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Torres-Irineo, E., Dreyfus-Leon, M., Gaertner, D., Salas, S., & Marchal, P. (2017). Adaptive responses of tropical tuna purse-seiners under temporal regulations. Ambio, 46(1), 88–97.
Résumé: The failure to achieve fisheries management objectives has been broadly discussed in international meetings. Measuring the effects of fishery regulations is difficult due to the lack of detailed information. The yellowfin tuna fishery in the eastern Pacific Ocean offers an opportunity to evaluate the fishers' responses to temporal regulations. We used data from observers on-board Mexican purse-seine fleet, which is the main fleet fishing on dolphin-associated tuna schools. In 2002, the Inter-American Tropical Tuna Commission implemented a closed season to reduce fishing effort for this fishery. For the period 1992-2008, we analysed three fishery indicators using generalized estimating equations to evaluate the fishers' response to the closure. We found that purse-seiners decreased their time spent in port, increased their fishing sets, and maintained their proportion of successful fishing sets. Our results highlight the relevance of accounting for the fisher behaviour to understand fisheries dynamics when establishing management regulations.
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Paulino, C., Aroni, E., Xu, H., Alburqueque, E., & Demarcq, H. (2017). Use of nighttime visible images in the study of the spatial and temporal variability of fishing areas of jumbo flying squid (Dosidicus gigas) outside Peruvian EEZ 2004-2015. Fish Res., 191, 144–153.
Résumé: We analyzed the temporal variability of the fishing fleet of Dosidicus gigas, located outside the exclusive economic zone of Peru (EEZ), with a spatial luminosity index. The nighttime satellite images were provided by the Operational Linescan System (DMSP-OLS) from 2004 to 2015. 2995 images were processed, selecting pixels in the range of 30-63 Digital Number (DN), to identify the presence of vessels in the image. The time series showed an extensive latitudinal distribution of the fishing fleet from 6 degrees S to 32 degrees S, with years of low (2005-2009) and high (2004, 2010-2015) presence, describing a recurrent seasonal pattern of latitudinal displacement measured from its center of gravity (CG). The CG reaches its southernmost position between February to April and its northernmost position between August to October. Some vessels were also detected within the Peruvian EEZ. The latitudinal inertia presented values of 0.3-1 indicating high fleet concentration between 12 degrees S to 17 degrees S and the longitudinal inertia presented values >2, showing the wide distribution of the resource. Luminous pixels showed high fishing occurrence (>18 times) on a single pixel, in front of Chimbote around 9 degrees 51'S-82 degrees 31'W from 2004 to 2011. From 2012 to 2015 areas of high fishing occurrence increased in front of Huarmey (10 degrees 36'S/82 degrees 41'W) and San Juan de Marcona (15 degrees 53'S/80 degrees 6'W). For both periods, high intensity pixels (DN >60) show extensive areas of fishing operation between 9 degrees S to 20 degrees S along 200 nautical miles from the coast, while values between 30 and 45 DN could be mostly associated with the search for fishing zones. Since 2012, pixels with DN >58 have increased, indicating a greater fishing activity likely related to a higher availability of the resource or a better knowledge of the fishing zones, associated with an increase of the fishing effort and a possible higher pressure on the resource. (C) 2017 Elsevier B.V. All rights reserved.
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Poisson, F., Abascal Crespo, F., Ellis, J. R., Chavance, P., Pascal, B., Santos, M. N., et al. (2016). Technical mitigation measures for sharks and rays in fisheries for tuna and tuna-like species: turning possibility into reality. Aquat. Living Resour., 29(4), 402.
Résumé: Tuna fisheries have been identified as one of the major threats to populations of other marine vertebrates, including sea turtles, sharks, seabirds and marine mammals. The development of technical mitigation measures (MM) in fisheries is part of the code of conduct for responsible fisheries. An in-depth analysis of the available literature regarding bycatch mitigation in tuna fisheries with special reference to elasmobranchs was undertaken. Studies highlighting promising MMs were reviewed for four tuna fisheries (longline, purse seine, driftnets and gillnet, and rod and line – including recreational fisheries). The advantages and disadvantages of different MMs are discussed and assessed based on current scientific knowledge. Current management measures for sharks and rays in tuna Regional Fishery Management Organizations (t-RFMOs) are presented. A review of relevant studies examining at-vessel and postrelease mortality of elasmobranch bycatch is provided. This review aims to help fisheries managers identify pragmatic solutions to reduce mortality on pelagic elasmobranchs (and other higher vertebrates) whilst minimizing impacts on catches of target tuna species. Recent research efforts have identified several effective MMs that, if endorsed by t-RFMOs, could reduce elasmobranchs mortality rate in international tropical purse seine tuna fisheries. In the case of longline fisheries, the number of operational effective MMs is very limited. Fisheries deploying driftnets in pelagic ecosystems are suspected to have a high elasmobranchs bycatch and their discard survival is uncertain, but no effective MMs have been field validated for these fisheries. The precautionary bans of such gear by the EU and by some t-RFMOs seem therefore appropriate. Recreational tuna fisheries should be accompanied by science-based support to reduce potential negative impacts on shark populations. Priorities for research and management are identified and discussed.
Mots-Clés: at-vessel mortality; Bycatch; california recreational fishery; circle hooks; eastern pacific-ocean; Elasmobranch; great-barrier-reef; j-hook performance; Mitigation; mortality; pelagic; pelagic longline fishery; postrelease survival; Purse seine fishery; rare-earth-metal; tuna regional fishery management organizations
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