A preliminary study on artificial propagation and seedling cultivation techniques of yellow croaker
Stingrays are widely distributed fish and can survive in rivers, lakes, ditches, and ponds in China. They like to inhabit quiet water and run benthos. The fish is very popular because of its tender meat, delicious meat, and less intermuscular tingling. The annual market price is 10 to 15 yuan per 500g. According to the analysis of the edible portion of the stingray per 100g of protein containing 16.1g, fat 2.1g, carbohydrates 2.3g, calcium 154mg, phosphorus 504mg, contains a variety of essential amino acids, especially glutamic acid, lysine content Gao said that medicine has anti-inflammatory and analgesic effects. Stingray grows faster and can reach sexual maturity in 1 winter, and it is a good breeding object. Cultured fishponds or broodstocks can not only increase yield and income, but also stingrays can eat sturgeon and larvae that parasitize on the surface of the fish and the water in order to reduce the breeding of fish diseases. Due to its calm nature, the young sturgeon larvae are commonly used as the carrier of the larval parasitizing larvae. In recent years, with the development of the aquaculture industry, the demand for stingray seedlings has been increasing. In order to meet the market demand, the author conducted artificial breeding and seedling cultivation tests of stingrays from May to June 2000. Two to three centimeters in length are more than 20,000 stingrays. The situation is summarized below.
1 Materials and Methods
1.1 Collection and Cultivation of Broodstock
From March to April 2000, a total of 51kg of stingray broodstock was collected. One-third is purchased from fishermen's cages, one-third is purchased directly from the market, and one-third is purchased from intensive ponds. The third batch of oxytocin was purchased directly from the market with 6 kg of mature individuals, and the oxytocin was delivered immediately after shipment. When the broodstock is selected, it requires 50g or more maternal parents and more than 100g paternity. After the broodstock was bought back, it was immersed in 3% saline solution for 10 minutes to enter the pool. The broodstock pool was 2 rectangular brick wall mud pools with an area of ​​60 ft. After buying back for 3 days, the baits were placed in the pool with a bamboo plate to feed and cut. Broken fresh fish (mainly white carp species), the amount of bait increases as the water temperature rises. Generally, the daily feeding amount is 2% to 4% of the broiler's body weight, and fresh water is added once a week. Times 5 ~ 8cm. After May 20, the broodstock became fully mature.
1.2 Induction hatching Stingrays are generally 2 years old for sexual maturity and can mature under conditions of good captivity and 1 winter. The broodstock male and female sexes are easily distinguishable. Generally, mature male individuals grow up in size. There is a 0.5-0.8cm long genital process in front of the anal fin, and the genitalia are at the top of the genital process. The female body is short and thick, and the abdomen is enlarged and soft, and there is no reproduction. Suddenly, the genital hole and urinary hole are separated, and the reproductive hole is round and red and swollen. The ovaries of mature females are cylindrical on both sides of the abdomen in the body, and their absolute fecundity is 2000-6000 grains; the testis of mature male fish is dendriticly separated on both sides of the abdomen in the body. Stingray spawning season is from May to July, water temperature is from 21 to 28°C, and spawning is at the bottom of water. Before spawning in nature, males first use the pectoral fins to sweep away contaminated sludge on the bottom of the water to form a shallow butterfly fish nest. Then the male fish ejaculates and is finished several times. A fish nest has a diameter of 20 to 25 cm. The eggs were round-shaped, pale yellow, and deliquescent. The egg membranes were transparent and highly viscous. The diameter of the eggs absorbed was 1.86-2.26 mm.
Artificial reproduction uses hormone aphrodisiac, natural spawning or artificial insemination. The drugs we use are salmon pituitary (PG), chorionic gonadotropin (HCG), luteinizing hormone-releasing hormone analogue (LRH?A2), and domoxone (DOM). Or dopamine (RES), using two or three mixed injections, the dose increase and decrease with the temperature, the maturity of the stingray. The male to female ratio was 1:1.2. The injection site was the base of the pectoral fin. The injection was performed twice. The needle distance was 18-24 h. The male fish was injected at half the dose of the female. Both males and females received two injections. The water temperature was 25-28°C. It is 15 to 20 hours. The spawning pond is a rectangular cement pool of 4m2.5m1m. The water depth is 0.6-0.7m. The new water is added intermittently. The brown nest is used to make the fish nest. The brown tablets are suspended on the bamboo raft and lined with bricks. level. The sturgeon spawned several times after spawning, and the eggs were concentrated in a single fish nest that was round and the second spawning still covered it. Batches 1 to 2 use 2 pools at a time, and batch 3 uses a pool.
