Artificial Propagation and Culture Technology of New Variety Changfeng Crucian Carp

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I. general situation of varieties

(1) nurturing background

Silver crucian carp is classified as Carassius auratus subspecies of Cyprinidae, which is widely distributed in Eurasia. Over the past decade, the scale and potential of crucian carp culture in China has become larger and larger, with a total output of 2.59 million tons in 2014, which is one of the freshwater farmed fish with steady and sustained growth, and occupies a very important position in freshwater aquaculture. Since 1996, 12 crucian carp varieties have been approved by the state. The popularization and application of new varieties have played a great role in improving the yield and quality of crucian carp. However, at present, the new varieties popularized and applied are diploid crucian carp or triploid crucian carp, and there is no new tetraploid crucian carp variety with obvious growth advantage.

The growth rate of crucian carp is lower than that of carp. Production experiments show that the growth rate of crucian carp hybrids such as hibiscus carp and Xiangyun crucian carp is much faster than that of crucian carp, showing obvious heterosis. Similarly, when the gynogenesis of silver crucian carp was carried out with carp sperm, the chromosomes of common carp were integrated into eggs under specific conditions and expressed stably, and the growth rate of this individual was theoretically higher than that of common silver crucian carp. Gui Jianfang (1993) confirmed that the probability of gynogenetic allogenic silver crucian carp integrating allogeneic sperm chromosomes was 0.1%-0.3%. The tetraploid silver crucian carp integrated into carp chromosomes grew more than 38% faster than common triploid crucian carp, showing a great growth advantage. Gui Jianfang et al. (1997, 2010) found that triploid allogenic silver crucian carp usually reproduce by gynogenesis. Under certain conditions, a small number of eggs not only have the ability of gynogenesis to maintain all their chromosomes, but also can fuse foreign spermatozoa. The ability to incorporate sperm chromosomes and co-develop. The tetraploid of silver crucian carp is obviously different from the common bisexual hybrids. It can not only break through the sterility barrier of intermediate hybrids through heterospermic gynogenesis, but also overcome the phenomenon of progeny separation in bisexual species. The phenomenon of triploid allogenic silver crucian carp integrating allogeneic chromosomes and stable inheritance provides a new idea and direction for the utilization of heterosis by introducing heterochromosomes into ploidy breeding of silver crucian carp.

The cultivation of tetraploid allogenic silver crucian carp with obvious growth advantage will play a great supplementary role in production and application, which is embodied in: first, it is an important supplement to the demand for the richness of germplasm resources, the integration of new crucian carp varieties with heterologous chromosomes can effectively reduce the potential hidden danger caused by a single germplasm resources; second, the demand for yield and breeding crucian carp with obvious growth advantages can effectively increase the yield per unit area and increase the income. The third is the demand of the culture model, and the varieties with faster growth speed can be selected successfully, and the culture model can be changed from 2 years of commercial fish listing to the same year's seedling breeding into a commercial fish listing model, so as to reduce the risk of long culture cycle; fourth, the demand for quality improvement, the integration of new varieties of crucian carp with heterologous chromosomes, muscle quality is more delicate, nutrition is better. Therefore, it is necessary to cultivate new crucian carp varieties with obvious growth advantages and good quality.

(2) Variety characteristics

The main results are as follows: (1) the observed number of chromosomes of Changfeng crucian carp is 208, including 3 sets of crucian carp chromosomes and 1 set of carp chromosomes, which is compound tetraploid crucian carp.

(2) the appearance of Changfeng crucian carp is the same as that of common silver crucian carp. The spindle-shaped, countable and measurable characters of Changfeng crucian carp are not significantly different from those of common allogenic silver crucian carp.

(3) under the same culture conditions, the growth rate is faster. Among them, the average weight growth of one-year-old long-abundant crucian carp is 25.06% faster than that of allogynogenetic silver crucian carp D line, and 16.77% faster than that of second-year-old crucian carp.

