Finfish Breeding and Hatchery Management (2+1)

Maturity stages
• With the exception of common carp, the other five species of carps used in polyculture do not spawn naturally in captivity, although they attain gonadal maturity.
• The age and size at  first maturity in these carps vary greatly with climatic and ecological factors.
• The age  at  first maturity varies between species and even within species. In carps, males mature earlier than females.
• While the males of Indian major carps and silver carp and grass carp mature at the end of second year, the females mature during second or third year.
• In India, the common carp matures in 4-6 months.
• An understanding of the maturity stages of fish in is important in order to achieve best results as ripe/gravid fish require less hormone than unripe fish.
• Based on the appearance of gonads to the naked eye, seven stages of gonadal maturity in carps are commonly recognized.
• They are as follows :

Stage of  maturation	Female	Male
I Immature	Ovary transparent, long narrow strip	Testis transparent, thread-like
II Immature	Translucent, thickened  strip	Translucent, thread-like
III Maturing	Opaque, granular, somewhat grayish, occupying about 1/3 of the body cavity	Opaque, pinkish-white, thin strip-like
IV Maturing	Dull grayish, ova discernible like granules, occupying about 1/2 of the body cavity	Thick strip-like, milky-white fluid (milt) oozes out on applying pressure on abdomen
V Mature	Dull gray to greenish, occupying almost the entire body cavity, ova distinctly round in shape	Thickened band-like, milky-white fluid oozes out on applying pressure on abdomen
VI Spawning	Ovary having loose eggs, eggs ooze out through genital opening on applying pressure on abdomen	Milky-white fluid oozes out freely on applying pressure on abdomen
VII Spent	Ovary blood-shot, pinkish-brown mass, greatly shrunk	Milky-white fluid oozes out freely on applying pressure on abdomen

• According to the above classification, the female and male brood-stock in Stage  V are considered ripe/mature and suitable for induced spawning.