Rainbow trout are named because their adults have a brownish-red longitudinal stripe along the line, resembling a rainbow. Rainbow trout has the advantages of delicious meat, rich nutrition, less thorns and more meat, high edible value, rapid growth, simple and easy artificial reproduction, etc., and has become one of the four major freshwater aquaculture species with high yield and excellent quality promoted by the Food and Agriculture Organization of the United Nations to the world, and has been listed as a high-grade fish. Rainbow trout living water temperature of 2 °C ~ 25 °C, the most suitable water temperature is 12 °C ~ 20 °C, its adaptability is very wide, can be farmed in ponds, can also be stocked in reservoirs, lakes, rivers, especially in the flow of water can grow all year round, the yield is very high. Large-scale aquaculture practice proves that the general mu yield of adult fish is 30,000 to 35,000 kg, up to more than 50,000 kg. Therefore, the prospect of flowing water culture of rainbow trout is attractive.
First, the construction and layout of the fish pond
A perfect farm should be based on the different growth stages of rainbow trout, with juvenile ponds, fry ponds, fingerling ponds, adult ponds, broodstock ponds and reserve broodstock ponds, etc., the area can account for 0.5%, 1.0%, 12.5%, 80%, 3.0%, 3.0% of the total area, respectively, and a small number of quarantine ponds should be set up in places where conditions permit, in preparation for the isolation and quarantine of sick fish. Fish ponds, fry ponds and fingerling ponds are preferably made of stone or concrete structures, and adult ponds and broodstock ponds can be either soil, stone or concrete. Regardless of the structure of the fish pond, its shape must be determined, must take into account the smooth flow of water, easy to discharge and give full play to the utilization rate of land, as well as reduce the cost of the project. The layout of each type of fish pond is as follows: the juvenile pond, the fry pond, the fingerling pond are placed in the front, and the adult and broodstock ponds are in the back. The quarantine pond should be used separately from the water, and the discharged water can no longer be used. According to the terrain, each row of fish ponds should have a certain drop to facilitate natural flowing water.
Each fish pond should have inlets, drains and sewage outlets. The size of the inlet and drainage outlet should be determined according to the flow rate of the water, the flow rate, the size of the fish pond and the shape of the fish pond, the water inlet method, and the number of water changes required. If the DC type of water inlet, drainage, the water inlet is a little wider, in order to facilitate oxygenation; such as spraying water or water and other methods of water, the size of the water inlet should be designed according to the required flow, water pressure, flow rate requirements. Fish barriers should be set up at the inlet and drainage outlets to prevent escaping fish. The fish barn should be tight, and the spacing should be determined according to the size of the fish body.
2. Breeding and management
The whole process of rearing rainbow trout, counting from the hatching of the egg rupture membrane, can be divided into several stages, such as the hatching stage (from hatching to two months after feeding), the fry stage (from two months to 6 months after feeding), the fish fingerling stage (from 9 months after feeding to the end of the year) and the adult stage (from January of the following year to the sale).
Within 20 days after hatching, the calves rely on the nutrients in their yolk sacs to maintain growth and development, and can put about 10,000 to 50,000 fish per square meter. Incubate for 20 days, start feeding, initially mix the cooked egg yolks into a slurry and drip into the fish pond. 1 month after the opening of the food, 500 to 1000 fish per square meter can be put, and the cooked egg yolk can be squeezed out with gauze, so that the yolk is finely granulated and dripped in the water, and the egg white can also be used together later. Animal livers and fresh trash fish can also be ground into a paste and dripped into the water for feeding. Feed 6 to 8 times a day. Daily bait can account for up to 12% of the fish's body weight.
After two months of feeding, the weight of the baby fish has reached about 1 gram, and it has entered the fry stage, and 200 to 500 fish can be stocked per square meter, at which time all of them can be fed pellet feed. However, the animal components in the feed need to be maintained at more than 80%. The amount of bait thrown per day can account for about 9% of the weight of the fish, and the bait is thrown 4 times a day. Half a year after the start of the meal, until the end of the year, it is the fish seed stage, and 50 to 200 fish can be stocked per square meter. It can be fed into adult fish feed, the amount of bait can account for about 5% of the fish body weight, and the number of baits per day is 3 to 4 times.
During the adult stage, 15 to 50 fish can be stocked per square, and the water depth is 1 m to 2 m. Animal feed accounts for 30% to 40% of feed, and plant feed accounts for 60% to 70%. The size of the particles is moderate, generally in diameter of 4 mm to 8 mm, fed twice a day, and the amount of feeding is 2% to 3% of the total weight of the fish. In order to achieve high yields of adult fish, it is first necessary to maintain sufficient water volume and set up aeration equipment in management, and once there is a lack of oxygen, it will be replenished immediately. Secondly, it is necessary to often catch and sell the adult fish that have reached the food standard in a timely manner, and the individuals with obvious differences will be selected for breeding in separate ponds.