Search

Trabajo presentado en el VIII International Symposium on Marine Sciences (ISMS 2022), celebrado en Las Palmas de Gran Canaria (España) entre el 6 y el 8 de julio de 2022., Callinectes sapidus, the invasive blue crab from the west of the Atlantic Ocean, has extended its distribution along the Atlantic coast around the Gulf of Cadiz and increased massively since 2016. Food web studies are useful for understanding changes in ecosystems caused by exotic species. Stable isotope analysis (δ13C and δ15N) were used to assess the potential carbon sources and its trophic relationships among different ecosystems (estuaries and saltmarshes), sexes (male and females) and seasons (summer vs. autumn). Significant differences were found in the δ13C of blue crabs from the estuaries and salt-marshes (-21.2 ±2.6 vs -14.2 ±0.9, respectively). These differences may be explained by an increase in the 13C of the blue crabs from the salt-marshes, probably due to the enrichment of this isotope in the primary producers such as the salt marsh plants (Menéndez and Sanmartí, 2007) and its preys inhabiting this ecosystem. Meanwhile, the more depleted 13C values in the estuary crabs seem to reflect a carbon source from mollusks and fish derived from decomposing detritus. Among the ecosystems analyzed, δ15N was only significantly enriched in the crabs of the Guadalquivir estuary and was higher in males than females. Also, seasonal differences were found in this estuary in both sexes, by a decrease in the 15N values between summer and autumn. Those differences, can be explained by the fact that the Guadalquivir estuary suffers nitrogen hyper-nitrification due to intensive agriculture and is more noticeable in the upper part of the estuary, to which the males are more associated due to their life cycle. Previous studies reported, the diet of C. sapidus seems to be opportunistic, dependent on the food availability in different habitats (Prado et al., 2022), with a divergence in sexes induced by different spatial distributions. Future studies analyzing the stomach content and trophic behavior should be conducted to clarify our results.

Trabajo presentado en Symposium on Decadal Variability of the North Atlantic and its Marine Ecosystems: 2010-2019, celebrado en Bergen (Noruega) del 20 al 22 de junio de 2022., The Spanish Institute of Oceanography (IEO) has been conducting a multidisciplinary study of the marine ecosystem in the Gulf of Cadiz (GoC; SW Iberian Peninsula) since 2009 within the frame of the program Time Series of Oceanographic data in the Gulf of Cadiz (STOCA, in Spanish). The program maintains repeated observations along five across-shelf transects: three times a year from 2009 to 2012 and quarterly on hereafter. In this paper we present the temporal evolution of the zooplankton community in the GoC. In particular, we focused on samples from three stations located off the Guadalquivir river mouth: GD1 (20 m depth), GD3 (80 m) and GD6 (450 m). Samples were taken with bongo-40 cm paired zooplankton nets (mesh size 200 m). Double oblique hauls were conducted from top to bottom or to a maximum depth of 200 m) while the ship was steaming at 2.5 kn. A total of 43 samples per station were included in the analysis. Samples were imaged with ZooScan. Full images were processed with ZooProcess which generated set of associated features measured on each identified object (Gorsky et al, 2010). These objects were sorted following a common taxonomic guide using the web application EcoTaxa (http://ecotaxa.obs-vlfr.fr). As a sanity check, a variable number of aliquots were directly identified by light microscopy. These results permitted the description of the mean and variable components of the plankton community, their seasonal in the context of the thermohaline and transport variability in the 2010s.

The standard gear for the International Bottom Trawl Survey (IBTS), a fisheries-independent research survey originating from the 1960s, will be replaced. The long-term monitoring pro-vides data on commercial pelagic and demersal fish species for stock assessments and facili-tates examination of changes in fish distribution and abundance. The remit of this Workshop on the Further Development of the New IBTS Gear (WKFDNG) was to design a simple gear, as standardised as possible, robust, and easy to maintain. Additionally, the workshop was tasked to provide input for the roadmap towards implementation of the new gear.

