively for each diet. Besides, no seed survival was observed for the commercial diet after a 10-day-fixation attempt. In contrast, ca. 16% of the individuals on the live diet that were allowed to settle reached the juvenile stage and could be released to the environment. Histological examination of obtained seed did not present any sign of disease and showed gonadal development for both sexes at ca. 6 months of age (16.1–19.1 mm). The growth curve obtained was fitted to a Schnute-Richards growth model which returned ages of up to 10 years for maximum local sizes of 45 mm. We conclude that although the Shellfish Diet 1800® is not an adequate diet for O. stentina, its hatchery production is feasible and might provide support to future conservation actions., Authors are grateful to the Biodiversity Foundation of the Ministry for Ecological Transition and the Demographic Challenge for supporting the Pinna Spat and Recupera Pinna projects in the 2019 and 2020 calls for proposals. P. Prado was contracted under the INIA-CCAA cooperative research program for postdoctoral incorporation from the Spanish National Institute for Agricultural and Food Research and Technology (INIA).

Aims To assess 1) the effect of the combination of flooding (winter flooding vs. non-winter flooding; WFL vs NWF) and timing of straw incorporation (early vs late straw incorporation; ESI vs LSI) in the post-harvest of paddy agrosystem, on a year-round global balance of greenhouse gases (GHG) exchanges, i.e. methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O); 2) the impact on the net ecosystem carbon balance (NECB) and 3) the resulting net global warming potential (GWP). Methods A field experiment was conducted with fortnightly samplings of main GHG emissions. Effect of the studied factors on GHG emissions was seasonally assessed. The net GWP is estimated from the balance between GHG (CH4 and N2O) and NECB. Results NWF-LSI reduced net GWP by 206% compared to conventional post-harvest management (WFL-ESI). NECB was similar in all treatments. Avoiding winter flooding reduced CH4 emissions significantly in the post-harvest and next growing seasons, while delay straw incorporation prevented CH4 and CO2 emissions during post-harvest. None of the treatments increased N2O emission. Environmental implications of post-harvest management options are discussed. Conclusions Post-harvest management affects net GWP of the paddy rice cultivation by modifying GHG emissions in post-harvest and next growing season without compromise sequestration C budget. The combination of non-winter flooding and late straw incorporation strategies were more effective in reducing both CH4 and CO2 emissions, due to avoiding higher temperatures at the time of the straw incorporation during post-harvest and increasing soil Eh conditions at the following growing season.

Sea level rise (SLR) is threatening low-lying coastal areas such as river deltas. The Ebro river Delta (Spain) is rep-resentative of coastal systems particularly vulnerable to SLR due to significant sediment retention behind up-stream dams (up to 99%), thereby dramatically reducing the capacity for deltaic sediment accretion. Rice production is the main economic activity, covering 66% of the delta area, and is negatively affected by SLR because of flooding and soil salinization. Therefore, appropriate adaptation measures are needed to preserve rice produc-tion. We combined Geographic Information Systems and Generalized Linear Models to identify zones prone to flooding and increasing soil salinity, and to calculate the so-called sediment deficit, that is the amount of sedi-ment needed to raise the land to compensate flooding and soil salinization. We modelled SLR scenarios predicted by the IPCC Fifth Assessment Report, and analysed the economic feasibility (not the technical feasibility) of reintroducing fluvial sediments retained in the upstream river dam reservoirs into the delta plain, which can con-tribute to maintaining land elevation and rice production with SLR. To do this, the costs of the sediment reintro-duction measures and their benefits in terms of avoided loss of rice production income were evaluated with an approximate economic cost-benefit analysis. Results predicted that between 35 and 90% of the rice field area will be flooded in the best and worst SLR scenarios considered (SLR = 0.5 m and 1.8 m by 2100, respectively), with a sediment deficit of 130 and 442 million tonnes, with an associated cost of sediment reintroduction of 13 and 226 million euro . The net benefit of rice production maintenance was 24.6 and 328 euro /ha. The proposed ad-aptation measure has a positive effect on rice production and can be considered as an innovative management option for maintaining deltaic areas under SLR. (c) 2021 Elsevier B.V. All rights reserved.

Rice cultivation is a major source of methane (CH4) emissions. Intermittent irrigation systems in rice cultivation, such as the mid-season drainage (MSD), are effective strategies to mitigate CH4 emissions during the growing season, though the reduction rates are variable and dependent on the crop context. Aeration periods induce alteration of soil CH4 dynamics that can be prolonged after flooding recovery. However, whether these changes persist beyond the growing season remains underexplored. A field experiment was conducted in Spain to study the effect of MSD implemented during the rice growing season on greenhouse gas (GHG) emissions in relation to the standard permanently flooded water management (PFL). Specifically, the study aimed at (1) assessing the CH4 mitigation capacity of MSD in the studied area and (2) testing the hypothesis that the mitigating effect of MSD can be extended into the following winter flooded fallow season. Year-round GHG sampling was conducted, seasonal and annual cumulative emissions of CH4 and N2O as well as the global warming potential were calculated, and grain yield was measured. MSD reduced growing season CH4 emissions by ca. 80% without yield penalties. During the flooded fallow season, MSD reduced CH4 emissions by ca. 60%, despite both fields being permanently flooded. The novelty of our observations lies in the amplified mitigation capacity of MSD by extending the CH4 mitigation effect to the following flooded winter fallow season. This finding becomes especially relevant in rice systems with flooded winter fallow season given the large contribution of this season to the annual CH4 emissions. info:eu-repo/semantics/acceptedVersion

The future success of rice farming will lie in developing productive, sustainable, and resilient farming systems in relation to coexistent ecosystems. Thus, accurate information on agricultural practices and grain yield at optimum temporal and spatial scales is crucial. This study evaluates the potential application of Sentinel-2 (S2) to monitor the dynamics of rice fields in two consecutive seasons (2018 and 2019) in the Ebro Delta growing area. For this purpose, time series of four different spectral indices (NDVI, NDWIMF, NDWIGAO, and BSI), derived from smoothed S2 data at 20 m spatial resolution, were generated. Then, a combination of the first and second derivative analysis on the temporal profiles of spectral indices was used to automatically identify key phenology and management features from regional to field scale; and for estimating crop yield at fields. Features extracted from NDVI and NDWIGAO were used for identifying significant phenological stage dates (i.e. Tillering, Heading Date, and Maturity), and field status (i.e. hydroperiod), although the performance of the proposed method at field-scale was limited by S2 data gaps. The absolute minimum of NDWIMF showed great potential for estimating rice yield, including different cultivars (r = - 0.8), and less sensibility to the number of valid images. Sentinel-2 alone cannot assure a consistent phenology monitoring at all fields but demonstrated strong capabilities for studying the performance of rice fields, thus must be considered in the development of new strategies for the management of rice-growing areas. info:eu-repo/semantics/acceptedVersion

