Review of elasmobranch behavioral studies using ultrasonic telemetry with special reference to the lemon shark, Negaprion brevirostris, around BiminiIslands, Bahamas

A review of past behavioral ultrasonic telemetry studies of sharks and rays is presented together with previously unpublished material on the behavior of the lemon shark, Negaprion brevirostris, around the Bimini Islands, Bah amas. The review, focusing on movement behaviors of 20 shark and three ray species, reveals that elasmobranchs exhibit a variety of temporal and spati al patterns in terms of rates-of-movement and vertical as well as horizonta l migrations. The lack of an apparent pattern in a few species is probably attributable to the scarcity of tracking data. Movements are probably gover ned by several factors, some still not studied, but data show that food, wa ter temperature, bottom type, and magnetic gradient play major roles in a s hark's decision of where and when to swim. A few species exhibit difference s in behavior between groups of sharks within the same geographical area. T his interesting finding warrants further research to evaluate the causes of these apparent differences and whether these groups constitute different s ubpopulations of the same species. The lack of telemetry data on batoids an d some orders of sharks must be addressed before we can gain a more compreh ensive understanding of the behavior of elasmobranch fishes. Previously unp ublished data from 47 smaller and 38 larger juvenile lemon sharks, collecte d over the decade 1988-1998, provide new results on movement patterns, habi tat selection, activity rhythms, swimming speed, rate-of-movement, and homi ng behavior. From these results we conclude that the lemon shark is an acti ve predator with a strong, apparently innate homing mechanism. This species shows ontogenetic differences in habitat selection and behavior, as well a s differences in movements between groups of individuals within the same ar ea. We suggest three hypotheses for future research on related topics that will help to understand the enigmatic behavior of sharks.