中西太平洋围网不同作业方式兼捕镰状真鲨渔获率和死亡率分析

我国在中西太平洋(Western and Central Pacific Ocean,WCPO)金枪鱼围网渔业作业的方式主要分为捕捞自由鱼群(free swimming school,FSC)和人工集鱼群(fish aggregation devices,FAD),镰状真鲨(Carcharhinus falciformis)是这两种作业方式中主要的兼捕鲨鱼。本研究根据2018—2019年我国围网渔业渔船在中西太平洋区域(15°S—15°N,140°E—180°E)共20个作业航次记录的渔捞日志,对FSC和FAD两种状态的捕捞作业下兼捕到的镰状真鲨渔获率、生存状态等进行比较分析,结果表明:(1) FAD作业相比FSC作业兼捕到的镰状真鲨分布范围更广,两种作业方式兼捕到的镰状真鲨单位捕捞努力量渔获(catch per unit effort,CPUE)主要分布区域均集中在基里巴斯和瑙鲁专属经济区;(2) FAD和FSC兼捕镰状真鲨CPUE出现较高月份均在5—9月,FAD兼捕镰状真鲨CPUE显著高于FSC (P 0.05);(3) FSC和FAD兼捕镰状真鲨的死亡率范围分别为0.00%～92.86%和20.26%～76.71%,经检验两种作业方式下镰状真鲨死亡率间无显著性差异(P 0.05)。研究结果有助于了解不同作业方式对鲨鱼兼捕的影响,以实现提高目标鱼种渔获率、降低鲨鱼兼捕率的目的。

The analysis of catch rate and mortality on the bycatch of silky shark(Carcharhinus falciformis) in different operating modes of purse seine in the Western and Central Pacific Ocean

The purse seine fishing in the Western and Central Pacific Ocean (WCPO) by Chinese fleet are mainly free swimming school (FSC) and fish aggregation devices (FAD). The silky shark(Carcharhinus falciformis) is the main species of bycatch in these two operations. Based on the data from the 20-trips logbook of Chinese purse seine fishery fleets during 2018-2019 in the WCPO (15?S-15?N, 140?E-180?E), comparison of catch rates and survival rate of silky shark after capture by FSC and FAD methods are analyzed. The results show that: (1) the range of distribution of silky shark from FAD operations iswider than that of FSC, and the main catch per unit effort (CPUE) distribution of silky shark in both operations is concentrated in the exclusive economic zones of Kiribati and Nauru respectively; (2) The CPUE of silky shark from FAD and FSC operations are both higher in 5~9 month, and the CPUE of silky shark from FAD is higher than FSC, and the significant differences in the silky shark CPUE between FSC and FAD is presented (P < 0.05); (3) The mortality range of silky shark from FSC and FAD were 0.00% ~ 92.86% and 20.26% ~ 76.71%, respectively, and there is no significant difference between the two methods (P > 0.05). The results shall facilitate understanding the effects of different methods of operation on bycatch of sharks and to achieve the increasing the catch rates of target species and reducing the by catch rate of shark.