The bedform morphology of Chinese sturgeon spawning sites in the Yangtze River

Quantitative measures of the relationships between channel morphology and the habitat use of Chinese sturgeon (Acipenser sinensis) can help management and regulatory agencies to quantify potential spawning habitats and develop recovery goals in view of the decreasing area of sturgeon spawning habitat. This study determined the specific bedform types at the pool-riffle scale and evaluated the slopes, aspects and bed load gradation composition of Chinese sturgeon spawning areas in the Yangtze River, China. A bedform differencing technique was used to objectively quantify the longitudinal riverbed profile into four distinct pool-riffle units that were independent of discharge. The vertical location of thalweg points within these units was quantified with a riffle proximity index. Chinese sturgeon spawning areas were mapped and correlated with the pool-riffle units, slopes and aspects. The results indicate that Chinese sturgeon spawning areas occur primarily in riffles. The majority of Chinese sturgeon spawning occurred at elevations greater than 75% of the difference in elevation between the nearest riffle crest and the pool bottom. The slope of spawning sites was distributed between 0.05 and 6.36, and the average aspects were 219.92 and 207.63, respectively. The bed load is mainly composted of gravel and pebble, sediment diameter concentrated on 50-500mm. These analyses of bedform morphology will assist regional fish managers in quantifying existing and potential Chinese sturgeon spawning habitats and will provide a quantitative framework for evaluating general ecological implications of channel morphology in the Yangtze River.