It is a small fresh carnivorous economic fish of the freshwater benthic origin.
1 Basic situation
1.1 Ponds The broodstock ponds, breeding ponds and breeding ponds used for the experiment were all rectangular ponds with east-west direction, covering an area of ​​2 mu/body, a depth of 1.5m, and sedimentation of 20cm.
1.2 The equipment for production of incubator and incubating equipment is the equipment for the breeding of the four major domestic fish. The spawning pond is round, with a diameter of 8m, and the depth of 1.5m fry incubator is a water throwing incubator, each cylinder holds about 500kg of water. The water filter cover is 60 mesh; the fish nest is brown and clam shell.
1.3 Selection of broodstock and cultivation of broodstock. Purchase of natural catches in the river ditch and lake near the site. From March 1st to March 10th, purchase and return broodstock 61kg, 2 years of age and above, specifications are 80g/tail. Normal body shape, no disease and no injury. The purchased broodstock is kept in ponds. When the water temperature is above 15°C, feed a small amount of small fish, snail meat, bean cakes, etc., and watch the ponds regularly and add new water as appropriate.
1.4 Identification of male and female broodstock, mating and identification of male and female hatching: Female individuals are significantly smaller than males; females have graphic urinary and almond-shaped reproductive pores, when the abdomen is inflated and soft, and the reproductive hole is slightly infrared inverted. Male fish have only one vent hole. Male and female ratio and oxytocin production: The broodstock male and female ratio is 1:1.2 matching group. The natural spawning of ponds did not inject oxytocin. In the first half of April, the water temperature reached 18°C. It was found that when sand ponds were swimming in the upper waters of the poolside, brown sheets and large clam shells were placed on the sides of the pool, and water injection was used. The pool water is micro-flowing to stimulate the estrus of the broodstock, allowing it to spawn naturally in brown and oyster shells. The broodstock that spawned in the spawning pool was injected with LRH-A and chorionic gonadotropin (HCG) in two injections at the site of the thoracic thoracic cavity. When the water temperature was 19°C on April 6th The first injection of LRH-A, the second injection of the mixed drug of LRH-A and HCG at intervals of 12 hours, the release of the broiler in the spawning pool, the stimulation of estrus in the broodstock with microfluidic water, and the placement of brown tablets and large clams, Let it spawn naturally. Incubation: Fertilized eggs yellowish, round. The egg membrane is transparent and strong in viscosity. After the spawning of the broodstock in the pond and spawning pool is completed, brown tablets and clam shells with fertilized eggs are promptly removed, and the mud and dirt are lightly washed, transferred to the hatching tank, and the brown tablets and clam shells are hung in the water. .
1.5 Seedlings are raised 3 days after emergence of fish seedlings. The fry can be used for swimming. Counting can be performed. The pond is placed in a pond that has been cleaned and applied with basal fertilizer. The depth of the pond is 70cm deep; For rotifers, small branches and larvae, etc. (mainly relying on basal fertilization culture), supplemented with egg yolk, fish pulp, soy milk, etc., were fed 3-4 times a day, and the survival rate and growth rate were measured periodically.
2 results
2.1 Determination of gonadal development and fecundity Purchase of broodstock from March 1 to March 10 to elicit labor in the first half of April. Within a month, it was discovered after several observations and anatomy that Tanggu was in early March. By mid-March, when the water temperature is below 15°C, the gonadal development is still in the state of petri dish- IU; and when the water temperature rises above 18°C ​​in the first half of April, the gonads develop quickly to the state of V (male and female). The rhythm of gonadal development of fish is basically the same). According to the results of anatomy, the absolute fecundity of female shatangtang from 55 to 115 g of body weight ranged from 1100 to 3500.
2.2 Oxygen Production Incubation The test was divided into three batches of oxytocin incubation. The first batch was hatched by the pond and incubated in the incubation tank. The 196 batches were put into production, the fertilization rate was 85%, the hatching rate was 43%, and 118,000 emerged; Three batches of eggs were spawned in the spawning tanks and the incubation tanks were hatched. The bred fish were grouped into 67 groups and 38 groups respectively. The rates of inoculation were 64% and 79%, and the fertilization rates were 78% and 87%, respectively. 26,000 tails. A total of 30l groups of broodstock were put into the experiment, and a total of 171,000 emerged. About 40 groups of broodstock that were not put into production in the broodstock pool were examined on April 30. Most of them had miscarriage or semi-abortion (see Table 1 for details).
2.3 Seedlings were cultivated from April 17 to 21, and counted as 171,000. Each of them was cultivated in a pond of 2 acres. After 1 month of cultivation, the size of summer flowers reached 2-3cm. When it is time to breed in eight 16-acre ponds, this time feeding is mainly bean cake paste, small miscellaneous fish, etc., the daily feeding amount accounts for about 5% of the amount of fish in Tangkou, and at the same time do a good observation of pond observation, water quality regulation and other management jobs. After 6 months of feeding, the net was checked on November 12 and its size was measured between 8 and 11 cm. The weight was between 12 and 16 g/tail. The number was estimated at 120,000 and the survival rate was 71%. The total output is 1680kg.
3 Discussion and Summary
3.1 From the perspective of gonadal development, the peak period should be in the middle or late April. The experiment found that when the water temperature was above 3°C for more than 3 days, there were prenatal symptoms. When the fish nests and attachments were placed on April 3rd, some of the broodstock estrus and spawned. However, the weather and water temperature in mid-April are not stable, and often the temperature rises and then drops to less than 18°C, which affects the hatching and emergence of seedlings, resulting in a lower hatching emergence rate. This issue needs to be further discussed and summarized in the future.
3.2 The sand-dwelling genus is a benthic fish. It prefers spawning in caves and sundries at the bottom of the shallow water layer during spawning. Artificial fish nests also provide shelters and fertilized egg attachments for spawning broodstock. The role. Therefore, artificial fish nests selected in this experiment were brown and large oyster shells, and brown and oyster shells were alternately placed on the bottom of the water to suspend. It was found that eggs were attached to the oyster shell and the eggs on the brown husk were rare. However, in the hatching process, the eggs in the oyster shell are tight and overlapped, and the hatching rate is low. This problem needs further discussion. The fertilized egg hatching method is roughly the same as that of the four major ones. The flow control in the incubating tank is that the flow rate in the incubating tank is larger, and the water flow should be gentle after the film is released. In the later period, the fish egg attachments should be taken out and the suspended dirt in the tank should be removed.
3.3. The incubation period of the second half of the month after hatching from the hatching tank is the key to raising the survival rate of the seedlings. The fry at the time is not only tender and small, but it is difficult to open the food for feeding, and there is a life close to the bottom. Habits. Therefore, the key points for nurturing this phase are:
(1) Open bait should be palatable. Apply enough base fertilizer to cultivate rich biological bait before the fish pond. In the initial stage after fry, the egg yolk, fish pulp and soybean milk should be fed.
(2) Peacetime management should pay attention to changing the water and keep sufficient dissolved oxygen;
(3) Pay attention to disease prevention and treatment. After the summer flower ponds are diluted and raised to the stage of fingerlings, they should be properly fed with proper food and water and other regular management work should be done. The survival rate can reach 70% to 80%.