Annual Movements of Acoustic‐Tagged White Sturgeon in the Lower Reaches of the Fraser River and its Tributaries

Details of the spatial ecology of White Sturgeon Acipenser transmontanus in the lower Fraser River, British Columbia, are needed for habitat conservation, assessments of impacts from spatially delimited threats, and refinement of abundance estimation methods. The abundance of threatened lower Fraser River White Sturgeon is assessed annually using a Bayesian, closed‐population, mark–recapture model. If individuals make prolonged departures from the lower Fraser River, either into marine waters or a tributary, the validity of the model's assumed closed population is questionable. There is also concern that fish might move far enough to be exposed to harvest in Puget Sound, Washington. From 2008 to 2012, White Sturgeon of various sizes were acoustically tagged in the Pitt River (n = 58) and in the lower reaches of the Fraser River (near Douglas Island, n = 52) to determine the timing, rate, and spatial extent of movements. Movements were monitored using acoustic receivers at 17 locations in the lowermost 92 km of the main‐stem Fraser River, three in the first 21 km of the Pitt River (a tributary to the lower Fraser River), and nine in the coastal waters of British Columbia and Washington State. Travel speeds showed a strong skew toward slower movements (74% were