Demographic analysis reveals a population decline of the Longnose stingray Hypanus guttatus in Northeastern Brazil

Abstract

High fishing pressure on elasmobranchs had caused declines in their populations worldwide, though these declines may not always be observed due to lack of monitoring. The Longnose stingray Hypanus guttatus is one of the most abundant and captured species in Northeast Brazil, mainly as bycatch by shrimp trawl. We aimed to estimate how the population of H. guttatus behaves in the face of different fishing pressures in the Northeast. For this purpose, we used a life matrix analysis from the metadata of three studies in the Northeast of Brazil (Bahia, Alagoas and Rio Grande do Norte). The average annual population growth rate estimated for the three states was strongly negative (−11.83%). However, there was considerable regional variation: data from Bahia showed in fact a low level of positive growth (3.24%) compared to the severe population decline (−29.47% per year) in Rio Grande do Norte, caused by the high mortality from shrimp trawling We conclude that the Longnose stingray has a high risk of long-term population decline in Northeastern Brazil, mainly caused by the high capture rate of juveniles.