The swimming performance of Freshwater Drum (Aplodinotus grunniens) below Claiborne Lock and Dam and in various temperature and dissolved oxygen treatments

Abstract

Alterations to temperature and dissolved oxygen regimes in the tailwaters below dams can cause harmful stress to fish. Although Freshwater Drum Aplodinotus grunniens are widespread in rivers across North America, this species has received little attention relative to effects of these potential stressors. Quantifying their detection and simulating their swimming performance in tailwaters can provide insight as to how riverine species are affected by these alterations. In an acoustic telemetry study, I categorized the tailwaters below Claiborne Lock & Dam along the Alabama River in southwestern Alabama into three distinct habitat zones and found a majority (51.6%) of Freshwater Drum detections occurred within the gated spillway habitat zone. One passage event was observed, likely over the crested spillway during inundation. I quantified Freshwater Drum critical swimming speed (Ucrit), tail beat frequency, and tail beat amplitude under all combinations of hypoxic (4 ppm), normoxic (9), and hyperoxic (14) conditions at low (10°C), intermediate (20°C), and warm (30°C) water temperatures in 90-L and 850-L swim flumes. Dissolved oxygen concentration did not affect swimming performance. Ucrit and tail beat frequency decreased with fish length but increased with temperature. Tail beat amplitude increased with fish length but did not statistically differ across temperature. Analysis of field data suggest a habitat preference in the downstream tailrace of Claiborne Dam in deep, open water. Hypoxia within the tested range may not be as detrimental to swimming performance as once thought. The influence of temperature on Freshwater Drum swimming performance suggests that the depth at which water is withdrawn at dams can impact the potential for fish to hold position or even pass that structure and may vary seasonally. Management practices can promote the probability of successful passage by reducing fishing pressure during winter months within the tailrace habitat. Appropriate water velocity criteria for withdrawal and by-pass channel design can be established using information presented in this thesis. Adjustments in flume size and solid-blocking correction should be considered for future experimentation.