Browsing by Author "Jose Acosta, Juan"
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- Discard practices in the gulf of Cadiz multispecies trawl fishery. Implications for the EU 'landing obligation'Publication . Gamaza-Marquez, Maria Angeles; Grazia Pennino, Maria; Angeles Torres, Maria; Jose Acosta, Juan; Erzini, Karim; Sobrino, IgnacioDiscarding has been a common practice in multispecies trawl fisheries since the first trawlers were used. To date there have been no studies reporting an integrated analysis of discarding in the gulf of Cadiz (SW Spain, GoC) to evaluate and support the latest fisheries policies, specifically the Landing Obligation (European Union Regulation 1380/2013). In this study we provide estimates of discard ratios, species composition, reasons for discarding, along with the identification of high-density discard areas (hotspots) over the last decade in the GoC area. The analysis was based on data collected by the Spanish onboard sampling program, involving commercial trawling vessels from 2006 to 2016. In particular, data on catches and discards were analyzed by applying Multivariate Regression Trees (MRTs) to assess the species dominance within the discarded and retained portions of the total catch. Temporal and spatial variability in discard ratios were also explored together with the identification of high-density discard areas (hotspots) modelled using Hierarchical Bayesian Spatial Models (H-BSM). A discard ratio relative to the total catch (i.e. both commercial and by-catch) of 34% in weight was estimated, corresponding to an average at about 3500 t discarded annually by the GoC trawl fleet. Non-commercial by-catch species accounted for more than half of the discarded biomass in weight (59.4%). Finally, our study focuses on research efforts towards relevant and efficient management solutions under the discard ban policy. Recommendations aiming to contribute to the establishment of alternative management strategies for this fishery are further discussed.
- Length-weight relationships for 22 crustaceans and cephalopods from the Gulf of Cadiz (SW Spain)Publication . Angeles Torres, Maria; Vila, Yolanda; Silva, Luis; Jose Acosta, Juan; Ramos, Fernando; Palomares, Maria Lourdes D.; Sobrino, IgnacioLife history traits are available for many fish species in different regions, but less so for invertebrates such as cephalopods and crustaceans, though, they are increasingly needed for implementing an ecosystem-based approach. Recent food web modelling in the Gulf of Cadiz has identified invertebrates as keystone groups. However, information on life history traits of such groups remains incomplete in this region. To fill this knowledge gap, we report length-weight relationships for 12 cephalopods and 10 crustaceans collected in the Gulf of Cadiz from 2009 to 2013. This study reports, for the first time, life history traits of nine species in the area (Chlorotocus crassicornis, Pasiphaea sivado, Plesionika heterocarpus, Plesionika martia, Processa canaliculata, Solenocera membranacea, Allotheutis media, Sepia orbignyana and Sepietta oweniana). For each species, length-weight relationships, minimum and maximum lengths, mean weights, and depth ranges are presented. Overall, the results revealed that all species showed negative allometric growth (hypoallometry), except P. sivado, the only species showing an isometric growth pattern. We expect that this study will contribute to link sustainable fisheries with biodiversity conservation goals enabling the implementation of operational ecosystem-based management in the Gulf of Cadiz.