Hybrid fish have large individuals and fast growth, and they are breeding breeds with huge development potential. However, the breeding techniques of seedlings need further breakthroughs. After many years of exploration, the Guangxi Nanning Aquatic Breeding Farm has successfully produced a large number of hybrid raw fish seedlings. The experience is worth learning from.
Text / Guangxi Nanning Aquatic Products Plant Lu Runpeng
Hybrid fish was obtained from the cross between two species of fish: Channa argus and Channa maculata. Umbellifera is a species of S. siniperus, S. sinica, S. genus and U. sinensis. It grows along the Yangtze River basin in China, and is particularly dominated by Hunan and Hubei provinces. Umbellolus is a fierce carnivorous fish. The fish and shrimp in its living waters are its food source. Therefore, it is also a natural enemies of pond fry breeding. The dorsal plague is a species of maggots, pupa, pupa, and dorsal species. The two people widely known as raw fish, black fish, snakehead fish, etc., grow in the Pearl River basin in China, with Guangdong and Guangxi provinces predominating. Spotted turtle is also a kind of carnivorous fish. It mainly feeds on aquatic insects, cockroaches, small fish, and shrimps. In recent years, the breeding of cantharidin in Guangxi is mainly nesting, which plays a role in reducing the cost of culture in tilapia adult culture ponds.
Through trials and explorations, it was possible to acclimate and feed artificial compound feed during the breeding process of the first-generation hybrid fish, which was bred from the crossbreeding of Wuhuan as the male parent and the candied turtle as the female parent, and solved the bottleneck problem of the low breeding yield of the candied turtle for many years.
The raw water temperature of hybrid fish is 0-40°C, and the optimal water temperature is 22-30°C. When the spring water temperature rises above 12°C, it often acts in the upper layer of the water body. When the winter water temperature drops below 10°C, it often lurks deep in the water bottom.
The hybrid fish have large individual size and fast growth. After 6 months, the individual weight of the cultured fish can reach 1.0-1.5 kilograms, and the breeding yield is more than 3,000 kilograms per mu. This is a new breeding breed with huge development potential. At present, it is imminent to solve the problem of breeding of seedlings. After years of exploration, a large number of hybrid fish seedlings have been successfully produced in Nanning City, Guangxi. Hybrid fish breeding methods mainly include the following aspects.
First, the choice of broodstock
1. Sources and retention conditions of broodstock of Wuchang:
Every autumn, the weather turns cold and it is suitable for long-distance transportation of fish. From Hunan, the adult scorpion fish with excellent biological characteristics are selected as broodstock. The Uzbek parents were selected to comply with the following conditions: (1) Age 2-3 years. (2) Body length and body weight: Individuals that are commonly used for artificial reproduction are about 30-40 cm in length and 0.75-1.5 kg in weight. Individuals who are too small are not only affecting the amount of eggs laid by the broodstock but also are not conducive to increasing the growth rate of the child. (3) Appearance: Wuyi body color pattern is clear, bright and bright, many mucus on the body surface, no injuries to the whole body. (4) Physical: The physique is robust, swimming is quick, and when the broodstock is held in hand, the fish tail swings vigorously.
2. Source and retention conditions of spotted broodstock:
Wild spots around Nanning. The method of selection is similar to that of Ujjain. The difference is that the species is smaller and has a weight of 0.6-1.0 kg per tail. In addition, the abdomen of the spotted turtle requires soft and smooth abdomen. It is better to dissect the sample fish if necessary.
Second, the cultivation of broodstock
Bred broodstock cultivation is the key to reproduction, broodstock cultivation is very smooth in the breeding process, the fertilization rate and hatching rate of the eggs are guaranteed.
1, the preparation of broodstock cultivation pool
The cultivation pond area is 1-3 mu, the bottom of the pool is flat, drainage and irrigation are convenient, the bottom sludge is 15-20 cm thick, and the pond raft is 50 cm above the water surface to prevent the brooding fish from jumping out. 15 days before use, dry ponds were disinfected and 120-150 kg/mu of quick lime was applied. After drying for 3 days, 1 m of fresh water was injected, and fertilization and water were used as light green. Inlet is filtered with a 40 mesh filter.
