Culture technology
Section 1 Selection and setting of breeding sites
1. Selection of breeding site
Farms are places where rainbow trout culture is carried out. In the process of site selection, the purpose of the natural condition survey is to select a series of good ecological environments for rainbow trout to meet the needs of different stages of normal growth, development and reproduction, and at the same time to facilitate production management to improve economic efficiency.
One of the first conditions for the selection of a site is the water source, including the amount of water, the annual water temperature changes and the water quality conditions.
Rainbow trout culture generally adopts the flowing water high-density rearing method, so the size of the water flow limits the scale of the aquaculture water surface. Under normal circumstances, the construction of 600 square meters of aquaculture water surface, the amount of water injected per second is 100 liters to ensure the exchange of water.
Rainbow trout requirements for culture water temperature range from 7 to 20 °C, so it is necessary to understand the indicators of the water temperature measured at the highest and lowest time of the year, the maximum water temperature is more than 22 °C, which poses a threat to the farmed rainbow trout, and below 7 °C, it will cause rainbow trout to have decreased appetite and slow growth. Water quality conditions are an important content, and the quality of water is directly related to the success and failure of rainbow trout aquaculture production.
Dissolved oxygen is generally required to be above 6 mg/L, with rainbow trout growing faster at 9 mg/L; below 4.3 mg/L, the gills of the fish are extensed for a long time and then die, and below 3 mg/L, they will die in large numbers. The color of the water should be clean and transparent, and the rainbow trout likes clean and transparent water, the color is generally less than 30 degrees, and the suspended solids in the water should be less than 15 mg/l. Chemical substances in water should meet the scope of the ministerial standards for fishery water use. In the case where the water source and water environment have the conditions, it is necessary to consider making full use of the terrain to cause a certain amount of water drop and flow rate, so as to achieve self-drainage and self-flow, reduce the power of water lifting, and reduce production costs.
In addition, traffic conditions, power supply and so on should also be considered.
2. The setting of the farm
The setting of farms should be considered according to different natural conditions, economic conditions and different types of culture. For example, comprehensive farms, from broodstock breeding to edible fish grow-out, should be designed to configure a full set of facilities, while farms that are simply engaged in fry production or edible fish production do not have to design and configure edible fish breeding facilities or fingerling breeding facilities.
(1) The type and size of the fish pond In the culture of rainbow trout, the types of fish ponds can be generally divided into fry ponds, fingerling ponds, adult ponds and broodstock ponds according to the purpose of use. In actual production, it can be used alternately as appropriate. The size of the fish pond should be determined according to the actual local situation. Generally, the area of the fry pond is 10 to 30 square meters, the water depth is 20 to 40 cm; the fish fingerling pond area is 50 to 100 square meters, the water depth is 40 to 60 cm; the adult pond area is 100 to 200 square meters, the water depth is 60 to 80 cm; the broodstock pond area is 100 to 300 square meters, and the water depth is 80 to 100 cm. The height of the fish pond should be 20 to 30 cm above the water surface.
(2) The shape of the fish pond Rainbow trout breeding pond has a circle, hexagonal, rectangular, etc., and the rectangular pool is more practical. The length-to-width ratio of fish ponds is generally 1:5 to 8. The general requirement is that the water flow must be smooth, there are no dead ends, and the feeding management is convenient and easy to fish.
Fish ponds are generally built into cement ponds, which are easy to clean and manage, and are suitable for high-density stocking. In the arrangement of fish ponds, the feeding effect of parallel ponds is better than that of tandem pools. If the amount of water is sufficient and the terrain permits, it can all be in the form of parallel pools. However, in order to make full use of the amount of water, the form of fry and fish species ponds is usually used in parallel, and the broodstock ponds and adult fish ponds are connected in tandem. The series form generally does not exceed 3. Fish ponds should have inlet and drainage outlets, and fish traps should be installed. The bottom of the pool generally has a slope of 1/100 to facilitate the cleaning of dirt.
Section 2 Fry cultivation
The first month of feeding on floating fry is the most difficult and technical stage of rainbow trout farming, which focuses first on survival and then growth. Since the size of the fry is larger, the stronger the vitality, and the speed of fry growth will directly affect the future growth, so the growth of the floating fry cannot be ignored.
Newly hatched fry are very tender, dark and afraid of light, slow activity, because of the yolk sac to provide nutrients, at this time there is no need to feed. When the yolk sac absorbs more than 2/3, most of the fry begin to float up foraging, at this time to feed nutrient-rich and easy to digest food, otherwise it is easy to cause black disease and death. At the beginning, egg yolks, water fleas, silk earthworms, etc. can be fed, and livestock liver and fresh fish can also be fed. The bait can be fed with a fine sieve of 0.4 mm mesh or applied to a thin wire mesh and hung in a pond for the fry to feed on their own. It needs to be fed 6 to 8 times a day, and the amount of bait per day is 10% to 12% of the total weight of the fish.
After 20 days of rearing, the general body is 2.5 cm long and weighs 0.2 g, which can be transferred to the fingerling pond for rearing.
