How to improve the survival rate of rainbow trout breeding and hatching and fry breeding?
Sun Yuzhi and others
Rainbow trout, as the main species of high-grade fish in fishery breeding and cold-water cultured salmon trout, because of its super high nutritional value and good mouth feel people's recognition and attention, the production and market demand of aquaculture are also steadily increasing year by year. Fishery technicians and small farms (households) have also discovered and summarized technical measures and recommendations that are more suitable for rainbow trout breeding and hatching, fry and fingerling cultivation in practical production applications while following the version of the culture technology of the 1980s and 1990s. [Yoshiyama Huayao self-media network debut]
1. Broodstock breeding
(1) Fish age and weight
The old version of the standard or book is that the female fish is 2 to 5 years old and weighs 0.75 kg to 4.2 kg; the male fish is 2 years old to 4 years old and weighs 0.5 kg to 4.2 kg. But in the actual production application, the number of eggs, the number of pregnant sperm and the quality of the broodstock weight relationship is greater than the fish age, if the broodstock breeding well, the female 5 years to 6 years old is a good time, generally available to 8 years old, with the increase in the weight of the breeding fish, not only the number of eggs increased (generally broodstock weight increased by 0.5kg, the amount of eggs increased by 1000 grains) The egg size of the eggs conceived also increased accordingly, and the size of the cultivated fry was large. Males generally weigh about 2 kg the best, the quality of the semen they carry is good, the amount is large, and the survival rate of fertilization will increase.
(2) Breeding conditions
1. Pond conditions. Fish pond area, fish pond area is generally 200m2 ~ 400m2, water depth 0.7m ~ 0.9m. Because the individual breeding fish is larger, it is recommended that the breeding pond is larger, generally recommended 400m2, the water depth is actually more than 1m is better, which is conducive to the growth and cultivation of breeding fish. It is recommended to use four-wall cement, bottom soil is the best, and drainage should be convenient so that the water quality can be adjusted at any time.
2. Water temperature. Broodstock breeding water temperature of 4 °C ~ 12 °C, perennial should not be higher than 12 °C, otherwise it will affect the quality and quantity of broodstock eggs, and even do not carry eggs, pregnant sperm.
(3) Stocking of seed fish
In the past, the experience is that the female and male fish are raised in separate ponds one month before spawning, and it is recommended that the breeding fish be directly cultivated in the breeding pond and directly raised in separate ponds to avoid biting and injury during the incubation period. It is recommended that each cubic water body is less than 5kg, and the ratio of females and males is increased to 3:2 to 4:2, in practical production applications, the amount of semen has a great impact on the fertilization rate during artificial insemination.
(4) Feeding
Feeding is given twice a day in the morning and afternoon. It is recommended that the feeding amount be based on 1% of the total weight of broodstock as the daily bait base, but according to the eating situation of broodstock, the principle of "three certainties" is adjusted at any time to cultivate broodstock in large individuals without affecting the sexual maturity of broodstock.
(5) Water quality regulation
Dissolved oxygen should be kept above 6mg/L, and the pool water exchange should be done so that broodstock do not top the stream and swim comfortably.
(6) Daily management
Timely patrol the pond, keep the fish pond clean, and treat fish diseases in time.
2. Artificial reproduction
(1) Identification of broodstock maturity
Male fish light pressure on the abdomen that is, there is semen outflow, female fish abdomen is expanded and soft, the genital foramen is convex, and there is egg outflow in the abdomen, which can be artificially inseminated. It is recommended to identify broodstock maturity at intervals of about 7 days.
(2) Artificial reproduction
1. Stop eating before egg collection. Broodstock are stopped 3 days before egg collection.
2. Broodstock anesthesia. It is recommended that broodstock anesthetize before sperm retrieval, which is not only convenient for operation, but also reduces the injury of breeding fish and helps broodstock recover after childbirth. It is recommended to add 5mL of commercially available glycol phenyl ether per 100 kg of water, and it is better to anesthetize the broodstock for 3min to 5min, the dosage and length of the drug, preferably depending on the size, physique and anesthesia of the broodstock.
