Biology of the cocktail shrimp, Trachysalambria curvirostris (Decapoda: Penaeidae) in the Yellow Sea of Korea

Abstract

Trachysalambria curvirostris occurs widely along the south and west coasts of Korea with a range extending from Kanghwado in the north-west, down to Sarangdo in the south-east. With seasonal warming of the waters starting in April, the shrimps begin to migrate from deep waters to the coastal area. Zoea and mysis larvae occurred from June to August. Sex ratio showed seasonal variations, with a mean value of 56·7% for the females. The species produces one cohort a year, with the ovaries ripening from June to July. Insemination appeared to take place from June to August, as more than half of the females sampled in the study over 15–16 mm carapace length were inseminated. Mean gonadosomatic index (GSI) reached a maximum between June and July. The smallest mature female found was 15 mm carapace length (CL). Size at 50% sexual maturity (CL₅₀), determined from both mature females and inseminated females, was 15·37 mm and 16·49 mm CL, respectively. Fecundity was directly proportional to the size of the female, with clutch sizes varying from 16,380 eggs in the smallest female to 114,621 eggs in the largest, and the eggs ranged from 230 μm to 340 μm in diameter. The life span of females appeared to be 14–15 months according to size frequency distributions, while that of the male was 13–14 months. Population growth was estimated by the modified von Bertalanffy growth function incorporating seasonal variation in growth. Based on the growth parameters (K=2·00 y⁻¹ and L_∞=24·64 mm CL for females, and K=2·00 y⁻¹ and L_∞=19·00 mm CL for males) growth curves showed that females grew faster and reached a larger size at age than males. This result is supported by differences in growth performance indices (ϕ′).