Artificial Propagation
(I) Parent selection and cultivation
The source of broodstock: Broodstock comes from the whole artificially-breeded, sexually mature sweetfish "Zhejing No. 1" that has been selected by the group 4 times, and the traits should be consistent with the above-mentioned related species characteristics.
The choice of broodstock: Select disease-free, healthy individuals as broodstock. The female's abdomen is enlarged and the amount of eggs is high. The weight is more than 150 grams. The male has a body weight of more than 100 grams. The abdomen has a white, thick semen out of the abdomen. The ratio of male to female is 2:1.5.
Bred broodstock cultivation: the breeding density of broodstock ponds ranges from 10 to 15 tails per square meter. During the broodstock breeding period, the compound feed supplemented with seaweed powdered ayu is generally fed, and the amount fed is 2% to 3% of the fish body weight. Uninterrupted feeding of VE and carotene.
The temperature of the broodstock culture pond should be controlled within 25°C. The amount of water changed depends on the water quality in the pool, generally 20% to 50%. The water to be exchanged is better with well water and stream water, keeping the dissolved oxygen above 5 mg/l. Keep water fresh and change water twice a day. Clean the bottom of the pool 2 times a day.
(II) Artificial propagation
Artificial egg-squeezing insemination: During the prosperous period of ayu fish (usually from mid-October to mid-December), with the cold air southward, in the case of temperature drop of 2 °C ~ 3 °C (can also be artificial cooling) can promote part A broodstock with a better gonad maturation ovulates on its own, but the eggs cannot be produced in vitro. Over time, they become over-matured and lose their ability to fertilize. Therefore, it is very important to have a proper manual squeezing time. Normally, dry fertilization of broodstock that has ovulated in the broodstock cultivation pool is selected every 2 days to obtain higher fertilization rate and hatching rate.
The broodstock capable of artificially squeezing the eggs must be evaluated for oocyte maturation. Identification method is: light pressure fish abdomen flow of eggs, eggs were pale orange, translucent crystal, egg round and uniform size, small and more oil balls, distributed evenly, this egg has basically mature, can be dry artificial insemination. Use a dry towel to dry the water on the body surface of the female fish and artificially squeeze the egg into the white porcelain bowl. Then squeeze the male semen (2:1.5 for male to female ratio) and mix gently with the feather for 1 minute to 2 minutes to make the sperm. The eggs are mixed well, and then the fertilized eggs are evenly attached to a clean brown tablet or a special oviposition device, with an egg density of 10 to 15/cm2. Avoid direct sunlight during artificial insemination.
Artificial hatching: The hatchery must be thoroughly inspected and tried before the artificial egg is inseminated. If it does not meet the requirements, it shall be promptly repaired. In particular, the water inlet and outlet systems, water flow conditions, influent water sources, whether the influent filter meshes are in good condition, and whether the required tools are available, etc., and the relevant tools and facilities are cleaned or disinfected before use.
Hundreds of fertilized eggs artificially inseminated with broodstock are attached to the brown chips. Then hundreds of eggs attached to the broodstock are floated together in a hatchery (or cage) with small bamboo rods, or the brown eggs attached are tied On the ropes in the wall of the hatchery (or cage), fully hatch, change water or hatch. Every 3 days (0.05 to 0.1) 10-6 copper sulfate bath or high salt water soaked brown eggs for 2 hours to damage the fish eggs or hatch larvae.
After the eyes of the fertilized eggs begin to grow, they are gradually salted on the day before the film is released, and are converted into seawater three days after the fish is released from the membrane. The increase in seawater salinity is 6-8 per day. Control of environmental conditions during incubation: water temperature 15 °C ~ 22 °C, pH 7.0 ~ 8.2, salinity 0 ~ 9, dissolved oxygen> 5 mg / liter.
(three) seed cultivation
Nursery ponds and utensils disinfection: The nursery ponds must be strictly disinfected before use. They can be disinfected with (100-200)10-6 bleach for one day and then (50-100) 10-6 potassium permanganate for half an hour. Wash the basin after disinfection. Nursery tools also have to be disinfected.
Cultivation density and aeration adjustment: larvae have a seedling density of 20,000 to 100,000 tails per cubic metre; larvae grow to 1.5 to 3.0 centimetres in size, and are conditionally separable, with a density of 0.5 to 10,000 tails/. Cubic meters; full-length 3 cm or more, control density of 0.2 to 0.5 million / cubic meter. At the initial stage of fish culture, the water surface is in the form of microwaves. With the growth and development of the fry, the amount of aeration is adjusted in time to approximate boiling.
Environmental factor control: The sedimentation, sand filtration of the seedlings use non-polluting natural seawater with a salinity of 10-30. The incubation water temperature is controlled between 15°C and 25°C, with 18°C ​​to 20°C being the most suitable. Since sweet fish are more sensitive to light than other fish, light control of the initial larval fish should be 2000 lux to 3000 lux, avoiding direct light. The larvae, 50 days to 120 days after hatching, are most sensitive to light. When juvenile fish weight more than 1g more than 4 months after hatching, they can grow normally under direct light.
