We assessed the relative importance of different prey types of the European pilchard (European sardine) from the late larval to the adult stage. Two different methodologies for analysing stomach ...contents were used to describe the trophic dynamics of sardine and the relationship of sardine feeding behaviour with the ontogenetic development of body structures used for feeding, such as gill rakers and pyloric caeca. This information is essential to accurately depict the use of the planktonic resources in the area by sardine and to discuss the extent to which the sardine population could be affected by environmental changes in the Mediterranean Sea. This study demonstrates that sardine populations, given their extremely high dependence on the lower marine trophic levels, could be strongly affected by alterations in the environment and in the planktonic community.Original Abstract: Analizamos la importancia relativa de los diferentes tipos de presas de la sardina europea, desde post-larvas hasta adultos. Se usaron dos metodos diferentes de analisis de los contenidos estomacales para describir la dinamica trofica de la sardina y la relacion de su comportamiento alimenticio con el desarrollo ontogenico de las estructuras corporales que usa en el proceso alimenticio, como las brianquispinas y los ciegos piloricos. Esta informacion es esencial para obtener una imagen precisa de los recursos planctonicos de los que dispone la sardina en el area y para discutir de que forma la poblacion de sardina podria verse afectada por cambios medioambientales en el mar Mediterraneo. Mostramos que los cladoceros, en verano, y las diatomeas, en invierno, fueron los tipos de presas mas importantes tanto para juveniles como para adultos. Sin embargo, las larvas de decapodos fueron las presas mas importantes durante todas las estaciones en terminos de contenido en carbono. En consecuencia, las diferencias metodologicas deberian ser tenidas en cuenta en el analisis de dietas. Con el analisis de la composicion del plancton se mostro que los copepodos pequenos eran fuertemente seleccionados por sardinas de todas las edades y en ambas estaciones. Tambien observamos que los ciegos piloricos empezaron a crecer cuando las sardinas alcanzaban aproximadamente 4-5 cm de longitud estandar (LE), y su desarrollo acababa cuando las sardinas alcanzaban aproximadamente 8 cm LE, mientras que las branquispinas parecieron ser completamente funcionales cuando las sardinas alcanzaron los 7 cm LE. Por tanto, la alimentacion por filtracion de pequenas particulas podria ser llevada a cabo con total eficacia cuando las sardinas tienen 7-8 cm LE. En vista de la ventaja energetica de la alimentacion filtradora en especies bien adaptadas a la filtracion como la sardina, la potencialmente limitada disponibilidad de pequenas particulas que ciertos autores han hipotetizado para el Mediterraneo podria tener consecuencias negativas para la sardina. Este estudio demuestra que las poblaciones de sardina, dada su extremadamente alta dependencia de los niveles troficos marinos inferiores, podrian verse fuertemente afectadas por alteraciones en el medio y en la comunidad planctonica.
Fisheries catches represent a net export of mass and energy that can no longer be used by trophic levels higher than those fished. Thus, exploitation implies a depletion of secondary production of ...higher trophic levels (here the production of mass and energy by herbivores and carnivores in the ecosystem) due to the removal of prey. The depletion of secondary production due to the export of biomass and energy through catches was recently formulated as a proxy for evaluating the ecosystem impacts of fishing-i.e., the level of ecosystem overfishing. Here we evaluate the historical and current risk of ecosystem overfishing at a global scale by quantifying the depletion of secondary production using the best available fisheries and ecological data (i.e., catch and primary production). Our results highlight an increasing trend in the number of unsustainable fisheries (i.e., an increase in the risk of ecosystem overfishing) from the 1950s to the 2000s, and illustrate the worldwide geographic expansion of overfishing. These results enable to assess when and where fishing became unsustainable at the ecosystem level. At present, total catch per capita from Large Marine Ecosystems is at least twice the value estimated to ensure fishing at moderate sustainable levels.
