Predicting population recovery rates for endangered western Atlantic sawfishes using demographic analysis

Abstract

Sawfish are a group of endangered elasmobranchs that were common in tropical inshore, estuarine and freshwaters. The demography of two species of sawfish that occur in the western Atlantic - Pristis pectinata and P. perotteti - was investigated using age-structured life tables. Life history parameters for use in the life tables were obtained from published data. Five scenarios were tested for P. pectinata to incorporate uncertainties about life history data. Values of intrinsic rate of increase ranged from 0.08 to 0.13 yr-1, and population doubling times from 5.4 to 8.5 yrs. Eight scenarios were tested for P perotteti. The most likely range for the intrinsic rate of increase was 0.05-0.07 yr-1, with population doubling times of 10.3-13.5 yrs. Four scenarios investigating the sensitivity to methods of estimating natural mortality produced similar results. The demographic results were sensitive to changes in reproductive periodicity and natural mortality. The results indicate that if effective conservation plans can be implemented for sawfish and sawfish habitats, recovery to levels where there is little risk of extinction will take at least several decades.