PRESENT STATUS OF SPAWNING STOCK OF CHINESE STURGEON, ACIPENSER SINENSIS,IN THE YANGTZE RIVER

The Chinese sturgeon, Acipenser sinensis, an anadromous fish, lives mainly in the continent shelf of the Yellow China Sea and the East China Sea, and spawns in the Yangtze River and the Pearl River.Since the establishment of the Gezhouba Dam in 1981, the spawning migration of the fish to the upper reaches of the river has been blocked.Commercial fishery of this species has been prohibited accordingly in order to protect its natural resources since 1983.Moreover, artificially propagated larved and juveniles have been released annually into the Yangtze River for the stock enhancement since 1984.In order to realize the function of the above conservation measures, the authors took an investigation on the status of population structure of the fish.From 1994 to 1998, 246 specimen of Chinese sturgeon were collected in the reaches between Yichang and Zhicheng sections below the Gezhouba Dam.Increases in average of the total length, body weight and age of the fish have been measured in the spawning stocks, especially in the male.Moreover, the ratio of fe-mals to male, and the percentage of gonad-matured individuals in the stoch have increased drastically in comparison with the historical data.For the purpose of the fish protection in the future, several measures should be taken into consideration, including the strengthening of the spawning stock management, the increase of artificial release of juveniles, the restoration of natural spawning habitats, and the establishment of fully artificial stocks.