Influences of Continuous Illuminations and Continuous Darkness on the Ovarian Functions in Indian Major Carp Catla catla during the Different Reproductive Phases in an Annual Cycle

In the present investigation, the adult Catla catla were transferred to either continuous illuminations (LL; LD 24:0) or continuous darkness (DD; LD 0:24) for 30 days on four different dates corresponding to the beginnings of four reproductive phases in an annual cycle. Exposure of fish to LL during the preparatory phase (February-March) caused a stimulation in the gametogenic activity of the ovary, and an increase in the serum concentrations of vitellogenin and the activity of the steroidogenic enzymes (i.e. D⁵3b-HSD and 17b-HSD) in the ovary, while the functional status of the ovary remained almost unaltered in DD fish compared to that in control fish.