Spatio-temporal distribution and target species of longline fisheries off Southeastern/Southern Brazil between 2000 and 2011

Abstract In the presente study, cluster analysis was performed to classify 1080 interviews with captains of national pelagic longline fleet (2000 to 2011), and 38 trips of the chartered fleet (2003 to 2008), in relation to the composition of species landed. For the national fleet 4 groups were identified: 1 - Albacores, 2 - Blue shark, 3 - Swordfish, and 4 - Dolphinfish. For the chartered fleet 3 groups were identified: 1 - Swordfish, 2 - Blue shark, and 3 - Albacores. The results indicated that part of the national fleet change their strategies according to the availability of the target species and market demand (internal and external). A part of the fleet from Espírito Santo state operates in the region between December and March, exclusively to capture dolphinfish. The chartered fleet differed from the national one as regards the fishing areas of each target species, mainly as regards swordfish and blue shark. Despite the great difference in the data sets, it is evident that both the national and the chartered fleets operated in accordance with their peculiarities and technological development, adopting strategies that optimize catches and net profits per trip.

摘要 本研究针对1080份国家级远洋延绳钓船队（national pelagic longline fleet）船长访谈记录（2000年至2011年）以及38艘租赁船队航次数据（2003年至2008年），基于上岸渔获物的物种组成开展聚类分析。针对国家级船队，共识别出4个类别：1. 长鳍金枪鱼类群，2. 大青鲨类群，3. 剑鱼类群，4. 鲯鳅类群。针对租赁船队，则识别出3个类别：1. 剑鱼类群，2. 大青鲨类群，3. 长鳍金枪鱼类群。研究结果显示，部分国家级船队会根据目标物种资源可获得性以及国内外市场需求调整作业策略。来自圣埃斯皮里图州的部分船队会在每年12月至次年3月期间前往该海域，专门捕捞鲯鳅。租赁船队与国家级船队在各目标物种的作业海域存在显著差异，尤以剑鱼与大青鲨的作业海域差异最为突出。尽管两类数据集存在较大差异，但显而易见的是，国家级与租赁船队均结合自身作业特点与技术发展水平，采用了能够优化单航次渔获量与净利润的作业策略。