Effects of high water level on the river residence period of juvenile Chinese sturgeon

The migration time of newly hatched Acipenser sinensis from the spawning area (river km 1675) to the Yangtze estuary (rkm 0) was ascertained in the years 1996–2007 (time range 192–243 days), and its relationship to water levels surveyed at 12 typical hydrological monitoring stations in the middle and lower reaches of Yangtze River was determined. Migration time showed a positive correlation (R = 0.621−0.738, P = 0.013−0.041) with the water levels surveyed during April at eight stations (from Jianli to Anqing, rkm 1356.2 to rkm 639.4). Stepwise regression analysis indicated that when the water level at a typical station, Luoshan (rkm 1244.2), increased by 1 m, migration time deferred 11.6 days. The high water level created expanded riparian habitat and thus may have prolonged juvenile residence time. This variable residence time due to variations in water flow caused by the Three Gorges Project needs to be addressed, and more investigation is required.