Fisheries biological characteristics of Japanese common squid (Todarodes pacificus) in spring in the La Niña year of 2018 in the East China Sea

Based on 1840 samples of Japanese common squid (Todarodes pacificus) collected from January to March in the spring in the La Niña year of 2018 in the East China Sea, the fisheries biological characteristics of T. pacificus were studied. The result indicated that the mantle length (ML) rangeos from 92 mm to 270 mm and 103 mm to 267 mm with a dominated concentration in 180 mm to 240 mm and 140 mm to 220 mm accounting for 71.44 and 89.31 % for females and males, the body weight (BW) rangeos from 21 g to 453 g and 21 g to 465 g with a dominated concentration in 120 g to 270 g and 60 g to 180 g, accounting for 66.54 and 81.26 % for females and males, respectively. The ratio of the somatic body weight (SBW) to BW ranged from 21.89 to 87.76 % with an average of 49.14 %. There was no significant difference between BW and SBW growth in sex, and the relationships between ML to BW and ML to SBW were both best described by the power functions by the result of Akaike’s information criterion (AIC). The ratio of females to males was 1∶1.255, and the samples were mostly composed of maturity individuals, accounting for 50.86 and 54.78 % for females and males. The feeding stage were mainly in 1 and 2 grade accounting for 64.24 %. All of the specimens and the prey were mainly composed of squids, pelagic fishes, mollusc and crustacean and so on. Our study shouwed that the fisheries biological features of T. pacificus were affected by La Niña in terms of a decrease in the body size, a faster growth speed and advanced gonad maturity stages.