Population structure of cascudo plescostomus albopunctatus Regan, 1908 (Osteichthyes, Loricariidae) in Jaguarí­­ River, São Paulo, Brazil

Abstract

 The purpose of the present paper was to study the structure of population (sex-ratio, length and the first sexual maturity) of Plecostomus albopunctatus Regan, 1908 in Jaguari River (Jaguariúna, São Paulo, Brazil) from June 1974 to September 1976. The data of 1,217 fishes were collected, being 711 males and 506 females. Males predominated in two cycles and were longer than females. It was observed predominance of mature fishes during spring and summer. The frequency distributions of young and adults individuals were analyzed by period, season and sex separately. They showed higher frequency of adults during all period. The young individuals (males and females) presented its highest frequency during spring and summer in the first cycle, and in winter, spring and summer during the second cycle. In the beginning of the first sexual maturity, the total length observed was around 173 mm for males and 168 mm for females. Up to 200 mm long, any individual is suitable to participate of the reproductive process.