In the recent years, there is an increasing interest to enhance the aquaculture production by farming the fishes from lower trophic levels such as rabbit fishes (Family:Siganidae). However the seed production of these fishes has not yet been developed for which basic information on reproductive biology need to be gathered. Rabbit fishes forms an abundant group in the marine fish landings from Gulf of Mannar region. The objective of the present study was to describe the phases of gonadal development and determine the spawning season of the fish. Gonadal developmental stgaes and sex ratio of three species, viz; Siganus javus, Siganus canaliculatus and Siganus lineatus have been studied. Annual and monthly changes in the gonadosomatic index (GSI) and the histological features of the testis and ovaries were documented.
Results showed that Siganus javus, Siganus canaliculatus and Siganus lineatus attains first sexual maturity at 24.5 cm, 22.4 cm and 31.2 cm (Total Length) for males and 22.5 cm, 21.6 cm and 31 cm (Total Length) for females respectively. Developmental stages, dimensions and fine structure of sexual cells during the course of maturation were examined microscopically and documented. During the study, five stages of spermatogenesis and oogenesis of the three species were observed and recorded.