Practical culture techniques of herring

1. Herbivorous herring is a carnivorous fish, which mainly feeds on zooplankton in fry and fingerling stage. When the body length is about 15cm, you change your eating habits and begin to eat small screws. With the development of the lower pharyngeal teeth, the crushing function is enhanced, and the young fish feed on molluscs, such as clams, snails and so on. In addition, they also eat shrimp, crabs and insect larvae.

2. The growing herring is large in size and grows rapidly, and the maximum weight can reach 70kg. 1-year-old fish can grow up to 500g, 2-year-old fish can grow to 2.53 kg,3-year-old fish, in a good environment, it can reach 6.57.5 kg. The growth rate of body length of herring was the fastest at 12 years old, slow after 5 years old, and the fastest at 34 years old, and then continued to gain weight.

3. The breeding herring is a migratory fish, which grows and develops in the water body attached to the river, overwintering in the river in winter, overwintering the parent fish after the beginning of spring, rapidly developing to maturity in the process of retracing, and reproducing in the spawning ground of the main stream of the river. after spawning, the parent fish fattened into the accessory water body. The breeding season is May and June every year, and the water temperature is required to be 1828 ℃. When the spawning ground rises, the water velocity 12m/s, the flow pattern changes, and the parent fish begin to spawn. Herring eggs float and hatch and develop with the flow of water. The age of sexual maturity of herring is 57 years old for females and 45 years for males. Type of spawning: the gonads of sexually mature individuals mature once a year and lay eggs once a year. The number of eggs laid by herring increases significantly with the increase of body weight. Generally speaking, the number of eggs laid by parent fish with 1520kg is about 60.1 million eggs.

2. Artificial propagation

1. Source of parent fish

The natural seedlings in the river basin or the seedlings produced by the national original seed farm, or the adults preferably collected from the natural species resource bank, or from rivers, reservoirs, lakes and other natural waters that have not been artificially released, and then cultivated as parent fish. Inbred offspring cannot be used as a source of parent fish.

2. Parent fish cultivation

The main results are as follows: (1) the parent fish should be more than 6 years old and weigh more than 15 kg. The ratio of female to male is 1: 1.5, and about 10 herring with 15 kg / mu are released.

(2) the bottom of the parent fish pond is flat, sandy loam is better, and the water quality is fresh, mainly feeding snail, clam and clam meat, supplemented with a small amount of bean cake and malt, adding new water and flushing water regularly, generally flushing once a month in winter and keeping the water depth more than 2 meters. After the beginning of spring, lowering the water level is easy to increase the temperature of the pool water, flushing once a week, increasing the flushing times in the middle of April, flushing once every 2-3 days to promote gonadal maturation.

(3) in the parent fish pond, a small amount of silver carp is used to regulate the water quality, and at the same time, carnivorous fish such as black fish and California perch can be properly raised to prey on the wild miscellaneous fish in the pond, which is beneficial to the cultivation of parent fish and increase the benefit of the pond.

3. Brood fish to induce spawning

(1) the time of induced labor and water temperature: in the middle and lower reaches of the Yangtze River, the time of induced labor is in the middle and late May, and the water temperature of 25: 28 is the most suitable.

(2) selection of parent fish: the maturity of parent fish directly affects the effect of induced spawning. the identification criteria are that the male fish gently squeeze the abdomen and release semen immediately after meeting the water, and the abdomen of the female fish is inflated, soft and elastic, and the abdominal scales are sparse. In order to improve the population maturity, we can check the net in the middle of April. For those with poor maturity, according to the individual size and maturity, according to the individual size and maturity, LRH-A3~5 micrograms / tail will be injected respectively.

(3) injection of oxytocin: commonly used oxytocin is LRH-A, DOM, PG, etc., usually the mixed effect of the two is better, our field uses three-needle injection, the rate of induction is higher, up to more than 95%. The first injection of LRH-A1 micrograms per kg of parent fish, needle distance of 20 hours; the second injection of LRH-A5 micrograms per kilogram of parent fish, needle distance of 8 hours; the third injection of female parent fish per kilogram of LTH-A20 micrograms plus PG3~4 mg or plus DOM4~5 mg, male parent fish dose according to the specific circumstances of the female parent fish dose of 1x3x1x2, the injection was done through thoracic cavity.

4. Estrus and artificial insemination

The length of the effect time varies with the water temperature. It is observed that the effect time is 6-7 hours when the water temperature is 26-28 degrees. When the parent fish are in estrus at a predetermined time and combined with the actual situation of estrus, the parent fish are caught for artificial insemination, and attention should be paid to light and fast action during insemination. When sperm and eggs are mixed, 0.6% normal saline is properly injected to prolong the insemination time. At the same time, direct sunlight and Rain Water splash should be avoided during insemination to improve the fertilization rate, and the normal fertilization rate is more than 90%.

5. Incubation

The fertilized eggs after absorbing water are put into the hatching loop or incubator to hatch, and the flow rate of the water is that it can wash and tumble the fertilized eggs. The water used for hatching should be separated and should not be recycled. After the fry comes out of the film, the flow should be appropriately increased to prevent the fry from sinking and suffocating to death. After 24 hours of hatching, the flow should be appropriately reduced to avoid excessive water consumption of the fry. In the same period of development, the flow rate of water during the day is lower than that at night, if the weather is abnormal, the temperature difference should be reduced appropriately to avoid excessive water consumption of fish fry. During the same period of development, the flow rate of water during the day is lower than that at night. If the weather is abnormal, the flow should be increased appropriately when the temperature difference is large.