Hatching of rainbow trout fry
_ Li Xiaoping
1. Preparation before incubation
1, the incubation tank soaking and disinfection after the hatchery pond is built, due to the high alkali content, can not be used immediately for fry hatching, to wash the alkali first, usually take the method of soaking and chemical reagent neutralization two. Soaking is to fill the fish pond with the water introduced into the field, so that it has been self-flowing, non-stop exchange, at least soak for more than half a month, during which the pond water can be drained and completely changed several times, and the alkali washing effect is better. This method is time-consuming, but inexpensive and simple. The chemical reagent neutralization method is to fill the pool with water and no longer enter the water, pour diluted hydrochloric acid or acetic acid into the pool water, release the pool water after 3-5 days, and then soak it with water (you can also pour diluted hydrochloric acid or acetic acid once again). This method is more expensive, but the advantage is that it takes a short time and the alkali washing effect is good. After washing the alkali, a few fish can be put in for trial culture, observed for two to three days, and if there is no harm, it can be disinfected and stored in water to hatch. The incubation tank is disinfected using 10ppm potassium permanganate solution, the four walls and the bottom of the pool are thoroughly cleaned, and then rinsed with water.
2. Preparation of incubators
In the process of rainbow trout incubation, the incubators generally used are vertical incubators, barrel incubators, flat grooves, etc., each with advantages and disadvantages. Here is a homemade simple incubator that is cost-effective and easy to use. Material: 1-2cm thickness, width of about 10cm wooden plank (or a hard material that can float on the surface of the water on the line), plastic mesh, fine wire can be. The planks are nailed into a box, smaller than the size of the hatchery, so that the hatchery can be placed in the hatchery. Then the plastic mesh is nailed to the bottom of the box and straightened, and then two thin wires are stretched diagonally at the bottom of the box to support the plastic mesh, so as not to collapse downward after laying the eggs, causing egg accumulation and affecting the incubation effect. After the simple incubator is ready, it is also disinfected in the same way as the incubation pool. After detoxification, put it into the hatchery and soak it for later.
3. Water storage
After the hatchery and hatchery tank have been sterilized, water can be stored 2-3 days before the spawning hatching.
2. Incubation and management
1. Purchase of eye-catching eggs
Rainbow trout eye egg shell is harder, the stimulation of the external environment is more stable, can be transported for long distances, so the purchase is eye eggs. The supply time of ocular eggs is generally in The first year from September, October to March and April of the following year, at present, the supply of domestic rainbow trout triploid ocular eggs is mainly concentrated in the northeast and Beijing, and there are also domestic agents importing ocular eggs from the United States, Denmark and other countries.
2. Weigh the temperature
2.1 After the eggs are transported to the hatching site, the foam box is filled with ice cubes, and the temperature is generally maintained at 2.5-3.5 °C, while the water temperature of the incubation water is generally between 10-17 °C, so the temperature treatment should be carried out before incubation. After the foam box is opened, it can be repeatedly poured on the eye eggs with a small amount of incubation water until the temperature of the eggs is close to the temperature of the incubation water (the temperature difference does not exceed 2 ° C). This process must not be too hasty, slowly weighing the temperature, otherwise the eye eggs will heat up too quickly and the seed hatching deformity rate is high, and even the phenomenon of egg death.
Remove the dead eggs during the temperature-leveling process and soak them in 5% salt water for a while.
2.2 Transfer the balanced temperature of the eye-catching eggs to the incubator, evenly lay flat on the plastic yarn, and lay only one layer of eggs, do not overlap. If the incubator is sufficient, each egg is laid on 1/2 of the incubator area and does not have to be filled, so as not to cause hypoxia. Once the eggs are laid, they can hatch.
2.3 Management of incubation
2.3.1． The water used for incubation should be fully guaranteed, and the water quality should be clean and not polluted. The water intake in the early stage of incubation can be appropriately smaller, and the water intake can be increased after entering the defilming period, so that the eggs are not impulsive.
2.3.2. Dissolved oxygen in water is the key to the success or failure of hatching, and sufficient oxygen must be ensured during the incubation process. In addition to the incubation water to ensure sufficient, but also to prepare aeration equipment, in the late incubation should be opened at any time, to avoid insufficient dissolved oxygen and affect the incubation effect.
2.3.3. Insist on patrolling the pool every day, observe the development of eggs, remove dead eggs in time, and disinfect once or twice with 3-5% salt water before egg defilming to prevent the occurrence of toxic diseases.
2.3.4. When the incubation temperature reaches about 340 ° C, the egg particles begin to defilm, and the yellow translucent baby fish with the yolk sac that has just hatched will not swim, lying on the bottom of the incubator, and there is a cluster phenomenon, at this time, it is necessary to increase the amount of water inlet appropriately, and the oxygenation equipment can also be opened in time to avoid hypoxia. Attention should also be paid to cleaning up residues produced during the hatching process on the surface in a timely manner.
3. The juvenile fish after the membrane is very tender, the organs and functional development are not perfect, and its growth mainly depends on the absorption of nutrients from the yolk sac, and does not require external bait. At this time, it is necessary to remove the dead seedlings in time to maintain the freshness of the water quality. With the growth of the juvenile fish, the yolk sac gradually decreases, the body color gradually turns darker to black, and the swimming ability gradually becomes stronger, becoming a floating juvenile fish.
4. The swimming ability of the floating fish is slowly strengthened, and when the yolk sac disappears, it begins to absorb nutrients to the outside world, which is a very important stage, marking the transformation of seedlings from absorbing yolk sac nutrients to external intake of exogenous nutrients. At this time, it should be fed in time to meet the life maintenance and normal growth of juvenile fish. The feed should be fed with a full-price rainbow trout opening material containing 40%-50% crude protein, fed 4-6 times a day, and the amount of feeding depends on the feeding of the fish. The swimming ability of juvenile fish is weak, and the ability to take bait is not strong, so when starting to domesticate food, the feed should be sprinkled in the incubator, and the juvenile fish fry should be appropriately scattered in places. At this stage, the amount of bait is slightly surplus, so that the seedlings that meet the active feeding can absorb enough nutrients as soon as possible to lay the foundation for healthy growth in the later stage (Note: The remaining residual bait should be removed in time to avoid polluting the water quality). After about 10 days of rearing, the fry grow to 2.5-3 cm, the body grows patterned, can swim freely, the hatching is over, and the fry can be sold or moved out of the outer pond for breeding.