The assessment of population structure and genetic diversity is crucial for the management and conservation of threatened species. Natural and artificial barriers to dispersal (i.e., gene flow) increase populations’ differentiation and isolation by reducing genetic exchange and diversity. Freshwater ecosystems are highly fragmented because of human activities. Threatened species with small population sizes are more sensitive to habitat fragmentation effects. Here, we investigate the genetic population structure and gene flow among seven populations of Aphanius sophiae in the Kor Basin by using sequences of the complete Cyt b gene and otolith morphometry. The Cyt b gene showed low level of genetic variation, only 4.12% of the identified sites were variable, and 2.42% were parsimony informative. Overall, haplotype diversity was low to moderate and nucleotide diversity was low to extremely low. Fish populations exhibited high levels of genetic differentiation, suggesting limited gene flow among them. These differences were obtained not only among geographically distant populations, but also among neighboring localities. Genetic population structure was supported by the AMOVA analysis and by the haplotype network (only one of 21 haplotypes were shared by two localities). Otolith morphometric analysis was in agreement with genetic results, the two most distant and isolated populations were clearly separated, and genetically close populations showed less differences in morphometry. A significant pattern of isolation by distance was also detected among A. sophiae populations, with genetic distance more correlated with hydrological distance than with geographic distance. Results suggested that limited gene flow due to habitat fragmentation is an important factor contributing to genetic structuring and to the loss of genetic variation of A. sophiae populations. Aphanius sophiae population structure seems to be the result of habitat fragmentation and water pollution, but other factors such as introduced species should be considered. Given the high degree of genetic structuring, the definition of conservation groups is of particular importance for A. sophiae, which should be considered endangered according to the IUCN criteria. Conservation plans must recognize the genetic independence of populations and manage separately preventing the loss of locally adapted genotypes. info:eu-repo/semantics/acceptedVersion

River deltas are ecologically and economically valuable coastal ecosystems but low elevations make them extremely sensitive to relative sea level rise (RSLR), i.e. the combined effects of sea level rise and subsidence. Most deltas are subjected to extensive human exploitation, which has altered the habitat composition, connectivity and geomorphology of deltaic landscapes. In the Ebro Delta, extensive wetland reclamation for rice cultivation over the last 150 years has resulted in the loss of 65% of the natural habitats. Here, we compare the dynamics of habitat shifts under two departure conditions (a simulated pristine delta vs. the human-altered delta) using the Sea Level Affecting Marshes Model (SLAMM) under the 4.5 and 8.5 RCP (Representative Concentration Pathways) scenarios for evaluating their resilience to RSLR (i.e. resistance to inundation). Results showed lower inundation rates in the human delta (~10 to 22% by the end of the century, depending on RCP conditions), mostly due to ~4.5 times lower initial extension of coastal lagoons compared to the pristine delta. Yet, inundation rates from ~15 to 30% of the total surface represent the worst possible human scenario, assuming no flooding protection measures. Besides, accretion rates within rice fields are disregarded since this option is not available in SLAMM for developed dry land. In the human delta, rice fields were largely shifted to other wetland habitats and experienced the highest reductions, mostly because of their larger surface. In contrast, in the pristine delta most of the habitats showed significant decreases by 2100 (~2 to 32% of the surface). Coastal infrastructures (dykes or flood protection dunes) and reintroduction of riverine sediments through irrigation channels are proposed to minimize impacts of RSLR. In the worst RCP scenarios, promoting preservation of natural habitats by transforming unproductive rice fields into wetlands could be the most sustainable option. info:eu-repo/semantics/acceptedVersion

Gull eggs are excellent bioindicators of environmental pollution as reflect the contamination levels of coastal areas, especially of persistent and bioacumulative compounds such as perfluoroalkyl substances (PFAS). This study aims to evaluate the geographical distribution and 10-year temporal trends (2009-2018) of 17 PFAS in eggs of two gull species (Larus michahellis and Larus audouinii) from 5 main Spanish colonies. ∑PFAS ranged from 13.7 ± 5.9 to 164 ± 17 ng g-1 wet weight and higher concentrations were observed in L. audouinii than in L. michahellis. Perfluorooctane sulfonate (PFOS) was the predominant compound in all samples, followed by perfluoroundecanoic acid (PFUnA) and perfluorotridecanoic acid (PFTriDA). Perfluorododecanoic acid (PFDoA), perfluorodecanoic acid (PFDA) and perfluorooctanoic acid (PFNA) were also found in all studied areas but at lower concentrations, while perfluorooctanoic acid (PFOA) was only detected in the Medes Islands. Principal Component Analysis revealed the co-occurrence of the 6 detected PFAS, and differentiated samples from Ebro Delta and Medes Islands, both located in the North-Eastern Mediterranean Sea, with high contribution of all PFAS, from Chafarinas and Atlantic Islands with lower concentration levels and variability. Also, different patterns were observed among colonies, suggesting the fish-based diet plays an important role in PFAS bioaccumulation. In all colonies, except for the Medes Islands, ∑PFAS decreased through the 10-year study period, with PFOS, PFUnA, and PFTriDA showing a significant concentration reduction in a colony-specific manner. This study demonstrates the usefulness and importance of continuous systematic long-term monitoring to determine the geographical distribution and temporal variations of PFAS in marine protected areas using gull eggs as bioindicators of environmental pollution., We acknowledge the Islas Atlánticas National Park, Refugio de Caza de las Islas Chafarinas, Delta de l'Ebre Natural Park, and Montgrí, les Illes Medes i el Baix Ter Natural Park to authorize sampling for our work. The Servei de Protecció i Gestió de la Fauna (Catalan Government) is acknowledged for sampling permission. We are especially grateful to José Antonio Fernández-Bouza and Vicente Piorno (Atlantic Islands), Javier Zapata (Chafarinas) for organizing the sampling, logistic support and transport of samples and for their valuable contributions to the study, and Mònica Cárdenas and Marc Bosch (Medes Islands) and Francesc Vidal and Antoni Curcó (PN Delta de l’Ebre) for facilitating sampling. We also thank Carles Domingo and Julia Piccardo (Forestal Catalana) for valuable field assistance. This research has been funded by the Spanish Autonomous Organism of National Parks (projects 038/2009 and 2012/768) and by the Spanish Ministry of Science and Innovation [PID 2019-105732 GB-C21, MCIN/AEI/10.13039/501100011033.

