Reproductive life history of the Atlantic stingray, Dasyatis sabina (Pisces, Dasyatidae), in the freshwater St Johns River, Florida

A population of the Atlantic stingray, Dasyatis sabina, resides in the freshwater St. Johns River system, Florida. The reproductive life history of the species in Lake Monroe near Sanford, Florida, was studied from November 1990 to January 1992. No major differences in reproductive timing or performance were noted between this freshwater population and marine populations studied elsewhere in Florida. Females matured at approximately 22 cm disk width (DW), and mature ovarian eggs were ovulated in early April. Embryos were obtained from pregnant females from 15 May to 17 July, and parturition occurred in late July, when embryos attained approximately 100 mm DW. Males matured at approximately 21 cm DW. Mate gonadosomatic index peaked in November and declined continually through the spring, but fluid was retained in the seminal vesicles until May. This population experienced total reproductive failure during the 1991/1992 season. Extremely low conductivity in the lake during the fall and winter of 1991 is suggested as a possible stressor.