Abstract:Statolith microstructure and growth characteristics were studied in 491 specimens (274 females and 217 males) of short-fin squid Illex argentinus collected by the Chinese jigging fishing fleet in 2007, 2008 and 2010. The results showed that growth increments of I. argentinus consisted of light and dark lines, with the initial point of increment formation (focus) being dark and like a drip of water. The growth increments were narrow to wide, light to dark from the focus to lateral dome, and were wide to narrow, dark to light form lateral dome to dorsal dome. Three zones (postnuclear, dark zone and peripheral zone) occurred in statolith dorsal dome. The results of principal component analysis on ten morphologic indices showed that total statolith length (TSL) and maximum width (MW) could be used to distinguish between different groups. There was no sexual dimorphism in the TSL and MW growth between different groups, and the relationship between age and TSL and MW were best described by linear functions for austral winter group and by logarithm functions for austral autumn group, respectively. However, there was a sexual dimorphism in the statolith weight (SW) between different groups, and the relationship between age and SW for females and males were best described by power and exponential functions for austral winter group and by exponential and logarithm functions for austral autumn group, respectively. The absolute growth rate (AGR) and instantaneous relative growth rate (IRGR) of TSL and MW tended to be high at young stages, and then decreased when the age increased. However, the AGR of SW tended to be higher with the increased age, and the IRGR of SW increased in the beginning and then decreased when age increased. The growth rate of austral winter group was higher than austral autumn group, and the growth rate of females was higher than males at the same age.