Ciguatera fish poisoning (CFP) is one of the most relevant seafood-borne diseases worldwide. It is caused by the ingestion of fish containing ciguatoxins (CTXs), lipophilic marine toxins produced by microalgae of the genera Gambierdiscus and Fukuyoa that accumulate into fish flesh and through the food webs. CFP is characterized by severe neurological, gastrointestinal, and cardiovascular disorders and affects approximately between 50,000 and 500,000 consumers annually worldwide. Real incidence of CFP is difficult to ascertain, due to under-reporting and misdiagnosis. Here, the first electrochemical immunosensor for the detection of CTXs is presented. Three different monoclonal antibodies (mAbs), two capture (3G8, 10C9) and a detector (8H4), were merged in a sandwich configuration for the combined detection of two main groups of CTX congeners (CTX1B and CTX3C ). Initially, the applicability of the immunosensor has been demonstrated with the analysis of fish samples coming from La Reunion island, providing results that correlate with mouse bioassay and cell-based assay. Then, fish coming from Mediterranean waters were analysed, giving promising results. Finally, extracts from Gambierdiscus and Fukuyoa were screened, allowing the separate detection of the two groups of CTX congeners, and giving new information regarding the toxin production of the genera. The developed bioanalytical tool is user-friendly, and can help to mitigate ciguatera risk, contributing to the protection of consumers health.

Ciguatera fish poisoning is one of the most relevant seafood-borne illnesses worldwide. It is caused by the ingestion of fish contaminated by ciguatoxins (CTXs). Primary producers of CTXs are dinoflagellates of the genera Gambierdiscus and Fukuyoa. This study is focused on the development of bioanalytical tools for the detection of Gambierdiscus and Fukuyoa. To achieve this objective, Recombinase Polymerase Amplification (RPA), which consists of an isothermal DNA amplification during a short period (30 minutes), was combined with an enzyme-linked oligonucleotide assay (ELONA). To evaluate the specificity of the RPA-ELONA, firstly primers for the genera Gambierdiscus/Fukuyoa were exposed to genomic DNA of different species (G. australes, G. excentricus, G. belizeanus, G. balechi and F. paulensis) and other microalgae used as controls (O. cf. ovata, P. lima and C. monotis). The same genomic DNA pools were also tested with species-specific primers for Gambierdiscus australes and Gambierdiscus excentricus. Finally, DNA was extracted from single cells of the previously mentioned genera and species, and tested with all the primer sets. For both the experiments, detection was achieved only when combining capture probes with their target RPA product, and no significant responses were observed in the presence of non-target DNA. Obtained results demonstrate the ability of the system to discriminate not only the genus Gambierdiscus/Fukuyoa from other microalgae, but also G. australes and G. excentricus species from their congeners. Furthermore, the limit of detection is as low as a single cell. Acknowledgments: The research has received funding from the Ministerio de Ciencia, Innovacion y Universidades through the CIGUASENSING (BIO2017-87946-C2-2-R) project. The authors acknowledge support from CERCA Programme/Generalitat de Catalunya. G. Gaiani acknowledges IRTA-Universitat Rovira i Virgili-Banco Santander for her PhD grant (2018PMF-PIPF-19).

Seafood contamination with marine toxins due to harmful algal blooms (HAB’s) is a global public health issue on the rise. Most Countries have monitoring programs for the detection of toxins in shellfish of toxic phytoplankton in seawater to prevent consumer intoxifications. The use of solid phase adsorbent and toxin tracking (SPATT) technology as toxin detection straight from the aquatic environment could complement the labour-intensive traditional monitoring methods. In this work, several types of cyclodextrins (cyclic oligomers with a conical structure and an internal cavity) have been evaluated as novel materials for SPATT. Cyclodextrins were tested at Masnou harbour (Catalonia, NW Mediterranean) during a Dinophysis sp. bloom. The cyclodextrins and the commercial Diaion (HP-20) were deployed twice for a 1-week period at five different locations of Masnou harbour. At the time of the experiment, Dinophysis sp. reached abundances as high as 91 341 cells /L. Successful accumulations of the lipophilic marine toxins; okadaic acid (OA) and pectenotoxin-2 (PTX2) were quantified by Liquid Chromatography- tandem Mass Spectrometry (LC-MS/MS). Higher levels of PTX2 were found in all cyclodextrins whereas OA and PTX2 contents were similar in the commercial resin. Accumulation of OA was higher in the commercial resin than in cyclodextrins, but these proved best for PTX2 adsorption. A clear correlation between cell abundance and toxin accumulation was observed. The research has received funding from the Ministerio de Ciencia, Innovacion y Universidades (MICINN), the Agencia Estatal de Investigacion (AEI) and the Fondo Europeo de Desarrollo Regional (FEDER) through the CIGUASENSING project (BIO2017-87946-C2-1-R and BIO2017-87946-C2-2-R). The authors acknowledge support from CERCA Programme/Generalitat de Catalunya.

Purpose To assess 1) the cumulative greenhouse gas emissions –GHG- and global warming potential (methane – CH4- and nitrous oxide) from rice fields in the growing and fallow seasons, and 2) the environmental and agronomic drivers of CH4 emissions, and their relative capacity to explain CH4 variation. Methods A two-year multisite field experiment covering the agronomic and environmental variability of a rice growing area in NE Iberian Peninsula was conducted with monthly samplings of GHG and monitoring of both environmental and agronomic factors. Information-theoretic framework analysis was used to assess the relative contribution of the environmental and agronomic variables on methane emissions. Results Two thirds of the CH4 is emitted in the fallow season. Edaphic factors exert more influence during the growing season whereas agronomic factors have a higher impact in the fallow. The implications of these findings on the design of improved mitigation options rice are discussed. Conclusions Soils with higher soil sulphate concentration, bulk density and clay content emit less CH4 in growing season. In the fallow season, the rates of both straw input and nitrogen fertilization stimulate CH4 emissions. Graphical abstract