This working document presents the results of the most significant cephalopods caught on the Porcupine Spanish Groundfish Survey (SP-PORC-Q3) in 2021. Biomass, abundance, geographical distribution and length frequencies for Eledone cirrhosa (horned octopus), Bathypolypus sponsalis (globose octopus), Todarodes sagittatus (European flying squid), Todaropsis eblanae (lesser flying squid), Loligo forbesi (veined squid), Illex coindetii (broadtail shortfin squid), Rossia macrosoma (stout bobtail squid) and other scarce cephalopods have been analysed. The species E. cirrhosa, R. macrosoma and L. forbesi increased in terms of biomass and abundance, especially R. macrosoma, reaching the highest biomass value in the time series, whereas T. sagitattus increased only in abundance terms but decreased slightly in biomass terms. In contrast, T. eblanae and B. sponsalis decreased strongly after the high values of the previous two years, as did I. coindetii. Most of the usually scarce species increased their biomass, with the exception of H. reversa.

On 15 September 2021 , during one of the experimen tal bottom trawls, ca rried out at a speed of 3.5 knot, SGB noticed a medium-sized dark petrel. It was feeding on discards from the fishing operation in the company of Northern Fulmars, Sooty Shearwaters, Great Shearwaters, Northern Gannets and Lesser Black-backed Gulls Larus fuscus. SGB identified it as White-chinned Petrel Procellaria aequinoctialis and took severa l photographs during the two hours that it spent around the vessel. It was seen by three more members of the scientific team. The initial observation took p lace at 14:48 UTC at position 52°27.45'N and 14°00.38'W, c 240 km off western Ireland, water depth 303 m. The conditions were 3-4 m swell, a 20 knot south w ind and 100% cloudy sky., SI

This working document presents the results on haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangius) and Norway lobster (Nephrops norvegicus) caught in the Porcupine Spanish Groundfish Survey (SP-PORC-Q3) in 2021. Biomass, abundance, distribution and length frequency were analysed. The biomass of these two fishes decreased compared to the previous year. Signs of recruits were found for both species, especially for M. aeglefinus. In addition, the incidental species Pleuronectes platessa and Solea solea were not found in 2021 and Pollachius pollachius has never been caught in the time series. The crustacean N. norvergicus has increased slightly in this last survey and has done so for all the groups of sizes, thought more markedly in those larger than 21 mm. However, the mean individual weight was slightly lower than in previous years.

Sandy ray Leucoraja circularis and shagreen ray L. fullonica are large-bodied skate species occurring in the Northeast Atlantic and Mediterranean on the edge of the continental shelf and upper slope. These areas are not sampled effectively by fishery-independent trawl surveys, and fisheries-dependent data are also limited, as these species are landed as a bycatch. Consequently, there are no formal assessments or reference points, even though they are harvested as part of the Total Allowable Catch (TAC) for generic skates and rays. The implementation of data-limited assessment methods is often reliant on robust life-history data, which was lacking. Therefore, biological data were collected from 116 specimens of L. circularis (21–116 cm LT) and 54 specimens of L. fullonica (19–100 cm LT). Length at 50% maturity for L. circularis was estimated at 81 cm LT and 100 cm LT for males and females, respectively. This large size at maturity makes them more biologically vulnerable than other skate species managed under the generic TAC. This inherent vulnerability, low representation of mature individuals in trawl surveys and bycatch risk due to spatial overlap with important commercial fisheries suggests that both species, assessed as Threatened, would benefit from precautionary species-specific management measures. L. circularis and L. fullonica are respectively, the only IUCN listed Endangered and Vulnerable elasmobranchs that are endemic to Europe and also occur in UK waters. Therefore, with the eastern Atlantic being the main part of their distribution, urgent research and management action is of even greater importance to conserve them.

This working document presents the results of the most significant elasmobranch species caught on the Porcupine Spanish Groundfish Survey (SP-PORC-Q3) in 2021. Biomass and abundance index, distribution and length frequency information is presented for Galeus melastomus (blackmouth catshark), Deania calcea (birdbeak dogfish), Deania profundorum (arrowhead dogfish), Scymnodon ringens (knifetooth dogfish), Scyliorhinus canicula (lesser spotted dogfish), Etmopterus spinax (velvet belly lantern shark), Dalatias licha (kitefin shark), Hexanchus griseus (bluntnose sixgill shark), Dipturus nidarosiensis (Norwegian skate), Dipturus batis (common skate), Dipturus intermedius (common skate), Leucoraja circularis (sandy ray) and Leucoraja naevus (cuckoo ray), Squalus acanthias (picked dogfish), Raja clavata (thornback ray) and Raja montagui (spotted ray). In 2021 the biomass of G. melastomus, D. calcea, S. ringens, D. licha, S. acanthias, L. naevus, L. circularis and D. batis increased, whereas it decreased for D. nidarosiensis, H. griseus, S. canicula and E. spinax. Signs of recruitment were found for G. melastomus, D. calcea, S. ringens, D. licha, D. nidarosiensis and D. batis. Only a few specimens of R. clavata, R. montagui, Centroscymnus coelolepis, Oxynotus paradoxus, Centroscymnus crepidater, Apristurus laurussonii, Galeus murinus and Centrophorus squamosus were caught. The species Centroscyllium fabricii and Neoraja caerulea were captured for the first time in the survey. The species D. profundorum and D. intermedius, with regular presence in the historical series, were not found in 2021 survey.