2, stocking density
The black locust and the brown pheasant are kept in separate ponds to avoid premature or sporadic spawning, which is conducive to batch hatching. 100-150 tails of broodstock are stocked per acre, and the weight is 100-150 kg. Individuals with small spots can increase their stocking capacity to 180 kg per mu. In addition, feeding a small amount of carp and carp is conducive to the cultivation of stable water quality. Before the broodstock enters the pond, the fish is disinfected with 2-3% saline for 10 minutes.
3, feeding and management
(1) feed feeding
After the long-distance transportation of the broodstock is weak, the first 10 days of feeding is a critical stage. Adhering to the daily feeding of fresh small bonito and shrimp, the daily feeding amount is 5% of the broodstock's weight, and gradually increases in the next 2 months. Domestication and feeding were mainly based on fresh chilled fish from seafood, supplemented by wolfberry and blessed snails, and it was appropriate to inspect food dailies every day for feeding within 2 hours after feeding, and 2 feedings per day. When the water temperature in winter is lower than 12°C, the broodstock is lurking at the bottom, and no feeding is required, but a batch of low-value fry is to be put in for emergency feed. By the end of March, as the weather became warmer and the water temperature increased, broodstock activities increased. In addition to feeding chilled fish from the sea, fresh small tilapia was put in order to restore physical energy consumption during the winter. May is the broodstock breeding season, do not feed the first 3 days of urging, so that the broodstock emptying the intestine of the slag, consume a certain body fat, which is conducive to the identification of broodstock maturity.
(2) Water Quality Regulation
Keep fresh water during cultivation. Water quality adjustments take corresponding measures in accordance with changes in water color. Increase the water level in winter to keep the water temperature stable. After the spring, the sunshine duration is long. Decreasing the water level will help increase the water temperature. Starting in early April and flushing water once a week, it can both improve water quality and promote gonad development in broodstock.
4, regular disinfection.
The broodstock is regularly sterilized during the breeding period, and once a month, the amount of quicklime is 30-40 kg/mu. The entire pool is splashed and the pathogenic bacteria are killed. The food table was sterilized using formalin 20ppm.
Three, broodstock artificial labor
Artificial oxytocin production is an important means of artificial breeding of hybrid raw fish, which will help improve the spawning effect and obtain large-scale fry with the same specifications, and provide seed protection for large-scale breeding of adult fish.
1. Preparation for incubating water
The storage tank is used for incubating water, and the pool water is drained 15 days before propagation to block the leakage. Use potassium permanganate 5ppm solution to disinfect the whole pool. Rinse and drain the residue the next day. Inject new water. After 7 days, turn the water color into light green.
2, the preparation of the hatchery ring pool
Thoroughly clean and sterilize the hatchery ring 2 days before hatching, check the strainer hole, inject new water, and use the disinfectant body with povidone-iodine 0.2ppm.
3, the selection of mature broodstock
Reduce the water level of the broodstock pool and fish it with the fishing nets. Manually select mature broodstock for oxytocin production. The proportion of mating male and female Umbrellas is 1:1. The males with good maturity are slender and dark purple on both sides. Their abdomen is straight. The dorsal fins are arranged in a white, transparent, round spot from bottom to top. The gonads are small and dimpled and pink. The maturity of the female spot beetle is characterized by obvious enlarged, soft and elastic abdomen, obvious ovary outlines on both sides, and depression in the center when the abdomen is upward, and the genital pore of the anus is reddish, protruded, and enlarged. In order to verify accurately, the ovipositor head was gently inserted into the genital foramen to remove the egg and observed under a dissecting microscope. If the egg was dispersed and uniform in size, it was golden yellow, clear and bright, full and complete. A large oil globules, most of which are off-center, are judged to be mature and can be artificially elicited.
