Breeding conditions of Henan triploid rainbow trout
Li Hui
With the improvement of people's living standards, high-quality fish is becoming more and more popular. Due to the rapid growth rate, large individual size, good meat quality and high population yield of triploid rainbow trout, many cold-water fish farms have begun to cultivate triploid rainbow trout.
The rainbow trout with three sets of chromosomes formed by using physical and chemical means to prevent the second meiosis of the fertilized egg and then inhibit the discharge of the second polar body is called triploid rainbow trout. Triploid rainbow trout compared with ordinary rainbow trout, because the body contains three sets of chromosomes can not be meiosis, so can not produce sperm and eggs, there is no gonadal development phenomenon, such a way of reproduction can avoid the gonadal development stage and spawning season due to energy transfer and marriage color and lead to a series of influencing factors such as the decline in fish meat quality, so it has the characteristics of fast growth, good meat quality, etc., is the preferred fish for making salmon sashimi, high economic value, and has become a popular high-quality commercial fish in the market.
1 Basic conditions for the cultivation of triploid rainbow trout
1.1 Requirements for water temperature
Rainbow trout is a typical bottom cold-water fish, triploid rainbow trout in the breeding process of water temperature requirements are higher, the maximum growth limit temperature range of adult fish is 0 ~ 30 °C, of which the suitable growth temperature range of 12 ~ 20 °C, especially in the range of 16 ~ 18 °C grows most rapidly. When the water temperature is lower than 8 ° C, the fish body metabolism level is low, the feeding becomes less, or does not feed, the growth rate becomes very slow; at less than 4 ° C, the fish do not feed and no longer grow. Water temperature above 20 ° C, loss of appetite; above 22 ° C, feeding stops, activity slows down; at 24 ° C, it will begin to die; above 27 ° C, it will die in a short time. Therefore, in the daily management process, when the water temperature is lower than 12 ° C or higher than 18 ° C, try to increase the amount of water flowing, assist in oxygenation, and reduce feeding or no feeding feed.
1.2 Requirements for flowing water
Due to the large size of the triploid rainbow trout, a richer amount of water is required during the culture process, so the cultivation of triploid rainbow trout must adopt the method of flow-through culture, which is different from the cultivation of other freshwater fish. The most suitable flow rate ranges for cultured triploid rainbow trout in the aquatic environment are greater than 2 cm/s and less than 30 cm/s. The larger the flow, the better, the greater the stimulation of the water flow, the more the normal movement of the fish body, which is beneficial to health. It can also promote appetite, increase food intake, and accelerate growth. The appropriate flow rate and large flow rate can not only continuously supply fresh, high dissolved oxygen aquaculture water, meet the harsh oxygen demand of triploid rainbow trout, but also discharge the excrement of fish feces and other solid wastes from the aquaculture pond with the water flow.
1.3 Requirements for dissolved oxygen
In its natural environment, the triploid rainbow trout prefers to inhabit mountain streams with clear water, gravel bottom and abundant dissolved oxygen. The dissolved oxygen content in the water suitable for the cultivation of triploid rainbow trout ranges from 6 to 10 mg/L. Within this range, fish feed vigorously, grow fast, have fewer or no diseases. When the dissolved oxygen content is less than 5 mg/L, it causes an increase in respiratory rate and the fish breathe heavily on the surface of the water. When the dissolved oxygen in the water is less than 4.3 mg/L, the fish will gather in the water inlet, the skin on the head will become lighter and yellow, the breath will be short, and death will occur for a long time. When the dissolved oxygen content in water is less than 3 mg/L, it can cause a large number of deaths. The dissolved oxygen of pond water bodies for the cultivation of triploid rainbow trout is generally about 8 mg/L, which can be improved by reducing the culture density, increasing the amount of water and assisting oxygenation. Dissolved oxygen in water 3 mg/L is the lethal point of summer culture of triploid rainbow trout.
1.4 Other WQT requirements
Other appropriate WQOs are listed in the table below, as detailed in Table 1.
Table 1 Appropriate water quality indicators for the cultivation of triploid rainbow trout
2 Breeding site selection table
The cultivation of triploid rainbow trout is environmentally demanding, and site selection before the construction of the farm is crucial. An environmentally qualified farm will directly affect the level of aquaculture production after the establishment of the farm, as well as the production efficiency and economic benefits.
2.1 Water sources
It is necessary to have cold water resources, the water body should be clear and transparent, not turbid, no pollution, to maintain sufficient flow all year round, and the change in water temperature should not be too large. Usually, mountain stream water is the preferred breeding water for the cultivation of triploid rainbow trout, and the bottom drainage of deep-water reservoirs and spring water in ravines can also be used as aquaculture water. The high-quality water environment produces high-quality triploid rainbow trout.