The AWD is an irrigation technology for rice cultivation, consisting in implementing alternate draining and flooded periods over the growing season, that delivers multiple environmental benefits, such as reduced water consumption, CH4 emissions and arsenic (As) grain content, but can be offset by yield losses. The trade-offs between the agronomic and environmental effects of AWD are crop context-dependent and they also vary among the different versions of AWD studied. Therefore, the implementation of a safe AWD needs to be preceded by studies conducted within a specific rice cropping system. A two-year field experiment was conducted to assess the effect of AWD on grain yield, As and heavy metal content in grains, and greenhouse gas emissions in nine representative European rice cultivars grown in a Mediterranean growing area. The experiment was performed in a split-plot design with four replications. The study revealed a significant cultivar effect on the agronomic response to AWD. Among the studied cultivars, one of them performed as tolerant to AWD while a group formed by four cultivars showed slight non-significant yield decline. AWD significantly reduced CH4 emissions and the global warming potential by 90% being such a large mitigation capacity explained by the negligible N2O emissions found in both water treatments. Finally, the implementation of AWD significantly reduced by ca. 40% As grain concentration but increased cadmium content, though the levels remained below the recommended thresholds. Further, AWD increased key nutritional elements like cupper, selenium, and zinc. In conclusion, this study confirms that AWD can be safely implemented in Mediterranean rice cultivation conditions with limited or null yield impact while obtaining the associated environmental benefits of this practice info:eu-repo/semantics/acceptedVersion

The effects of dietary phospholipids (PL) on the performance of juvenile stellate sturgeon (Acipenser stellatus) was evaluated in terms of growth and feed efficiency parameters, muscle and liver fatty acid profiles, activity of digestive and antioxidative stress enzymes, and expression of lipoprotein lipase (lpl) and insulin-like growth factor (igf1). For this purpose, seven isoproteic (44% crude protein) and isolipidic (17% crude fat) diets containing graded levels of soybean lecithin (0, 1, 2, 4, 6, 8 and 10%) were prepared, resulting in 0.3, 0.9, 1.6, 2.7, 3.9, 5.3 and 5.4% of dietary PLs, respectively. At the end of the nutritional study (75 days), we found that there was a positive quadratic polynomial response between growth performance parameters and dietary PLs; somatic growth increased with increasing dietary PL levels up to 3.9% when growth parameters remained stable. Dietary PLs reduced the accumulation of fat stores in the liver and up-regulated the expression of the lipoprotein lipase gene, confirming the important role of this enzyme in incorporating plasma lipids into tissues, whereas the activities of CAT and SOD showed a positive linear increase with dietary PL levels. Increasing dietary PLs from 0.9 to 3.9% promoted the activity of gastric (pepsin) and pancreatic (trypsin, chymotrypsin, bile salt-activated lipase and α-amylase) enzymes, whereas higher inclusion levels of PLs did not provide any advantage in terms of A. stellatus digestive capacities. The analysis of fatty acid profiles in diets and selected tissues (liver and muscle) showed the capacity of A. stellatus juveniles to desaturate and elongate linoleic (C18:2n–6) and alpha-linolenic (C18:3n–3) acids to arachidonic (C20:4n-6), eicosapentaenoic (C20:5n-3) and docosahexaenoic (C22:6n-3) acids. Based on the results of growth performance, feed efficiency and physiological parameters, the inclusion of 3.9% of PLs in compound diets for juvenile stellate sturgeon are recommended. info:eu-repo/semantics/acceptedVersion

Consumption of seafood contaminated with ciguatoxins (CTXs) leads to a foodborne disease known as ciguatera. Primary producers of CTXs are epibenthic dinoflagellates of the genera Gambierdiscus and Fukuyoa. In this study, thirteen Gambierdiscus and Fukuyoa strains were cultured, harvested at exponential phase, and CTXs were extracted with an implemented rapid protocol. Microalgal extracts were obtained from pellets with a low cell abundance (20,000 cell/mL) and were then analyzed with magnetic bead (MB)-based immunosensing tools (colorimetric immunoassay and electrochemical immunosensor). It is the first time that these approaches are used to screen Gambierdiscus and Fukuyoa strains, providing not only a global indication of the presence of CTXs, but also the ability to discriminate between two series of congeners (CTX1B and CTX3C). Analysis of the microalgal extracts revealed the presence of CTXs in 11 out of 13 strains and provided new information about Gambierdiscus and Fukuyoa toxin profiles. The use of immunosensing tools in the analysis of microalgal extracts facilitates the elucidation of further knowledge regarding these dinoflagellate genera and can contribute to improved ciguatera risk assessment and management. info:eu-repo/semantics/acceptedVersion

We analyzed variation at the GPI-2 locus and eleven microsatellite loci of eastern mosquitofish Gambusia holbrooki populations introduced to the Ebro River (Spain), sampling above and below a dam (Flix Reservoir) where severe chronic pollution has been well documented. Allele frequency changes at the GPI-2 locus in the sites nearest to the polluted sediments agree with previous results from studies in mercury-exposed populations of this highly invasive fish. Genetic distinction of the mosquitofish collected close to the polluted sediments was detected at the GPI locus but also at the presumptive neutral microsatellite loci. Recent migration rates estimated from microsatellites indicated that around 30% of fish collected in a specific location were immigrants from upstream and downstream sources. Such high migration rates probably contribute to the mosquitofish's invasive success and suggest that the consequences on the mosquitofish regional genetic structured of high levels of water toxicants could be mediated by immigration from other sites, but the effect of pollutants on local diversity might be higher than observed here. info:eu-repo/semantics/acceptedVersion

Cyclodextrins, cyclic oligomers that form a conical structure with an internal cavity, are proposed as new and sustainable materials for passive sampling of lipophilic marine toxins. Two applicability scenarios have been tested. First, disks containing β-cyclodextrin-hexamethylene diisocyanate (β-CD-HDI) and β-cyclodextrin-epichlorohydrin (β-CD-EPI) polymers were immersed in Prorocentrum lima cultures for different days (2, 12 and 40). LC-MS/MS analysis showed capture of free okadaic acid (OA) and dinophysistoxin-1 (DTX1) by cyclodextrins at contents that increased with immersion time. Cyclodextrins resulted more efficient in capturing DTX1 than OA. In a second experiment, disks containing β-CD-HDI, β-CD-EPI, γ-CD-HDI and γ-CD-EPI were deployed in harbor waters of El Masnou (NW Mediterranean Sea) during a Dinophysis sacculus bloom in February 2020. Free OA and pectenotoxin-2 (PTX2) were captured by cyclodextrins. Toxin contents were higher at sampling points and sampling weeks with higher D. sacculus cell abundance. In this case, PTX2 capture with cyclodextrins was more efficient than OA capture. Therefore, cyclodextrins have provided information regarding the toxin profile of a P. lima strain and the spatial and temporal dynamics of a D. sacculus bloom, proven efficient as passive sampling materials for environmental monitoring. info:eu-repo/semantics/acceptedVersion

