Characteristics and breeding techniques of salmon

Salmon, also known as salmon or salmon, is a cold-water highly migratory fish. Salmon is one of the most healthy fish in the world because of its delicious meat, good taste and rich nutrition.

I. species and characteristics of salmon

There are more than 30 species of salmon with commercial value in the world, but at present, only 6 species of salmon and 2 species of trout are the most common. there are Pacific salmon, silver salmon, Atlantic salmon, Arctic white spot salmon, golden trout, salmon and colorful trout.

Under natural conditions, salmon like to live in clear and pollution-free waters. The limit temperature of its life is 0 ℃ and 30 ℃, and the optimum temperature for growth is 16-18 ℃. It eats vigorously and grows rapidly in the range of suitable temperature. Less than 8 ℃ or more than 20 ℃, loss of appetite and slow growth. Salmon is a kind of fish that likes countercurrent and oxygen. Abundant water and stimulation of water flow can maintain its good metabolism and promote growth. Therefore, salmon are cultured in running water. The suitable dissolved oxygen content is more than 6 mg / L, and the optimum pH range is 6.5-6.8. It is a widely salty fish, which can not only live in sea water, but also grow in fresh water. Under the condition of artificial feeding, it has gradually changed to omnivorous food, which can ingest artificial compound pellet feed well and can be domesticated intensively.

2. Seedling breeding of salmon

1. Reproduction

There are many species of salmon, but the scale of culture is small. Fish can spawn and reproduce naturally under pond conditions, and generally mature sexually in 2 ~ 3 years. The water temperature of spawning is less than 15 ℃, the suitable water temperature is 4: 13 ℃, and the optimum water temperature is 10: 11 ℃. In the natural environment, mature parent fish often choose the river with clear water quality, current and gravel bottom as the spawning site. Spawning many times, the number of eggs laid each time is 2000-3000 eggs.

① parent fish breeding because the number of eggs and egg diameter of parent fish are usually positively correlated with their body weight, but have nothing to do with age, so the fish with strong physique and weight of more than 0.81kg should be selected as parent fish. Parent fish weighing less than 4 kg lay about 2000 eggs per kg of body weight. The ratio of female to male parent fish is 4 ∶ 1. If 1 million eggs are planned to be produced, the total weight of parent fish should be 700kg. The suitable density of parent fish is 510kg / m2, the water temperature is 413kg / m2, the dissolved oxygen is more than 8mg / L, and the flow rate is 3050L / s.

Full-price compound feed for parent fish breeding, crude protein should not be less than 40%, crude fat should not be higher than 6%, and carbohydrates should not be higher than 12%. Use the following bait formula: crayfish 5%, fish meal 20%, miscellaneous fish 10%, pig blood 5%, feather meal 3%, beer yeast 3%, bean cake 12%, bran 20%, green feed 2%, plus fish multivitamin and vitamin E. When the parent fish are cultivated, the eggs collected are all orange-red high-quality eggs, and the average eye-opening rate and hatching rate are high. Daily feeding of animal feed accounted for 30%-45%, plant feed accounted for 55%-70%. 1-2 months before and after delivery, all can be fed with low-fat animal bait, and the amount of vegetables in winter should be increased to 3% and 5%. The daily feed intake is 2% of the total weight, which should be reduced to about 1% in one month before delivery. The fish pond should be discharged and kept clean in time. One month before delivery, the water flow should be increased appropriately to promote gonadal development and maturity.

In ② artificial insemination, one person holds the head of the fish with both hands, and the other holds the tail handle of the fish obliquely, pointing the head up and abdomen down at the filtering porous egg collection basin (beakers, etc.), using hands along the abdomen to the direction of the reproductive pore, squeezing from top to bottom until most of the eggs are squeezed out. When the weight is less than 2kg, the skilled operator can operate alone. When the eggs are well matured and handled properly, the eggs will flow out smoothly under the squeeze, and the fish can endure the squeeze. When collecting eggs, the water on the surface of the fish should be wiped clean to prevent any water droplets from the surface of the fish from entering the egg basin. The collected eggs need to be washed with isotonic solution (NaCl90.4 g, KCl 2.4 g, CaCl2,2.6 g, dissolve them in 10 liters of water in turn, pH 7, and adjust the temperature to more than 4 ℃) to wash away the yolk substance from the eggs. Artificial insemination is used, that is, for every 10,000 eggs, 10 milliliters of semen are added or squeezed and stirred quickly and evenly for 1 to 2 minutes, so that the eggs are fertilized quickly, and then stand still for 1 hour. Change the water several times, and remove excess sperm and bad eggs, egg skin, blood clots, etc., until the water in the basin is clean and transparent. After the fertilized egg completely absorbs water and expands, it is moved into the incubator to hatch.

During the incubation period, ③ hatching management should avoid light and ventilation to prevent vibration and mechanical stimulation; at the same time, dead eggs are easy to breed water mold, so it is necessary to arrange several egg-picking operations during the hatching process. When the fertilized egg develops to the eye stage, the following matters should be paid attention to: prevent anoxia and asphyxia, the oxygen consumption rate of the eye egg is high, do not put the egg in still water, otherwise it is easy to cause egg asphyxia; control the temperature, the egg hatching and disposal is carried out strictly at 5: 13 ℃; avoid light, the resistance of the egg to light before and after the eye period is the weakest, and the bright light should be avoided; to prevent vibration, the resistance of the eye egg to vibration is enhanced to avoid strong vibration.

two。 Cultivation of juvenile fish

Newly hatched larvae are nourished by absorbing yolk sac. Fish fry up to 50 mm after hatching should use open bait with very small particle size, with a protein content of 45%-50%. This kind of feed is specially used for the opening of fish fry. At 50-150 mm, the feed protein content is about 45%, of which animal protein should not be less than 40%-45%. In the process of feeding, once the water temperature exceeds 20 ℃, cooling measures should be taken. Low water temperatures only affect the growth rate of salmon without danger. If the water temperature is too high, the dissolved oxygen content will decrease, which will directly affect the survival of salmon. The feeding rate is directly related to the body weight, water temperature and feed quality of salmon. At different water temperatures, the feeding rate of salmon with a certain weight should not exceed 10% for dry feed with low water content and 20%-50% for wet feed with high water content. Dry feed should be stored at dry and low temperature, and wet feed should be processed before feeding, otherwise mildew will cause toxicity and cause mass death of salmon.

The most effective way to prevent and cure the disease is to keep the salmon growing environment at the cleanest level, the use of high-quality feed and the use of reasonable management means. All salmon farming utensils and equipment should be kept clean when in use, and operators should clean and disinfect them again after use. Fish ponds should have the function of automatic cleaning. The deposited feces and bait residues will compete with fish for dissolved oxygen and induce the reproduction of harmful bacteria or fungi, which is not conducive to the healthy growth of salmon and should be modified.

III. Salmon culture

At present, intensive running water culture is adopted in salmon culture. The suitable pond area is 80,160 square meters, the stocking density is 1520 tails / square meter, the source of water is cold spring water, the water flow rate is 0.15 cubic meters per second, and the water quality is clear and pollution-free. PH value 6.8, dissolved oxygen 11.5mg / L, water temperature 5.5mg / L 11.5℃. The use of imported adult fish pellet feed can be used until the salmon is on the market, twice a day, should pay attention to the amount of feed, not more than 1% of the fish body weight, otherwise, the fish will get sick. Daily management is mainly bait feeding, water adjustment, fish pond decontamination, injection and drainage management and care. Ensure that the water flow is smooth, clean the pond dirt every half a month, and keep the water quality clean.