The effect of temperature and acute hypoxia/hyperoxia exposure on swimming performance and kinematics of Freshwater Drum

Objective: Altered temperature and dissolved oxygen (DO) regimes in the tailwaters below dams can cause stress to fish. Despite their widespread distribution in rivers across North America, Freshwater Drum Aplodinotus grunniens have received little attention relative to the effects of these potential stressors. Quantifying fish swimming performance and kinematics in simulated tailwater conditions can help to determine how riverine species are affected by dam water releases, with the ultimate goal of identifying improved management strategies for these systems. Methods: We quantified Freshwater Drum swimming performance and kinematics by measuring critical swimming speed (in both relative [RUcrit; body lengths/s] and absolute [AU(crit); cm/s] units), tailbeat frequency, tailbeat amplitude, and Strouhal's number under all combinations of low-DO (4 mg/L), normoxic (9 mg/L), and high-DO (14 mg/L) conditions at low (10 degrees C), intermediate (20 degrees C), and warm (30 degrees C) water temperatures using both 90- and 850-L swim flumes. Result: Dissolved oxygen at these concentrations did not affect swimming performance. The effect of temperature on swimming performance depended on fish size; RUcrit, AU(crit), and tailbeat frequency decreased with fish length but increased with temperature. In contrast, tailbeat amplitude increased with fish length but did not differ across temperatures. Conclusion: These results suggest that acute low- and high-DO exposure within the tested range may not affect swimming performance or kinematics. However, the influence of temperature on Freshwater Drum swimming performance suggests that the ability of fish to hold position in a tailrace or to successfully pass upstream of a dam may vary seasonally and may depend on the depth from which water is released from a reservoir, as release depth determines the water temperature.