(4) the meat is delicate. The number of muscle fibers per unit area of Changfeng crucian carp is 23% and 37% less than that of Pengze crucian carp and common silver crucian carp.

(5) the nutrition is richer and the content of beneficial fatty acid is higher. The content of highly unsaturated fatty acid (n ≥ 3) of Changfeng crucian carp was 115.16% higher than that of allogenic silver crucian carp D line and 255.17% higher than that of allogenic silver crucian carp D line.

(6) the scales are compact and not easy to fall off. Changfeng crucian carp scales are tight, sales will not be affected.

(7) the genetic characters are stable and convenient for species conservation. Changfeng crucian carp adopts heterogenetic gynogenesis, and the progeny characters are not separated.

(8) strong resistance. Changfeng crucian carp is more resistant to disease than silver crucian carp because it contains exogenous genetic material of common carp.

2. Artificial propagation technology

(1) selection and cultivation of parents

1. The breeding parents choose the parents of Changfeng crucian carp to be provided by the variety selection unit or the authorized breeding unit, and the offspring of self-breeding and untested offspring in the seedling production farm can not be used as parents.

Breeding parent fish are selected with intact body surface, strong physique and spinning type, the female fish is 1-3 years old, not more than 4 years old, and the body weight is more than 0.4 kg, while the male fish is 2-4 years old and weighs more than 1 kg. Changfeng crucian carp spawns in batches, and the maturity of cultured populations varies greatly. Therefore, parents with high maturity must be strictly selected for each induced birth, so as to ensure the induction rate, insemination rate, hatching rate and survival rate of fish fry. The standard of mature parent fish is as follows: the abdomen of female fish is enlarged, the outline of ovary is obvious, the abdomen is soft and elastic, and the cloaca is slightly convex and reddish; the pectoral and ventral fins of male fish chase stars, feel rough, and gently press the abdominal cloacal hole with milky white semen flowing out.

two。 Parent fish cultivation

(1) selection of cultivation pond: the suitable area is 0.1-0.4 ha, convenient for injection and drainage, flat bottom, no silt or silt thickness less than 15 cm, water depth 1.2-2.5 m, the water quality is fat, sunny, east-west or north-south, and there are no weeds in the pool water. Clean the pond with quicklime for 2 days, then inject new water and wait for the parent fish to enter the pond after aeration.

(2) feeding management: the feeding and management of parent fish is based on feeding concentrate feed and regulating water quality, so that it can develop well and produce a large number of eggs with good quality in the next year.

Reasonable feeding. After the northern region comes out of the pool in spring, it can be fed when the water temperature rises to more than 10 ℃. The feed should be concentrate feed, and the protein content of prenatal cultivation should be more than 30%. The protein content of postpartum culture was 28%-35%, and the parent fish were fed with formula feed with protein content of 30%-35% before and one month before overwintering. The appropriate particle size is about 5 mm, and the feeding amount is 2% 4% of the body weight. During the prenatal and postpartum period of one month, the feeding amount of the parent fish is 3% 4% of the body weight, and the feeding amount during the normal breeding period from July to August is 2% 2.5%. And it is adjusted according to the water temperature and the feeding intensity of the fish.

Regulate the water quality. A good water quality environment is very important for the development and spawning of parent fish. Flushing can improve the water quality, meet the current requirements of parent fish, and provide a good ecological environment for the gonadal development of parent fish. Regular replenishment of new water can meet the oxygen demand of fish and improve the food intake intensity. The dissolved oxygen should be more than 4 mg / L, and the transparency of the pool water should be kept at 20-25 cm at noon on a sunny day.

(2) artificial propagation

The spawning season of Changfeng crucian carp is spring. When the water temperature rises to 16 ℃ ~ 18 ℃, it begins to lay eggs. The optimum water temperature for spawning is 18 ℃ ~ 20 ℃.

