Breeding and enhancement of original species of yellow-covered flounder
Li Xiumei and others
Yellow-covered flounder is a kind of cold-water turbot fish endemic to the Yellow and Bohai Sea regions, with Penglai coastal area as the main production area, and the local name is also known as local raw, ground-born fish, partial-mouthed fish, yellow cover, sand board, small mouth, sand cover. The flounder is flattened and oval, with a small head and a small mouth, with unequal lengths in the clefts on both sides. Both eyes are small and grow on the right side of the head, and the side of the eye is the posterior head, dark brown, scaled, and irregularly mottled. The geographical range of "Penglai DiShengzi" is 120°40'32.25"~121°01'26.23"E and 37°42'39.01"~37°50'43.45"N, which is a specialty of Penglai City, Yantai City, Shandong Province. The cultivation and preservation technology of the original species of yellow-covered flounder is to maintain the original genetic traits of the yellow-covered flounder to achieve the stabilization effect of the traits of the species. It includes original seed breeding technology, spawn incubation technology, seed breeding technology, seed preservation and breeding technology, isolation and protection measures and quality management. The parents cultivated by seed preservation have many excellent traits and show high biological value, which creates greater economic benefits for the breeding and breeding of yellow-covered flounder seedlings. The test has been successful in the national Penglai Huanggai flounder seed farm in Shandong, and the technical points are summarized as follows.
1 Technical conditions
1.1 Production facilities
The original seed farm has 38 000 m2 of factory nursery and breeding workshop, of which 4 000 m2 of seed workshop (effective nursery water body area of 3 200 m2), 1 000 m2 of original breeding workshop, 2 000 m2 of broodstock breeding and breeding workshop, 2 open-air seed preservation ponds, a total of 30 hm 2. All kinds of nursery breeding facilities in the farm area are complete, with a bait breeding workshop of 2 000 m2 and a cold storage (600 t) for bait processing. Water, electricity, gas and heating systems are complete.
1.2 Experimental equipment
1 set of electron microscope camera system, dissecting mirror, surgical scissors and conventional instruments.
2 Original breeding
2.1 Broodstock sources and selection
Wild broodstock in the Penglai Yellow Cover Flounder National Aquatic Germplasm Resources Conservation Area or original broodstock preserved in the original seed farm were collected, and after preliminary screening, individuals with full bodies, normal body color (bright color, no albinism), complete scales and fin membranes, and healthy and disease-free were selected. [Yoshiyama Huayao self-media network debut]
2.2 Intensive rearing of broodstock
2.2.1 Incubation pond requirements The indoor breeding pool is adopted, the shape of the breeding pool is preferably round, the water body is required to be above 25 m3, the water depth is more than 1.2 m, the water source is sufficient and equipped with sufficient water supply and drainage system and inflation equipment.
2.2.2 Strengthen the cultivation conditions The use of natural seawater is purified by sedimentation
After treatment, open circulation water is carried out to cultivate broodstock, and the water quality of the water source meets the requirements of GB 11607, and the water quality of the aquaculture water should meet the requirements of NY 5052. The daily exchange of flowing water was 4 to 6 full amounts/day, the density of broodstock intensive cultivation was 3 to 5 tails/m2, the light intensity was 500 to 800 lx, the water temperature was 10 to 20 °C, the salinity was 29 to 32, the pH value was 7.6 to 8.6, the dissolved oxygen was greater than 5 mg/L, the ammonia nitrogen was less than 0.02 mg/L, and the total number of bacteria was less than 5/mL.
2.2.3 Breeding bait In the cultivation of broodstock, its bait should be based on fresh fish, preferably fish with low fat content and high protein content, such as small yellow croaker, which can also be fed with compound feed, through the intensive feeding of high-quality bait to promote the active feeding of broodstock, in the breeding period, should be fed as early as possible with high protein, highly unsaturated fatty acids, and appropriately add vitamin E, vitamin C and other trace nutrients. Feed has soft pellets and feed fish. The main ingredients of soft pellet feed are powdered compound feed, feed fish and so on. Feed fish should use fresh, frozen, non-deteriorating fish. The compound feed should meet the requirements of NY 5072, the feed should be of a suitable size, feeding 1 to 2 times a day, and the daily feeding amount is 1% to 3% of the body mass of the fish.