4, the type of injection and use of drugs
There are a variety of oxytocin drugs, and the best ones are the mixed oxytocic LRH-A2 (fish stimulated ovulation number 2) and HCG (human chorionic gonadotropin). The broodstock was injected with 210 micrograms of LRH-A and 500 international units of HCG per kg of body weight. When used, the drug was dissolved in a sterile saline mortar and stirred thoroughly. The broodstock was injected into the body cavity one by one and then placed into the spawning pool.
5. Calculation of injection times and effect time of oxytocin
When the broodstock has a good maturity, one shot can be used. The broodstock is not mature enough to use two injections. The first dose is 1/3 of the total dose, the second is 2/3 of the total dose, twice the interval 10 Hours. The spawning effect of the broodstock is determined by the water temperature and the degree of gonad maturation. Under normal circumstances, the water temperature is 22-24°C and the effect time is 40 hours. When the water temperature is 25-27°C, the effect time is 24 hours. The water temperature is 28-30. The effect time is 18 hours at °C. The best method is to spawn early in the morning the next day.
6, broodstock spawning and collecting eggs
In the hatchery, several artificial fish nests are arranged in advance and evenly distributed. When the drug effect time arrives, the brooding fish show that the females constantly shake their bodies to produce mature eggs, while the male fishes closely to the females and shoot sperm, sperm and eggs. Fertilization is done in water. A total of 2000-4000 eggs were spawned by each spotted turtle, and the freshly produced fish eggs were round, golden yellow, and the egg membranes were thin and transparent, with an egg diameter of 1.8-2.0 mm, no stickiness, and concentrated floating in the middle of the fish nest. Before harvesting the fertilized eggs, remove the post-partum broodstock and collect the fish eggs in the dense network of the outlet. When the eggs are dense, use a water scoop to scoop the eggs with the water and gently pour them into the egg-filling tool and transfer them to the incubation ring. Road incubation.
Fourth, artificial hatching
Incubation adopts the loop incubation method, which is the method of new water flowing from a high place into the meridian channel and flowing out from the lower place. The loop incubation method is suitable for the incubation of inviscid fish eggs, which can hatch 1.5-2 million eggs at a time. The density of fertilized eggs is set at 100,000 pellets/m3 in the hatchery ring, and fresh water is continuously injected throughout the day, after 6 days of incubation. , you can hatch seedlings.
1. Incubation management
(1) The water source is clean, the water temperature is stable, the water inlet adopts a filter cloth with more than 100 mesh, and the water quality is measured twice a day. The dissolved oxygen in the water is maintained at more than 5.0 mg/L, the pH range is 6.5-7.5, and the ammonia nitrogen content is less than 0.2 mg/L.
(2) Regular cleaning of white eggs or dead eggs that cannot develop normally. Because there is a large oil ball in the bad egg and ulcerated internal solution, it is easy to pollute the water and breed bacteria.
(3) Wash the eggshells that block the loop filter frequently to prevent water from passing over the top of the loop filter. Especially during the breakage period of sea flower, the egg shell was the most, and special attention was paid to cleaning.
(4) Regular microscopic examination of embryo development to ensure normal development. Fertilized eggs develop from cleavage to blastula stage to gastrulation stage to embryonic body stage. Every developmental stage is important.
(5) Control the inflow and outflow of water, keep the water flow in the ring of the hatchery slowly tumbling, and the temperature difference per hour does not exceed 2°C.
(6) Use a black shading net to block the morning and evening sun rays, to prevent fish eggs from being injured or deformed.
2. End of incubation
When the incubation temperature is 24-26°C, the hatching passes for 30-35 hours. The embryonic body breaks the egg membrane with a tail strike, followed by a fierce rhythmical oscillation of the head and tail. The larvae break out of the membrane.
Just out of film larvae body length 0.4cm, body color grayish yellow, the body spreads over the melanin cell, looks like small èŒèšª. With the help of oil buoyancy in the body, the fish body is suspended on the water side and swings with the water. After 4 days of incubation, the fish's endogenous yolk sac was absorbed. The body length was 0.8cm, and it was able to swim horizontally.
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