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•Biological and ecological processes of European anchovy relevant to recruitment and connectivity are reviewed.•An egg and larval dispersal model was used to explore European anchovy connectivity in ...NW Mediterranean.•Rhône River plume plays an important role in the modulation of the spawning areas and late larval recruitment.•Indices from a dispersal model are coherent with existing recruitment proxies for European anchovy.•The use of recruitment indices from dispersal models open new possibilities for fisheries management.
We show the application of a Spatially-Explicit Individual-Based Model (SEIBM) to understand the recruitment process of European anchovy. The SEIBM is applied to simulate the effects of inter-annual variability in parental population spawning behavior and intensity, and ocean dynamics, on the dispersal of eggs and larvae from the spawning area in the Gulf of Lions (GoL) towards the coastal nursery areas in the GoL and Catalan Sea (northwestern Mediterranean Sea). For each of seven years (2003–2009), we initialize the SEIBM with the real positions of anchovy eggs during the spawning peak, from an acoustics-derived eggs production model. We analyze the effect of spawners’ distribution, timing of spawning, and oceanographic conditions on the connectivity patterns, growth, dispersal distance and late-larval recruitment (14mm larva recruits, R14) patterns. The area of influence of the Rhône river plume was identified as having a high probability of larval recruitment success (64%), but up to 36% of R14 larvae end up in the Catalan Coast. We demonstrate that the spatial paths of larvae differ dramatically from year to year, and suggest potential offshore nursery grounds. We showed that our simulations are coherent with existing recruitment proxies and therefore open new possibilities for fisheries management.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Anchovy and sardine in the Mediterranean are known to share the same habitat and, consequently, to interact with one another. These two sympatric pelagic species are planktivorous and consume a wide ...range of planktonic prey items during all their developmental stages, potentially overlapping their ecological niches, although the feeding interactions between these species have been poorly investigated. Here we compare the dietary habits of the juvenile phases of anchovy and sardine during different seasons in the northwestern Mediterranean Sea, through analysis of their stomach contents and of their feeding-related anatomical characteristics. In this study we show that juveniles of anchovy and sardine do not compete for food, and we describe significant dietary differences between anchovy and sardine due to their different alimentary tract morphology.
•We compare the dietary habits of the juvenile phases of anchovy and sardine.•We study their stomach contents and their feeding-related anatomical characters.•Anchovy juveniles prey on larger preys than sardine juveniles do.•Differences in diet between both species are explained by the different morphologies.•Anchovy and sardine can respond differently to climatic changes.
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► We model the egg and larval transport of anchovy in Mediterranean. ► We examine the influence of biological behavior on the dispersion and recruitment. ► The position of larvae at recruitment can ...be influenced by diel vertical migration. ► The schooling is facilitated by the inclusion of egg-buoyancy and DVM. ► Our model can explain the interannual variability in anchovy recruitment.