2.2.4 Daily management In broodstock breeding, water temperature, salinity, dissolved oxygen, pH and other water quality factors are measured in real time for 24 h per day to ensure the stability of water quality, and the bottom of the pond is thoroughly cleaned once every 5 to 7 days, and the pond is poured once every half a month.
2.3 Spawning and artificial insemination
Insemination is performed by artificial squeezing of the egg stem method. Dry the fish and utensils to prevent water and excrement from mixing in. Then press 1×105 eggs to add 1 to 5 mL of semen, stir quickly and evenly so that the fertilized eggs are in full contact. Then insert a small amount of seawater filtered by sedimentary sand, so that the volume ratio of semen, eggs and water is about 0.5:100:100, continue to stir for 1 minute, then stand for 5 minutes, then add seawater, stand for 10 to 15 minutes, after the egg absorbs water and expands, clean water 1 to 2 times, put into 2 000 mL volume cylinder, add seawater to separate the floating eggs and the precipitated eggs. The fertilized eggs are rinsed 2 to 3 times with water and then washed with demucus 5 to 10 times until the fertilized eggs do not adhere to each other. The debonded fertilized eggs are placed in a barrel incubator for flowing water incubation or moved into a flat cage for incubation.
2.4 Incubation of fertilized eggs
2.4.1 Incubation control conditions In the incubation tank, the fertilized eggs are inflated and incubated with running water or still water, the incubation density is 500,000 to 100,000 grains/m3, the daily water turnover is 50%~70% of the total amount, the dead eggs and dirt are sucked up regularly, the incubation water temperature is 10~13 °C, the salinity is 29~30, the pH value is 7.8~8.0, the dissolved oxygen is 5~8 mg/L, and the light is 500~1 000 lx.
2.4.2 Hatching management Under the condition of water temperature 10 ~ 13 °C, because the fertilized eggs of the yellow lid flounder must go through about 80 h to hatch the calves, so in the incubation process, it is necessary to strengthen management, maintain the relative stability of the water environment, regularly clean the mucus on the surface of the water during incubation, suck out the dead eggs at the bottom of the pool; normally developed fertilized eggs, after incubation for 24 hours, can float, at this time stop flowing water and inflation, let the good embryos float, and fish them out, move to a new incubation pool for later cultivation, Removing deformed embryos and immature or inseminated eggs from the bottom is highly beneficial to improving hatching rates.
2.5 Seedling cultivation
2.5.1 Selection of nursery ponds The hatched calves are placed in indoor seed breeding ponds according to the breeding density of 20,000 to 40,000 fish/m3, and the nursery ponds are round, with an area of 10 to 20 m2 and a water depth of 0.6 to 1.0 m.
2.5.2 Water quality management Seedling breeding requires fresh and stable water quality, seawater should be filtered, the suitable water temperature for cultivation is 10 to 17 °C, and the daily change of water temperature is not more than 2 °C; the salinity is maintained constantly during the breeding process is 28 to 32, the pH fluctuation should not be too large, generally the pH value is 7.8 ~8.4, continuous inflation, the dissolved oxygen in the water is required to be greater than 5 mg/L, and the ammonia nitrogen in the water is less than 0.02 mg/L; the juvenile fish is cultivated in still water before becoming a juvenile fish, and the daily water change is 10% of the total water body before feeding the bait 20%, after the baby fish becomes a juvenile fish, the water change rate gradually increases from 20% to 100% to 200%, and the sewage is sucked up once a day.
2.5.3 Feeding management After hatching for 3 to 5 days, the baby fish gradually open their mouths to feed, starting from day 3 to feed rotifers and add chlorella, chlorella feeding density of 250,000 to 300,000 per milliliter, wheelworm density of 5 to 10 per milliliter, feeding 2 to 3 times a day; on the 15th day began to feed halogen alee avalons, feeding density of 0.2 to 1.0 per milliliter, feeding twice a day, the 25th day began to feed artificial bait.
