Reproductive biology of the tropical abalone Haliotis varia from Gulf of Mannar

Abstract

The annual reproductive cycle of two populations of the abalone, Haliotis varia Limaeus, sepa- rated by 90 km, in the Gulf of Mannar, was studied. Six maturity stages were distinguished. The sex ratio of abalone (>25mm shell length) at Tuticorin and Mandapam did not differ significantly from 1:l ratio. Sexual maturity was first attained at a size of 18-20 mm and 22-24 mm for males and females respectively at Tuticorin, and 20-22 mm and 22-24 mm at Mandapam. The gonado-somatic index (GSI) and the relative abundance of different maturity stages were used in determining the annual reproductive cycle. The breeding season of the population extended from December to February in Tuticorin and November to January in Mandapam. The spawning season coincided with the end of northeast monsoon period in both populations. The gonad maturation was linked to the variation in water temperature and salinity. Seasonal low values in both these parameters coincided with the breeding season of H. varia. The results indicated the scope for production of mature specimens throughout the year by induced maturation through regulation of salinity and temperature.