Multivariate allometry patterns and length at metamorphosis (Lm) were determined in Acipenser stellatus by means of principal component analysis from 12 morphometric characters. The multivariate analysis differentiated three growth stanzas: the prelarval, larval, and early juvenile stages. The prelarval stage comprised the period from hatching (9.7 mm in total length, TL) to the transition to exogenous feeding (17.7 mm TL, Lm1), a period characterized by yolk sac depletion and fast growth of the anterior and posterior body regions. These changes coincided with the development of sensory, feeding, respiratory, and swimming systems to improve foraging behavior and predator avoidance. During the larval period (17.7–52.8 mm, Lm1–Lm2), specimens reached a juvenile phenotype characterized by the development of median fins, elongation and flattening of the snout and formation of bony scutes, and the improvement of their swimming capacities, allowing larvae to regulate their dispersal distance from the spawning grounds. The end of the larval period and acquisition of the juvenile phenotype were found after Lm2when some variables reached isometry or even displayed a negative allometric growth.

Ostreopsis cf. ovata is a benthic microalga distributed in tropical and temperate regions worldwide which produces palytoxins (PlTXs). Herein, an electrochemical biosensor for the detection of this toxic microalga is described. The detection strategy involves isothermal recombinase polymerase amplification (RPA) of the target using tailed primers and a sandwich hybridisation assay on maleimide-coated magnetic beads immobilised on electrode arrays. The biosensor attained a limit of detection of 9 pg/μL of O. cf. ovata DNA (which corresponds to ~640 cells/L), with no interferences from two non-target Ostreopsis species (O. cf. siamensis and O. fattorussoi). The biosensor was applied to the analysis of planktonic and benthic environmental samples. Electrochemical O. cf. ovata DNA quantifications demonstrated an excellent correlation with other molecular methods (qPCR and colorimetric assays) and allowed the construction of a predictive regression model to estimate O. cf. ovata cell abundances. This new technology offer great potential to improve research, monitoring and management of O. cf. ovata and harmful algal blooms. info:eu-repo/semantics/acceptedVersion

Shellfish aquaculture has a major socioeconomic impact on coastal areas, thus it is necessary to develop support tools for its management. In this sense, phytoplankton monitoring is crucial, as it is the main source of food for shellfish farming. The aim of this study was to assess the applicability of Sentinel 2 multispectral imagery (MSI) to monitor the phytoplankton biomass at Ebro Delta bays and to assess its potential as a tool for shellfish management. In situ chlorophyll-a data from Ebro Delta bays (NE Spain) were coupled with several band combination and band ratio spectral indices derived from Sentinel 2A levels 1C and 2A for time-series mapping. The best results (AIC = 72.17, APD < 10%, and MAE < 0.7 mg/m3) were obtained with a simple blue-to-green ratio applied over Rayleigh from Sentinel 2A levels 1C and 2A for time-series mapping. The best results (AIC = 72.17, APD < 10%, and MAE < 0.7 mg/m3) were obtained with a simple blue-to-green ratio applied over Rayleigh corrected images. Sentinel 2–derived maps provided coverage of the farm sites at both bays allowing relating the spatiotemporal distribution of phytoplankton with the environmental forcing under different states of the bays. The applied methodology will be further improved but the results show the potential of using Sentinel 2 MSI imagery as a tool for assessing phytoplankton spatiotemporal dynamics and to encourage better future practices in the management of the aquaculture in Ebro

Summary Studies quantifying the content of fine particulate matter (organic and inorganic) retained in macrophyte stands are scarce. Thus, little is known about the relationship between retention of fine particulate matter and macrophyte architecture, especially in rivers. Here, we quantified the amount of organic and inorganic fine particulate matter retained by three different macrophyte species having two contrasting plant architectures (‘mesh-like’ and ‘strap-like’), to test the role of plant architecture on retention. Results showed that plant architecture and water velocity were related and their interaction was important for particle sedimentation/retention by macrophyte leaves and stems. The complexity of plant architecture appeared to be the main factor explaining variation in the amount of trapped matter. Increases in water velocity led to a decline of both the organic and the inorganic particulate matter retained by macrophytes, while a decrease in water velocity was related to an increase in macrophyte cover. The concentrations of trapped matter (both organic and inorganic) also differed significantly among seasons, indicating the existence of a seasonal cycle in the retention of fine particulate matter mainly associated with macrophyte cover (and biomass) and water velocity. Although there were seasonal and spatial variations in sediment retention in both ‘mesh-like’ and ‘strap-like’ architectures, macrophytes were effective sediment traps.

Ostreopsis is a toxic benthic dinoflagellate largely distributed worldwide in tropical and temperate areas. In the Mediterranean Sea, periodic summer blooms have been reported and have become a serious concern due to their direct impact on human health and the environment. Current microalgae identification is performed via light microscopy, which is time-consuming and is not able to differentiate among Ostreopsis species. Therefore, there is mature need for rapid, specific and easy-to-use detection tools. In this work, a colorimetric assay exploiting a combination of recombinase polymerase amplification (RPA) and a sandwich hybridisation assay was developed for O. cf. ovata and O. cf. siamensis detection and quantification. The specificity of the system was demonstrated by cross-reactivity experiments and calibration curves were successfully constructed using genomic DNA, achieving limits of detection of 10 and 14 pg/μL for O. cf. ovata and O. cf. siamensis, respectively. The assay was applied to the analysis of planktonic and benthic environmental samples from different sites of the Catalan coast. Species-specific DNA quantifications were in agreement with qPCR analysis, demonstrating the reliability of the colorimetric approach. Significant correlations were also obtained between DNA quantifications and light microscopy counts. The approach may be a valuable tool to provide timely warnings, facilitate monitoring activities or study population dynamics, and paves the way towards the development of in situ tools for the monitoring of harmful algal blooms. info:eu-repo/semantics/acceptedVersion

