A Detailed Guide to the Latest Scientific Rainbow Trout Farming Techniques
In some tourist areas of Beijing, rainbow trout is a culinary highlight. Because the young fish is tender and tasty and the production cycle is short, rainbow trout can generally be sold at around one jin. How is this popular rainbow trout farmed? Follow along with the editor below to learn about rainbow trout.
The Latest Scientific Rainbow Trout Farming Techniques
1. Stocking density. To achieve high yields, an adequate amount of fingerlings must be stocked. Usually, over the course of a one-year growing period, the annual production is about 3.5-5 times the stocking amount. Under permissible conditions, stocking amount and production amount are directly proportional, so to achieve the planned annual output, the stocking amount must reach 20-30% of the production target.
2. Feed. The main feeds for raising adult fish include imported fishmeal, domestic fishmeal, meat-and-bone meal, meat meal, blood meal, yeast powder, brewer's yeast, soybean cake, soybeans, soybean meal, wheat bran, cornmeal, flour by-products, plus added vitamins and minerals, fish oil, soybean oil, etc. In the feed, the crude protein content is about 43%, crude fat about 13%, crude ash 6-12%, crude fiber 2-5%, nitrogen-free extract 20-25%, carbohydrates 20-30%, phosphorus 0.8% or more, calcium 0.2-0.25%, magnesium 0.1%, sodium chloride 1-2%. The metabolizable energy in the feed should be greater than 300 kcal/100 g.
Feed ingredients must be guaranteed to be of good quality. Moldy or spoiled feed must never be used.
3. Management
(1) Water management and control. Water used for trout farming must be clean and pollution-free, with a water renewal rate of 10-15. The optimal growth temperature for raising adult fish is 12-18°C. Year-round water temperature should preferably not be lower than 10°C and at most not exceed 22°C. Dissolved oxygen in the water should preferably be above 9 mg/L, and the minimum dissolved oxygen in the pond water should not be lower than 5 mg/L.
(2) Aeration. To obtain the greatest possible production under a limited water supply, aeration is needed. There are two aeration methods: one is using the natural drop of inflowing water, i.e. cascade aeration. The other method is to use aerators to add oxygen. Aerators used include paddle-wheel type, YL impeller type, turbine type, spray type, waterwheel type, etc.
(3) Grading. In the same pond, obvious differences in growth appear among the fish. This is a common phenomenon. If fish that have reached market size can be sold promptly or stocked separately through timely grading, this benefits the growth of smaller fish. Adult fish can be graded using a cross-bar grader as wide as the fish pond.
(4) Feeding. The hand-scattering method is used; large-scale producers use automatic feeders. Feeding frequency is generally twice a day. Feeding must be rationed to prevent the fish from overeating; generally, about 80% satiation is sufficient. When the fish are observed to grab food less aggressively and some fish leave the group and swim away, feeding can be stopped. Refer to Table 1 for the feeding amount. Feeding should be even, so that as many fish as possible can get enough feed, and care should be taken to reduce feed waste.
(5) Fish disease prevention and control. Fish diseases should be prevented first. If effective preventive measures are taken before the fish are infected, fish diseases can be eliminated or reduced and losses lowered. Once a fish disease is discovered, some losses are unavoidable, so fish diseases should be detected early and treated promptly.
Common Types of Rainbow Trout Diseases
Viral diseases: IPN, IHN, VHS. Bacterial diseases include furunculosis, vibriosis, gill disease, kidney disease, intestinal diseases, etc. Fish diseases caused by fungi are mainly saprolegniasis. Diseases caused by parasites include: white spot disease, Ichthyophthirius, Gyrodactylus, hookworm, fish lice, etc. There are also nutritional ones: hepatic steatosis and vitamin deficiency.
Methods for treating fish diseases use oral medication: that is, mixing the drug into the feed to make medicated feed and feeding it, and external disinfectants: that is, methods such as stopping the water flow, semi-flowing water, or bath disinfection.
Drugs for Treating Rainbow Trout
Furazolidone, chloramphenicol, and sulfonamide drugs mixed into medicated bait or used as medicated baths. For medicated bait, add 0.1 g of furan agent per kilogram of feed, and add 25-50 mg of chloramphenicol per kilogram of fish body weight. For bath disinfection, malachite green at 2 ppm with the water flow stopped for 40 minutes; copper sulfate at a concentration of 1/2000 for a 30-second bath; formalin at 1/4000 for a 60-minute bath; trichlorfon at 50 ppm for 40 minutes. When making medicated bait and carrying out disinfection, be especially careful. An insufficient dose has no effect, while an overdose can easily create the danger of killing fish, so weighing must be accurate and additions must strictly follow the instructions. When using disinfectants, the water volume must be measured accurately and the timing controlled well, to avoid unnecessary losses.
Rainbow Trout Habitat Environment
Rainbow trout usually inhabit fresh water and like to live in cold water. 10-16°C is the most suitable; 16-23°C reduces their desire and ability to reproduce or prey; above 23°C it is fatal. Some species swim into the sea during the breeding season. Trout and salmon belong to the same order and family and have a close kinship. Many places attach great importance to artificial propagation and rearing of trout. The mouth is terminal, with a projecting mouth cleft in an arc shape. The lips are thick, and there are 2 pairs of indistinct short barbels on both sides of the upper jaw, with a blunt snout. Trout mainly belong to two genera, Oncorhynchus and Salvelinus. The genus Oncorhynchus includes salmon and several kinds of trout, and the genus Salvelinus includes several kinds of trout that can also be called char.
The main difference between these two genera of trout lies in their body color and the different shapes of the vomer and teeth above the mouth. Trout of the genus Salvelinus have red or milky-white spots on a relatively dark skin color. The vomer of char is boat-shaped rather than straight.
Trout of the genus Oncorhynchus have a relatively lighter skin color, with red or black spots on it, and their teeth are relatively sparse. Trout spawn in spring and autumn; the female digs a hole in the gravel layer at the bottom of the river and then lays her eggs in the hole. Those trout that inhabit the sea also return to inland rivers to spawn at this time. The eggs hatch in about 2-3 months. After the newly hatched fry leave the hole, they rely on plankton for food. They live in rivers and lakes, generally inhabiting slower-flowing water. In China, apart from the northwest and southwest, they are distributed in rivers and lakes across the north and south.
Rainbow trout is a cold-water fish species and is one of the most widely farmed fish in the world. Due to high yields and a broad market, its economic value is also increasing, and rainbow trout is also the most suitable for artificial farming. Farming techniques are now getting better and better, so rainbow trout farming is developing rapidly, and the farming area and output are also increasing year by year.