Reproduction and population dynamics of Acetes chinensis (Decapoda : Sergestidae) on the western coast of Korea, Yellow Sea

Reproduction and population dynamics of Acetes chinensis were studied on the western coastal areas of Korea, Yellow Sea, between May 2000 and October 2001. Female maturity was determined from the ratios of females with maturing ovaries by size. The size at which 50% of females are mature is estimated as 8.96 mm carapace length. The mature females first appeared in April, reached a peak in July, and then did not appear after September. The main breeding season (percentage of females with mature ovaries greater than 50%) was from July to September. Similar pattern could be found in monthly changes of gonad index (GI), showing relatively higher GI during the annual breeding season. Mean gonad index examined weekly during the breeding season (June-September) peaked both in the middle of June and early September. Parameters of growth were estimated using the modified von Bertalanffy growth function (VBGF) model incorporating seasonal variation in growth. Females grew faster and reached a larger size at age than males (L-infinity = 13.51 mm CL and K = 0.69 yr(-1) for females, and L-infinity = 10.48 mm CL and K = 0.84 yr(-1) for males). The mortality rate (Z) (+/- 95% confidence limit) calculated by length-converted catch curves was estimated as 3.93 (+/- 2.00) yr(-1). The structure of the recruitment patterns obtained by the ELEFAN program indicated two normally distributed groups. The estimated longevity was 0.75-1.0 yr for the summer generation and 0.58-0.83 yr for the winter generation.