POPULATION BIOLOGY OF TOPMOUTH GUDGEON IN THE BAOAN LAKE V. PRODUCTION

Production by P. parva from the 1# experimental enclosure of the Bao-an Lake, Hubei province, was estimated during the period of from October 1995 to November 1996. Monthly instantaneous growth rate changed with both age and season. Growth in weight decreased with increasing age, being maximal during the early months of life. The growth rate was generally higher in spring and summer. Mean biomass, annual production and P/ B ratio of the population were 18.27kg穐m-2, 36.53kg穐m-2穉-1, and 2.0, respectively. The 1996 year class contributed 67.9% of the total annual production, the 1995 year class, 30.5%, and the 1994 year class only 1.6%. Mean monthly biomass and production of the whole population showed a markedly seasonal variation. Maximum biomass occurred in early autumn(September), while maximum production was observed in mid-summer(July). The summer production(June to August)contributed 77.6% of annual production by the population.