SEPULVEDA , C. A.*; GRAHAM , J.B.; BERNAL, D.; Pfleger Institute of Environmental Research; Scripps Institution of Oceanography; University of Massachusetts, Dartmouth: Swimming performance studies of the mako shark, Isurus oxyrinchus

The mako shark, Isurus oxyrinchus, is an active epipelagic predator that has been shown to possess several adaptations for a heightened aerobic swimming performance. Although several studies have documented the degree to which the mako shark is specialized for fast, efficient locomotion, few studies have focused on live sharks, and metabolic measurements (indirect calorimetry or respirometry) are limited to only one individual juvenile. The present study used a large swim tunnel respirometer to measure the swimming metabolic rate of juvenile mako sharks under controlled conditions. This work tested the hypothesis that the mako shark has an elevated standard metabolic rate when compared to other active sharks swimming at the same water temperature. Swimming VO₂ and tail beat frequency were measured at 18+/- 2�C for 9 makos ranging in size from 70 to 95 cm fork length and 4.50 to 8.20 kg. The range of swimming speeds for which makos were tested was from 28 to 50 cm s^-1 or 0.3 to 0.7 bl s^-1, and for all individuals replicate VO₂ measurements were made at each test speed. This paper reports on mako shark swimming metabolic rate, standard metabolic rate, tail beat frequency and for some individual�s heart rate.