Meeting Abstract
Swimming performance is considered a key trait determining the ability of a fish to find food, refugia, and mates, and to avoid unfavorable conditions and escape predators. Typically, metabolic rates increase with speed up to a critical point: the critical swimming speed at which fish fatigue. At the same time, fish must stabilize their body posture at very low speed and thereby incur high energetic costs. The combination of high metabolic costs at extreme speeds and relatively-lower costs at an intermediate cruising speed, may result in a non-linear metabolic-speed relationship. However, to date there are no complete data sets to confirm this hypothesis. In this study we quantified the metabolic costs associated with varying speed (0.75-2.25 BL × s-1) in a negatively buoyant fish, the clearnose skate Raja eglanteria. We employed two approaches, a classic critical swimming speed protocol and a single-speed exercise and recovery procedure. We found a discrepancy in the metabolic-speed relationships using the two methods: when using the critical swimming protocol, metabolic rates increased with speed, but the single-speeds approach showed a J-shaped aerobic metabolic-speed relationship and an anaerobic component at each velocity tested. When the anaerobic portion was added to the aerobic costs of locomotion, the energetic curve resembled that quantified using the critical swimming speed protocol. These results suggest that anaerobic metabolism is involved during low as well as high swimming speeds in the clearnose skate and that critical swimming protocols might misrepresent true costs of locomotion across speeds in negatively buoyant fishes.
