Biologia reprodutiva de Oligosarcus jenynsii (Günther) (Characiformes, Characidae) da Lagoa das Custódias, Tramandaí, Rio Grande do Sul, Brasil Reproductive biology of Oligosarcus jenynsii (Güntiier) (Characiformes, Characidae) from Custódias Lagoon, Tramandaí, Rio Grande do Sul, Brazil

<abstract language="eng">The Custódias lagoon has a great importance in the Tramandaí system, because it works as reproduction area, feeding and nursery grounds to several fish species. The aim of this work is the study of aspects related to the reproduction of Oligosarcus jenynsii (Günther, 1864) as such as reproductive period, sexual ratio, fecundity and size of the first gonadal maturation. The specimens were sampled monthly from October/1994 to October/1995. For each sex, maturation curves were established, based on the monthly variation of the gonadossomatic index mean values, as well as, the relative frequencies of the sexual maturity stages. Breeding seasons took place during the winter and spring. The sex ratio was significanthly different from 1:1, with more females than male in almost all month. The species had a average fecundity of 9.694 ovocytes. The estimated size of first sexual maturation was 114 mm for male and 131 mm for females