Using speed-sensing transmitters to construct a bioenergetics model for subadult lemon sharks, Negaprion brevirostris (Poey), in the field

Several methods to indirectly estimate metabolism of aquatic animals have been reported, including heart rate, electromyograms, video recording, and averaging velocity of an animal moving between two or more points. The present study carried out in the lagoon at Bimini Islands, Bahamas, used acoustic, speed-sensing transmitters to indirectly estimate energy consumption of 1.5-2 m subadult lemon sharks (Negaprion brevirostris). Speed records from three sharks tracked a total of 170 h, yielded average swimming speeds of 0.44-0.71 m s^-1. These speeds were converted into energy consumption to obtain metabolism. By combining the estimates of metabolism with calculated values on assimilation and production, we are able to present a balanced bioenergetics model for the subadult lemon shark: 100C = 7P + 66M + 26E, where C = consumption, P = production, M = metabolism, and E = excretion. When comparing juvenile lemon sharks to subadults, an ontogenetic shift is seen: 0 to 2 yr olds allocate 22% of consumed energy to production and 50% to metabolism while 6 to 9 yr olds show values of 7% and 66%, respectively. We believe this to be the first field-based, balanced equation presented for any large elasmobranch.