2.6 Adult culture
2.6.1 Breeding pond The breeding pond is preferably round, and can also be used to spread the angle square pond or oval pond, the area is generally 30 ~ 50 m 2, the water depth is 1.0 ~ 1.2 m, and the inlet and drainage design is reasonable.
2.6.2 Aquaculture water quality should comply with NY5052 standards, and seawater should be fully precipitated and sand filtered to ensure clean and free of suspended solids and impurities.
2.6.3 Breeding conditions Light intensity 500 ~ 1 000 lx, water temperature is normal temperature, control summer water temperature is not more than 27 °C, winter is not less than 2 °C, salinity 25 ~ 32, pH value 7.8 ~ 8.4, dissolved oxygen is greater than 5 mg / L, so to be slightly inflated, the daily water turnover is not less than 2 full amounts; ammonia nitrogen in water is less than 0.02 mg / L.
2.6.4 Feeding management The feed is compound feed or fresh fish, and the daily feeding amount of the compound feed is 1% to 2% of the body quality of the fish, and the daily feeding amount of fresh trash fish is 3% to 5% of the body quality of the fish, and the daily feeding is 2 times.
3 Seed preservation
3.1 Seed preservation pool conditions
3.1.1 Conditions for outdoor seed preservation ponds The cofferdam seed protection pond is 50 m wide and 300 m long, and the top of the cofferdam is equipped with a wave-retaining chest wall. Because the yellow-capped butterfly has a habit of lying in the sand layer, the substrate must be modified. The main measure taken is to clear the pond and lay a sand layer in the deep water area of the pond to increase the content of sand in the substrate to facilitate the habitat of the yellow-covered butterfly. In order to prevent bad weather such as storm surge from posing a threat to the seed pond, it is necessary to regularly carry out risk removal and reinforcement of the seed pond, dredging and slope protection, especially on the sea side of the pond.
3.1.2 Indoor breeding pond conditions Indoor wintering greenhouses adopt a north-south orientation, and the workshop is designed as a single-span building with a row structure. Broodstock breeding pond is the best round fish pond, diameter of 5.0 m, single pool nominal water surface 19 m2, water depth 0.6 ~ 1.10 m (adjustable), the inner wall of the pool adopts waterproof method, each pool is equipped with a separate solid-liquid separation device, clean water recovery, a small amount of concentrated sewage regular discharge; sewage ditch, with circulating water backwater pipeline.
3.2 Stocking of broodstock
When fishing and transporting broodstock, it should be strictly prevented from body surface injury, and the net gear woven with soft texture (nylon thread) and small mesh (less than 5 cm) should be used for fishing, and the operation of catching fish should be accurate and skilled, the action should be light, and the inner wall of the fish container should be smooth. When transporting, inflate and shorten the transport time as much as possible. Male stocking density of 15 to 20 fish / m2, female stocking density of 8 ~ 12 fish / m2, before stocking should pay attention to the temperature difference of not more than 2 °C.
3.3 Feeding management
The natural water temperature, no more than 20 °C in summer and not less than 10 °C in winter, should be moved to indoor rearing ponds when the water temperature is above 20 °C or below 10 °C. Salinity 25~32; pH 7.8~8.4; dissolved oxygen above 5 mg/L, so it should be slightly inflated; natural light intensity; daily water turnover is 1/3 to 2/3 of the cultivated water body. The bait should be mainly fresh fish, preferably fish with low fat content and high protein content, such as small yellow croaker, which can also be fed with compound feed (should be in accordance with NY 5072). Feeding 1 to 2 times a day, the daily feeding amount is 1% to 3% of the fish's body weight. It is necessary to be diligent in observing the feeding, activity and growth of fish, and deal with problems in a timely manner.
