A preliminary study on catch rate and characteristics of silky shark in longline fishing in tropical Pacific
MA Yeyang
DAI Xiaojie
GAO Chunxia
Abstract：Silky shark(Carcharhinus falciformis)is caught as an important bycatch in tropical tuna longline fishery,which situates at the top of the marine food chain as an apex predator and plays an im-portant role in maintaining the balance of the marine ecosystem.Silky shark stock is in decline under o-verfishing and it has been listed for protection under Appendix Ⅱ of the Convention on International Trade in Endangered Species of Wild Fauna and Flora in 2017.Based on the sample data(5 617 ind.)collected by Chinese longline fishery observers in tropical Pacific(90°55′W～139°58′E,37° 20′ N～36°49′S),preliminary analyses of catch rate,sex ratio and fork length were conducted.Higher catch per unit effort(CPUE)was found in area of 105°W～165°E and 10°N～20°S.There was a decline trend of CPUE of silky sharks from year 2015 to year 2019(the highest in 2017).There was a significant difference between years(P＜0.05),but monthly CPUE was higher from June to October,with a sig-nificant difference in CPUE between months(P＜0.05).The overall dominant fork length(FL)of fe-males and males ranged from 90 to 170 cm.The ratio of females to males conformed to 1∶1(P＞0.05).The dominant fork lengths varied between 90 and 110 cm for females and males in tropical west-ern and central Pacific,and between 150 and 170 cm for females and males in tropical eastern Pacific.There were significant differences between the mean fork lengths of females and males in both seas(P＜0.05).
Keywords：silky sharklongline fishingcatch rateFLtropical western and central Pacifictropical eastern Pacific
Publication Date：2025-10-30
Online Publishing Date：2026-05-22(First online date of this platform, not the publication date of the document)
Pages：11( 147-157 )