Seasonal effects of exposure to temperature and photoperiod regimes on gonad growth and plasma gonadotropin in goldfish (Carassius auratus)

High temperatures inhibited goldfish (Carassius auratus) oogenesis at three different season(fall, winther, spring) in spite of an increase in plasma gonadotropin level.In winther, long photoperiod stimulated gonad growth.When fish were kept at a constant high temperature for 9 consecutive months from September to January, the gonads remai- ned regressive during the first 4 months and then developed normally. Introduction.Vlaming (1972), both photoperiod and temperature may be important environmental factors in the determinism of the cyprinid reproductive cycle.