use of Dual‐frequency IDentification SONar (DIDSON) to document white sturgeon activity in the Columbia River, Canada

The feasibility of using Dual‐frequency IDentification SONar (DIDSON) for monitoring white sturgeon (Acipenser transmontanus) presence and activity was tested near a known spawning area in the Columbia River, British Columbia, Canada. A fixed‐station DIDSON system was deployed near the river bank adjacent to the spawning site in each 3 years (2007–2009). Fixed‐station data were collected at this site in July and August each year, with an additional fixed‐station site established in 2009 approximately 1.6 km upstream. A total of 267, 64, and 210 observations of sturgeon were documented based on fixed‐station DIDSON sampling in 2007, 2008, and 2009, respectively. Sturgeon detections within the sample area (standardized by time and day) generally increased during late evening/early morning hours but did not appear to be related to flows. The DIDSON provided estimates of white sturgeon total lengths consistent with known length distributions for this population. Most sturgeon were detected at least 10 m away from the shoreline. These results demonstrate the feasibility of using fixed‐station DIDSON for remotely monitoring white sturgeon in areas of known use. Observational data from this study also provided information on general sturgeon behaviour that is often difficult to assess with more conventional sampling methods.