Photoperiod and Temperature Effects on the Gonads of Green Sunfish, Lepomis cyanellus (Rafinesque), during the Quiescent, Winter Phase of its Annual Sexual Cycle

Gonadal maturation normally occurs in green sunfish during spring, under long daylengths and elevated water temperatures. Experiments on fish with regressed gonads during winter indicate that gonadal recrudescence is stimulated in both sexes of this species only by a combination of both elevated water temperatures (> 15C) and long (artificial) photoperiod (15 hr). This suggests that the natural appearance of this combination of stimuli during spring is essential for stimulating the maturation of green sunfish gonads at this time of the year.