1. During 1998 and 2001, using a FUSO 405 echo-sounder, we investigated the numbers of spawning stocks of the Chinese sturgeon, AcipensQr sinensis, below the Gezhouba Dam of the Yangtze River. The population sizes of the planktivorous, silver and bighead carps, in the East Lake were also estimated monthly in 2000 by using a PS-20R portable echo-sounder.Based on echo strength and signals size, the Chinese sturgeon was discriminated from other fish species. The spawning ground between the Gezhouba Dam and the Zhenjiang Pavilion has a surface area of about 5.49 km2, and the spawning stocks prior to and after the spawning activity were about 380 and 265 individuals in 1998, respectively, and about 395 and 156 individuals in 1999, respectively. The spawning stocks prior to and after the second spawning activity in 2000 were about 177 and 103 individuals, respectively in 2000, and those prior to and after the first spawning activity in 2001 were about 212 and 34 individuals, respectively. No sturgeon was found after the second spawning activity in 2001.No significant difference in annual distributions of Chinese sturgeon was observed in the spawning ground among 1998 - 2001. The sturgeon was detected in depths between 8.2 and 24 m, with 90 % between 9 and 21 m. In spite of a wide vertical distribution, the sturgeons prefered to inhibit near the bottom.The number of stocked fish in the East Lake fluctuated seasonally probably mainly due to fishery activities. The surveys by using a PS - 20R echo-sounder shows that in 2000, the population size was about 0.54 millions in January, but dropped down from 0.67 millions in February to 0.42 millions in April, moved up from 0.5 to 1.9 millions from May to August, and declined again from 1.78 to 1.28 millions from September to December.The stocked fish were mainly distributed below 1.5 m vertically. Horizontally, heterogeneous distribution of stocked fish in the East Lake might be caused mainly by aggregation activity, water temperature, and sewage discharge. However, no significant correlation was found between the aggregation activity and water depth, or distances from the sampling sites to the shores.