1.3 Artificial Insemination Check the browns. After laying eggs, put the shallow pool of water, select the best male to cut the abdomen, gently remove the testes, and then cut and crush them in the sperm diluent, and place the unfinished or unproduced eggs of the female fish. Extrude, pour the sperm diluent into the egg, gently stir with feathers, and then attach the fertilized egg to the brown tablet.
1.4 Artificial Incubation After artificial insemination, the cement pool is thoroughly drained and the broodstock is completely drained. The original pool is plugged and the water depth is 60 to 70cm. The brown pieces are floated in water for incubation. Microfluidic water is added for 24 hours. The cement pool is overlaid with black. Shade shade. In the third batch, eggs were inseminated and inoculated with 2 mg/m3 malachite green for 20 minutes to prevent the occurrence of watery mildew.
1.5 seedling cultivation water temperature 25 ~ 28 °C, after 48 ~ 56h all stripping hatch, fresh fish just shed 4.8 ~ 5.5mm larvae, fish colorless and transparent, abdominal yolk sac is larger, side water bottom, film After 2 to 3 days, the yolk sac disappeared, and it began to swim. At this time, the ovaries were removed and the larval stage was mainly fed with zooplankton (rotifers, cladocera, and copepods). Every morning and evening, they are fed one time. After 7 days, the larvae reach a body length of 12-15mm and all the fins have been formed. At this time, they can start to feed and feed the minced fish pulp, artificial compound feed or micro pellets. After 15 to 25 days from the membrane, juvenile fish can be raised in ponds up to 25 to 30 mm.
2 test results
2.1 The amount of spawning of female fishes was determined by anatomy. The absolute fecundity of individual catfish of 40-60g in Dongting Lake was 2500-3500; the individuals with body weight of 60-70g had absolute fecundity of 3500-4500; For individuals between 80 and 100 g, the absolute amount of eggs is between 5,000 and 7,000 eggs. During the anatomical process, it was also found that several sizes of eggs existed in the ovary of stingrays, indicating that the stingrays were batch-type spawning types. Counting unproduced broodstock, the spawned stingrays produce an average of 1,000 eggs per group.
2.2 Induction rate A total of 3 batches of oxytocin were produced. The first batch was used as a pre-inflation test. The rate of inspiration was low (20%), and the second batch of oxytocin was increased by 30% to 50%. There are many factors affecting the rate of production, such as broodstock breeding and selection, water temperature and climate at the time of production, types and doses of injectable oxytocic agents, and broodstock spawning environments, which directly or indirectly affect the spawning of stingrays.
2.3 Fertility rate and hatching rate The fertility rate of each batch of oxytocin differs greatly, with only 10% being low and 70%-80% being high. The factors affecting the fertility rate are mainly the proportion of males and females, the types and dose of hormones, and the control of the spawning environment. Each batch of 3 batches was artificially inseminated and the fertilization rate was low (only 10%). Three batches of about 208,000 eggs of stingray eggs were obtained. The hatching rate has always been relatively low, with an average of 44.5%. The factors affecting the hatching rate are mainly the quality of the fertilized eggs, the eggs stick together and lead to hypoxia, the fertilized eggs are prone to saprophytic diseases and the incubation environment.
2.4 The amount of seedlings
Three batches of 48,000 fry were hatched.
2.5 The seedlings were reared and the yellow snapper eggs were removed from the film. After the film was removed, 2 to 3 days after the film was removed, the filtered blisters were fed, once or twice a day, and after 7 days of feeding, the minced fish paste was added. Feeding at the bottom of the pond, after feeding for 15 to 20 days, the seedlings of the stingrays are as long as 2.5 to 3.0 cm. From June 25 to July 5, dry ponds have a total of 2 to 3 cm fry for 20031. The first batch is only 31. Tail (3 cm), the second batch of 5000 tails (2.5 to 3.0 cm), the third batch of 15000 tails (2 to 2.5 cm). Part of the sale, the rest of the main pond raising, pond raising and cage culture experiments.
3 Discussion
3.1 Breeding season of stingray
In mid-April, we checked the stingrays and found that they were not matured well. In early May, some stingrays were sexually mature. In the end of May, most of the stingrays have been sexually mature, so the artificial breeding time of stingrays It was better in the middle of May and we postponed 15 to 25 days for other fry hatching tasks.