Section 3 Fingerling breeding
The stocking density of fry and fingerlings varies according to the size of the fish, the water temperature and the amount of water injected. Fry are usually reared under conditions with slightly lower water temperatures and are less susceptible to disease and have a high survival rate. The average weight reaches 1 g, and it takes about 60 days from the beginning of the meal at 15 °C and about 75 days at 10 °C. After another 20 to 30 days, the weight can reach 2 grams. As the fry grow and swim ability increases, the amount of water can be appropriately increased. Stocking densities and water requirements are shown in Table 6-3.
Table 6-3 Area and water required per 100,000 rainbow trout fry
Fry size (g) Area required (m2) Density (tail/m2) Water injection (tail/m2)
5℃ 10℃ 15℃
1 60 1600 1 2 3
2 80 1200 2 3 6
5 100 100 3 7 14
10 125 800 7 15 26
15 160 625 9 22 39
20 170 588 12 29 52
25 200 500 15 35 62
The smaller the rainbow trout fry, the more protein is needed in their feed and the higher the feed conversion rate. With the growth of seedlings, the content of animal protein such as fishmeal in the feed can be gradually reduced, and the proportion of plant protein can be increased.
The nutritional content of the full-price feed used for seedlings is 40% to 50% crude protein, 4% to 15% crude fat, 1% to 3% crude fiber, 10% to 16% coarse ash, and 8% to 12% water.
Rainbow trout feed is mostly processed into granules or crushed grains, and the amount of bait is adjusted at any time according to the size of the fish body and weather conditions, and the bait rate is shown in Table 6-4.
In the feeding process, due to the different physique and feeding ability of the fry, the growth is inconsistent, and the fish body is large and small, so when the fry grows to 2 grams, it is necessary to carry out screening and separation work. The selected fry are raised separately according to different sizes and sizes to prevent large fish from competing for food and affecting the growth of small fish. Screening can be carried out every 20 to 40 days and the stocking density can be adjusted according to the size of the individual seedlings.
Table 6-4 Daily bait rates of rainbow trout seed (percentage of fish weight by dry feed weight)
Average size of seedlings Average daily water temperature Daily feeding Particle size
Weight (g) Length (cm) 6°C 8°C 10°C 12°C 14°C 16°C Times (mm)
<0.2 <2.5 2.2 2.6 3.0 3.5 4.1 4.7 6 <0.5
0.2～0.5 2.5～3.5 2.1 2.5 2.9 3.4 3.9 4.5 6 0.5～0.9
0.5～2.5 3.5～6 1.9 2.1 2.6 3.0 3.5 4.5 4 0.9～1.5
2.5～12 6～10 1.5 1.7 2.0 2.2 2.6 3.0 3 1.5～2.4
12～32 10～14 1.1 1.3 1.5 1.7 2.0 2.2 2 2.4～3.0
Section 4 Rearing of adult fish
In order to achieve higher trout farming efficiency, it is necessary to strive for maximum production in terms of limited fish pond area and water consumption. To this end, maximum rearing density and good feed efficiency should be maintained regularly in all fish ponds, so that rainbow trout can grow healthily. Since the water supply is mainly the supply of oxygen, and oxygen is related to temperature, so the amount of water, temperature and oxygen are the three major factors that affect the feeding density. The rearing density and water required for rainbow trout are shown in Table 6-5:
Table 6-5 Rearing density and water requirements of rainbow trout
Specification (g) Area required (m2) Density (tail/m2) Water injection (l/s)
5℃ 10℃ 15℃ 20℃
40 266 375 21 47 89 148
50 334 299 23 59 98 185
60 400 250 28 62 117 199
70 435 230 31 73 136 231
80 533 188 36 83 155 265
90 600 167 41 93 176 300
100 665 150 46 104 196 333
150 1000 100 60 132 254 428
200 1330 75 78 154 270 500
Feed is the key to high-density grow-outs. Since the nutrition of fish under intensive culture conditions is completely dependent on the artificial feed ingested, the quality of the feed is key. In order to make the nutrition of the feed meet the needs of fish growth, the protein content in the feed reaches the needs of rainbow trout through scientific cooperation, so that the essential amino acids are balanced and the nutritional value of the protein in the feed is improved.
The nutritional content of rainbow trout fingerlings and full-price feeds for adult fish is 40% to 45% crude protein, 6% to 16% crude fat, 2% to 5% crude fiber, 5% to 13% ash content, and 8% to 12% water content. The daily amount of bait is generally not more than 3% of the total weight of the fish, and the bait is 2 to 3 times a day.
The dissolved oxygen status of pond water is an important indicator of water quality control under intensive maintenance, and when the amount of water is sufficient, a considerable production volume can be obtained without oxygenation. Usually the water injection rate is the best when the feeding efficiency is 10 to 15. The water injection rate can be obtained from the following equation:
Water Injection (l/sec)
Water injection rate = ×1000
Weight of reared fish (kg)
When the water injection rate is too small, indicating that the amount of water is not enough, it is necessary to improve the dissolved oxygen of the pool water by increasing oxygen, so that the dissolved oxygen volume of the drainage part of the pool water is controlled at more than 5 mg/l.