Environmental correlate of the testicular events in a major carp Catla catla in an annual reproductive cycle

Current communication describes annual testicular events in free-living Indian major carp Catla catla and their probable environmental synchronizer(s). The study was initiated with month-wise evaluation of gametogenic and steroidogenic status of the testis, and thus dividing the annual testicular cycle into the preparatory spawning (November to March), the pre-spawning (April to June), the spawning (July to August) and the post-spawning (September to October) phases. An exhaustive statistical analysis of the data on the studied variables of testicular functions and various components of the environment indicated seasonal fluctuations of photoperiod as the major environmental factor associated with the seasonal reproductive activity of this carp. Ambient temperature appeared as a dependent variable of photoperiod, and thereby, may have substantial influences on the development of testis in Catla catla. Rainfall, on the other hand, showed significant correlation only with the peak reproductive activity, i.e. the act of spawning. Collectively, it appears logical to surmise that photo-thermal conditions may act as proximate and rainfall may play a role of ultimate environmental factor in the regulation of annual testicular events in Indian major carp Catla catla.