A new global database of 86 deltas and river basins was analyzed to investigate the relative importance of deforestation and land use changes versus natural forcings in determining long-term total delta size. Results show that mean river flow and shelf slope were the most important variables, whereas population density and sediment load had a much lower importance. Deforestation and other variables related to land-use generally had a very small effect, but were more influential in a subset comprising Mediterranean and Black Sea deltas. As most deltas have developed over thousands of years, the much shorter-lived anthropogenic signals from deforestation and other landscape perturbations have had only secondary impact on the total area of deltas. Also, delta progradation is strongly influenced on sand deposition, whereas anthropogenic impacts on sediment load have more often impacted mostly the finer sediment being deposited offshore (prodelta deposits) or in the deltaic plain. These data disproves the hypothesis that delta size and growth is strongly influenced by human forcings, particularly for larger deltas, since Holocene delta building is mainly determined by natural forces. However, humans are influencing the geomorphology of deltas, particularly over the last century when the Anthropocene nature of deltas has become manifest. A more precise terminology is proposed to clarify concepts such as “human-made”, “human-engineered” or “human-influenced” deltas. info:eu-repo/semantics/acceptedVersion

Dispersal is a critical determinant of animal distribution and population dynamics, and is essential information for management planning. We studied the movement patterns and the influence of habitat and biotic factors on Mediterranean brown trout (Salmo trutta) by mark-recapture methods in three headwater streams of the Ebro Basin (NE Iberian Peninsula). Fish were sampled by electrofishing on five occasions over 18–24 months and movements of over 3,000 individually tagged trout (age 1+ onwards) were recorded. Most of the tagged fish exhibited limited movement and were recaptured within 100 m from the initial capture section. Small seasonal differences in the movement pattern were observed, but in two of the streams, displacement distances increased prior the spawning period in autumn. The frequency distributions of dispersal distances were highly leptokurtic and skewed to the right and fitted well to a two-group exponential model, thus trout populations were composed of mobile and stationary individuals, the latter being the predominant component in the populations (71.1–87.5% of individuals). The mean dispersal distances, for fish captured at least in three sampling events, ranged 20.7–45.4 m for the stationary group and 229.4–540.5 m for the mobile group. Moving brown trout were larger than non-moving individuals and exhibited higher growth rates in two of the streams. Habitat features were not consistently linked to movement rates, but there were some interaction effects between stream and habitat characteristics such as depth, cover and water velocity. This research was supported by the Biodiversity Conservation Plan of ENDESA through the project PIE 121043-00-FECSA.

Paddy rice fields are one of the most important sources of anthropogenic methane. Improving the accuracy in the CH4 budget is fundamental to identify strategies to mitigate climate change. Such improvement requires a mechanistic understanding of the complex interactions between environmental and agronomic factors determining CH4 emissions, and also the characterization of the annual temporal CH4 emissions pattern in the whole crop cycle. Hence, both the growing and fallow seasons must be included. However, most of the previous research has been based on single-factor analyses that are focused on the growing season. In order to fill this gap, a study was conducted in a Mediterranean rice agrosystem (Ebre Delta, Catalonia) following a farm-to-farm approach with the purpose of 1) evaluating the cumulative and temporal pattern of CH4 emission, and 2) conducting a multi-variate analyses to assess the associative pattern, relative contribution and temporal variation of the main explanatory variables concerning the observed CH4 emissions. Measurements of CH4 emissions and agronomic and environmental parameters in 15 commercial rice fields were monitored monthly, during a whole crop field cycle. The temporal pattern of CH4 emission followed a bi-modal distribution peaking in August and October. The cumulative annual CH4 emissions from rice fields amounted 314 kg CH4 kg ha-1, of which ca. 70% were emitted during the fallow season. The main controlling factors of the CH4 emission rate in the growing season were positive related to water level and plant cover, while soil redox was negatively related. The main controlling factors in the fallow season were water level (negatively related, conversely to the growing season), as well as straw incorporation and soil temperature (positively related). The results of this study highlight the importance of the often neglected fallow season in the accurate estimation of CH4 emissions and, thus, the necessity of measurement programs that cover the whole crop field cycle. This information is the first step for setting effective mitigation strategies based on straw and water management.

Trophic ecology is essential to understand ecosystem functioning and structure and assist biological conservation. Here we investigate, for the first time, the feeding ecology of Aphanius farsicus, a cyprinodontid fish endemic of a single landlocked river basin in central Iran. We sampled monthly a population of this fish species during a year and examined differences in food across seasons, sexes and sizes. Similarly to other cyprinodonts, A. farsicus showed sexual dimorphism and more abundance of females. Size structure and individual condition varied across seasons, with larger fish in spring and better condition in summer and less in winter. We found no empty guts, suggesting that these fish feed all year round due to the warm climate of its native distribution. Farsi toothcarp diet was based on detritus, algae (particularly diatoms, green algae, and cyanobacteria), and small invertebrates. Seasonal variation in diet was more important than variation due to fish size and the Farsi toothcarp consumed more green algae in spring and early summer and more diatoms and insects the rest of the year. Herbivory was considerable, similarly to a few other cyprinodonts, and increased with fish size, particularly because of higher consumption of green algae. As with species composition in diet, season was more important than size in the variation of number, biovolume, mean size, and diversity of prey captured, with higher number, richness and size of prey captured in summer. The ontogenetic diet shift was less marked in this cyprinodont than in many other Aphanius species, probably due to its reduced size and the resource availability of its habitat, but was also shown by size-dependent feeding selectivity for a few invertebrates Financial support was provided by the Deutscher Akademischer Austauschdienst (DAAD) through a doctoral fellowship to ZG and by the Spanish Ministry of Science (projects CGL2009-12877-C02-01 and Consolider-Ingenio 2010 CSD2009-00065)