Select mature Xiongxing Guohong carp parent fish with rough scales. Gently press the rear abdomen of the male parent fish, and there is milky semen flowing out of the cloaca. It is better to disperse quickly after meeting water. When artificial insemination is used, the ratio of female to male fish is 50: 100: 2. In practice, it should be flexibly controlled according to the number of eggs laid by female fish and the semen quantity of male fish.

1. Cleaning and management of spawning ponds and hatching ponds for artificial insemination, most of the spawning ponds are square or round, and there is no fixed shape requirement. The area is 3 to 5 meters 2 is suitable for operation, and the pool has a certain amount of water exchange. Special facilities need to be built for incubation in incubators, incubators or loops, which can be produced quantitatively according to the amount of water and the number of seedlings needed in each batch. The diameter of the incubator varies from 0.2 to 1.0 meters; the hatching pool is a cement pool or a water tank welded with iron plates, with a rectangular shape and an area of 16 square meters; and the hatching ring is similar to the hatching facility for silver carp and bighead carp, with a diameter of 6 million 10 meters. The water used for hatching is required to be clean with oxygen content above 5 mg / L. All spawning pools and incubators should be thoroughly cleared before use.

two。 Artificial labor was induced by HCG+LRH-A2: (400IU + 1 μ g) / kg, or oxytocin 1 + LRH-A2: (400 μ + 1 μ g) / kg, the mixture of the two drugs had a good effect. The dose of male fish is halved. One or two injections are used, usually two injections (injection at the base of the chest fin). The total dose of the first injection was 1 beat 8 and the injection margin of the second injection was 6. The water for injection should not exceed 5~l6 ml for each parent fish. The distance between the two stitches is usually 8 ~ 10 hours.

3. After injecting drugs into the parent fish of artificial insemination, the female and male fish were put into different spawning pools for running water stimulation to assist the parent fish in estrus and spawning. When the water temperature was 16 ℃ ~ 24 ℃, the effect time was 8 hours and 10 hours, and the spawning began. The parent fish are temporarily reared separately after being urged to estrus. 2-3 hours before the effect time, the dynamics of the parent fish should be observed. When there is egg outflow from the abdomen of the female fish, the eggs should be squeezed to inseminate immediately. Dry the water on the body surface of the female parent fish with a dry towel, squeeze the eggs into a dry basin or bowl, and squeeze the male fish semen into the basin, stir well, gently stir with appropriate amount of water, let it be fully fertilized, and then immediately transfer the fertilized eggs to yellow mud water for debonding for 1 minute or 2 minutes, and then randomly transfer to the incubator or incubator for hatching. Avoid direct sunlight when handling fertilized eggs.

4. The fish fry hatched Changfeng crucian carp eggs as sunk eggs, which sunk to the bottom in still water and washed up in running water, so the way of hatching was running water hatching. Before the fertilized eggs were hatched, the concentration of methylene blue was 1100.00 mg / L, and the time was 10: 15 minutes. In order to prevent and control the occurrence of egg water mold, the drug was applied for 1 or 2 times during the hatching of fish eggs. The water used for hatching must be filtered to prevent the harm of enemies such as Daphnia Magna.

The water for hatching requires fresh water quality, sufficient dissolved oxygen (more than 5 mg / L dissolved oxygen), pH7~8; non-toxic and harmless, and water must be filtered through 70-80 mesh nylon sieve to prevent enemy organisms. The incubation water temperature was 18 ℃ ~ 25 ℃.

When hatching in running water, the flow of fertilized eggs can be larger at the beginning of hatching, and it is better for the fish eggs to turn up and down in the water. When the eggs come out of the film, the flow can be slightly smaller, and the larvae can be adjusted smaller after coming out of the film. When the fish fry waist point (swim bladder) appears, it can only get out of the pool when it can swim horizontally.

