Swimming Behavior and Energetics of Sharks

摘要

Acoustic telemetry was used to record depth, swimming speed and tailbeat frequency from free-ranging blue sharks (Prionace glauca) in the northwestern Atlantic. Records obtained from five sharks show a consistent pattern of vertical migration between the surface and depths to 450 meters. The sharks actively swam downward during most of the descent, with brief periods of gliding asociated with the most rapid descent rates. Calculated dive angles averaged less than 10 degrees from the horizontal for both descent and ascent, and the estimated gliding angle was 22 degrees. The observed diving behavior does not match that predicted by theory to be energetically optimal for migration, and may instead represent a strategy for encountering and capturing prey. Heart rate, oxygen consumption rate, and activity were simultaneously recorded from lemon sharks (Negaprion brevirostris) and leopard sharks (Triakis semifasciata) during rest, spontaneous exercise, and forced swimming to evaluate the usefulness of heart rate as a measure of metabolic rate. Heart rate was approximately as closely correlated to oxygen consumption rate as was swimming speed.