3.2 Ratio of male to female In natural water bodies, there are more females than males in the early stage of the stingray breeding. The artificial propagation of stingrays should be more male than female, and the male to female ratio should be 1.2 to 1.5:1. Our The test was 0.8 to 1.2:1 with an average of 1.06:1, slightly less male.
3.3 Injection Methods Two-needle injections should be taken early in the breeding period of the stingray and in individuals with poor sexual maturity. The interval between the two needles is 10 to 18 hours. The specific time interval depends on the water temperature. In the late post-breeding and sexually mature individuals of the stingray, one shot can be taken. The effect time is 18 to 28 hours. The effect time varies with the water temperature. At the injection site, the pectoral fin base of the stingray is preferred. When injecting, the needle is 2~3mm shallower than the normal oxytocin injection of fish, and the injection direction is 45 degrees to the ventral surface of the body axis. Be careful not to tie the liver and gallbladder, or injection from under the dorsal fin. In the case of two injections, the second needle and the first needle should have different injection surfaces. Otherwise, if the medicine is taken from the new needle hole, it will come out of the old needle hole. This may also occur in skin-damaged stingrays. Therefore, for the artificial stingray stinging parents, the skin must be intact. The amount of drug injected per tail is controlled at 0.2-0.5 mL.
3.4 Comparison of the oxytocin production effects of several oxytocins The oxytocin-producing hormones include salmon pituitary (PG), domostone (DOM), dopamine (RES), chorionic gonadotropin (HCG) for fish, and ovulation number 2. The use of these commonly used oxytocyanins can induce spawning of stingrays, but only the pituitary glands used alone or in combination with several other hormones can achieve better oxytocin production.
3.5 Incubation method Because of the strong stickiness of the fertilized egg of the stingray, it is often piled together on a block basis, it is easy to cause lack of oxygen, so that the hatching rate is low, you can use a few brown pieces together to lay eggs, after spawning, Separately hung on the bamboo poles for hatching. At the same time, because the fertilized eggs of the stingrays are particularly prone to grow in the water, it should be disinfected with malachite green for 2 to 3 times. The brown tablets should be hung in the water and incubated with microfluidic water.
3.6 Fertility methods The production of large-scale yellow sturgeon fry should not be performed by artificial insemination. The first reason is that artificial insemination has high labor intensity, high technical requirements, and the effect is often not ideal. Second, stingray parents are more expensive and artificial insemination must be killed. After the males were removed from the testis and the males were killed, the loss of the fish was greater and the artificial priming costs of the stingrays increased.
3.7 Artificial Fish Nests In the natural world, stingrays reproduce nesting habits and colonize and sink. Artificial breeding of stingrays must also mimic the spawning environment of natural water bodies, placing artificial fish nests in spawning waters, such as sinking plants, branches, and large tiles. The stingray spawns at the bottom of the fish's nest, rather than laying on the top of the fish's nest. Its artificial fish nest is not the same as the artificial fish nest of other viscous egg fishes. It does not provide eggs for stingrays. Attachments, but provide concealment for spawning broodstock.
3.8 Seedlings Cultured stingray fry fish hatched when the yolk sac was larger, the need to go through 3 ~ 5d to consume the oocysts exhausted, so stingray hatched hatched 3 ~ 5d before they started feeding. After the fry swims flat, you can transfer it to a small cage or a small cement pool for feeding. During the breeding process, microfluidic water is needed. The stocking density should not be too large. You should feed the zooplankton every day. After 2 to 3 days, you can feed the blisters. After 7 days, it can be fed with minced fish or crushed meat, etc., or the compound feed can be made into a paste for feeding. After 7-10 days, pure fish pulp or compound feed can be eaten. Stingray has the habit of welting, often adsorbed on the edge of the pool, so when feeding feed should be fed mainly on the side, or take the sink feed table from the bottom 10 to 20cm. The daily feed should be sufficient, feed 1/3 in the morning and 2/3 in the afternoon, because the larva feeding pattern increases after 4:00 in the morning and peaks at 22:00 in the evening. After the fish grow up, they should be divided into pools in time to prevent them from killing each other. The requirements of the leeches fed during the fry cultivation are cultivated after the ponds are sterilized. It is easy to induce disease in the sewage and cause the large-scale death of fry.
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