The reproduction of the tadpole

First, the choice and cultivation of broodstock

Breeding broodstock can be harvested from natural waters or cultivated in ponds. The broodstock used for reproduction requires a healthy, disease-free, injury-free body weight of 1.5 kg or more. The broodstock cultivation pond requires a quiet environment without interference, the pond area is 2~3 mu, the water depth is about 2m, the water quality is fresh, and the drainage is convenient. The broodstock per acre is about 120kg, while 20% to 30% of the fish, including oysters and clams, are mixed to fully utilize the water and control the water quality of the pond. The bait fish can be used to put fresh fish that are suitable, such as rusta, wilderness, coriander, cockroach, etc. It is often ensured that the pond has enough bait fish. Cultivating broodstock in large waters can use cages. The cages are set in waters where the water quality is fresh, pollution-free, and the environment is quiet and micro-flowing. The cage uses a 3cm mesh and puts 2 tails per m2. Check the cage regularly for breakage. Feed the baitfish with plenty of palatability at any time. The stocking specifications in the cage should be roughly the same.

Second, natural reproduction

In the Xinjiang Autonomous Region in the Irtysh River in the Altay Region and the Brent Sea in the Fuhai County, the breeding season of the barracuda is at the end of May to June of each year, and in Beijing in April, when the water temperature rises to 8~12°C. When the shuttlecock can reproduce. The general sexual maturity of broodstock is 3 years old. Under the conditions of artificial rearing, mature and mature at age 2. Breeding water temperature and natural breeding habits are basically similar to California salmon.

In natural waters, the brood broodstock selects places where there are fibrous roots and algae. The male fins and body are used to build the fish roots, weeds, and gravel into nests for spawning, and then the mature females Arrive at the nests for spawning and spawning. After spawning and fertilization, males guard their nests until they are hatched.

It is also possible to breed naturally in broodstock ponds. In the broodstock pond, artificial fish nests are set with palm tree pieces. The number of fish nests is 10-20% higher than that of females. The fish nests are set along the perimeter of the pond. Fish nests are set at a depth of about 30cm from the edge of the pond 50cm. But not close to the bottom of the pool to prevent sludge from covering the eggs. The fertilized eggs can be hatched in the original pond, or they can be moved to ponds in cement pools or clear ponds. After the fish nests with the fertilized eggs are removed, new fish nests are added.

Third, artificial breeding

(I) Identification of male and female differences and maturity

Unlike other species of fish, the scorpion fish is less obvious in the reproductive season, and it can only be roughly identified from the circumparental status of the broodstock. In the breeding season, the abdomen of the female fish is soft and has a pale yellowish-and-bright color tone. The female reproductive fish's reproductive hole before or after spawning has a red convex shape. When the ovaries of the female broodstock develop to the V stage, their maturation coefficient is 8%~16%, and the large, plump eggs of the abdomen are gently squeezed by hand and the eggs are light yellow in color. Male abdomen and body side light blue or light gray. Male broodstock does not protrude around the hole. The testis of the male broodfish is ribbon-shaped and milky white. It is a radial type of testis, and its maturation coefficient is much smaller than that of females. It is generally 1% to 2%. Sexually mature male fish gently squeeze the abdomen with white semen out of the abdomen.

(b) Spawning ponds

The spawning ponds used for artificial breeding of the scorpionfish can be from a few square meters to several tens of square meters in size. The water depth is 60 to 70cm. An old mesh or palm piece is placed every 1m or so at the bottom of the pool. Tearing, disinfecting, and spawning ponds can also be used in clear ponds. Before spawning, fish nests need to be laid in the spawning pool. The number of fish nests should be more than 10% of the number of broodstock groups, and the number of male broodstock should be more than 10% of that of female broodstock.

(c) induced spawning

When the water temperature of the pond reaches 12~14°C, artificial propagation of the scorpionfish can be started. Breeding hormones include salmon pituitary (PG), human chorionic gonadotropin (HCG), and LRH-A. We all use LRH-A, but the dose is higher than the usual dose. In the early stage of spawning, it is generally better to use the second injection. The first injection dose was 1/3, and the rest of the oxytocide was injected after about 12 hours. During the prosperous period of spawning, the effect of one injection is generally better. The injection site can be in the base or abdominal cavity of the pectoral fin, but the effect of intraperitoneal injection is better. The spawning effect of one injection of oxytocin was 24~36h, and the spawning effect of the second injection of oxytocin was 12~18h. The general spawning time is at dawn. Spawning lasts for 1~2h. It is a sticky egg with an egg diameter of 1.2~1.3mm. There are one or more transparent oil balls in the egg membrane.

(four) artificial hatching

After the male and female fish have completed the entire process of spawning and fertilization, the fertilized eggs can be adhered to the fish nest for natural hatching in the original spawning pond or pond. After spawning and fertilization, the females leave the nest and the male guards the nest until the fry is hatched. The newly hatched fry is still guarded by male fish and grows under male guarding. When the fry grows to about 1.5cm, the male and female broodstock can be taken away, leaving the fry to continue cultivation.

When the male and female fish are fertilized and spawned, the fish nests with the fertilized eggs can also be transferred to concrete pools, cages, water cluster boxes or other hatching tanks for running water or aerated hatches. When large-scale production of seedlings is carried out, the fish nests with the fertilized eggs can be hung in a pond in Qingcaotang to start the natural aeration with an aerator, and the hatched seedlings are cultivated in ponds. When hatching water temperature is 12~16°C, it takes 3~4d to hatch fish fry. When the water temperature is above 20°C, it is easy to appear malformed seedlings. Therefore, the incubation temperature of the fertilized eggs of the squid should be controlled below 20°C and above 12°C. The hatching rate is closely related to the incubation temperature, water quality, and dissolved oxygen. The developmental speed of the embryo is closely related to the water temperature. Within the temperature range of 12~20°C, the water temperature is high and the development is fast; otherwise, it is slow. The optimum incubation temperature of the scorpion fish is lower than that of California squid. The temperature of 12~20°C is suitable for the growth of aquatic molds. At the same time, some of the zooplankton in the water also began to grow and multiply. Therefore, in addition to ensuring that there are good-quality fertilized eggs in production, all disinfection work should be done carefully before and during hatching to minimize the threat of harmful organisms to the embryos in the water and ensure proper temperature, dissolved oxygen, and light. And other natural conditions to meet the needs of embryonic development.

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