Tamanho corporal e impactos ambientais associados com o risco de extinção em peixes de água doce

Abstract

Body size is a biological attribute that may be associated with the risk of species extinction. However, this relationship may be context dependent, varying according to the environmental impacts to which submitted species. In addition, the distribution of endangered species among river basins and taxonomic groups should occur in a non-random manner, reflecting the degree of anthropic pressure and the particular characteristics of the groups, respectively. In this study, we tried to answer the following questions: Do the fishes with the highest risk of extinction have smaller body sizes? Do endangered species vary in size depending on the type of impact to which they are susceptible? Do the main environmental impacts of endangered fishes vary among river basins and taxonomic groups? These questions were answered in two chapters, which were developed from the evaluation of a database containing 3,115 species of freshwater fish occurring in Brazilian territory. The distribution frequencies of body size were asymmetrical, with most species having a smaller body size. However, this asymmetry is bigger between AM (endangered) and NT species, indicating that these species have smaller body size. Species whose main threat is the damming are larger in size than species threatened by other impacts. The main impacts on endangered species vary among river basins and among taxonomic groups. The results indicate that body size is a predictor of extinction risk, but this relationship is context dependent. In addition, the extrinsic factors associated with the risk of extinction, as the environmental impacts are spatially predictable and among taxonomic groups.