2.2 Water temperature
The ideal water for the cultivation of triploid rainbow trout is the annual water temperature change within 5 to 20 °C, and the average annual water temperature is 8 ~l5 °C, which can be used for annual feeding. Other breeding conditions are suitable for seasonal rearing, such as mountain streams and streams in alpine areas and reservoir discharge water, which may freeze in winter; in southern China, due to the hot summer, the water temperature often climbs to more than 20 °C.
2.3 Water Flow
The larger the amount of water, the better, when building the site, it is necessary to carry out scientific planning and design according to the annual amount of water, consider the maximum water flow of the year and the minimum water flow when the water is most scarce, and prepare the response plan for flood disasters and little rain and drought. The amount of water directly determines the annual production of the cultured triploid rainbow trout.
2.4 Dissolved oxygen
In the case of the same amount of water injection, the dissolved oxygen content is a key factor in limiting feeding. There are many ways to improve dissolved oxygen, if you encounter a low oxygen content of water, you must take measures such as auxiliary microporous oxygenation or aerator mechanical oxygenation.
2.5 Other Conditions
The choice of triploid rainbow trout breeding site also requires attention to other conditions such as site traffic and power supply. Therefore, if you want to breed triploid rainbow trout, you need to do a good job in the overall planning and scientific survey design of the farm, and at the same time, you must conduct a thorough investigation of the environmental conditions such as water temperature and water flow around the selection point, and record the numerical range in time.
3 Construction of triploid rainbow trout ponds
3.1 Species and size of culture ponds
The types of ponds are hatchery ponds, juvenile fish farming ponds, adult fish farming ponds and broodstock breeding ponds for breeding fry. The more suitable area and water depth in production are shown in Table 2.
The actual depth of the fish pond should be 30 to 50 cm above the water surface.
Table 2 Area and water depth of cultured triploid rainbow trout ponds
3.2 Shape and structure of culture ponds
The shape of the cultured triploid rainbow trout pond is round, oval, rectangular and so on. No matter what the shape should be designed and built according to local conditions, it is necessary to consider the convenience of management, easy fishing and low cost, but also to facilitate the exchange of water bodies, smooth flow of water, no dead ends. The structure of the breeding pond can be used whether it is a brick-concrete structure or a cement frame, and it should be planned and built according to the environment of the site after in-depth research.
3.3 Design of the inlet
The cultivation of triploid rainbow trout should ensure the amount of water, so the setting of the water injection port and drainage port of the breeding pond is very important, and the water injection port should ensure that the pond water is unimpeded and prevent the escape of the fish, so special attention should be paid. For a culture pond 4 m wide, two inlets are usually required, each with a width of 1. 2 m, 1.0 m apart between the two inlets. The water injection port should have two layers of fences to prevent fish from escaping from the water.
3.4 Design of drains
The drain is set up with 2 or 3 layers, if it is a surface drainage, the first layer is set as an anti-escape gate, and the second layer is set as a sluice plate to control the water level. If it is the bottom layer of drainage, the first layer is set as a gate to prevent escape, the second layer is set to control the bottom drainage gate, and the third layer is set to control the water level.
3.5 Anterior and posterior slopes at the bottom of the pool
The breeding pond should maintain the slope before and after, and the conditions of the slope reduction should be 0.8% of the adult fish pond and 0.2% of the juvenile fish pond. At the same time, the fish pond should strictly prevent water leakage and ensure that the injected water can be fully and effectively utilized.
3.6 Suitable area for the construction of fish ponds on farms
The farm area of triploid rainbow trout is usually calculated based on the amount of water injected and the rate of exchange of pond water. The exchange rate of pool water is to indicate the number of times the pool water is exchanged per hour, that is:
Exchange rate = water injection (m3)/h÷ total fish pond capacity (m3)
Fish pond area (m2) = [water injection (m3)/h÷ average depth of fish pond (m)] ÷ water exchange rate
3.7 Calculation of the number of fish ponds built
When the area of the fish pond built is determined, the number of fish ponds built is calculated. The number of fish ponds can be determined according to the flow rate of the pond water. Our common triploid rainbow trout culture ponds have a flow rate of 2 to 5 cm/s. Press the formula to first find the width of the fish pond, and then calculate the required number of fish ponds based on the width of the fish pond.
Planned pool width = ÷ of water injection per second (predetermined water depth× planned flow rate per second).
For example, the total area of the aquaculture pond is 300 m2, and the length of the pond is 75 m when the design width is 4 m. Two fish ponds with a width of 4 m and a length of 37.5 m can be built.
4 Conclusion
Triploid rainbow trout due to the large individual, long breeding cycle, strict requirements on water temperature, dissolved oxygen and water flow, so the choice of breeding triploid rainbow trout must be careful and accurate investigation of cold water resources. When building a farm, it is necessary to carry out scientific planning according to the natural conditions and the purpose of farming.