Activity of Young-of-the-Year Kootenai River White Sturgeon and Connecticut River Shortnose Sturgeon in Response to the Winter Temperature Cycle

In artificial stream tanks during November 2009−April 2010, we examined the effect of the winter temperature cycle on activity of YOY Kootenai River White Sturgeon, Acipenser transmontanus, (hereafter, KRWS) and Connecticut River Shortnose Sturgeon, A. brevirostrum (hereafter, CRSNS). Temperature range during tests was 11 to 3°C. Daytime activity (number of grid lines crossed in a 10 cm bottom grid array per 3 min) was recorded by video every 3-7 d at 0800h and 1400h in two replicate tanks for each species. Both species had a similar seasonal decrease-increase in activity with temperature that was best fit by an exponential function. For both species, activity rate declined more steeply in fall than it increased in spring. Activity in response to the winter temperature cycle was common among these two unrelated species. Warming of rivers from anthropogenic point sources or climate change could create a mis-match between the evolved behavioral response of YOY to winter temperature and temperatures that never decrease to 2-3°C. If wild YOY are active at wintering temperatures of 5-6°C, as the results suggest, this could create energetic problems for YOY to survive the winter.