Abstract

HERNANDEZ, Omar  and  ESPIN, Rodolfo. EFFECTS OF REINFORCEMENT ON THE ARRAU TURTLE (Podocnemis expansa) POPULATION IN THE MIDDLE ORINOCO, VENEZUELA. INCI [online]. 2006, vol.31, n.6, pp.424-430. ISSN 0378-1844.

The Podocnemis expansa reinforcement program in the Middle Orinoco River, whereby 86677 juveniles bred in captivity were released into their natural habitat from 1993 to 2001, was assessed. In 1988, 2000 and 2001, 244 P. expansa and 73 P. unifilis individuals were collected along the Arrau Turtle Wildlife Refuge and its surroundings, using fishing nets. Statistically significant differences were found in the average length of P. expansa individuals captured during the three years, with average length increasing through the years. A high percentage of the captured P. expansa individuals belonged to the juvenile class, it being concluded that the release program of juveniles of this species has effectively increased the proportion of this class, in contrast with the collected P. unifilis individuals, which were all adults. Based on the Von Bertalanffy model, it is inferred that in P. expansa the adult size is reached at 17 years old. The average length of the captured specimens did not differ in comparison with those consumed, concluding that the local population has no preference for a specific size, eating more frequently the most abundant sizes. Out of the P. expansa individuals caught, 96.83% were females, whereas the sex ratio for P. unifilis was 1:1. It is suggested that the P. unifilis population in the area could be in danger of extinction by the alleged absence of recruitment.

Keywords : Orinoco; Podocnemis; Reforzamiento de Poblaciones; Tortugas de Río.