The International Bottom Trawl Survey Working Group (IBTSWG) coordinates fishery-independent bottom trawl surveys in the ICES area in the Northeast Atlantic and the North Sea. These long-term monitoring surveys provide data for stock assessments and facilitate examina-tion of changes in fish distribution and relative abundance. The group also promotes the stand-ardization of fishing gears and methods as well as survey coordination. This report summarizes the national contributions in 2021–2022 and plans for the 2022–2023 surveys coordinated by IBTSWG.

The workshop on the production of swept-area estimates for all hauls in DATRAS for biodiver-sity assessments (WKSAE-DATRAS) considered three groups of surveys for which data are sub-mitted to the Database of Trawl Surveys (DATRAS): various Beam Trawl Surveys, the Northeast Atlantic International Bottom Trawl Survey (Northeast Atlantic IBTS), and the North Sea Inter-national Bottom Trawl Survey (North Sea IBTS). All countries contributing to the above-mentioned surveys were represented by at least one par-ticipant during the workshop, apart from the Netherlands and Norway. The main objectives of the workshop were to establish tow-by-tow swept-area estimates for time-series as far back in time as possible, compare different approaches for the estimates of missing observations, and harmonize the resulting dataseries for biodiversity assessments. For all of the surveys considered, problems with data quality were detected. This included the Beam Trawl Surveys but was most pronounced for the North Sea IBTS. Outliers and potential erroneous data were listed for reporting back to the respective national institutes. In particular, missing observations or algorithms affected wing spread-based swept-area, which is needed in several applications. This workshop compared the Marine Scotland Science-MSS/OSPAR approach, which includes a data quality check for the information needed for the calculation of swept-area, and the DATRAS approach, which depends solely on correctly reported data from the national institutes. Larger data gaps were identified, in particular for several years of the North Sea IBTS. For those surveys, it is proposed that the best possible way forward at this moment is to use estimates based on the MSS/OSPAR approach. However, if dubious records (i.e. extreme outliers) were identified by the MSS/OSPAR and no other information was available, values (e.g. speed over ground or the depth at which a change from short to long sweeps should have happened) were taken from the manual. However, expe-rience has shown that the survey manuals are not followed in all instances, and so persistent country-specific and survey-specific deviations may occur. The national institutes are encouraged to check, correct, and fill in missing survey data through re-submissions to DATRAS. It is recommended that DATRAS data quality control on data sub-mission is extended for the information needed for the calculation of swept-area (e.g. distance, depth, door spread, and wing spread) and that this is done in close cooperation between the ICES Data Centre and the respective ICES survey working groups, WGBEAM (Working Group on Beam Trawl Surveys) and IBTSWG (International Bottom Trawl Survey Working Group).

The Workshop on the production of annual estimates of abundance of sensitive species (WKABSENS) met to define sensitive species, collate ICES assessments of abundance where these are available, and estimate indices of their abundance per swept-area where not, for the OSPAR area. The analyses identified 140 potentially sensitive species or species complexes, among which 10 are diadromous and three are coastal, 20 have uncertain species ID and nine were identified as sensitive in only one of the sources examined. Among the sensitive species and species complexes, there was sufficient data to provide abundance indices for 50 species, of which 16 had existing stock assessments whereas the workshop derived abundance estimates for the remaining 34 species from survey data. Three statistical modelling approaches (binomial, General Additive Models (GAMs) and VAST) and were explored and the final abundance indices were calculated using GAMs. The species were divided into stocks before estimating abundance indices where these could be identified from the spatial distribution of the species in the survey. The group considered that a similar analysis using data from additional surveys, commercial indices or data from bycatch observers can potentially provide improved abundance estimates for species with variable or low catchability, such as deep-water and pelagic species.

