First, materials and methods
1. Collection and cultivation of broodstock
(1) Collection of broodstock In November 1998, a group of parents of Vallisnaria coeruleus was purchased from the Yangtze River and transported using canvas bags. Females typically weigh between 250 and 360 grams, and males are over 500 grams. This batch of pro-majority is strong, disease-free and injury-free. The survival rate of transportation is 100%. Before brooding fish enter the pool, it is sterilized with 3% saline for 5 to 10 minutes.
(2) Broodstock Breeding The broodstock breeding pond is a pond of 1 mu of 2 mu. The walls of the pond are made of cement, and the bottom is less muddy and flat. The water depth is 1.5 meters. There is a fish net at the inlet and outlet. The pro-fish were disinfected with 75 kg/mu of quick lime two weeks before entering the pool. After broodstock rearing, send special personnel to manage and feed pelleted feeds with a protein content of more than 35%. In order to promote gonad development and early maturation, brood meat feed once every 3 to 5 days, such as: animal organs, wild fish Such as, cut into small pieces with a meat grinder stranded fish slurry feeding, the amount of feed increase and decrease with the water temperature changes. Feeding twice a day, 9:30am to 10:30am; 3:30am to 4:30pm, feeding a daily amount of 3% to 7% of the broodstock's body weight. The broodstock pond often keeps microfluidic and every 5 to 7 Change fresh water once a day, so that the dissolved oxygen in water is kept above 5 mg/l.
2. Fertility, incubation
(1) Oxygen production On May 20, 2000, the spawning of the spawning sturgeon was carried out. A total of 3 groups of 46 broodstock were spawned. The mature broodstock was selected and placed in a cage set up in a cement pool. The broodstock is kept open, and the water inlet valve is turned on for microfluidic stimulation. Artificial reproduction uses hormone aphrodisiacs to spawn naturally. In the experiment, the use of ginseng pituitary (PG), human chorionic gonadotropin (HCG), domperidone (DOM), fish ovulating hormone (LRH-A) and other drugs were used alone and mixed with four drugs. The dose will increase or decrease with the water temperature and broodstock maturity. The injection site will be the base of the pectoral fin and dorsal fin. It will be injected in two shots. The first needle will be 1/4 to 1/5 of the total amount, and the second needle will be injected in the balance. The male dose 0.7 times that of a female fish, and the needle distance is 10 to 15 hours. After the second injection, the broodstock was placed into the spawning tank at a ratio of male to female ratio of 1:1 or 1:1.5, respectively. The spawning pond is a small mouthful of cement ponds (6m2) with inlet and outlet pipes. Two 60-mesh nets with the same size as the bottom of the pool were laid on the bottom of the spawning tank. Bamboo slats were placed around the nets. The bamboo slats were pressed with bricks to ensure no gaps between the nets and the bottom of the pool. Then the nets were placed on the nets. Lay a layer of brown tablets with bamboo clips, and lay eggs with their broodstock.
(2) Incubation of broodstock is 20 to 26 hours (ie, effect time) after the injection of the second needle. The eggs are continuously and intermittently spawned several times. The eggs are concentrated on the brown sheet and mesh cloth near the side of the drainage Tube . The spawning pool The wall also disperses the granules. The granules on the other side of the mesh are less. When the eggs are laid, the water from the spawning pool is discharged by 4/5. Carefully move the fertilized eggs produced on the brown sheet and mesh cloth into the hatchery pool for hatching. Suspend in water, increase the amount of water flow appropriately, and inflate with a small oxygen pump. The dissolved oxygen is kept above 5 mg/L. The incubation water temperature is between 24°C and 26°C.
Second, the results
1. Breeding of broodstock and development of gonads The broodstock began to ingest large amounts of bait at temperatures above 15°C. After 18 months of incubation, when the larvae were examined on May 10, 2000, most of the female brooded abdomen was found to be softer and swollen. Occipital contours appear, and the vents are sunken and reddish. Eggs are removed with an egg digger. The eggs are round, orange, viscous, fuller, and uniform in size. Most of the eggs are separated and the egg diameter is approximately 1.67 mm. Males are large, robust, and slightly reddish at the end of the genital mastoid, making it difficult to extrude semen.
