Temas prioritários para conservação de elasmobrânquios marinhos e métodos alternativos para determinação de risco de extinção

Abstract

Elasmobranchs, popularly known as rays and sharks, are among the oldest vertebrates still alive, at approximately 400 million years. They play crucial roles for a healthy and functioning marine ecosystem, controlling the populations of their prey. However, elasmobranchs are one of the main groups most threatened by extinction, due to overfishing, ocean pollution and habitat loss. In this context, the present thesis aims to understand the trends of scientific research on this group of animals and to identify methods to facilitate rapid and safe assessments of extinction risk. To this end, in the first chapter we explore the scenario of scientific research on marine elasmobranchs, trying to understand which factors may drive further research and which topics are of greater urgency. We have observed that the scientific production on marine elasmobranchs is growing exponentially, and that this production is more concentrated in more economically developed countries with high fishing production. Regarding the themes approached, there was a clear change over time, being more common until the 2000s themes such as morphology and anatomy, and more recently themes such as life history, conservation, and ecology. This change was extremely important, as it highlights the need to better understand these animals and to seek more effective conservation measures. In the second chapter, we applied an already known methodology (demographic analysis) to evaluate the local population status of the stingray Hypanus guttatus, commonly captured in the Northeast of Brazil by trawl fisheries. For this assessment, we used only previously published data on life history and fisheries in the region. We detected that the species has a negative population growth (-11.83%) in the region, caused mainly by the capture of juvenile’s individuals. Therefore, the main individuals that need attention for the continuation of the species in the Northeast of Brazil would be the juveniles and neonates. In the last chapter, we analyzed the marine elasmobranchs globally and at the community level, trying to identify which bioecological attributes can be predictive of extinction risk. We observed that species that present viviparity and that are in environments closer to the coast and inhabit shallower waters tend to have higher extinction risks. And that the areas with the highest amount of shark and harpoon catches are also where the highest amount of threat species occurs. Therefore, greater surveillance is needed in these areas to prevent endangered species from being caught.