Populational biology of tilapia, Oreochromis niloticus, of Guarapiranga Reservoir, São Paulo í I. Population structure, age and growth

Abstract

The present work deals with the population structure, age and growth of Oreochromis niloticus Linnaeus, 1757 in Guarapiranga Reservoir/SP, from August, 1996 to July, 1997. The population showed similarity in the frequencies of both males and females in the intermediate length and age classes. A predominance of males during the period studied was observed. The scales age rings were yearly formed during the reproductive period and up to six and five age rings in the scales of males and females, respectively. The length growth was rapid until the fishes reached the size of first sexual maturation. The males showed a greater asymptotic length whereas the females showed a greater growth rate. The results suggest that the weight is of the isometric type. The parameters values estimated indicates that the species has a rapid growth and is well adapted in the Guarapiranga Reservoir.