SUSTAINABLE YIELD OF THE RED SWAMP CRAYFISH (PROCAMBARUS CLARKII) THROUGH UNDERSTANDING ITS POPULATION STRUCTURE AND DYNAMICS IN POYANG LAKE

With increasing commercial demand for its delicacy, Procambarus clarkii has become an important fishery resource of Poyang Lake in recent years. However, habitat loss, overfishing, and the crayfish plague have diminished P. clarkii populations throughout their area of distribution. In consequence, this study systemically analyses the population structure and dynamics of P clarkii in the wetland of Poyang Lake using the analytical methods of Bhattacharya and Von Bertalanffy. The main purpose was to collect biological data necessary for the management of this species. The present study showed that the population structure consisted of a maximum of 5.58 age classes for females and 3.25 for males, which indicated that P. clarkii is a relatively short-lived species. The Y'/R analysis showed that E-present > E-0.5, which exceeded the optimization (E-opt) criterion of 0.5 for sustainable exploitation of fisheries, so this species was overexploited in Poyang Lake. The L-c (mean length at first capture) equals 67.5 mm. The estimated mesh size for catching the red swamp crayfish is 13.5 cm. The virtual population analysis model (VPA) showed that the largest annual catch of P clarkii is 3.43 x 10(4) t. The Maximum Sustainable Yield (MSY) is 1.18 x 10(4) t. The low natural mortality rate range of 0.68-1.11 year(-1)uggested that it is ecologically worthwhile to allow the individuals of P clarkii to grow to larger sizes in order to contribute to the biomass for biologically optimal exploitation. This could be facilitated by the adoption of measures involving a closed season, which would help to conserve the fishery.