Survival of Juvenile Lemon Sharks at Bimini, Bahamas, Estimated by Mark–Depletion Experiments

Abstract

The survival rate of juvenile lemon sharks Negaprion brevirostris in North Sound, Bimini, Bahamas, was estimated by marking a cohort of small sharks (≤53 cm precaudal length) each spring from 1995 to 1999 and by estimating the number of survivors 1 year later by using a depletion method on the marked population. Annual survival rate estimates varied between 38% and 65%, which was somewhat higher than the 39% steady-state survival predicted from a life cycle (Leslie matrix) model. These are the first direct estimates of the survival rate of a juvenile elasmobranch, and the results support modeling efforts that have been used in determining limits to sustainable exploitation of elasmobranchs. Estimates of survival rates in the present study were negatively correlated with estimated initial abundance and are consistent with strong, density-dependent survival.