Fish fry should be sold or cultivated in the pond in time when swimming. If you can't get into the pond in time in case of sudden weather, you should feed the boiled egg yolk suspension twice a day, and 1 million fish fry should be fed with 2 egg yolk suspensions at a time.

(3) Seedling cultivation

1. Cultivation of fish fry of Wuzai and summer flower

(1) cultivation pond: the bottom of the pond is flat, the silt is moderate, the thickness is 10 to 15 centimeters, and the pond area is 0.15 to 0.4 hectares. Five to 10 days before the fry went into the pond, the fish fry were thoroughly cleaned and disinfected with 1125-1500 kg / ha quicklime or 375-450 kg / ha bleach. After clearing the pond, base fertilizer was applied and fermented manure was 2250kg / ha. After fertilization, the pond water gradually changed to tea brown or light green into fertilizer water. The purpose was to cultivate small zooplankton such as rotifers as biological bait for fish fry after entering the pond.

(2) Fish fry restocking: fish fry are reared in the pond after swimming and opening. When entering the pond, you should pay attention to the difference between the water temperature of the incubator and that of the pond, and choose the leeward place of the pond. in case of strong wind, postpone stocking or place artificial fish nests or grass curtains in the leeward place to avoid wind and waves. The stocking density is 7.5 million ~ 22.5 million tails per hectare, which should be adjusted according to the conditions of the pond. The fry of each pond should be propagated in the same batch and should be released at one time. In addition, fish fry net is used to check or thoroughly remove aquatic insects, miscellaneous fish and other pests in the pond before fish fry is released.

(3) feeding and management: fish fry should be fertilized or sprinkled with soybean milk in the pond with a depth of 1 meter after 3-5 days. Soak soybeans 15-75 kg / ha every day and sprinkle them in the whole pond after soaking and grinding, and feed them twice a day. According to the water quality, topdressing once every 3-5 days to keep the pond water brownish green or oil green. It can also be used with 1.5 kg / ha of bait and 1.5 kg / ha of aquatic bait yeast and sprinkled twice a day. After 10 days, as the fish grew up, the feeding amount should be adjusted appropriately or the microparticle feed should be increased, and water should be injected by stages at the same time. The water in the pond is generally about 50 cm to 70 cm when the fry goes into the pond, and then it is injected every 5 days, 15 cm to 20 cm each time, to improve the water quality, promote the reproduction of biological feed and promote the growth of fish fry. When injecting water, a dense net should be installed at the water injection mouth to prevent wild miscellaneous fish and other enemies from mixing with the water. Continue to patrol the pond in the morning, middle and evening to observe the changes of water color and the activity of fish fry, so as to determine the amount of fertilization and feeding. Remove weeds, sundries and frog eggs from the pool at any time.

The fish fry can be divided into ponds and sold after 15-25 days, with a total length of about 1.5-3cm. In order to improve the survival rate of getting out of the pond, fish body exercise should be carried out. The method is: choose a sunny day around 10:00 in the morning to draw the net for intensive exercise, stop eating 2 days before pulling the net, operate carefully, and put the fish fry back into the original pool immediately after a slight floating head begins to appear.

two。 Fish fingerling culture in pond

The main results are as follows: (1) Fish fry culture pond: the conditions of fish fry culture pond are basically the same as those of fry culture pond. The suitable area is 0.4-0.8 hectares and the water depth is 1.5-2 meters. Before the summer flowers are released, the summer flowers should be carefully cleaned and thoroughly cleaned and disinfected. The method is similar to that of the fry breeding stage.

(2) Summer flower stocking: summer flowers are released as early as possible to prolong the growing period of fish species. Fish fry should be strong and neat. The stocking density varies greatly due to the climate, production conditions, culture methods and technical level of different areas, as well as the expected specifications of fish species. The stocking density in the northern region is 45000 ~ 75000 fish per hectare, which is appropriately adjusted according to the actual culture conditions. and match with the right amount of silver carp and bighead carp fry.

