Recovery potential of smalltooth sawfish, Pristis pectinata, in the United States determined using population viability models

Carlson, John K.;Simpfendorfer, Colin A.

Abstract

1. Determining the recovery potential of endangered species is an important component for developing strategies necessary to return populations to healthy levels.Many species of endangered marine animals have been regarded as having low productivity and therefore, an inherent inability to rapidly recover from severe depletion. 2. An age-structured Leslie matrix model was constructed for the US population of smalltooth sawfish, Pristis pectinata, to determine their ability to recover under scenarios using different life history inputs and the effects of bycatch mortality and catastrophes. 3. Population growth was highest (λ=1.237 yr-1) when age-at-maturity was 7 yr and decreased to 1.150 yr-1 when age-at-maturity was 11 yr. 4. Despite a high level of variability throughout the model runs, in the absence of fishing mortality or climate catastrophic effects the population grew at a relatively rapid rate approaching carrying capacity in 40 or 50 yr when the initial population was 600 or 2250 females, respectively. Population projections under various levels of fishing mortality resulted in extinction when mortality was highest, initial population size was small, and age-at-maturity was 11 yr. Scenarios testing the potential effects of extreme cold exposure showed little difference to those scenarios testing the effects of fishing mortality. 5. Using the optimistic estimates of population size, lower age-at-maturity and the lower level of fisheries-related mortality, smalltooth sawfish in US waters appear to have the ability to recover within the foreseeable future. Effective management and recovery of this species can only be achieved by keeping fishing-related mortality low.

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1099-0755

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Wiley-Blackwell

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DOI

10.1002/aqc.2434