Seasonal movements of lake sturgeon in Lake of the Woods and the Rainy River, Ontario

Lake sturgeon (Acipenser fulvescens) inhabiting the southern portion of Lake of the Woods and the Rainy River, a north-temperate watershed straddling the Canada - United States border, were studied to test hypotheses concerning seasonal movement patterns, including spawning migrations, and habitat use. We implanted radio transmitters into 26 fish and monitored seasonal movements during 3 consecutive years. Data indicated the existence of two discrete populations of sturgeon in this watershed, differentiated by seasonal habitat use, movement patterns and rates, and timing of spawning. The ''lake'' population, a designation suggested by a consistent preference for lentic winter habitat, appeared to spawn and initiate extensive spring and summer movements later than the ''river'' population, which consistently inhabited the river during the winter months. Overall, movement rates were significantly greater in the spring and summer months than at other times of the year and decreased with water temperature. General preferences exhibited by lake sturgeon for certain habitat types at different times of the year appeared to be linked to foraging behaviour. The results suggest that population differentiation may be prevalent for this species inhabiting large lake-river systems, given some diversity in habitat structure and spawning cues. In management efforts, this potential should be taken into consideration and reflected.