The effects of cold on routine activity and food consumption of juvenile Atlantic sturgeon (A. oxyrhynchus oxyrhynchus) and shortnose sturgeon (A. brevirostrum)
University of New Brunswick
Fishes living at poleward latitudes are exposed to challenging environmental conditions in the winter, such as cold temperatures that slows physiological processes (e.g., metabolic rate, swimming activity) and poor food availability that constrains energy supply. Atlantic (A. oxyrhynchus oxyrhynchus) and shortnose (A. brevirostrum) sturgeon co-exist in the Saint John River basin in New Brunswick but have divergent overwintering strategies. During winter, adult Atlantic sturgeon leave the river and move into the warmer seawater of the Bay of Fundy (~6-8°C), while shortnose sturgeon remain in the colder freshwater (~1°C), where they appear to be less active and possibly dormant on the riverbed. Using laboratory experiments, I investigated how acute cold challenge (15°C to 2°C) and low temperature acclimation (2-3°C) affects the routine activity and food consumption of two different juvenile age/size classes (1 year) Atlantic and shortnose sturgeon. During an acute cooling challenge both food consumption and activity declined in juvenile Atlantic and shortnose sturgeon, but never ceased. Atlantic sturgeon showed a drastic decline in activity around 12°C, whereas shortnose had a more gradual change and were more active at lower temperatures. Overall, the behavior of Atlantic sturgeon was more thermally sensitive to cooling compared with shortnose sturgeon, even after cold acclimation, suggesting these two species have distinct responses to cold that may be associated with their divergent overwintering strategies.