(IV) Training Management
Sewage and water exchange: 10 days after the opening of the fry, suction is started, and every 2 days to 3 days, one day, and once every 30 days, one day. In the early stage of nursery, the addition of water is the main factor. After the fish is released from the membrane, the water changes from the first 10 days to 1/2 times, 1/6 to 1/3 each time. The water change time is 7:00 and 18:00.
Feed feeding: The rotifers were fed within 80 days after hatching, and the feed amount was 400 to 500/day per day, and 2 to 3 shots per day. Generally changing the water after feeding can reduce the loss of rotifers. Before the rotifers were fed, they were incubated for 12 hours with P. tricornutum. Supplementary egg yolk can be used when there is a shortage of rotifers. The Artemia nauplii was fed 15 days to 20 days after opening and fed 3 times a day to maintain aquaponic bodies of 3 to 4/500 ml. Before the feeding, it is necessary to strengthen the nutrition with marine fish oil for 24 hours. In conditional units, when Artemia nauplii is fed for one week, it can be gradually added to small live copepods, gradually feeding live copepods. 1 to 2 times a day to maintain live copepods in the water. If chilled copepods (frozen not) are fed, they are fed once every 1 hour to 3 hours, and the dosage is 2g-10g/m2 each time. The whole pool is scattered, and when the fry is more than 2.5 cm in length, it gradually acclimates to the side of the designated feeding. About 7 days to 14 days after hatching, feed pellets were started. The microfeed corresponding to the size of the juvenile larvae was fed at 3% to 6% of the body weight of the fish and fed 2 to 4 times daily. Conditioned feeding units of live copepods were only domesticated to feed pellet feeds 1 week to 2 weeks before emergence.
Disease prevention and treatment: 1 day before the fish fry with an allicin spilled once, until the fish out of the film to continue to spit garlic disease prevention, dosage reference manual.
Fish hatching: When fish fry are raised to a total length of 1.5 cm to 2 cm, the seedlings are divided into different groups. The fry used for seed production is selected among different seedlings in different artificial insemination batches but on the same day, and the selected fry mixes are selected. Continue to nurture.
(e) Desalination, discharge and transportation of fry
Freshwater domestication: Juveniles begin to acclimate when they grow to an average of 0.5 g or more. Gradually, the first week will gradually reduce the specific gravity to 1.010, and then slowly fade to 1.002 within a week.
Out of the pool: When the body up to 4.5 cm to 6 cm or more can go out of the pool. One week before leaving the pond, the fry should be trained. Stop bait 12 hours before leaving the pool.
(3) Transportation: It is generally transported by an oxygen-filled water pump or a live bucket. For short-distance transport, fry weighing about 1200/kg can be transported from 50 kg to 100 kg per cubic meter of water; The specific method is: in advance, the water in the living water tank (bucket) is cooled down to 10° C. to 12° C. with crushed ice, and pure oxygen is filled in the fry, so that the water surface is in the form of micro-bubbles. After about 12 hours of long-distance transportation, the survival rate can reach 95% or more. During the transportation process, the amount of inflation must be observed at any time. If the aeration rate is too high, it is easy for the fish to become poisoned by oxygen and the air bubble disease die. If the aeration rate is too low, the fish fry easily die due to lack of oxygen.
The fragrant fish seedlings can also be transported using nylon bag oxygenation and cooling. The packaging also generally uses a 50 cm-70 cm double nylon bag, which contains 5 kg of water at 8°C to 10°C. The total length of 5 cm or so of fry is 300 to 800 tails per bag; then the air in the bag is filled and filled with oxygen. Use rubber bands to tie the bag and put it into the carton. Since the temperature is not high during the months of transport in January and March, the temperature of the water at around 8°C is generally maintained in the box without adding ice. This packaging and transportation of about 8 hours, the survival rate of up to 70%.
Healthy breeding
(I) Main breeding methods and supporting technologies
There are two types of auspicious fish “Zhejing No. 1†from the seed culture to the commercial fish specification. There are two kinds of suitable fish farming conditions: (1) The area with suitable breeding water (groundwater or stream water) adopts factory farming. (2) Reservoirs with appropriate water quality and water temperature, and cage culture in rivers. At present, cement tanks are mainly used for factory breeding in China.
Seed stocking: General spring stocking, water temperature above 14 °C. Fish species require a total length of 4.5 cm or more, healthy and lively, of good quality, disease-free, non-injury, parasite-free, and undistorted. The density of fish species at the beginning of stocking can be higher, from 200 to 300/m3. With the growth of sweetfish, it is gradually divided into groups. The density of late fish is 50 to 150/m3. Equipment and other specific determination.
Feed and feeding: The feed is artificially mixed pellet feed, according to the specifications of the fish feed pellets of different specifications. After the seedlings are released, they are domesticated and fed 5 to 6 times a day to start baiting in the whole pond, but the amount is not much, the fish can eat it, and then the feeding area is gradually reduced, and the sweet fish are induced to feed near the intake. After successful domestication in a few days, the bait field was fixed near the inlet. After the fish weighed more than 5 grams, it was changed to 1 shot each morning and evening. The feeding method is to slowly cast and cast while eating, and the amount of feeding is 5% to 10% of the fish body weight. Daily feeding control should be done in two seven-points, that is, 70% of the fish that satisfies the full-fledged, full-fledged fish should be full of seven points in order to reduce the feed coefficient and reduce feed costs.
