Population dynamics and estimation of maximum sustaining yield for Parapenaeopsis hardwickii in the northern area of East China Sea

Based on the monthly length-frequency data obtained from the northern area of East China Sea during the periods of 1986 - 1987 and 1993 - 1995, the population dynamics and maximum sustaining yield of Parapenaeopsis hardwickii were studied. The dominant length group for the female was 70- 90mm, which was 63% of the total female. By using ELEFAN.and òtechnique, the growth parameters were estimated: K= 1. 7, L = 128mm and t0= - 0. 1185, the approximate longevity was 1. 3234 years. Total mortality z= 8. 3280 , and mean selection length Lc = 59. 67mm. Natural mortality M = 2. 7427 was est imated by using the empirical relationship between M, the growth parameters and mean environmental temperature, and the exploitation rate, E = F/ Z = 0. 6706, was obtained. Yield-per-recruit and the value of yield-per-recruit analysis indicated that the stock of Parapenaeopsis hardwickii had been fully exploited. An increase in yield-per-recruit and the value of yield-per-recruit may be expected if the size of first capture has a moderate increase. The value of yield-perrecruit would be reduced with the increase of f ishing mortality.