(3) feeding and management: the summer flowers were domesticated and cultured after 3 to 5 days in the pond, and the pellet feed containing more than 35% protein was fed. The particle size of the feed must be gradually adjusted with the growth and development of the fish. Feeding should adhere to the "four fixed" principle, ① positioning: feed should be a fixed position-feeding point, concentrate should be put on the feed table, summer flower fish fingerling should first be sprinkled around the feed table, and then gradually narrow the range to guide the fish to feed on the feed table, the area of each feed table is about 1 to 2 meters, one for every 5000 fish fingerlings, and the green feed is put into the feed frame. ② timing: when the weather is normal, the daily feeding time should be fixed, concentrate feed should be fed twice every day from 8: 00 a.m. to 10: 00 a.m. and 2: 4 p.m., green fodder should be fed once a day, generally 1-2 hours earlier than concentrate; ③ ration: feed should be appropriate and uniform to prevent too much or too little, and it is appropriate for concentrate to be finished in 2 to 3 hours and 4 to 5 hours after each feeding. Rainy days, fish disease epidemic period, the amount of feeding should be reduced as appropriate; ④ quality: the feed must be fresh, not with corrupt feed feeding, so as to avoid fish disease, green feed should be fresh and tender and palatable, concentrate feed shall not be moldy and deteriorate, and pellet feed should be prepared according to all kinds of fish nutrition. Daily feed intake is 5% to 12% of body weight, but it should be adjusted flexibly according to weather, water temperature and fish intake.

Add fresh water regularly and change water 2times and 20cm each according to the water quality during the peak growth period from July to September, one is to supplement the amount of leakage and evaporation, and the other is to adjust the water quality of fish ponds to ensure a good living environment for fish. promote the growth of fish. This phase lasts for several months, and it is very important to prevent floating heads, floodponds and other accidents. The aerator is used for mechanical aeration, and in the pond with high density, a multi-function surging machine or impeller aerator is used at noon, and the water layer exchange is carried out for 2 to 3 hours to improve the water quality. Persist in patrolling the pond every morning and evening, pay attention to observing the water color, water quality and the feeding situation of fish, and adjust the water quality and feeding quantity in time, especially in muggy weather, we should pay more attention to avoid unnecessary economic losses caused by floating head of fish.

(4) Pond overwintering management techniques: from late September to early October, fish breeding should be strengthened in the northern region, and more concentrate should be fed to enhance the physique of fish, which is the internal material basis to ensure the safety of fish species in winter. In late autumn and early winter, when the water temperature dropped to 8 ℃ ~ 10 ℃, fish seldom ate. In order to facilitate management, it is necessary to merge the pond and store the fish species in the culture pond with deep water and good water retention, or overwintering in the original pond.

The overwintering pond should choose a pond with flat bottom, good water retention, less silt, sunny leeward, convenient injection and drainage, no leakage, with an area of 0.4 to 2.0 hectares and a water depth of 2.5 to 3.5 meters, and the thickest water depth under the ice should be more than 1.5 meters. Drain the pond water 10 days before fish release, remove dirt and weeds in the pond, and expose to the sun for 1 to 3 days, pour 10 cm fresh water into the pond to clear the pond, the acid water is sprinkled with quicklime pulp throughout the pond, the dosage is 1200 kg / ha, and the alkaline water is bleached with 30% chlorine, the dosage is 225kg / ha. Fresh water is injected 24 hours later, and fish can be released when the water depth reaches about 1 meter after 3-5 days, and the water level is gradually injected to the highest water level. Can also use good water retention, deep pool of the original pool overwintering, the old water discharged 1 beat 3 or 2 stroke 3, per cubic meter with 0.5 million 0.7 grams of trichlorfon whole pool sprinkled to kill zooplankton and fish parasites, a week after each cubic meter with 1.0 grams of bleach whole pool sprinkled, replenish new water to the highest level.

