Statolith microstructure and growth characteristics of Sthenoeuthis oualaniensis in the northwest Indian Ocean

Abstract

Statolith is one of the most important hard tissues to study the age, growth, population structure and life history of cephalopods. In order to stuty statolith microstructure and growth characteristics of Sthenoeuthis oualaniensis in the northwest Indian Ocean, 1009 samples were collected by Chinese light falling-net fishery fleets during investigation and production in the northwest Indian Ocean from February to May of 2019. Total statolith length (TSL), lateral dome length (LDL), wing length (WL) and maximum width (MW) were taken as the indicators of morphological feature of the statolith, combined with the age data, the statolith microstructure and growth characteristics of S. oualaniensis were studied. The results showed that the statolith microstructure could be divided into postnuclear zone, dark zone and peripheral zone according to the width of growth increment. The analysis of covariance showed that there was no growth difference of TSL, LDL, WL and MW between different sexes. The relationships between TSL, WL, MW and age were best described by the power functions, while the relationship between LDL and age was best described by the linear function. In general, with the increase of age, the instantaneous relative growth rate and absolute growth rate of TSL, WL, LDL and MW decreased, and 140-180 d may be the age of sexual maturity for this squid.