A study on catch rate, sex ratio and fork length of blue shark (Prionace glauca) in longline fishing in Western and Central Pacific Ocean

Blue shark (Prionace glauca) is a widely distributed pelagic species with relatively high catch rate of longline fishery targeting tunas. Based on the 51-trip observer data for the blue sharks collected in the Western Central Pacific Ocean during 2015–2018, we anayzed their catch rate, sex proportion and fork length. The results show that higher catch per unit effort (CPUE) was found in the area of 170°30'E−124°50'W and 33°30'N−34°40'S. It is noted that the CPUE fluctuated greatly during 2015−2018 (highest in 2017). There was no significant difference between CPUE and month (P>0.05). The distribution range of male and female was basically the same. The sex ratio for female and male was 1.75. The dominant fork length (FL) for both male and female ranged from 160 cm to 220 cm, accounting for 89.26% and 85.19%, respectively. There was significant distribution difference between male length and female length by t-test (P<0.05).