金枪鱼延绳钓钓具的最适浸泡时间

根据2010年10月—2011年1月金枪鱼延绳钓海上调查数据,分两种起绳方式,建立每次作业每一根支绳的浸泡时间计算模型。将钓具的浸泡时间以1 h为间隔分别统计每个区间的支绳数量及大眼金枪鱼(Thunnus obesus)、黄鳍金枪鱼(Thunnus albacores)的渔获尾数,并计算其钓获率(CPUE)。结果表明:1)大眼金枪鱼和黄鳍金枪鱼的CPUE都随浸泡时间的增加呈现先增后减的趋势,这是由于饵料的诱引效果变化及渔获的丢失引起的;2)二次曲线可拟合浸泡时间与大眼金枪鱼和黄鳍金枪鱼CPUE的关系;3)大眼金枪鱼和黄鳍金枪鱼CPUE最高的浸泡时间分别为9.9 h和10.1 h。建议:1)今后在金枪鱼延绳钓作业中,保证每一根支绳在水中的浸泡时间为9.5~10.5 h,以提高捕捞效率并减少副渔获物;2)可把延绳钓钓具的浸泡时间作为有效捕捞努力量,并用于CPUE的标准化。研究结果可用于提高捕捞效率并减少副渔获物的技术方案制订,并为渔业生产和CPUE的标准化提供科学参考。

Optimum soak time of tuna longline gear

basis of the data collected from October 2010 to January 2011 in the tuna longline survey, the soak time calculation models of every branch line in each operation were developed by both modes of hook retrieval. The soak time of longline gear divided into one hour interval for the quantity of hooks and the individuals of bigeye tuna (), respectively. The respective catch rates (CPUEs) of bigeye tuna and yellowfin tuna in each hour interval were calculated. The results showed that (1) both CPUE of bigeye tuna and yellowfin tuna presented increasing at first and then decreasing trend along the increase of soak time. The reason was the lure effect fluctuation of bait and the lose of hooked fish; (2) the quadratic curves can be fit the relationships between soak time and the CPUE of bigeye tuna, and yellowfin tuna; (3) the CPUE of bigeye tuna and yellowfin tuna was the highest when soak time was 9.9 h and 10.1 h, respectively. This study suggested that (1) the soak time of each hook lasted about 9.510.5 h in the tuna longline operation for improving the fishing efficiency and decreasing the bycatch; (2) the soak time of the longline gear could be considered as the effective fishing effort and used to standardize the CPUE.improve the fishing efficiency and to decrease the bycatch and will be for the references to the fishing strategy and CPUE standardization.