Spatial distribution and habitat choice of adult Chinese sturgeon (Acipenser sinensis Gray, 1835) downstream of Gezhouba Dam, Yangtze River, China

Abstract

Eight hydroacoustic surveys were conducted between 2007 and 2010 to determine the spatial distribution and habitat choice of adult Chinese sturgeon (Acipenser sinensis) within 85km immediately downstream of Gezhouba Dam, which is the lower-most dam blocking upstream sturgeon migration in the Yangtze River. A potential 32 A.sinensis were identified; depth, velocity, etc., characteristics were determined at the sturgeon site with an Acoustic Doppler Current Profiler. Most targets (26 individuals, 81.3%) were in water >12m deep, and most (29 individuals, 90.6%) targets were near the river bottom. All targets stayed in or were close to the river channel (distance to the thalweg about one tenth of the river width). Fish were primarily distributed among four separate and deep areas. Variations in the water level played no significant role in fish distribution. Large, deep areas attracted the most fish. A preliminary analysis of environmental factors including water depth, flow velocity, Froude number and Reynolds number indicated that the bedform morphology (deep areas) was probably the key factor determining the A.sinensis habitat preference. Future conservation of the sturgeon will be more effective when special attention is given to the four refuges.