The International Bottom Trawl Survey Working Group (IBTSWG) coordinates fishery-inde-pendent multispecies bottom-trawl surveys within the ICES area. These long-term monitoring surveys provide data for stock assessments and facilitate examination of changes in fish distri-bution and abundance. The group also promotes the standardization of fishing gears and meth-ods and survey coordination. This report summarizes the national contributions in 2020–2021 and plans for the 2021–2022 surveys coordinated by IBTSWG. In the North Sea, the surveys are performed in quarters (Q) Q1 and Q3 while in the Northeast Atlantic the surveys are conducted in Q1, Q3, and Q4 with a suite of 14 national surveys covering a large area of continental shelf that ranges from North of Scotland to the Gulf of Cádiz. Despite the COVID-measures and bad weather, most surveys were able to complete the majority of the planned hauls. The Portuguese survey (PT-GFS-Q4) was cancelled in 2020 due to issues associated with the new vessel and a COVID-outbreak. A COVID-related delay in submitting the cruise application form for the French CGFS20 survey resulted in no authorisation to trawl in UK waters and only 70% of the core stations were completed. Issues with the UK permits, were also experienced in the North Sea surveys, only being resolved at the last moment, expected to be a returning issue. Therefore, IBTSWG addressed the permit issue in further detail in order to better evaluate the impact and propose possible solutions. All surveys, except for the Spanish GCGF-Q1 21 which is cancelled due to a vessel refit, are planned to take place according to the manuals in the next year. The SCOROC Q3 20 survey recorded second highest recruitment of zero group haddock on the Rockall Bank since the start of the new survey series in 2011. The North Sea Q1 21 survey rec-orded good recruitment of haddock as well, and high recruitment of mackerel, while overall herring recruitment seemed low except for three exceptionally large catches in the Skager-rak/Kattegat bringing the index above average. Both North Sea surveys reported large amounts of target species outside their index areas, which may warrant a revision of the species-specific areas on which the standard abundance indices are calculated. IBTSWG will continue a number of collaborative activities later this year. The Workshop on the Further Development of the New IBTS Gear (WKFDN) will focus on updating results of gear trails with the potential new gears. The Workshop on the production of swept area estimates for all hauls in DATRAS for biodiversity assessments (WKSAE) will continue work on the North-eastern Atlantic Flexfile available via DATRAS, for which country specific algorithms are used to fill data gaps relevant for the calculation of the swept area. This and the already available North Sea Flexfile can be used to produces swept area indices. IBTSWG also met with members of the assessment groups, Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK) and Working Group on Elasmobranch Fishes (WGEF), to improve communication on for example circumstances affecting the execution of the surveys but also changes in survey design potentially impacting the indices.

This working document presents the results of the most significant cephalopods caught on the Porcupine Spanish Groundfish Survey (SP-PORC-Q3) in 2020. Biomass, abundance, geographical distribution and length frequencies were analysed for Eledone cirrhosa (horned octopus), Bathypolypus sponsalis (globose octopus), Todarodes sagittatus (European flying squid), Todaropsis eblanae (lesser flying squid), Loligo forbesi (veined squid), Illex coindetii (broadtail shortfin squid), Rossia macrosoma (stout bobtail squid) and other scarce cephalopods. The biomass and abundance of the most common cephalopods increased, especially I. coindetii and T. sagitattus. In contrast, T. eblanae and B. sponsalis decreased in this last survey. E. cirrhosa and L. forbesi remained at very similar values to the previous year and most of the usually scarce species also generally increased their biomass, with the exception of A. lichtensteinii, R. minor and S. oweniana, which decreased.