3. Artificial insemination. Use the artificial extrusion method to collect eggs and sperm, and use a cotton dry towel to dry the broodstock and utensils before operation to prevent water and excrement from mixing in. Squeeze the eggs in a porous plastic egg collection basin and wash the eggs with an isocondition (see Appendix 1) to wash away the blood and dirt. After the washed eggs are poured into a fertilized basin without holes, and then squeezed in semen, it is recommended that 3 females use 2 males, and the males can be reused after 7 days of sperm collection. Stir the sperm-egg mixture quickly, uniformly and gently for 1min to 2min, so that the sperm and egg are fully mixed and contacted. It is recommended to add a small amount of isocondition to continue stirring for 1min to 2min, and then rinse with water, it is recommended to rinse several times until the dirt is basically rinsed, which can actually greatly improve the hatching rate of fish eggs. All operations should be handled lightly and carefully to avoid injuries to the fish. The inseminated eggs are stationary in clean water for about 60 minutes, and after the fertilized eggs are completely absorbed and expanded, they are placed in an incubator for incubation.
Rainbow trout fingerlings after anesthesia
3. Artificial incubation
(1) Incubation facilities
There are barrel incubators and tank incubators, although the trough incubator is convenient to operate in actual production, the bucket incubator has better water exchange and shading effect, and the hatching survival rate is higher.
(2) Egg laying density
For 270mm high and 275mm diameter barrel incubators, it is recommended that each barrel contain 30,000 to 40,000 eggs with an egg diameter of 5 mm, and the water injection volume is 4L/min~5L/min. The trough incubator is reduced to 30,000 eggs per cubic meter, and it is not recommended to be too dense, which can reduce the number of eggs dying due to lack of oxygen and reduce the occurrence of water mold.
(3) Incubation conditions
It is recommended to avoid light and shock as thoroughly as possible. The water quality requires clear, free of impurities and suspended solids, preferably source water. The dissolved oxygen content is required to be greater than 6.5mg/L, the water temperature is 7 °C ~ 13 °C, and the optimal incubation water temperature is 9 °C.
(4) Incubation time
From the time the eggs are fertilized to the fry emerge, it takes 46 days at an average water temperature of 7.5 °C, or 343 cumulative temperatures (343 degrees Celsius days). The number of days from fertilization to the eye-opening phase is about half the number of days it takes to hatch. The eggs must remain stationary until the cumulative incubation temperature is 220 degrees Celsius.
Rainbow trout are artificially inseminated
(5) Fertilization rate calculation
When the incubation cumulative temperature reaches 100 ° C, arbitrarily take a certain number of eggs into a Petri dish containing the identification solution, soak for about 5 minutes, the eggs with white linear embryonic bodies are fertilized eggs, and the percentage of fertilized eggs in the total number of eggs is the fertilization rate. The preparation of the identification solution is shown in Table 2.
(6) Incubation management
Be sure to keep the water flow uninterrupted, it is recommended to disinfect it with formaldehyde every 5 days to prevent the occurrence of water mold. Before the accumulated temperature reaches 220 °C, the fish eggs are completely stationary, and after the accumulated temperature reaches 220 °C, the eggs are poured into the flat groove for egg picking operations, and it is recommended to bring water to pick out the dead eggs, otherwise the survival rate will be affected. Remove the dead eggs and place them in the incubator to continue hatching. The barrel incubator transfers the eggs into the flat groove when the cumulative incubation temperature is 320 degrees per day, and the flat groove is a freupad type fish egg hatching flat groove, with a specification of 6m in length, 0.4m in width, 0.25m in height, and 6 small slots built in, covered with shading. It is recommended that no more than 3000 eggs be laid in each small slot, and the amount of water injected per slot is 40 L/min. Keep the water flow smoothly, strictly prevent hypoxia and suffocation, and pick out dead eggs in time.
Fishermen's homemade simple salmon trout egg incubator
4. Fry rearing
(1) Cultivation ponds
The cultivation pond is a feeding tank or a mud pond, and it is recommended that the cement pond specifications be 5m~10m long, 1.5m~2m wide, and about 1.0m high, so that the water depth can be adjusted in time with the size of the fry, and also save the seedling breeding pond and reduce the loss of the sub-pond. The cultivation ponds should be set upstream of the water source and arranged in parallel.
(2) Water temperature
The suitable water temperature is 8 °C ~ 12 °C.