2. Fertility effect and fertility rate The oxytocin test consisted of 3 batches of 46 groups of broodstock. The temperature of the water was between 24 and 28°C. About 20 hours after the second injection, the broodstock began to persist and discontinued the eggs, and the eggs were concentrated in the drainage pipe. On one side of the brown sheet and mesh, there are also few distributions on the pool walls, bricks, and bamboo poles. From the first batch of oxytocin effect, it is obviously inferior to the second and third batch of oxytocin production. The urgency yield is 50%, and the fertilization rate is only 40%. In the second and third batches of oxytocin, appropriate adjustments were made to the oxytocin drugs. As a result, the two batches of infusion rates reached 85% and 90%, respectively; the fertilization rate was 81% and 85% (see Table 1). 3. Hatching rate and number of seedlings During incubation, the water temperature is generally between 24 and 28°C. The fertilized eggs begin to be stripped after about 58 hours, and the seedlings end after about 6 hours. The first batch of hatching results are poor and the emergence is rarely More than 8,000 tails; the second and third batch hatching rate is relatively high, between 80% and 90%, with about 178,000 tails hatched.
Third, summary and discussion
1. Breeding season of Wattlewort trout In the natural environment, the breeding season of the fish is from May to July. After artificial incubation, the gonads develop rapidly and most broodstocks mature. In early May, the broodstock was checked for maturation, and the ovaries of the abdomen of females were more conspicuous and elastic. Observing the eggs with an egg digger revealed that the egg size was even and full, and most of them had been separated. Due to the importance of fostering and management of broodstock, on May 20th it was checked that broodstock had matured and the water temperature was appropriate. At this time, it was the ideal season for hatching and breeding of broodstock. When the water temperature exceeds 30°C, embryonic development ceases and the eggs start to suffocate and die. Therefore, the artificial breeding season of Wattlewort yellow sturgeon is suitable from May to June.
2. Artificial oxytocin and natural spawning have tried artificial oxytocin production. Its effect is not ideal, and hormone aphrodisiac and natural spawning are used. The effect is ideal. Natural fertilization, in addition to the first batch of unsatisfactory, the second and third batch of spawning rate reached more than 85% and the fertilization rate of more than 80%, the survival rate of broodstock was 98%, and the mortality rate of broodstock after artificial oxytocin production was higher. Usually around 40%.
3. Female and male proportions and injection methods When fertility herring are naturally fertilized, the male parent is better than the female and the effect is better, which is beneficial to aphrodisiac and spawning. In oxytocin, if the number of male parents is limited, the proportion of males to females should also reach 1:1. Injection site for the pectoral fin base or back muscles, divided into two injections, needle distance of 10 to 15 hours, injection needles to be appropriate, usually about 3 mm, pectoral fin injection direction and the pro-fish body axis into a 45 degree angle, or dorsal fin base 45 degrees In the corner, be careful not to tie the heart and the hard bones of the rays.
4. Oxygen production drugs Carp pituitary gland (PG), domoxone (DOM), chorionic gonadotropin (HCG) for fish, and LRH-A for fish alone can induce broodstock production Eggs, but the effect is poor, after the change of the above four drugs mixed use, the dose adjusted with the water temperature, maturity, the oxytocin effect is excellent.
5. Spawning and Incubation From several tests, it was found that spawning pond walls disperse a lot of eggs, and eggs are concentrated on brown sheets and mesh cloths near the side of the drainage pipe. Therefore, the mesh should extend to the wall so that the broodstock eggs do not stick to the wall as much as possible during the egg laying process. The fertilized eggs are round, orange-yellow and egg-viscous. The eggs are soft, with a strong stickiness, and the egg membrane is smooth and transparent. It swells after being exposed to water. During the hatching process, the fertilized eggs should be hung up from the fish nest, and the water inlet valve should be unscrewed so that the flow of water can be continued and the air can be continuously inflated with the oxygen increasing pump to keep the dissolved oxygen above 5 mg/l. In the hatching, special attention should be paid to the water quality. The inlet valve is preferably filtered with 60-80 mesh mesh cloth, and is sterilized once a day with 0.25 mg/L malachite green to avoid the occurrence of water mold in the hatching process of the fertilized eggs. It helps to improve the hatching rate.
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