Date of Award
Ph.D. in Biological Science
Glenn R. Parsons
Brice P. Noonan
Paddlefish often frequent oxbows and backwater habitats between periods of migration. Speculation as to the use and energetic savings associated with this seasonal residence has not been substantiated. This study used radio telemetry to track the seasonal movements and swim tunnel respirometry to estimate metabolic rates and swimming efficiency of paddlefish within an oxbow located just north of Clarksdale, Mississippi (Moon Lake). Paddlefish overwintered in the deepest portions of Moon Lake with little movement into shallower areas. Paddlefish swimming performance was measured at four swimming speeds (76.04, 91.27, 106.50, and 121.72 cm/s) to determine the cost of locomotion over season as measured by oxygen consumption and reported as the cost of transport: cost in calories to move one gram of body mass one kilometer. The optimal swimming speed (uopt), the swimming speed at which the cost of transport is the lowest, for any given month (January, February, May, and September) was between 106.50 and 121.72 cm/s and was estimated to be 0.078 calories/g/km for February, May, and September, and 0.045 calories/g/km in January. The caloric availability within the lake was monitored by zooplankton sampling to determine the potential energetic gain from paddlefish filter feeding. The ratio of calories expended to calories gained (cost: benefit ratio) was calculated for each of the four swimming speeds tested during swimming trials. The cost-to-benefit ratios in January and February were less than 1 at all speeds tested and suggested that paddlefish swimming efficiency was high and zooplankton abundance was adequate to support energetic gain. The most efficient swimming speed during January and February was 121.17 and 91.27 cm/s, respectively. Cost-to-benefit ratios in January and February were 0.20 and 0.50 cal/g/km, respectively. Costs began to exceed benefits in May and September as zooplankton densities dropped drastically. This was evidenced by the decline in average caloric value of lake water (29.89 and 4.79 calories/cubic meter for May and September, respectively. In September the cost of locomotion was around 200 to 400% of benefit. The significant drop in zooplankton may have cued paddlefish to move out of Moon Lake.
Cage, Bryan Andrew, "Behavior, Energetics, And Swimming Performance Of The American Paddlefish, Polyodon Spathula, In A Lower Mississippi River Oxbow" (2015). Electronic Theses and Dissertations. 910.