Suchergebnisse

Trabajo final presentado por Elena Fernandez Corredor para el Máster en Oceanografía y Gestión del Medio Marino impartido por la Universitat de Barcelona (UB) y la Universistat Politècnica de Catalunya (UPC), realizado bajo la dirección de la Dra. Marta Coll y del Dr. Joan Navarro del Institut de Ciències del Mar (ICM-CSIC).-- 49 pages, 15 figures, 4 tables, supplementary material ; Fisheries, climate change and habitat degradation are triggering the depletion of marine animal populations worldwide. In particular, the ecological impacts of the removal of keystone species such as chondrichthyans can be far reaching through the food web. In this study, we investigated the trophic ecology of the 81 Mediterranean chondrichthyan species occurring in the basin through a literature review. We found data for 50 species, which highlights research priorities for the future to complement missing information. Regarding the trophic ecology of studied species, prey composition was compared between taxonomic groups (Batoidea, Selachimorpha and Holocephali), habitats (pelagic and demersal) and sizes (small, medium and large). We found significant differences between taxonomic groups, with dissimilarities mainly due to crustaceans and cephalopods consumption between Batoidea and Selachimorpha. We then represented the Mediterranean meta-web by means of a qualitative modelling approach, putting emphasis on the chondrichthyan groups, with a resulting food web network topology of 73 nodes and 1335 trophic links. Finally, we used the qualitative food web representation to test seven extinction scenarios of chondrichthyans extinctions. We found out that large species, pelagic species and sharks had a major contribution to trophic dissimilarity of the ecosystem when compared to small and medium-sized species, demersal species and rays, respectively. Systems with the former species had also higher omnivory rates. Therefore, conservation efforts within the Mediterranean Sea chondrichthyan community seem to be especially important for these groups. This study provides a first overview of the chondrichthyans ecological role in the Mediterranean Sea marine food web and highlights the urgent need to improve available knowledge on these species and to adopt an ecosystem-based management approach in order to decelerate the depletion of chondrichthyans populations and prevent them from local extinctions, with important effects to the marine food web ; I was supported by a JAE Intro grant of the CSIC (JAEINT200_EX0215) that was extended with funding from the EU FutureMARES project. This work acknowledges the Severo Ochoa Centre of Excellence accreditation (CEX2019- 000928-S) and is a contribution to the European Union's Horizon 2020 research and innovation program under grant agreement No 869300 (FutureMARES project)

20 pages, 15 figures, supplementary material https://www.frontiersin.org/articles/10.3389/fmars.2020.00622/full#supplementary-material ; In the Northwestern Mediterranean Sea, the European sardine (Sardina pilchardus) and the European anchovy (Engraulis encrasicolus) are the most important small pelagic fish in terms of biomass and commercial interest. During the last years, these species have experimented changes in their abundance and biomass trends in the Northwestern Mediterranean Sea, in addition to changes in growth, reproduction and body condition. These species are particularly sensitive to environmental fluctuations with possible cascading effects as they play a key role in connecting the lower and upper trophic levels of marine food webs. It is therefore essential to understand the factors that most profoundly affect sardine and anchovy dynamics. This study used a two-step approach to understand how the environment influences the adult stages of these species in the Northwestern Mediterranean Sea. First, we explored the effects of environmental change over time using Random Forests and available datasets of species occurrence, abundance, biomass and landings. We then applied species distribution models to test the impact of the extreme pessimistic and optimistic Intergovernmental Panel on Climate Change (IPCC) pathway scenarios, and to identify possible climate refuges: areas where these species may be able to persist under future environmental change. Findings from the temporal modeling showed mixed effects between environmental variables and for anchovy and sardine datasets. Future pathway projections highlight that both anchovy and sardine will undergo a reduction in their spatial distributions due to future climate conditions. The future climate refuges are the waters around the Rhone River (France) and the Ebro River (Spain) for both species. This study also highlights important knowledge gaps in our understanding of the dynamics of small pelagic fish in the region, which is needed to progress towards an ecosystem approach to fisheries management ; This study was carried out within the Spanish Research project PELWEB (CTM2017-88939-R) funded by the Spanish Ministry of Science, Innovation and Universities, the European Research Contract SPELMED (EASME/EMFF/2016/032) funded by the ECEASME and the Catalonian Government PELCAT projects (CAT 152CAT00013 and TAIS ARP059/19/00005) ; Peer reviewed