Landscape-scale ecology comprises complex structures where a flow of energy, materials and organisms among ecosystems conditions the dynamics of populations. Several natural and anthropogenic stressors are likely to affect the landscape composition, generally leading to the rupture of ecological connectivity among populations. Although contamination is considered one of the most threatening factors for biodiversity, its impact on spatial dynamics of populations (e.g., distribution, persistence and abundance) from an eco-toxicological perspective is still unknown. In the current study, the potential effect that contamination can exert on the loss of connectivity among populations (chemically fragmented habitats) leading to population isolation was assessed. The estuarine shrimp Palaemon varians was used as model organisms and a novel version of the HeMHAS (Heterogeneous Multi-Habitat Assay System) was used to simulate spatially heterogeneous landscapes. In order to provide more ecological relevance to the study, besides copper as stressor [at low (0.5 μg/L) and high (25 μg/L) levels], other two factors were simultaneously tested: fish kairomones (as a predation signal) and food availability. Different scenarios were simulated in the HeMHAS to create heterogeneous landscapes that vary depending on the presence or absence of these stressors. The behavior observed by the population of P. varians clearly showed that the shrimp detected copper and avoided the regions with the highest levels of contamination. However, when fish kairomones were added to previously preferred regions, the behavior of shrimp populations did a radical turn: they escape the predator signals, moving towards contaminated regions, but with a clear preference for less contaminated areas. When faced whether to stay in a clean area with no food or moving through disturbed regions to colonize a clean region with food, shrimps’ populations crossed the regions, but with a more dynamic transit in the region with kairomones and no copper. These results indicate that contamination might interfere in the spatial dynamics of shrimps’ populations by: (i) triggering avoidance, (ii) preventing colonization, (iii) isolating populations and (iv) making them more susceptible to local extinction.

Since its first record in Europe as an exotic species back in 2009 at the Schelde estuary (Belgium), the weakfish Cynoscion regalis -native from North America East coast- has increased its presence in the Iberian Peninsula waters. Identified for the first time in the Guadalquivir River estuary (2011) and later in the Sado estuary (2014), C. regalis population is increasing in the Gulf of Cadiz and is becoming a fisheries resource. Its introduction into Europe probably occurred through maritime transatlantic trade. Morais et al (2017) suggested that weakfish could have been introduced through multiple independent ballast water release events. The Guadalquivir, Sado and Schelde estuaries show similar transoceanic ship traffic to upstream important commercial ports, supporting multiple direct or secondary transatlantic introductions among European ports. The first genetic studies suggest that C. regalis populations in southern European estuaries are connected and come from a single transoceanic commercial route. Currently, the Gulf of Cadiz maintains a well-established population with frequent catches by artisanal fishing, especially in coastal waters and the estuary, where it is sold in local markets of the surrounding cities. The population in the area is constituted by mature specimens (ranging from 234 to 453 mm) that are using the estuary as a spawning area, where larvae and juvenile have also been found. In recent years, an increase in the abundance of larvae and juvenile has been observed through monthly samplings in the estuary, which indicates the culmination of the complete life cycle in the Gulf of Cadiz. These findings represent new evidence that the Guadalquivir estuary constitutes a remarkable nursery habitat for this species. This could have effects on native fauna and the ecosystem, which is why it is currently under study and evaluation (EcoInvadiz project) for helping the local Administration to establish, if needed, an appropriate management program.

This working document presents the results of the most significant elasmobranch species caught on the Porcupine Spanish Groundfish Survey (SP-PORC-Q3) in 2020. Biomass, abundance, distribution and length frequency were analysed for Galeus melastomus (blackmouth catshark), Deania calcea (birdbeak dogfish), Deania profundorum (arrowhead dogfish), Scymnodon ringens (knifetooth dogfish), Scyliorhinus canicula (lesser spotted dogfish), Etmopterus spinax (velvet belly lantern shark), Dalatias licha (kitefin shark), Hexanchus griseus (bluntnose sixgill shark), Dipturus nidarosiensis (Norwegian skate), Dipturus batis (common skate), Dipturus intermedius (common skate), Leucoraja circularis (sandy ray) and Leucoraja naevus (cuckoo ray), Squalus acanthias (picked dogfish) and Raja clavata (thornback ray). In 2020 the biomass of D. calcea, S. ringens, D. nidarosiensis, H. griseus and D. licha increased, whereas it decreased for G. melastomus, S. canicula, E. spinax and L. circularis. Signs of recruitment were found for S. ringens and E. spinax. Only a few specimens of S. acanthias, D. profundorum, R. clavata, D. batis, L. naevus and D. intermedius were captured. The species R. montagui, with regular presence in the historical series, was not found in 2020 survey.

