The three hurdles of parent fish in summer

The Beginning of Summer to Lesser Fullness of Grain is the best time for parent fish to induce spawning. at this time, the water temperature is suitable, the spawning rate and hatching rate of parent fish are high, and the survival rate of fry is also high after entering the pond. If we seize this favorable opportunity and strictly control the selection of parent fish, the use of drugs and the management of induced labor, the success of induced labor can be achieved.

Whether the mature parent fish is mature or not determines the effect of spawning. When selecting parent fish, its maturity is generally identified according to its external characteristics. The abdomen of mature female parent fish is dilated, round, soft and flexible. Grass carp and silver carp can touch their ribs, protruding and reddish reproductive pores when touching with their fingers. Immature female parent fish have rounded foreabdomen but thinner rear abdomen, not soft enough, inelastic, reproductive foramen is not prominent or slightly protruding, and does not appear red. Overcooked female parent fish show overinflated abdomen, elastic but inelastic, like the appearance of gas, protruding reproductive pores, hyperemia is fuchsia. Therefore, the choice of parent fish cannot be determined by the size of its abdomen alone.

When choosing male parent fish, you should make the abdomen of the fish upward, gently squeeze both sides of the rear abdomen, and it is better to have milky thick semen flowing out and disperse in case of water. The male parent fish with small or banded semen that can not be dispersed rapidly after entering the water are immature parent fish, while those with thin and yellowish semen are overmature parent fish. When inducing spawning, the ratio of male and female parent fish is 1: 1. 5, and the individual size should not be too wide. After selecting the parent fish, use a pencil, ballpoint pen or smooth bamboo stick to number the top of the head, weigh it in a parent fish bag and record it, waiting for injections to induce labor.

The commonly used labor-inducing drugs are carp pituitary, chorionic gonadotropin, ovulation-stimulating hormone and its analogues, mixed hormones and so on. The chemical composition and action mechanism of various drugs are different, so the species of fish used to induce spawning are not the same. Generally speaking, the pituitary gland of common carp can be used in all kinds of fish. Gonadotropin and its analogues are often used to induce the delivery of grass carp and herring. Mixed hormones are mainly used to induce the production of silver carp and silver carp. The doses commonly used in production are determined according to the dose injected per kilogram of female parent fish, which are generally 4mg of pituitary gland of carp, 1 international unit of mixed hormone, 800,1200 international unit of chorionic gonadotropin, 20,80 micrograms of gonadotropin and its analogues. In the initial stage of induced delivery or during the induction of parturition, the dosage should be taken to a high limit, otherwise it should be reduced. The dosage of grass carp and silver carp is less than that of herring and silver carp. The dosage of male fish is 1 pm 2 of that of female fish. Pectoral fin injection is generally used, some once and some twice. One injection is usually carried out in the afternoon and the eggs are collected the next morning. The first injection of the two injections was usually around 10:00, with a full dose of 1x10 to 1max 8, and the second in the evening, with a full dose of 7x8 to 9x10, with an interval of 6 hours and 12 hours. When the female is injected for the second time, the dose used by the male is injected into her body at one time.

Strengthen the management of spawning and put the injected parent fish into the spawning pond, there should be a special person to take care of the parent fish to prevent the parent fish from jumping out, and pay attention to the parent fish activities and make a good record. In addition, the fish should be flushed once after the second injection, and once more before oestrus and spawning, each time for about 30 minutes, so as to stimulate the fish with running water to increase their spawning rate.