Age, growth and population structure of swordtip squid (Uroteuthis edulis) in the East China Sea based on statolith age information

The Uroteuthis edulis is one of the important economic squid resources in the East China Sea. Studying the composition, age, and growth pattern of population is the basis for understanding its life history. Based on the samples of the East China Sea U. edulis collected by the trawl nets from September to March of 2017 and 2018, this study used the age information of statoliths to study the sex and year differences in population structure and growth patterns. The results showed that there were differences in population mantle length and body weight composition between years, but there was no significant difference between genders. It was found by reading the age of statoliths and performing backward calculation that the two-year dominant age group was 190-220 d, and there were significant differences in age composition of male during the year. The backward calculation results showed that the peak hatching period was from March to May and August. The spring and summer stocks are the dominant hatching groups. The mantle length and body weight growth of the spring stock were best fitted with a Logistic curve, and the summer stock were best fitted with a von-Bertalanffy and a Logistic curve. In 180-270 d, the mantle length and body weight growth rate of spring stock was faster than that of summer stock. After 240 d, the male mantle growth rate was faster than that of female, and the body weight growth rate was slower than that of female. The age of the 50% maturity of the spring stock is younger than that of the summer stock, and the male is younger than the female. The results showed that different spawning populations existed in two years, and the growth pattern also had difference between sexes. Therefore, this study can provide a scientific basis for comprehensive understanding of the life history characteristics of the U. edulis.