Although temporal and spatial match and mismatch of sh larvae with their potential prey organisms is considered the main factor regulating the year-class strength in marine sh populations, di erent environmental forcings also in uence the survival rate of larvae and therefore recruitment. In 2020, the highest abundance of year-class recruits (total lenght < 20 cm) of Micromesistius poutassou was observed in the record of the Spanish Bottom Trawl Survey on the Porcupine Bank (September) from 2001-2020. Various environmental parameters, namely chlorophyll concentration, surface salinity, temperature, ocean currents, and wind data were used to study their potential impact on the blue whiting eggs and larvae survival. Our results showed that in 2020, during the blue whiting-spawning season (March-April), the calm wind situation along with weaker ocean currents above the Porcupine Bank helped to accumulate phytoplankton biomass, thus promoting secondary productivity. The optimal salinity concentration, as well as surface temperature during this time, helped the buoyancy of eggs and larvae to the food-rich surface, thus improving the larval condition and enhanced the survival rate, which in turn resulted in the largest recruitment since 2001

Contamination is likely to affect the landscape composition, usually linked to ecological fragmentation, which may impact the distribution, persistence and abundance of species. In the current study, the estuarine shrimp Palaemon varians was exposed to copper (25 and 0.5 μg/L) simultaneously to predation signal and food to evaluate the organism’s spatial distribution within a spatially heterogeneous landscape. All experimental landscapes were simulated in the Heterogeneous Multi Habitat Assay System (HeMHAS). As results, P. varians detected and avoided copper, however, predation signal shifted the response to preference over regions with conditions previously avoided, even if that meant to increase copper exposure. When confronted to move towards environments with high food availability, lower connectivity occurred among the shrimps’ populations isolated by contamination and predation risk simultaneously. This indicate that contamination might: (i) trigger avoidance in shrimps, (ii) prevent the colonisation towards foraging areas, (iii) enhance the populations’ isolation and (iv) make populations more susceptible to local extinction.

Feeding habits, diets and trophic relationships among three demersal sharks (Galeus melastomus Rafinesque, 1810; Etmopterus spinax (Linnaeus, 1758); and Scyliorhinus canicula (Linnaeus, 1758)) from the Porcupine Bank, Northeast Atlantic were studied. The stomach content analysis revealed differences between the diet of the three species, with a clear preference for benthonic preys in the case of S. canicula, and benthopelagic preys in the case of E. spinax and G. melastomus. The results of this study provide new knowledge about the ecological role of these species in the Porcupine Bank and will be of vital importance for their management and conservation of these species.

To understand the extent of fishing activities within NAFO Regulatory Area (NRA), a characterization of distribution of fishing effort for a four-year period (2016 to 2019) was carried out. This characterization was done on the basis of two data sources: Haul by haul logbook information and Vessel Monitoring System (VMS) data. The results indicate that logbook data and VMS are complementary and the coupling of both datasets is a powerful methodology for describing the spatial distribution of fishing activity. The objective of this document is to describe some problems detected on the original “coupling VMS with Logbook data” methodology (NAFO, 2017) and suggest the improvements developed in order to tackle them by the implementation of a new “coupling VMS with Logbook data” methodology. Problems detected in the quality of VMS and Logbook data are also raised by this study.