International audience; To study the influence of temperature (4, 6, and 12 °C) on the development of brown trout (Salmo trutta) from hatching to the end of metamorphosis, an analysis of allometric growth patterns was conducted to identify two different groups of individuals, namely developmental phases at total lengths (TL) ranging from 2.72 cm at 4 °C to 2.22 cm at 12 °C. Then, a multitrait approach considering different variables like the survival rate, development time, morphometric characteristics, energetic value, and skeletal mineralization was conducted on these two groups. Results indicated that the first growth phase was slower at 4 °C, whereas the second was also slower at this temperature, even though swimming behavior was already present. However, at 12 °C, fry showed a delay in their development (i.e., lower levels of skeletal mineralization and energetic content) during the first growth phase, but they compensated during the second growth phase, reaching the same size in TL when compared with the other temperatures (4 and 6 °C); fry at 12 °C showed low energy reserves. Our study demonstrated that the use of an allometric analysis to identify different developmental stages coupled with a multitrait approach was more efficient than a classical distinction between biological stages (hatching, emergence, first food intake, and exogenous feeding), and this procedure is of interest when evaluating the impact of rearing conditions on early development in fish.; Le but de ce travail est l’étude de l’influence de la température (4, 6 et 12 °C) sur le développement de Salmo trutta de l’éclosion à la fin de la métamorphose. Pour cela, nous avons utilisé une analyse allométrique des caractéristiques morphologiques. A la suite de cette analyse, nous avons identifié deux phases différentes lors du développement des alevins, correspondant à des groupes d’individus (allant de 2,22 cm à 12 °C à 2,72 cm à 4 °C) pour lesquels nous avons comparé les autres traits de développement (ossification, valeur énergétique) par une approche multi traits. Nous avons montré que durant les deux phases du développement, la croissance était lente à 4 °C, mais la nage était présente. A 12 °C, les alevins présentent un déficit de croissance durant la première phase, mais il est compensé pendant la deuxième phase et les alevins atteignent ensuite une taille identique à celle des autres températures (4 et 6 °C), avec des réserves énergétiques faibles à la fin de la métamorphose. Cette étude a montré que l’utilisation d’une analyse allométrique des paramètres morphométriques couplée à une approche multi traits était plus efficace pour étudier le développement des larves de poissons qu’une étude basée sur les stades classiquement définis (éclosion, émergence, prise de nourriture exogène).

Summary Hatchery reared beluga (Huso huso) were observed from hatching until the juvenile stage in order to analyse their early development and allometric growth patterns using bivariate and multivariate allometric analyses for different body regions (e.g. head, trunk, tail) and test whether there existed similarities in the growth patterns of beluga compared to other fish species, especially other sturgeon species belonging to the genus Acipenser. Results from Principle Component Analysis on morphometric characters (total length, head length, head height, trunk length, rostrum length and eye diameter) in specimens showed that there were shifts in the relative growth of these characters in early development (length at metamorphosis, Lm). A first stage comprised of hatching to 17.03 ± 0.14 mm in total length (Lm1), a second stage was between 17.03 and 25.41 ± 0.21 mm (Lm2), and a third developmental stage at larger sizes (larvae larger than Lm2). Most morphological (feeding, swimming, sensorial and respiratory systems) and morphometric changes in beluga development took place during the second growth stanza, which may be considered as a transitional period from the larval to the juvenile stage, whereas at larger sized fish may be considered as early juveniles. The allometric growth of beluga matched developmental and behavioral events (e.g. swimming-up, schooling and free benthic swimming) observed in the early ontogeny of this species, and showed the priority of growth of the cephalic and tail regions in beluga pre-larvae for feeding and respiratory functions, and the tail for cruising and escape reactions prior to the full development of the digestive system. This study provides information on the ontogeny of the species, establishing a reference for its normal development that might be useful for evaluating the suitability and quality of fish produced for restocking purposes and improving the current beluga management plans.

Summary We report the first description of the ontogenic development of the axial skeleton and unpaired fins of hatchery reared bay snook (Petenia splendida, Perciformes: Cichlidae) from hatching (5.3–5.5 mm in standard length, SL) to the juvenile stage (16.1–17.5 mm SL) by means of alcian blue-alizarin red staining. The study of axial skeleton development was complemented by digital analysis of its level of ossification (number of red pixels) in order to identify major changes in vertebral column and caudal fin complex development. The main events of the skeletogenesis of the vertebral column and unpaired fins in P. splendida larvae were comprised between the onset of notochord segmentation and completion of the caudal fin complex at 6 (171 degree days post hatch, ddph; 6.4–6.5 mm SL) and 24 days post hatching (dph) (684 ddph, 8.9–9.4 mm SL), respectively; whereas the anal and dorsal fins completed morphogenesis at older ages (36 dph, 1026 ddph, 11.0–11.8 mm SL). In this sense, the development of a subcarangiform swimming mode in early juveniles was achieved with complete ossification of vertebral bodies and caudal lepidotrichia, as well as partial ossification of the caudal-fin complex elements (hypurals, epurals, uroneural and parahypural). This information can be considered as a reference for other studies evaluating the quality of larvae and the influence of rearing biotic and abiotic factors in the skeletogenesis of this cichlid species and the occurrence of skeletal deformities.

Biodiversity is currently declining in the Mediterranean, particularly in freshwater ecosystems. The Iberian Peninsula is not an exception with many fish species threatened or endangered. This is the case of Parachondrostoma arrigonis, which has experienced a marked reduction of more than 80 % in both number and area of occupancy in the last 20 years. Species historical records showed a widespread distribution in the Jucar Basin, but according to recent records, P. arrigonis was completely absent in the main river course, being restricted to only some tributaries. Current fish distribution was grouped into only seven fish population nuclei geographically isolated among them. Only two population nuclei showed with well-developed fish populations. Factors affecting P. arrigonis distribution are associated to human activities, such as river channelization, flow regulation, pollution and habitat degradation, being concentrated in the middle and lower river reaches where the Jucar nase is in marked regression. Another key factor was the presence of introduced species, reporting a strong spatial segregation with the translocated Pseudochondrostoma polylepis, an ecologically similar species, and with the exotic piscivorous Micropterus salmoides and Esox lucius, which are currently occupying most of the P. arrigonis historical range. Because its dramatic situation, conservation measures must be urgently taken, for instance, by establishing conservation areas, an exotic fish removal programme, and by developing a flow regulation program to minimize dam effects. However it is necessary to increase our knowledge regarding the habitat requirements of the Jucar nase and its interactions with invasive species. If measures are not implemented its extinction seems inevitable.

