Tolotti Mariana Travassos, Bach Pascal, Hazin Fábio, Travassos Paulo, Dagorn Laurent
Institut de Recherche pour le Développement, UMR MARBEC (IRD, Ifremer, Univ. Montpellier, CNRS), Avenue Jean Monnet CS 30171, Sète cedex, France; Programa de Pós-graduação em Oceanografia, Universidade Federal de Pernambuco, Departamento de Oceanografia, Recife-PE, Brasil.
Institut de Recherche pour le Développement, UMR MARBEC (IRD, Ifremer, Univ. Montpellier, CNRS), Avenue Jean Monnet CS 30171, Sète cedex, France.
PLoS One. 2015 Oct 22;10(10):e0141396. doi: 10.1371/journal.pone.0141396. eCollection 2015.
A combination of fisheries dependent and independent data was used to assess the vulnerability of the oceanic whitetip shark to pelagic longline fisheries. The Brazilian tuna longline fleet, operating in the equatorial and southwestern Atlantic, is used as a case study. Fisheries dependent data include information from logbooks (from 1999 to 2011) and on-board observers (2004 to 2010), totaling 65,277 pelagic longline sets. Fisheries independent data were obtained from 8 oceanic whitetip sharks tagged with pop-up satellite archival tags in the area where longline fleet operated. Deployment periods varied from 60 to 178 days between 2010 and 2012. Tagging and pop-up sites were relatively close to each other, although individuals tended to travel long distances before returning to the tagging area. Some degree of site fidelity was observed. High utilization hotspots of tagged sharks fell inside the area under strongest fishing pressure. Despite the small sample size, a positive correlation between tag recorded information and catch data was detected. All sharks exhibited a strong preference for the warm and shallow waters of the mixed layer, spending on average more than 70% of the time above the thermocline and 95% above 120 m. Results indicate that the removal of shallow hooks on longline gear might be an efficient mitigation measure to reduce the bycatch of this pelagic shark species. The work also highlights the potential of tagging experiments to provide essential information for the development of spatio-temporal management measures.
利用渔业依赖型数据和独立数据相结合的方式，评估远洋白鳍鲨对远洋延绳钓渔业的脆弱性。以在赤道和西南大西洋作业的巴西金枪鱼延绳钓船队为例进行研究。渔业依赖型数据包括航海日志（1999年至2011年）和船上观察员（2004年至2010年）提供的信息，共计65277次远洋延绳钓作业。渔业独立数据来自在延绳钓船队作业区域用弹出式卫星档案标签标记的8条远洋白鳍鲨。2010年至2012年期间，标签部署时间从60天到178天不等。标记地点和弹出地点相对较近，不过个体在返回标记区域之前往往会远距离游动。观察到一定程度的地点保真度。被标记鲨鱼的高利用热点区域位于捕捞压力最大的区域内。尽管样本量较小，但仍检测到标签记录信息与渔获数据之间存在正相关。所有鲨鱼都强烈偏好混合层温暖且较浅的水域，平均有超过70%的时间处于温跃层上方，95%的时间处于120米以上。结果表明，去除延绳钓渔具上的浅水鱼钩可能是减少这种远洋鲨鱼兼捕的有效缓解措施。这项工作还凸显了标记实验在为时空管理措施的制定提供关键信息方面的潜力。
