太平洋金枪鱼延绳钓渔业小吻四鳍旗鱼兼捕特征及影响因素分析OA

The shortbill spearfish(Tetrapturus angustirostris)is a large pelagic fish species inhabiting tropical and temperate waters,primarily distributed in the Pacific and Indian Oceans.To clarify its biological traits and bycatch status in longline fisheries,this study conducted an integrated analysis of its bycatch patterns,including bycatch per unit effort(BPUE)and on-deck mortality,and population structure(such as fork length,sex,and sexual maturity)using observer data from the Chinese Pacific tuna longline fishery(2010-2021).A Tweedie Generalized Additive Model(Tweedie-GAM)was employed to analyze the effects of spatiotemporal factors,environmental variables,and operational parameters on the BPUE of the shortbill spearfish.The results indicated an annual average BPUE was 0.21ind./1 000 hooks;the on-deck mortality was notably high at 56.43％;the sex ratio was approximately 1:1(0.97:1);the dominant fork length for both male and females was 150-170 cm;males exhibited significantly greater mean fork length than females(P<0.01).The cumulative deviance explained by the Tweedie-GAM was 39.07％,with sea surface temperature(SST)exhibiting the highest individual deviance explained(27.65％),followed by latitude(4.94％),salinity(1.90％),year(1.20％),and hooks per basket(1.35％).Contributions from all other variables were below 1％.Bycatch hotspots were concentrated in the area 100°W-130°W,10°S-20°S,with two potential hotspot regions identified at 170°E-180°W near 20°S and 170°E-170°W,15°N-25°N.This study elucidated population structure characteristics and bycatch dynamics of the Pacific shortbill spearfish,providing critical references for monitoring resource fluctuations and formulating science-based conservation measures.