Recruitment of European anchovy has been traditionally thought to largely depend on the passive transport and dispersion of eggs and larvae from spawning to nursery areas. Knowledge of the factors influencing the vertical distribution of fish early stages, and consequently influencing the transport, is a crucial issue in fisheries science. The aim of this study is to assess the relevance of diel vertical migration (DVM) as a mechanism involved in the transport of European anchovy larvae toward nursery areas taking into account age/stage-dependent vertical migration (i.e., the maximum migration). We developed a simplified vertical migration sub-model for anchovy larvae included in an Individual-based (IBM) hydrodynamic coupled model. Two types of simulation experiments were conducted: (1) ‘Pure’ Lagrangian (passive) transport experiments and (2) biological behavior transport experiments with a realistic scheme for egg-buoyancy, larval growth, and DVM scheme. We detected high variability in the trajectory and final position of larvae with 14mm length between the passive and biological behavior experiments. The particles were less clustered in the passive transport experiment. In the biological experiment the particles were aggregated depending on the mesoscale oceanographic structures, evidencing a transport associated to filaments and meanders. The formation of schools was facilitated by the transport in filaments and larvae transported within filaments generally avoided the nucleus of the eddies and the central part of the North Current. Moreover, our results suggest that there is interconnectivity between all the anchovy sub-populations in the NW Mediterranean and that the Gulf of Lions and the shelf waters surrounding the Ebro River Delta are the most important areas for anchovy reproduction in this region. Additionally, we detected that the pre-recruitment is higher in those years when the larvae retention is favored. We underline that bottlenecks in larval transport modeling are related to the scarcity of knowledge in developmental biology and behavior of anchovy larvae and emergent mechanistic processes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
An exploited ecosystem from the continental shelf and upper slope of the Northwestern Mediterranean Sea was described by means of an Ecopath mass-balance model with the aim of characterising its ...functioning and structure and describing the ecosystem impacts of fishing. This application included some complexities added to the general modelling methodology due to the high biodiversity of the Mediterranean Sea and the multispecific nature of the fishery, and to the difficulties of working with fishing data which are usually irregularly or imprecisely collected. The model comprised 40 functional groups including primary producers, the main species of benthic, demersal and pelagic invertebrates, fishes and non-fish vertebrates and three detritus groups. In addition, trawling, purse seine, longline and troll bait fishing fleets were included.
Results showed that the functional groups were organized into four trophic levels with the highest levels corresponding to anglerfish, dolphins, large pelagic fishes and adult hake. The system was dominated by the pelagic fraction, where sardine and anchovy prevailed in terms of fish biomasses and catches. Detritus and detritivorous groups also played key roles in the ecosystem and important coupled pelagic-demersal interactions were described. Considering Odum's theory of ecosystem development, the ecosystem was placed on an intermediate-low developmental stage due, at least partially, to the impact of fishing activity. This highlighted the high intensity of fishing in the ecosystem, in accordance with the general assessment of western Mediterranean marine resources, and fishing fleets were ranked as top predators of the system. The low trophic level of the catch was in line with the long history of exploitation in the area. However, the steady decline of pelagic landings between 1994 and 2003, coupled with a decrease of the pelagic biomass within the system, underlined the low resistance of the system in front of perturbations. This decline was reproduced under Ecosim dynamic simulations combining different scenarios of moderate increase of fishing effort and an environmental forcing affecting the availability of preys to small and medium-sized pelagic fishes under wasp-waist flow control.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Ante el indudable interés de conocer a los usuarios de información y la escasa práctica española en este sentido, especialmente en el ámbito de los archivos, el objetivo fundamental del presente ...trabajo es conocer las necesidades de información, comportamiento informativo y grado de satisfacción de los usuarios del Archivo Histórico de la Universidad Complutense de Madrid, utilizando una metodología cuantitativa basada en un cuestionario. Entre los principales resultados obtenidos está que los escasos usuarios que acuden a este archivo buscan información sobre un personaje a través de la base de datos del centro y están satisfechos con la información obtenida. Entre las conclusiones destaca que existe aún camino por recorrer en torno a la cuestión de si está consolidado el binomio Investigación-Archivos Universitarios y que se deben plantear estrategias acomodadas a las necesidades de los usuarios, adaptando los recursos a los cambios sociales y tecnológicos y siguiendo determinadas líneas de actuación.
Ecological knowledge of food web interactions within pelagic marine communities is often limited, impairing our capabilities to manage these ecologically and economically important marine fish ...species. Here we used stable isotope analyses to investigate trophic interactions in the pelagic ecosystem of the northwestern Mediterranean Sea during 2012 and 2013. Our results suggest that European sardine, Sardina pilchardus, and anchovy, Engraulis encrasicolus, are consumers located at relatively low levels of the pelagic food web. Unexpectedly, the round sardinella, Sardinella aurita, appeared to be located at a higher trophic level than the other small pelagic fish species, although previous studies found similarity in their diets. Isotope data suggested that trophic niches of species within the genera Trachurus spp. and Scomber spp., were distinct. Atlantic bonito Sarda sarda, European hake Merluccius merluccius and European squid Loligo vulgaris, appeared to feed at higher trophic levels than other species. Despite some intraspecific seasonal variability for some species, community trophic structure appeared relatively stable through the year. These data provide an important step for developing models of food web dynamics in the northwestern Mediterranean Sea.