La mayoría de las especies de peces tienen ciclos de vida complejos, en los que pasan a través de diferentes niveles tróficos y ocupan diferentes hábitats. En este sentido, los estuarios son ampliamente reconocidos como importantes zonas de cría, que soportan de manera natural, debido a su elevada productividad, altas densidades y elevadas tasas de producción de estadios jóvenes de numerosas especies marinas de peces. Desde 1997 se está llevando a cabo un extenso programa de muestreos mensuales de la comunidad acuática del estuario del Guadalquivir. Esta serie temporal ha revelado el papel esencial de este estuario en el golfo de Cádiz. Alrededor de 30 especies de peces marinos, algunas con gran interés pesquero, como boquerón (Engraulis encrasicolus), sardina (Sardina pilchardus), lubina (Dicentrarchus labrax) o corvina (Argyrosomus regius), lo utilizan regularmente como zona de cría. Algunas de estas especies realizan la puesta en el estuario, pero la mayoría entran estacionalmente como larvas, acumulan biomasa y regresan, como juveniles, al mar. La distribución y abundancia de las especies peces y sus presas en el estuario está controlada fundamentalmente por las variables ambientales. De hecho, la coincidencia espacio-temporal de las máximas densidades de peces y de sus presas en la parte externa del estuario del Guadalquivir en primavera y verano señala a la disponibilidad de alimento como el factor clave que sustenta el papel esencial del estuario como zona de cría. Sin embargo, hasta ahora, no existía información sobre las relaciones tróficas en el estuario. Por ello, se ha obtenido una serie de datos única, con gran resolución a nivel individual, de la red trófica del estuario, que incluye dietas de individuos capturados en distintos muestreos y estimaciones independientes de la abundancia de predadores y presas. Esta serie ha sido obtenida en 95 pescas realizadas mensualmente a lo largo de un año en dos estaciones de muestreo (polihalina y oligohalina) e incluye 53 taxa y casi 100.000 individuos muestreados entre predadores (5.725 peces de 10 especies) y presas (88.101 presas de 43 taxa). Presenta, por tanto, la suficiente resolución espacial, diaria, mensual y estacional como para realizar inferencias a distintas escalas: individual, de especie y de red trófica. Estos datos indican que existen dos grupos tróficos diferenciados, cuyas presas principales son copépodos y misidáceos, respectivamente. Sin embargo, a pesar de que el grado de solapamiento de las dietas a nivel de especies es elevado, encontramos una enorme variabilidad en las dietas a nivel individual, que es, además, consistente a lo largo de las distintas condiciones ambientales. El uso de estos datos con modelos de base individual (IBM's) ha permitido observar variaciones intraespecificas en la fuerza de selección de presas entre las distintas clases de conectividad o fenotipos de los predadores, que podrían estar afectando a la coexistencia de especies en la red trófica. En concreto, se ha encontrado que los individuos más fuertemente conectados (con muchas presas en sus estómagos) seleccionan preferentemente las presas más comunes, mientras que los individuos con menos presas en sus estómagos seleccionan preferentemente presas menos abundantes. Este patrón sugiere que la distribución de los distintos fenotipos en las poblaciones de predadores y la variación individual en la selección de presas podrían estar determinando la diversidad de la red trófica. No obstante, la variabilidad individual observada en la selección de presas representa, por el momento, el primer paso para llegar a entender las consecuencias de las relaciones tróficas en las dinámicas ecológicas y evolutivas de las poblaciones naturales., Most fish species have complex life-cycles, in which they pass through different levels of the food web and occupy different habitats. In that sense, estuaries have long been postulated as nursery areas which naturally support high densities and production levels of juvenile marine fish. A long-term ecological research program, which has carried out monthly suprabenthos-nekton surveys in the Guadalquivir estuary (Gulf of Cadiz, SW Spain) since 1997, has pointed out the essential role of this estuary as a nursery ground for several marine fish species. Around 30 marine fish species, some with a high commercial value such as Engraulis encrasicolus, Sardina pilchardus, Dicentrarchus labrax and Argyrosomus regius, regularly use the estuary as a nursery. Some species are estuarine spawners but most enter the estuary on a seasonal basis as larvae, accumulate biomass, and migrate offshore. Both the distribution and the abundance of fish species and its prey are principally driven by differences in environmental variables throughout the estuary. The spatio-temporal coincidence of maximal fish densities and their prey in the outer part of the estuary in spring and summer suggests that food availability may be a major factor influencing the nursery function of the estuary. However, the role of trophic interactions in that function has not been studied. To help fill this gap, a unique and high resolution individual-based food web dataset has been set up, including multiple samples of individual diets, and independent estimates of predator and prey abundance. The acquired dataset consists of 95 samples collected monthly at two sampling stations (polyhaline and oligohaline). It contains 53 taxa and approximately 100,000 individuals. Of those, 5,725 individual fish represent 10 predator species, and 88,101 prey items represent 43 taxa. The dataset has sufficient daily, monthly, and seasonal resolution to make inferences at the level of the individual, the species, and the food web, simultaneously. The results showed two main fish trophic guilds, whose preferential prey were copepods and mysids, respectively. While there is a high degree of overlap in the diets of both these guilds at the species level, there is also a high individual-level variability, which is maintained across environmental gradients. Using the dataset along with individual-based models (IBM's) considerable intra-population variation was observed in the strength of prey selection by different connectivity classes or predator phenotypes, which could potentially alter the diversity and coexistence patterns of food webs. In particular, strongly connected individual predators were found to preferentially consume common prey, whereas weakly connected predators preferentially selected rare prey. Such patterns suggest that food web diversity may be governed by the distribution of predator phenotypes and individual trait variation in prey selection. Nevertheless, the observed individual variation in prey selection within, and among predator populations, is a first step towards understanding the potential for eco-evolutionary dynamics in natural populations.