(3) Stocking
In the flat groove, the yolk sac of the fish eggs is absorbed at 2/3 time and begins to swim, with a total length of 18 mm to 28 mm and a body weight of 70 mg to 250 mg. The recommended stocking density of the nursery tank is 6000 fish/m2 and the cement tank is 3000 fish/m2. Floating fry can be reared in a feeding tank for 2 weeks before being moved into a cement tank or directly into a cement tank for rearing. Direct sunlight should be avoided within one month, so it is recommended that the feeding tank and the cement nursery pond be built indoors.
The water injection volume in the early stage of fry rearing was 1 L/s of 100,000 fry, and the water supply was gradually increased with the growth of individual fry and the stocking density of fry was adjusted.
Rinse rainbow trout fertilized eggs
It is recommended to use full-price compound pelleted feed, and the feed particle size is 0.3mm~0.5mm. Feeding begins when the upper floating fish is 2/3 of the total number of fry in the nursery tank, and is fed 6 times a day.
After the fry are moved into the cement breeding pond, it is recommended to use a fully automatic bait machine, which not only saves labor, but also adjusts the feeding situation of the fry at any time, which can improve the survival rate and growth rate of the fry.
(5) Daily management
Keep the tank and the pool clean, brush the gate frequently, pick out the dead seedlings in time, regularly test the water quality, and maintain the smooth flow of water and a good pool water environment.
Floating fry on rainbow trout in hatching tanks
5. Fingerling breeding
The cultivation pond is suitable for rectangular shape, the recommended area is about 60m2, which is easy to manage, and the depth of the pond water is controlled at 0.3m~0.5m.
The water temperature is controlled between 8 °C and 18 °C.
The stocking density is proportional to the water injection of the breeding pond, and the water injection increases with the growth of the fish body and the enhancement of swimming ability, and the water depth gradually deepens with the weight of the fish body.
(4) Daily management
Feeding high-quality full-price compound pellets should be regular and quantitative. Adjust the feeding volume at any time according to the proportion of feeding percentage. Regular screening, grading, and breeding in separate ponds. Keep the environment of the fish pond clean.
Barrel incubator
Identification of fertilized eggs
6. Prevention and treatment of fish diseases
Rainbow trout are mainly affected by IHN disease (hematopoietic organ necrosis), which causes the fry survival rate of rainbow trout to be very low, especially in some small and medium-sized hatcheries. Many large rainbow trout farms have adopted disease control methods and are well controlled, but they still do not solve the problem fundamentally. When fry are moved into outside ponds for adult rearing, if vaccination is not given, fingerlings will still develop diseases and mortality rates will be high. At present, there are vaccines injected into broodstock according to immunogenetics in China, and the effect is very good, but the results have not been identified and have not been applied to production practices.
(1) Necrosis of hematopoietic organs in rainbow trout
(IHN disease)
1. Adopt risk prevention and control technology. That is, the water source is disinfected with ultraviolet rays, the fish eggs are disinfected with formaldehyde or povidone iodine, the fry are fed a special immune enhancer, and the povidone iodine is disinfected at the same time, and the fry grows to about 20g to inject IHN immunization inactivated vaccine, and then put into the outdoor fish pond to cultivate into fish, which greatly improves the survival rate of rainbow trout farming.
2. Fish fry breeding pond empty pond disinfection technology. Before the fry are put into the nursery pond, the fish in the nursery pond are fished away, disinfected with copper sulfate and bleach powder, and then disinfected with povidone iodine or Traditional Chinese medicine after entering the pond, which also plays a very good effect, and also proves that ultraviolet rays are ineffective against retroviruses (IHN is retroviruses, and it is recorded that ultraviolet rays do not play a killing role in retroviruses).
(2) Gill rot, enteritis, and furuncles
According to practical experience, chlorine dioxide effect is good; enteritis can be taken internally on an empty stomach; bactericidal drugs can be taken internally for furuncles; and the effect of external glutaraldehyde preparations is better. Dosage can be used according to the instructions.
(3) Water mold disease
Juveniles are bathed in 1% brine for 20 min, and adults are bathed in 2.5% brine for 10 min to see if the fish's activity is shortened or extended. Or it can be treated with commercially available drugs to treat water mold.
(4) Three generations of insects and small melon insects
Three generations of insects use commercially available insecticides, according to the instructions to use the dose; small melon insects need Chinese herbal medicine at about eight or nine o'clock in the evening, according to the dose.