3.4 Clear the pool and eliminate harm
3.4.1 Clean up the whole pool The outdoor cultivation pool has been used for more than 3 years, and the whole pool must be cleaned. The sludge in the pond and ditch should be drained clean, the sludge should be sealed, the embankment should be repaired, and the sludge in the pond should not be directly discharged into the sea; the indoor cultivation pond should also be regularly cleaned, brushed and disinfected.
3.4.2 Disinfection and pest removal After cleaning the whole pond, the predator organisms, pathogenic organisms and intermediate hosts carrying pathogens should be removed.
4 Isolation protection measures and quality management
The original species of yellow-covered flounder in the original breeding farm are bred by technicians with high technical level and strong sense of responsibility, and managed by special personnel, reducing the occurrence of diseases and reducing the number of deaths by controlling environmental conditions such as bait, temperature, light, and running water; every year, the parents in poor state and aging are continuously eliminated, and the collected wild yellow-covered flounder parents and the parents of the original population are bred and preserved to the original population, while controlling the ratio of males and females, and always making the parental group have original hereditary traits. The time, place, quantity, specification, survival rate and parents of the original breeding of yellow-covered flounder were recorded in detail; the area, water depth, stocking and breeding of reserve parents; and the water body, breeding and out-of-pond of yellow-covered flounder seedlings. Germplasm determination of ecological environment, morphology, growth, physiology and genetic traits is carried out on a regular basis for preserved original species. Follow-up surveys of the seeds sold to grasp the growth and quality status. Judging from the aquaculture effect in the past 5 years, the traits of the yellow-capped flounder are stable, and there is no germplasm degradation.
6 Summary and discussion
6.1 Parental origin and gonadal development
Parental selection is the key to the success or failure of the preservation and cultivation of the original species. The coastal waters of Penglai are an important producer of yellow-capped flounder, which is rich in germplasm resources. The first is to harvest wild fish nearby, and then through measures such as selection and intensive breeding, it will eventually be cultivated into the parents of the original species; the second is to be selected from the offspring of the artificial breeding of the original parents. After years of practice, we have proved that both technical routes can ensure that the parent has the original germplasm characteristics of the yellow-covered flounder.
Yellow-capped flounder belongs to the multi-spawning fish that matures in batches, the eggs are sticky eggs, the egg diameter is about 600 to 700 μm, it is not transparent, it is not easy to observe the oil balls, the fully transparent and unbony eggs are overripe eggs, and the eggs that do not appear translucent are immature eggs. The ovoid maturity of the immature yellow lid flounder varies greatly, which is very easy to cause the development after fertilization to be out of sync, or even not develop, which will seriously affect the hatching effect, causing the juvenile fish to fall off in a large number of metamorphosis during the metamorphosis process due to insufficient supply of yolk nutrients, affecting the success or failure of seedling production.
6.2 Control the ratio of males and females
In order to ensure that the number of sperm is sufficient and improve the fertilization rate of eggs, the ratio of female and male broodstock is generally 3:1 to 4:1, and the few can also be matched with 3:1. Strictly follow a certain proportion of male and female to squeeze eggs and artificial insemination in order to achieve synchronous fertilization, improve the hatching effect and development synchronization.
6.3 Keep the original trait stable
First of all, the seedlings are bred by the original species of wild yellow lid flounder, the seedlings are cultivated in the middle to become reserve parents, and then the high-quality reserve parents are selected for intensive cultivation, and the seeds are preserved in the outdoor seed preservation pond, and the seedlings are bred every year during the breeding season, so repeatedly, the stability of the traits of the yellow cover flounder is maintained to the greatest extent, and the germplasm is not degraded.
6.4 Indoor wintering summer
In summer and winter, we should pay close attention to the changes in water temperature to avoid too high or too low water temperature, causing the death of yellow-capped butterflies. When the water temperature is too high or too low, deep well water is generally used for cultivation, and the water temperature is suitable and stable. Although the yellow-covered butterfly is a broad-temperature fish with a temperature range of 2 to 29 °C (the optimal growth temperature is 16 to 26 °C), it can theoretically overwinter naturally in the cofferdam pond, but winter is a critical period for gonadal development, and it is best to move into indoor breeding ponds for intensive cultivation.