The stocking density was determined according to the sediment of the overwintering pond and the condition of rehydration. The bottom of the pool has good water retention, less silt, good water quality, convenient overwintering pond 0.75 kilograms per cubic meter, and general overwintering pond stocking density 0.5 kilograms per cubic meter.

In the north, the temperature is low in winter. In some places, the ice is frozen for several months, and the thickness of the ice varies from 20cm to 100cm. Management during the overwintering period is particularly important. ① is responsible for timely inspection of overwintering conditions: regular inspection of water quality, water color, activity of index fish, especially regular determination and analysis of dissolved oxygen in water, usually once a week, when oxygen content is low and decreases rapidly, it should be checked once a day. When the dissolved oxygen content is reduced to 4 mg / L, oxygen enhancement measures should be taken. Determination of ② pond icing and dissolved oxygen: whether the overwintering pond can form bright ice is the key to the overwintering effect, which directly affects the oxygen production of phytoplankton in the overwintering pond. When it rains and snows to seal the pool, measures should be taken to stir the water with an aerator so that it does not form ice and re-freeze it on a sunny day; if the ice is thicker and cannot be broken by an aerator, it is necessary to use an icebreaker to break the ice and then re-freeze, the ice-breaking area is not less than 40% of the pond area, so as to facilitate the photosynthesis of phytoplankton in the water under the ice and increase the dissolved oxygen in the water. The dissolved oxygen is determined regularly, the change of dissolved oxygen is small in the early stage, it can be measured once every 10-15 days, and from late December to February, the pond dissolved oxygen needs to be measured every 3-5 days. If the daily decrease of dissolved oxygen is more than 1 mg / L, it needs to be measured once a day. When the dissolved oxygen content drops to about 4 mg / L, oxygen replenishment measures such as circulation in the original pool should be adopted to ensure the fish to survive the winter safely. During the overwintering period, we should also often observe the water color and the activity of fish under the ice, and find that fish diseases should be prevented and treated in time. ③ ice cleaning: after freezing, when the ice surface can bear the weight of human and snow cleaning machinery, snow should be cleared in time, the snow has a great influence on the penetration of sunlight, the snow clearing area should reach about 80% of the pond ice surface, and the amount of overwintering should be small, so as to improve the lighting conditions, increase the photosynthesis of phytoplankton and increase the amount of dissolved oxygen in water. ④ regularly replenish new water: replenish water frequently to keep the overwintering pond at a high water level, usually once every 10 to 20 days, and properly adjust the injection interval and water injection quantity according to the falling degree of water level, dissolved oxygen and water quality.

III. Healthy breeding techniques

(1) suitable conditions for culture

1. The choice of aquaculture site has sufficient water source, soil water conservation and no pollution. Convenient transportation is conducive to the transportation of fish species, feed, fertilizer and fish products; reliable power supply can ensure the normal operation of drainage and irrigation equipment, feed processing machinery, aerator, bait machine, etc., so as to ensure the needs of production.

2. Pond conditions the area of fish ponds should be more than 0.4 hectares depending on the condition of their respective farms, but it is inconvenient to operate more than 2 hectares. The water depth should be 1.0 ~ 2.5m, the water source should be sufficient, the water quality should be good, the water body pH6.5~8.5, the water temperature should be 18 ℃ ~ 28 ℃, and the dissolved oxygen should be more than 4 mg / L. The ridge of the pond should be firm, do not leak, do not collapse, and clean up and disinfect the fish before releasing the fish.

(2) matching techniques for aquiculture

1. The stocking specifications and quantity of fish species in the main pond culture model shall be determined according to the expected adult fish production target, the size of commercial fish specifications and the actual conditions of pond and production. Early stocking of fish is one of the important measures in production. Free-range fish species should be physically strong, the requirements of stocking in the same pond are the same species, the specifications should be neat, and they should be fully released at one time. The culture density in the northern region is 35000-50, 000 tails per hectare, which is appropriately adjusted according to the pond culture conditions, with a stocking specification of 10% 50 grams per tail, and then 10% fish species such as 30% silver carp and bighead carp.

two。 In the pond model of growing and abundant crucian carp, the number of summer flowers was 1000 / mu, the individual reached more than 300g in that year, and 2000,000g / mu in the same year, and the individual reached 80,130g in that year.