The hydrological connectivity between the salt marsh and the sea was partially restored in a Mediterranean wetland containing isolated ponds resulting from former salt extraction and aquaculture activities. A preliminary assessment provided evidence that ponds farther from the sea hosted very large numbers of the endangered Spanish toothcarp,Aphanius iberus, suggesting that individuals had been trapped and consequently reach unnaturally high densities. In order to achieve both habitat rehabilitation and toothcarp conservation, efforts were made to create a gradient of hydrologically connected areas, including isolated fish reservoirs, semi-isolated, and connected salt marsh-sea areas that could allow migratory movements of fish and provide some protection forA. iberus. The fish community was monitored prior to, and for three years after rehabilitation. Results showed an increase in the number of fish species within semi-isolated areas (Zone A), whereas areas adjacent to the sea (Zone B) increased the number of marine species and decreased that of estuarine species (ES). Yet overall differences in fish assemblages were much higher between zones than among study years. Generalized linear models (GLMs) evidenced that distance to the sea was the most important variable explaining the local diversity of the fish community after restoration, with occasional influence of other factors such as temperature, and depth. The abundance ofA. iberuswas consistently higher in semi-isolated areas at greater distances from the sea, but a decline occurred in both zones and in isolated reservoir ponds after restoration efforts, which may be attributable to interannual differences in recruitment success and, to a lesser extent, to dispersal into adjacent habitats. A negative effect of restoration works on fish population cannot be excluded, but the final outcome of the intervention likely needs a longer period.

Climate change and sea level rise (SLR) are global impacts threatening the sustainability of coastal territories and valuable ecosystems such as deltas. The Ebro Delta is representative of the vulnerability of coastal areas to SLR. Rice cultivation is the main economic activity in the region. Rice fields occupy most of the delta (ca. 65%) and are vulnerable to accelerated SLR and consequent increase in soil salinity, the most important physical factor affecting rice production. We developed a model to predict the impacts of SLR on soil salinity and rice production under different scenarios predicted by the Fifth Assessment Report of the Intergovernmental Panel on Climate Change by coupling data from Geographic Information Systems with Generalized Linear Models. Soil salinity data were measured in agricultural parcels and rice production from surveys among farmers. The correlation between observed and soil salinity predicted values was high and significant (Pearson's r=0.72, P

The zebra mussel (Dreissena polymorpha Pallas, 1771) and the quagga mussel (D. rostriformis Deshayes, 1838) are successful invasive bivalves with substantial ecological and economic impacts in freshwater systems once they become established. Since their eradication is extremely difficult, their detection at an early stage is crucial to prevent spread. In this study, we optimized and validated a qPCR detection method based on the histone H2B gene to quantify combined infestation levels of zebra and quagga mussels in environmental DNA samples. Our results show specific dreissenid DNA present in filtered water samples for which microscopic diagnostic identification for larvae failed. Monitoring a large number of locations for invasive dreissenid species based on a highly specific environmental DNA qPCR assay may prove to be an essential tool for management and control plans focused on prevention of establishment of dreissenid mussels in new locations We are indebted to different colleagues for zebra mussel sample collections: Concha Durán (Ebro Hydrografic Confederation, Spain) for the logistic advice; Anna Terrats and Carolina Solà (Catalan Water Agency from the Government of Catalonia, Spain) for the filtered-water environmental samples. We would thank to Mariona Palacios for her collaboration in the analysis into her Final Master Project. This research was carried out within the objectives of the research project CGL200909407 of the Spanish Ministerio de Ciencia e Innovación (MICINN)

The aim of this work was to characterize stress coping styles of Senegalese sole ( Solea senegalensis ) juveniles and breeders and to select an operational behavioural screening test (OBST) that can be used by the aquaculture industry to classify and select between behavioural phenotypes in order to improve production indicators. A total of 61 juveniles and 59 breeders were subjected to five individual behavioural tests and two grouping tests. At the end of the individual tests, all animals were blood sampled in order to measure cortisol, glucose and lactate. Three tests (restraining, new environment and confinement) characterized the stress coping style behaviour of Senegalese sole juveniles and breeders and demonstrated inter-individual consistency. Further, the tests when incorporated into a principal components analysis (PCA) (i) identified two principal axes of personality traits: ‘fearfulness-reactivity’ and ‘activity-exploration’, (ii) were representative of the physiological axis of stress coping style, and (iii) were validated by established group tests. This study proposed for the first time three individual coping style tests that reliably represented proactive and reactive personalities of Senegalese sole juveniles and breeders. In addition, the three proposed tests met some basic operational criteria (rapid testing, no special equipment and easy to apply and interpret) that could prove attractive for fish farmers to identify fish with a specific behaviour that gives advantages in the culture system and that could be used to establish selection-based breeding programmes to improve domestication and production.

Multimesh nylon gillnets were set in three Ebro Delta (North-East of Spain) lagoons to determine mesh selectivity for the inhabiting fish community. Each gillnet consisted on a series of twelve panels of different mesh size (ranging from 5.0 to 55.0 mm bar length) randomly distributed. The SELECT method (Share Each Length’s Catch Total) was used to estimate retention curves through five models: normal location, normal scale, gamma, lognormal and inverse Gaussian. Each model was fitted twice, under the assumptions of equal and proportional to mesh size fishing effort, but no differences were found between approaches. A possible situation of overfishing in the lagoons, where artisanal fisheries are carried out with a low surveillance effort, was assessed using a vulnerable species inhabiting these brackish waters as case study: the sand smelt, Atherina boyeri . The minimum size for its fishery has not been established, thus remaining under an uncontrolled exploitation situation. Therefore, a Minimum Landing Size (MLS) is proposed based on sexual maturity data. The importance of establishing an adequate MLS and regulate mesh sizes in order to respect natural maturation length is discussed, as well as, the proposal of other measures to improve A. boyeri fishery management.

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)

The lower Ebro River (Catalonia, Spain) has recently undergone a regime shift from a phytoplankton-dominated to a macrophyte-dominated system. This shift is well known in shallow lakes but apparently it has never been documented in rivers. Two initial hypotheses to explain the collapse of the phytoplankton were considered: a) the diminution of nutrients (bottom-up); b) the filtering effect due to the colonization of the zebra mussel (top-down). Data on water quality, hydrology and biological communities (phytoplankton, macrophytes and zebra mussel) was obtained both from existing data sets and new surveys. Results clearly indicate that the decrease in phosphorus is the main cause of a dramatic decrease in chlorophyll and large increase in water transparency, triggering the subsequent colonization of macrophytes in the river bed. A Generalized Linear Model analysis showed that the decrease in dissolved phosphorus had a relative importance 14 times higher than the increase in zebra mussel density to explain the variation of total chlorophyll. We suggest that the described changes in the lower Ebro River can be considered a novel ecosystem shift. This shift is triggering remarkable changes in the biological communities beyond the decrease of phytoplankton and the proliferation of macrophytes, such as massive colonization of Simulidae (black fly) and other changes in the benthic invertebrate communities that are currently investigated.