Abstract
Within the Ecosystem-based fisheries management framework, we evaluated the changes over time in bycatch species of the European tuna purse-seine fishery operating in the eastern Atlantic Ocean. Bycatch data was collected during two scientific observer programs conducted in the late 1990s and in the late 2000s. Over these two time periods, we compared the temporal trends in bycatch species composition, the probability of occurrence of functional groups per fishing set, the spatio-temporal species richness and the potential impact on several species listed in the red list of the International Union for Conservation of Nature (IUCN). The analyses were performed separately on the two main fishing modes of the fleet, i.e. sets on free-swimming school sets and on fish aggregating devices (FADs). Owing data quality constraints, we did not estimate bycatch rates. Ours results showed that the species composition of sharks caught on FADs decreased over time. The total species richness was higher for FAD sets than for free-swimming school sets (87 vs. 61 species respectively), such difference is common between fishing modes worldwide. For the species catalogued as threatened by the IUCN, in free-swimming schools, 25.5 % of the species caught during first period increased to 30.4 % during second period, while for FAD-fishing the increase was from 28.8 % during first period to 34.9 % in second period. Ours findings suggest that tropical tuna purse-seine fisheries should include ecosystem-based governance of bycatch. Effective tuna management will require a combination of technological improvements for mitigating incidental catch of vulnerable species, best use of byproduct species, regulations in fishing practices and in spatial distribution of fishing effort, and international agreements that, together, can monitor and manage bycatch, reducing the negative fishing effects on the epipelagic ecosystem biodiversity.
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Acknowledgments
The observer data analyzed in this study were collected by the Institut de Recherche pour le Développement (IRD) part of the Mixed Research Unit 212 ‘Exploited Marine Ecosystems’ (IRD/Ifremer/U. Montpellier 2), Instituto Español de Oceanografía, and AZTI-tecnalia through the EU Research Bigeye Program (Reg 96/028) and the EU-funded Data Collection Framework (DCF, Reg (EC) 1543/2000 and 199/2008). We wish to acknowledge the contributions of ORTHONGEL, the staff of the Observatoire Thonier (IRD), and all the technicians and fishermen that have been involved in data collection, processing, and management. This study was part of the Ph.D. thesis conducted by the first author (ETI) at the University of Montpellier 2 (ED SIBAGHE) and funded by Consejo Nacional de Ciencia y Tecnología (CONACYT), Mexico, Scholarship No. 199730.
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Communicated by David L. Hawksworth.
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Torres-Irineo, E., Amandè, M.J., Gaertner, D. et al. Bycatch species composition over time by tuna purse-seine fishery in the eastern tropical Atlantic Ocean. Biodivers Conserv 23, 1157–1173 (2014). https://doi.org/10.1007/s10531-014-0655-0
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DOI: https://doi.org/10.1007/s10531-014-0655-0