Life history and population dynamics of the lemon shark, Negaprion brevirostris, in the northwest Atlantic Ocean Fisheries Research

The life history and population dynamics of the lemon shark, Negaprion brevirostris, in the northwest Atlantic Ocean were determined by investigating the age, growth, maturity, natural mortality, and intrinsic rate of population increase (Rmax). Age and growth were estimated using multiple models fitted to observed and back-calculated size-at-age data. The modified Gompertz growth model based on a combined-sex back-calculated size-at-age was the most parsimonious model with growth parameters predicted as L0= 55.8 cm fork length, k = 0.15 year−1 and G= 0.143. The oldest aged sharks were 21 and 23 yrs for males and females, respectively. Median length and age at maturity determined using logistic modeling was 196 cm and 183 cm FL, and 11.8 and 11.4 years for females and males, respectively. Litter size averaged 12.0 (±3.6). Estimates of survivorship from 7 independent methods range ranged from 0.67 yr−1 for Age 0 sharks to 0.92 yr−1 at maximum age. The estimates of survival to first age of breeding were (la)=0.285, the probability of adult survival (e-M)= 0.89 yr-1 and the total instantaneous rate of natural mortality (M)= 0.089 yr-1. Depending on the method to determine Rmax, values ranged from 0.055 to 0.203 yr−1 with the mean and median from all methods= 0.106 yr−1. Overall, based on the revised estimates of life history, the lemon shark exhibits population growth rates among those species ranked as "medium-growing" among 65 populations of sharks.