Reproductive biology of Argis lar from the East Sea of Korea (Decapoda, Natantia)

Abstract

We studied the reproductive biology of Argis lar from the East Sea of Korea, based on a total sample of 4172 shrimp collected over a 12 month period. The sample included 40 males (size range: 9.91-24.11 mm carapace length, CL), 2797 non-ovigerous females (size range: 7.22-38.33 mm CL), and 1335 ovigerous females (size range: 19.70-37.43 mm CL); size differed significantly among the three groups. Ovigerous females occurred during every month of the year, in varying percentages, with a minimum abundance of 2.48% in August; the extended reproductive period indicates that multiple spawnings occur during the year. All ovarian stages were present in non-ovigerous females, whereas only spent ovarian stages were present in ovigerous females. Two modes were present in the abundances of females at each ovarian stage. In the first mode, females at the mature ovarian stage were most abundant in September (61.98%) and females in the spent ovarian stage were most abundant in November (32.52%). In the second mode, females at the ripe ovarian stage were most abundant in December (62.96%) and females at the spent ovarian stage were most abundant in March (66.00%). The gonadosomatic indices of non-ovigerous females and ovigerous females varied significantly by month. The percentages of ovigerous females with eggs at different stages of development were: non-eyed eggs, 32.06%; eyed eggs, 25.69%; and hatching eggs, 42.05%. Females with hatching eggs occurred from November to June. The relationships between CL and ovary weight differed significantly between ovigerous females with eggs in the non-eyed and eyed stages. Our results indicate that the highest indices of reproductive potential (IRP) occurred in females in the 29.1-31.0 mm CL size class (IRP = 405).