Natural drivers, acting at various spatio-temporal scales firstly determine the distribution and abundance of species. On top of this natural forcing we usually find anthropogenic effects. Disentangling the relative influence of these two sources of variability has always been a challenge in ecology, and particularly in fisheries science. The Guadalquivir Estuary (SW Spain) serves as nursery ground for several commercial species in the Gulf of Cadiz. This study aims at quantifying the relative influence of biological (predator-prey effects), environmental (e.g. temperature, winds) and anthropogenic (dam discharges) effects on this nursery function with the focus on an important species, anchovy. We used data from a monitoring programme consisting of monthly records since 1997 at two sites: Tarfia (32 km) and Bonanza (8 km) (distance from the river mouth). Nonparametric models (GAM) were fit to the data to estimate the partial effects of the various covariates. We found positive and linear effects of temperature and mysids on anchovy abundance in both stations, while turbidity, winds and freshwater input had a negative effect, reducing fish abundance. A dam, 110 km upstream from the Guadalquivir mouth regulates freshwater discharges, directly influencing the estuarine habitat quality and extent, as captured by our models. In order to separate the anthropogenic effects from natural variability we further ran the models on a number of scenarios combining a range of dam discharges and environmental conditions. Water management stands out as a key node where potentially conflicting interests (irrigators, electric power, shipping, aquaculture, fisheries) converge. By focussing on the consequences that the effects of these activities ultimately have on the anchovy fishery, through this nursery function, our study aims to contribute to the process of making the ecosystem approach operational in the Gulf of Cadiz.

This working document presents the results on four of the most significant deep fish species of the last Porcupine Spanish survey carried in 2014, as well as it updates previous documents presented with the information on the fourteen years (2001-2014) of the Spanish bottom trawl survey on the Porcupine Bank. The document presents total abundances in weight, length frequencies and geographical distributions for Argentinaspp. (mostly A. silus, results on proportions by Argentine species distribution in last surveys are provided), Bluemouth (Helicolenus dactylopterus), Greater fork-beard (Phycis blennoides) and Spanish ling (Molva macrophthalma). Argentinaspp. and Spanish ling presented a decrease in their abundances, whereas Bluemouth remained stable and Greater forkbeard increased slightly. In terms of recruitment 2014 showed larger values than previous years for A. sphyraena, Helicolenus dactylopterusand Molva macrophtalmabut weaker for Phycis blennoides, and A silus. Furthermore results for ling (Molva molva) on the Spanish Porcupine Bank survey are summarizedpresenting the results to the WG so their utility for the assessment could be considered., Versión de editor

This working document presents the results on the most significant elasmobranch species of the Porcupine Bank Spanish surveys in 2014 and updates the documents presented in previous years with the information in the whole historical series from 2001. The main species in biomass terms in this survey were Galeus melastomus (blackmouth catshark), Deania calcea (birdbeak dogfish), Scymnodon ringens (Knifetooth dogfish), Dipturus nidarosiensis (Norwegian skate), Scyliorhinus canicula (lesser spotted dogfish), Etmopterus spinax (velvet belly lantern shark), Hexanchus griseus (bluntnose sixgill shark), Dalatias licha (Kitefin shark), Leucoraja circularis (sandy ray), Dipturus cf. flossada, Leucoraja naevus (cuckoo ray) and Dipturus cf. intermedia (common skate). Biomass, distribution and length ranges were analysed for these species. All the species analysed increased its biomass in 2014, except S. canicula and D. cf. flossada that decreased. D. calcea individuals smaller than 65 cm were captured again in 2014 after not having been captured the previous year, although catches were very low. Raja brachyura was recorded for the first time in the survey area.

This working document presents the results on four of the most significant deep fish species of the last Porcupine Spanish survey carried in 2014, as well as it updates previous documents presented with the information on the fourteen years (2001-2014) of the Spanish bottom trawl survey on the Porcupine Bank. The document presents total abundances in weight, length frequencies and geographical distributions for Argentina spp. (mostly A. silus, results on proportions by Argentine species distribution in last surveys are provided), Bluemouth (Helicolenus dactylopterus), Greater fork-beard (Phycis blennoides) and Spanish ling (Molva macrophthalma). Argentina spp. and Spanish ling presented a decrease in their abundances, whereas Bluemouth remained stable and Greater forkbeard increased slightly. In terms of recruitment 2014 showed larger values than previous years for A. sphyraena, Helicolenus dactylopterus and Molva macrophtalma but weaker for Phycis blennoides, and A silus. Furthermore results for ling (Molva molva) on the Spanish Porcupine Bank survey are summarized presenting the results to the WG so their utility for the assessment could be considered.