The present study investigated the reproductive biology of Cathorops spixii (Agassiz, 1829) in Pinheiros Bay, littoral of Paraná State, Brazil. Fishes were captured monthly from June 2003 to May 2004 by using bottom trawls. For each individual, total body length, total weight, sex, and gonadal weight were recorded. The oogenesis (six ovarian follicle phases of development) and gonadal development stages (five stages) were also defined based on the histological examination of the ovaries. It was defined that the reproductive period of C. spixii extends from September to November, based on the analyses of individual gonadosomatic index (GSI) values distribution in relation to the sampling periods, on the monthly variation of the GSI mean values (Curve of Maturation), both for males and females, and on the monthly variation of the relative frequencies of the female maturation stages. The spawning period happened in the end of the spring and females with spawned ovaries were observed until middle autumn, among the months of November to April, being the spawning of the total type.
Oogenesis; histology; reproductive cycle