Daily management: Change the water 1 to 2 times a day during the cultivation period, changing 30% to 50% each time, depending on the water quality. Conditional water culture can be carried out, and the breeding density can be appropriately increased in this breeding mode. The cleaning is usually carried out when changing the water. During the cultivation, it is necessary to ensure that the dissolved oxygen is sufficient and that the oxygen is increased by 1 to 2 times a day. Generally, oxygen is increased once a day and oxygenation time is 2 hours. In the afternoon, it depends on the weather. When the weather is hot, increase oxygen continuously. In addition, fish should be observed every day for growth, feeding, presence of floating heads, dead fish, etc. If problems are found, the cause should be identified in a timely manner and appropriate measures must be taken to resolve them. Do a good job of daily management records, generally measuring growth once a month, measuring 30 to 50 each time, to understand the growth of fish.
Delayed spawning: As a result of the development of the gonadal after the breeding season in autumn and the marriage color, the value of the commodity will be reduced and it will die after reproduction. To increase the value of the commodity and increase the sales time, the method of increasing the illumination time can be adopted to delay the maturation and spawning. . Generally, a 200-watt energy-saving lamp or a high-pressure mercury lamp can be mounted on a 300-square-meter aquarium rearing pond so that the surface illumination of the pool water reaches 125 lux-340 lux. From August to mid-November, the daily illumination time (including sunshine) can be based on The planned sales time is controlled from 18 hours to 24 hours.
(B) Disease Prevention
The disease prevention and control of sweetfish always adheres to the principle of prevention and supplementation.
Fish ponds and tools should be thoroughly disinfected: Before the stocking, the culture ponds and various tools should be cleaned and disinfected. Generally, quicklime (concentration 20010-6) or bleaching powder concentration (30-40) 10-6 should be soaked and splashed to eliminate Various pathogens.
The purchased seedlings should be disinfected in the pool: the purchased agarics “Zhejing 1†seedlings should be disinfected and then disinfected. Generally, penicillin and streptomycin are used at a concentration of (8 to 10) 10-6, or soaked in water with a salinity of 5 to 8 for 15 minutes to 20 minutes, and a 1010 to 6 potassium permanganate solution may be used for 10 minutes.
The breeding density should be reasonable: reasonable control of density, timely culture, and consistent specifications are one of the important measures to prevent aphid disease from occurring. If the density is too high, sweet fish is prone to lack of oxygen and floating heads, and the disease will be transmitted. However, if the density is too low, the breeding resources will be wasted. According to the current state of the art, the density of fresh water (1 g to 2.5 g/tail) is 360 to 380 per square meter under the aeration conditions of flowing water, and the density is adjusted to 200 when reaching about 15 g/tail after 20 days. Tail ~ 240/m2; density is adjusted to 150 to 180/m2 for about 25 g/tail after breeding for 20 days, and to 80 for two months or more after reaching 40 g/to tail. ~ 120 tails/square meter. Based on this, to a certain specification, it is necessary to carry out the division of support in time. At each time of division, fish of different sizes are bred to pools of different densities. Individuals have lower density and individuals have higher densities, and the fish size of the same pool must be the same.
Control water quality: Contaminated water must not enter the pool. In the aquaculture process, the water quality must be controlled from beginning to end. The physical and chemical environment for normal growth of ayu is: about pH 7.6, dissolved oxygen > 4 mg/l, ammonia nitrogen
Feed quality should be high: Feeding high quality feed is the key to improving the disease resistance and growth rate of ayu. At present, the feed for sweetfish is a special pellet feed for sweet fish. The principle of feeding shall be determined in four stages (qualitative, quantitative, timing, and orientation). The amount of feeding must be determined in three respects (active feeding of fish, weather, and water quality). When the water temperature exceeds 28°C, the feeding amount should be reduced.
To clear the pathogens in time: alternately use garlic (5kg/ton feed), Chinese herbal medicine hepatobiliary (3kg/ton feedstuff) to feed each month for 3 consecutive days; alternate use of povidone every month. Iodine ((0.2-0.5)10-6), quicklime ((1.5 - 3)10-6) was splashed in the whole pond for 3 consecutive days. The above technical measures have a good effect on the control and elimination of pathogens.
Operation to prevent damage: avocados are irritable and have a strong activity. When catching, clearing the pond, grading operations in the cage, handling, etc., the fish is easily injured. The bacteria or parasites already existing in the water are You will gain the opportunity to invade the fish and cause the fish to get sick or die. Therefore, the fish should be domesticated when clearing the fish, and then carry out the water operation to disinfect the infected sweetfish to salt water with a salinity of 5-8, or to use (0.1-0.3) 10-6 10% povidone iodine solution. Perform routine disinfection to heal wounds, restore strength, prevent fish injuries and become infected.
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