ABSTRACT
There and great variety of reproductive styles in fish, usage of aquaculture in increasing fish production needs to have a proper understanding of endocrine physiology. In this study three different sets of experiment were designed 19L/5D at 200C, 12L/12D at 200C, 18L/6D at 200C photoperiod and temperature effects on these experimental regimes on reproduction are compared with control group. The gonadal maturation was assessed by microscopic and histological obervations. Gonadosomatic index (GSI) have been calculated. The results from our research revealed that at 19L/15D at 200C temperature the gonads are in more developed conditions than other photoperiodic regimes. GSI values is also high. Therefore,it was concluded that long photoperiod are useful to accelerate gonadal activity in goldfish Carassius auratus.