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.
Keywords : Carassius auratus, gonadal, photoperiod, endocrine