First, the introduction of ovum eggs and incubation
1. Introduction and transportation of ovary eggs On March 12, 2004, 80,000 floating Atlantic salmon eggs were imported from Washington, USA, and transported to the hatchery after nearly 50 hours of transportation by means of low temperature air transportation. With 7,524 pellets, the survival rate was 90.6%. The accumulated temperature of the ovum reaching the hatchery was 364Â°C, and the transportation effect was good.
2. Incubation of the ophthalmic eggs The oviducts are transported to the hatchery site, first open the package so that the temperature gradually transitions to the incubation temperature, then use 100ppm iodine solution for 15 minutes to 20 minutes, and then wash the residual drug with water at the same temperature, The dead eggs are placed in a temporary appliance and finally placed in an incubator for hatching (including isolation and quarantine).
Incubation adopts a flowing water hatching method. The incubating water uses pure, non-polluting groundwater. The incubating water temperature is 8Â° C. to 10Â° C., the water flow rate is controlled at 8 L/min to 12 L/min, the dissolved oxygen in the water is controlled at 8 mg/L, and the pH is 7 Between ~8. The hatchery is kept dark and the hatchery is disinfected daily with potassium permanganate. During the incubation process, some eggs will die and the color of the dead eggs will be lighter than the normal orange color, or even become white. Each morning and evening, the eggs are picked one at a time to prevent the dead eggs from damaging the water quality and affecting the hatching rate. During the normal incubation process, the number of operations should be minimized to avoid disturbing the ovum.
Second, larval rearing
1. Pre-cultivation of larvae The larvae fall out of the egg tray of the incubator and fall into the sink after breaking the membrane. During this period, the larvae rely on the yolk to provide the nutrients needed for growth, and their activity is poor. Generally, the group prefers to sit on the bottom of the sink. During this period, it is still necessary to maintain a dark environment until the yolks of the larvae are consumed and float up to feed. The incubation water temperature during this period was 10Â°C-14Â°C, the water flow rate was controlled at 10L/min to 15L/min, the dissolved oxygen was 8mg/L, and the pH was between 7-8. Every morning and evening, the dead fish are sorted out once and the bottom of the sink is brushed to ensure that the larvae have a good living environment and improve the survival rate. The larvae in this period are extremely sensitive to light and sound, so in addition to normal operations, they should also reduce their fright, so as to avoid unnecessary death.
2. Open mouth food intake is the most important stage in the breeding process of Atlantic salmon, and it is also the highest stage of mortality. The timing of opening requires some experience, too early or too late will affect the effect of open food intake, and directly determine The success or failure of the entire nursery stage. The opening feed we use is Canadian imported Atlantic opening special feed. After larval opening, the water temperature is 12 Â°C ~ 14 Â°C, the water flow is increased to 18L/min ~ 20L/min, the dissolved oxygen is controlled above 8mg/L, and the pH is between 7 ~ 8. During this period, because there will be a large amount of residual baits and feces in the water, the flow rate of water needs to be increased. The water exchange time of the water body should be completely exchanged every 0.5 hours. During this period, larvae have increased respiration and increased oxygen consumption. Pure oxygen should be added to the water to ensure the dissolved oxygen content in the water. In order to ensure that the larvae have a good vision for feeding, this period begins to give light, the light intensity is around 1000 lux, the lighting time should be guaranteed to be not less than 18 hours a day, and the feeding of feed should follow a small number of multiple principles, generally in accordance with the fish The body weight of 5% of the feeding, but the specific amount of feeding should be based on the larvae dietary intake, the previous period should ensure that the amount of feed is sufficient.
3. Late larval rearing When all the larvae feed, they enter the late larval rearing stage and the fish body weight reaches about 1.0 g. During this period, the water temperature is required to be between 14Â°C and 16Â°C, the water flow rate is 18L/min to 20L/min, the dissolved oxygen is controlled at more than 8mg/L, and the pH is between 7-8. During the cultivation process, siphon the bottom baits, feces and dead fish once a day to ensure a good water quality environment. The principle of lightness, slowness, and fineness should be followed during operation, and damage to the fish should not be caused.
Third, fry cultivation
1. Sorting of fry When fish body weight reaches 1.0g, the fry should be sorted in time. During the sorting process, special sieves were used to eliminate small fish weighing less than 0.5 g, and the sorted fish fry were transferred to deeper sinks for cultivation at a stocking density of 15 kg/m3. Timely sorting of fry is conducive to the rapid growth of fish, so that the size and size of the fry will not appear.
