Survival of juvenile lemon sharks at Bimini, Bahamas, estimated by mark-depletion experiments

The survival rate of juvenile lemon sharks Negaprion brevirostris in North Sound, Bimini, Bahamas, was estimated by marking a cohort of small sharks ( less than or equal to 53 cm precaudal length) each spring from 1995 to 1999 and by estimating the number of survivors 1 year later by using a depletio n method on the marked population. Annual survival rate estimates varied be tween 38% and 65%, which was somewhat higher than the 39% steady-state surv ival 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 i n the present study were negatively correlated with estimated initial abund ance and are consistent with strong, density-dependent survival.