3. In daily management, each pond should be inspected once a day in the morning and evening, pay attention to the changes of weather, water quality and the activity and feeding of fish, and determine the corresponding feeding and management measures. If it is predicted that it is possible to float the head, it should be turned on in advance to increase oxygen or add new water. Pond feed residue, sundries, sick and dead fish should be removed every day.

Establish aquaculture files. In accordance with the regulations on Safety and quality Management of Aquaculture issued by decree No. 31 of the Ministry of Agriculture of the people's Republic of China (2003), we should conscientiously do a good job in the whole process of aquaculture and the records of production and drug use in order to carry out traceability. The establishment of aquaculture technical files should be reflected by the establishment of cards in each pond, in addition to filling in the "Aquaculture production record" and "Aquaculture Drug use record" as stipulated in the regulations on the quality and Safety of Aquaculture. Pond environmental conditions, water sources, water quality, sediment conditions and culture patterns should also be recorded, and pond cleaning, water injection, fertilization, fish stocking, feeding and floating head should also be recorded. The important technical measures such as increasing oxygen, fish disease and prevention, drainage and replenishment, water quality measurement, net pulling and fish coming out of the pond are recorded in detail one by one and filed at the end of the year.

(3) Prevention and control methods of major diseases

The diseases that may occur in the culture process of Changfeng crucian carp include water mildew, bacterial septicemia, rotifer disease, anchor head disease and so on.

1. Preventive measures the occurrence of fish disease, in most cases, is caused by the invasion of pathogens, such as poor aquaculture water environment, poor breeding and management, and fish body injury. Therefore, comprehensive prevention should be carried out from the following aspects:

(1) thorough cleaning and disinfection of culture ponds. No matter the fry, fry or edible fish are raised, the fry should be cleaned and disinfected before going into the pond.

(2) the stocked fish species shall conform to the corresponding quality standards of all kinds of fish species, and the purchased fry shall pass the quarantine inspection.

(3) Fish fry and fingerling shall be disinfected before entering the pond, which can be soaked in 3%-5% brine for 5 minutes; grass carp species with vaccine conditions should be injected and immunized.

(4) half a month after fish fry and fry are put into the pond, 1g of bleach (28% available chlorine) should be sprinkled once per cubic meter of water.

(5) in the high temperature season, 5 grams of garlic or 0.47 grams of allicin per kilogram of fish body weight were mixed with appropriate amount of salt for 6 consecutive days.

(6) from March to April, the whole pool was sprayed with crystal trichlorfon (90%) solution once, so that the water content was 0.3 × 0.5 mg / L, and from May to June, the pool water was sprayed with quicklime solution twice, so that the amount of water was 250.30 mg / L.

(7) disinfection of food grounds. The methods are as follows: first, disinfect with bleach once or twice a month, each time 250 grams of bleach, dissolve in 12.5 grams of water, and sprinkle in the food field; second, use medicine hanging bags and baskets to prevent fish disease in the epidemic season. Each food farm can hang 3-6 baskets (bags), each containing 100-150 grams of bleach. From April to June, twice a month; after July, once a month for three consecutive days. Can also use copper sulfate and ferrous sulfate mixture to hang bags, each food farm can hang 3-6, each containing 100 grams of copper sulfate, 40 grams of ferrous sulfate. From April to June, twice a month for three consecutive days.

(8) adhere to the "Siding" feeding; do a good job of feed disinfection, aquatic plants, duckweed and other aquatic green fodder should be soaked in 8 mg / L bleach solution for 5 minutes for 10 minutes before they can be put into the food farm.