2. Cultivate and manage the fry cultivation stage, the suitable water temperature range is 16Â°Cï½ž18Â°C, water flow speed is 20L/minï½ž22L/min, dissolved oxygen is controlled above 7mg/L, pH is between 7ï½ž8, light time is daily At 16 hours, the feed was controlled at 3.5% of body weight. When the body weight of the fish reaches 1.0g, the feed specifications must be changed. The transitional period should follow the principle of gradual and orderly progress. The adaptation time of the fry for 3 days to 5 days should be given, and the ratio should be 1:2, 1:1, 2:1. transition. Similarly, when the body weight of the fish reaches 2.0 g, the feed specifications are changed; when the body weight of the fish reaches 3.0 g or more, the feed having a particle size of 1.2 mm is replaced, and when the body weight of the fish reaches 10 g or more, the feed having a particle size of 1.5 mm is fed. Every day before the lighting is stopped, the residual bait, excrement and dead fish in the sink should be cleaned to ensure a good water quality environment and improve the survival rate of the breeding. During this period, as long as good water quality conditions are ensured, the survival rate of fry can usually reach 95% or more. During this period, the stocking density should be adjusted several times. When the stocking density of the fry in the water reaches 40 kg/m3, the pool should be divided in time. Overfishing density is too high to cause problems such as lack of oxygen in fish fry, excessive ammonia levels in water, and death of fry.
3. Disease control The most common disease of the Atlantic salmon is the disease of the rotting fin. Due to the intense activity of the fish, the fins of the fins usually begin to fester after being sorted by sorting or pooling. Usually the sick fish should be picked. Out, and the use of drugs for medicinal bath treatment, for severe fin fish body but also eliminated in time to avoid cross-infection and affect the growth of normal fish. In addition, common diseases of the Atlantic salmon seedlings during the cultivation stage include rotten roaches, rotten lips, and the like. Under normal circumstances, the fish fry will recover quickly if they are treated in time.
Fourth, seed cultivation results
1. Hatching rate In the water temperature of 8 Â°C ~ 10 Â°C, the ovum eggs hatched after 12 days to 14 days, accumulated temperature reached more than 485 Â°C, to March 24 larvae began to break out of the film, to March 26 After the basic incubation was completed, a total of 3623 dead eggs were selected during the entire incubation process, and the hatching rate was 95%.
The survival rate of larvae in the early stage of larval rearing from the completion of hatching on March 26th to April 16th during fry opening and feeding, there were 564 dead fishes. The dead fish at this stage were mainly deformed fish, and the survival rate was 99.2%.
3. Survival rate of the open-feeding stage Under the appropriate conditions of various water quality indicators, larvae can be consumed after 18 days to 20 days of larvae cultivation, and the larvae should be ready to open when the proportion of floats reaches 20% on April 16th. Feeding and entering normal breeding management. By May 1, all fry were already feeding. The number of fry deaths was 2124 at the end of the entire period, and the survival rate was 96.8%.
4. Survival rate of fry cultivation period From the 1st of May to the 1st of 6 months, we recorded a total of 1,150 dead fish and the survival rate was 98%.
5. The growth rate from May 1st to normal cultivation management until October 1st, fish body weight from 0.259g had grown to 25g, the average monthly weight gain rate was 250%, the growth rate is faster.
V. Analysis and discussion
1. Selection and use of incubators We use the upper layer of the incubator as the egg tray. The bottom of the egg tray has holes that allow the larvae to pass through and the eggs do not pass through. The lower layer is the sink. After the larvae are broken, they can be removed from the egg tray. The holes directly fall into the lower sink to ensure no damage to the larvae. Each incubator can hatch 40,000 to 50,000 eggs. The advantage of this incubator is that it ensures the continuity of hatching and does not require excessive manual operations, which greatly reduces the damage of human factors to newly hatched larvae, and improves hatching efficiency and survival rate of larvae.
2. The technical control of fry open feeding stage choose the best feeding time, the general accumulated temperature reaches 800 Â°C is the theoretical basis, but also according to the specific circumstances. If the larvae have good control during the early period of brooding, the yolk consumption rate of the larvae is balanced, and the larvae are relatively well-developed, which will greatly increase the survival rate of the grazing food. The choice of open feed is crucial. The biggest feature of the Atlantic salmon opening is the direct feeding of artificial compound feeds. It does not require the replacement of fresh live feeds and does not require food conversion. It can greatly improve the survival of the open food intake stage. rate. Because there is no open feed suitable for its nutritional requirements in the country, we have also introduced foreign mature Atlantic Atlantic opening feeds. This can be said that the quality of feed can directly affect the open food intake of larvae. Affects the survival rate and growth rate of the open feeding phase.
3. Control of water quality conditions Atlantic salmon is a kind of swimming fish. Its activity is intense and the physiological metabolism is relatively strong. Therefore, the required water quality conditions are relatively high, mainly because the dissolved oxygen concentration in water cannot be lower than 6.0 mg/L. Nitrogen content can not be higher than 0.01mg/L. The measures we take are on the one hand to increase the flow rate of the water body and ensure that the exchange rate of the water body is once/hour. On the other hand, pure oxygen is supplemented to the pond water in the aquaculture pond, and the most advanced nano-aerobic stone in the country is used to increase the oxygenation efficiency. It reaches 30% to 40%. Good dissolved oxygen conditions and water flow rate control can ensure good water quality, which is a very important factor to improve the survival rate of aquaculture and the growth rate of fry.
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