Estrutura populacional de Podocnemis erythrocephala (Testudines, Podocnemididae) no rio Unini, Amazonas, Brasil.

Abstract

The species Podocnemis erythrocephala, the red headed river turtle, is the smallest of the genus, inhabiting rivers and lakes of black water and clear, being distributed by the basins of the Rio Negro, Tapajós and Trumpets, Brazil, Colombia and the Amazon of Venezuela. As with all species of the family Podocnemididae, individuals and eggs are caught by indigenous and riverine and has caused a rapid decline of most populations. Fact that contributed heavily to the current classification of the species as vulnerable by IUCN, studies with respect to sex ratio, reproductive success and population dynamics, among others, are of atmost importance for conservation of this species, considering that it suffers human pressure on the river Unini, as elsewhere in the basin of Rio Negro and its distribution area. Since there, is no rule or recommendation for use species-specific irapuca (P. erythrocephala) in the document Use Plan RESEX Unini River. The objective of this study was to characterize the population structure of P. erythrocephala in three riverine communities in the Unini River, the Lower Rio Negro. Turtles were marked and recaptured throughout the year in both rainy and dry seasons. The size of sexual maturity for males and females based on this study was 161 and 218 mm in length straight carapace, respectively. During the study, 352 individuals were marked, 162 males, 150 females and 40 immatures. The sex ratio of adults was 1,05 males per female, not significantly different from 1:1. The males captured had a straight line carapace length mean of 210 ± 14,02 mm (163-262) and females mean of 251 ± 17, 75 mm (221-303). The population structure showed in females the distribution was bimodal, with the most common sizes between 230 and 270 mm. Most individuals are in the intermediate, and few appear in the smallest and largest size classes in both sexes: males (200-210 mm) and females and (230-270 mm). All the sizes (carapace length, carapace width, plastron length and plastron width) and weight were significantly larger in females than in males. Catches of individuals occurred mainly when the water level was decreasing: ebb and dry (spawning period) and when the flood level was increasing. The turtles were recaptured just one time, five males, five females and two immatures. The population showed recruitment and the adults are in equilibrium.