Estimating the Riverine Abundance of Green Sturgeon Using a Dual-Frequency Identification Sonar

To determine the total number of Green Sturgeon <i>Acipenser medirostris</i> present in the Rogue River, Oregon, we compared plot sampling using a dual-frequency identification sonar (DIDSON), a density-based estimation technique combining the number of individuals detected and the area sampled, to a concurrent mark–recapture estimate. Using the DIDSON-based method, we estimated the total abundance of Green Sturgeon to be 223 (95% confidence interval = 180–266). The mark–recapture method resulted in an estimate of 236 individuals (150–424). The noninvasive DIDSON transect estimates resulted in tighter confidence intervals and required fewer technician hours to collect the data than did the mark–recapture method (37 h versus 232 h, respectively). Precise estimates of the abundance and distribution of Green Sturgeon are important components to species recovery and management. Thus, this new technique has the potential to greatly improve population monitoring and is an excellent tool to identify occupied habitats.Received June 9, 2014; accepted January 28, 2015