Estrutura populacional de Podocnemis sextuberculata Cornalia, 1849 (Testudines: Podocnemididae) na Reserva Biológica do Rio Trombetas, Pará, Brasil

Abstract

Podocnemis sextuberculata is one of the smallest species of the genus Podocnemis, with populations in Brazil, Colombia and Peru. In Brazil it is abundant in white and clear water river systems. Despite being one of the most exploited species in some regions of the Brazilian Amazon, knowledge about the conservation status of their populations is limited. The aim of this study was to evaluate some population parameters such as relative abundance, size structure, sex ratio and proportion of adults in two areas within the Biological Reserve of Rio Trombetas, Pará State. Area I includes the Jacaré Lake and two backwater beaches. Area II covers the Erepecu Lake. Between October 2010 and November 2011 we carried out experimental collecting, using trammel nets (1.50 m x 100 m). We captured 862 individuals (786 males, 71 females and 5 animals sex not identified). The recapture rate was 3. 54%. The sex ratios within the Biological Reserve of Rio Trombetas was 21.6 ♂: 1 ♀. The sex ratios were male-biased, in both areas and in all phases of the hydrologic cycle. The mean catch for the entire study was 0.11 animal/hour. The capture rate differed significantly between the areas studied and the period of the hydrological cycle. The population sampled comprised 94.5% of mature individuals and 5.45% immature. The highest catch rates occurred during the falling and rising waters was attributed to the movement pattern of the species. The influence of the phase of the hydrologic cycle in catch rate indicates that the monitoring of the species should be performing mainly the falling and rising waters.