•We analyzed the trophic interactions of 11 pelagic species in the NW Mediterranean Sea.•Sardina pilchardus and Engraulis encrasicolus partially overlap their isotopic niches.•Species within the genera Trachurus spp. and Scomber spp. had segregated isotopic niches.•Squids, Illex coindetii and Loligo vulgaris had different trophic positions.•Overall community trophic structure appeared relatively stable through the year.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
To date, there are numerous transport simulation studies demonstrating the relevance of the hydrodynamics for the advection, dispersion and recruitment of early stages of marine organisms. However, ...the lack of data has conditioned the use of realistic locations for the model setup and configuration in transport studies. This work (I) demonstrates the key role played by the use of the realistic initial position of the eggs of small pelagic fishes in the analysis of late-larval recruitment in coastal nursery areas and (II) provides a general solution for deriving future egg positions and abundances from adult biomass obtained from acoustic surveys and available fecundity data. Using European anchovy in the NW Mediterranean as a case study, we first analyzed the impact of the initial location, timing, egg buoyancy and diel vertical migration of larvae on the potential late-larval recruitment to coastal areas. The results suggested that prior knowledge of the initial spawning grounds may substantially affect the estimates of potential recruitment. We then integrated biological and acoustics-derived data (the biomass and size structure, sex ratio, a weight-batch fecundity model, mean weight, number of fish and mean spawning) to build a predictive model for interannual egg production. This model was satisfactorily contrasted with field data for two years obtained with the Daily Egg Production Method (DEPM). We discuss our results in the context of the fluctuations of European anchovy egg abundance from 2003 through 2010 in the NW Mediterranean and in terms of the potential applicability of the acoustics-based spatial predictive egg production model.
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► Field and modelling results are used to assess the ecological role of a Mediterranean endemic skate. ► The skate is an important predator but shows moderate-low ecological importance due to low ...abundance. ► The species has been highly impacted by fishing and it is sensitive to increasing fishing impacts. ► Simulations show the skate could substantially recover if trawl fishing effort decreases. ► This may be a good sentinel species to indicate ecosystem health in Mediterranean Sea ecosystems.
The Mediterranean endemic starry ray (Raja asterias) is one of the few demersal skates that are still present in Mediterranean exploited ecosystems. However, this species has declined with time, its presence in survey data is scarce, and limited information is available about its ecology and the impact of fishing on its populations. We examined key ecological features of this species such as reproduction, trophic behaviour and growth. We assessed the ecological role of this species within the food web using an ecological model of a North-Western Mediterranean ecosystem and setting the new information in an ecosystem context. We then explored impacts of fishing on the starry ray population using a dynamic temporal model and we developed fishing scenarios aiming at recovering the species. Field and modelling results showed that the starry ray is a potentially ecologically important predator of the Mediterranean demersal ecosystems, but its ecological importance in the food web is moderate-low since it is present at a low abundance. Results confirmed that the species has been and still is highly impacted by fishing and it is very sensitive to increasing fishing impacts. However, alternative fishing scenarios showed that Mediterranean starry ray populations may respond under decreasing trawl fishing effort and could substantially recover. The recovery of the starry ray may be accompanied by recovery of other demersal species and could have wider ecosystem impacts. Therefore, this skate could be a good sentinel species to indicate ecosystem health in current Mediterranean Sea ecosystems. These new insights may be useful to ensure the recovery and conservation of this species while triggering the recovery of exploited marine communities in the Mediterranean Sea.
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