Abstract:Mandarin fish (Siniperca chuatsi) is a rare and precious economic species of freshwater fish with a long standing reputation because of its fast growth, meat delicate, delicious and nutrient rich. The mature artificial propagation technology has created good conditions for Siniperca chuatsi large- scale cultivation since 1980 s. However, the wild Siniperca chuatsi population is declining due to over exploitation and environmental pollution in their habitat, which may cause the decline of genetic diversity. Mandarin fish is one of abundant species in Poyang Lake and plays an important role in the lake ecosystem. Based on Poyang Lake fishery resources investigation data, we assessed biological parameters and stock biomass of Siniperca chuatsi using FiSAT II software. The results indicated that the length of Siniperca chuatsi population ranged from 77 to 526 mm, and that the relationship between body length (mm) and body weight (g) can be expressed as W = 1.888´10-5L3.042(R2=0.951, n = 577). The estimated parameter for von Bertalanffy growth equation was L∞= 551.25 mm, K= 0.210, and t0 = -0.601. Total mortality (Z) was 1.06 a-1; natural mortality was (M) 0.44 a-1; fishing mortality (F) was 0.62 a-1; the optimum catchable size was 150 cm. The exploitation rate was 0.58, which is in the situation of over exploitation. The initial stock of Siniperca chuatsi in the Poyang Lake was up to 1.92´104 tons, and the Maximum sustainable yield (MSY) was 4384.93 tons. The recruitment and young surplus populations of the spawning stock increased significantly in the reproductive population. Low-age and miniaturization tendency was obvious; however, the growth potential was still high based on the growth equation. The results suggest that active strategies such as reducing fishing intensity of the reproductive population and protecting the spawning grounds are imperative to maintain this precious fishery resources.
