Age, growth and maturation of swordtip squid (Photololigo edulis) in the southern East China Sea.

Abstract

The reproductive biology, and age and growth of the swordtip squid (Photololigo edulis) in the East China Sea were examined based on the growth ring of statoliths from 1797 specimens during the period of November 2002 to November 2004. The maximum age observed was 261 days in female and 253 days in male, an evidence showing that swordtip squid has a longevity of about 9 months in both sexes. Growth in mantle length (ML) and body weight (BW) in both sexes was best described by the exponential model. There was significantly difference in somatic or statolith growth between the sexes. However, absolute daily growth rates (DGRs) and instantaneous relative growth rate (G) for ML and BW were similar for both sexes until 200-220 days, after which they became higher for males. In our samples, the youngest mature squid was 139 days in female and 102 days in male. Females matured about two months later in age than males in average. The hatching season was throughout the year but with several peaks, namely, October-November in 2002, March-April and November in 2003, March in 2004. Therefore, we suggested that swordtip squid has two main spawning seasons, spring (March-April) and autumn (October-November).