Effects of photoperiod and temperature on ovarian activity in the Indian murrel, Channa (Ophiocephalus) punctatus (Bloch)

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Abstract
Channa punctatus (Bloch) is a seasonal breeder and spawns during the monsoon season. Ovarian regression occurs at a time when day length begins to shorten and temperature reaches a seasonal minimum, while the ovarian recrudescence coincides with the increase in day length and temperature. The close relationship between increasing day length and temperature suggests that these two factors are in some way involved in inducing gonadal recrudescence. Responses of the ovary to various combinations of photoperiod and temperature were studied during the postspawning and preparatory periods. Temperatures of 25 °C and above, regardless of photoperiod, were more favorable for the formation of yolky oocytes and ovarian development occurred as a function of warm temperature even under conditions of continuous darkness or continuous light. These studies have revealed that ovarian recrudescence, which normally occurs during the prespawning period, can be advanced by photothermal manipulations. It was concluded that photoperiod may be responsible for timing the seasonal reproductive activity; nevertheless, the rate of photosexual response is temperature dependent.