(9) strengthen pond patrol, often remove weeds and residual feeding on the edge of the pond, do a good job in pond cleaning and hygiene, and find dead fish should be fished out in time and buried deeply.

(10) in the process of net-pulling exercise, pond separation, starting fishing, screening and transportation, the operation should be careful to prevent fish injury.

(11) do a good job in dealing with epidemic diseases. Once infectious diseases occur in farmed fish, they should be isolated, and their water bodies should not be discharged casually to avoid further spread of the disease. Drug treatment or disinfection should be carried out in the original pool. Sick fish and dead fish should not be abandoned casually, but should be treated innocuously.

(12) to wash and disinfect fishing gear used in diseased fish ponds, you can use 2%-4% salt water for 5 minutes, or 20 mg / L (20 ℃) potassium permanganate solution for 20 minutes for 30 minutes, or 30 mg / L povidone iodine solution (1% available iodine) for 5 minutes, or exposure to the sun to prevent the spread of pathogens.

As long as the prevention work is done carefully, the occurrence of fish disease can be controlled, and at the same time, fishery drugs can be avoided or less used, which is conducive to the improvement of the quality of cultured fish.

two。 Disease treatment

(1) Water mildew: this disease is mainly caused by careless operation such as net pulling and transportation, resulting in the shedding of fish scales, skin damage and water mold invasion. It can be seen with the naked eye that a large number of hyphae propagated on the body surface of diseased fish grow into clumps, like old cotton wool, showing white or gray, so it is also known as "white disease". The fish suffering from this disease began to swim restlessly and dyskinesia. later, the fish body burden is too heavy, swimming slowness, loss of appetite, and finally die of weakness.

Prevention and treatment: soak in 1% salt solution for 20 minutes or 3% salt solution for 5 minutes.

(2) bacterial septicemia: this disease is also called fulminant infectious disease and is caused by bacteria. Diseased fish head, body surface congestion or bleeding, some anus red and swollen, some diseased fish are also accompanied by eye and orbital protrusion and congestion, muscle bleeding. The body cavity has ascites, the intestines are empty and reddish, and the fat has bleeding spots. There are also cases where the symptoms are not obvious. According to the investigation, there are two types of the disease: acute type and chronic type. The acute type is severe, fulminant and has the peak period of death, while the chronic type dies slowly and there is no peak period of death.

The epidemic season is from April to October, the peak is from June to August, and the water temperature is 25 ℃ ~ 35 ℃. The species that endanger the fish include silver carp, bighead carp and other freshwater fish. Disease can occur from fingerling to adult fish, but it is mainly harmful to adult fish.

Prevention and treatment methods:? Thoroughly clean the fish ponds, clean up the silt and disinfect it with quicklime. ? Do a good job of fish seed disinfection, fish stocking density and matching proportion should be reasonable, not too dense. ? Drug prophylaxis should be carried out regularly and quicklime should be sprinkled in the whole pool once a month, with a dosage of 20mg / L. For the treatment of ④, quicklime was sprinkled once in the whole pond and fed with Scutellaria baicalensis Georgi at a dosage of 2kg / kg body weight for 4 days. When feeding, it should be used with rhubarb and Cortex Phellodendri (the ratio is 2 ∶ 5 ∶ 3). When ⑤ was complicated with bacterial Gill rot, trichloroisocyanuric acid was sprinkled in the whole pool on the first day, the dosage was 0.2mg / L. From the second day, Scutellaria baicalensis Georgi was mixed and fed with the same method as above.

(3) Anchor head disease: this disease, also known as needle disease, iron anchor disease, coir coat disease, is caused by the invasion of the fish, and the worm body can be seen with the naked eye on the body surface of the diseased fish. The tissue around the parasite is often red, swollen and inflamed, and the scales near the wound are dissolved by the secretion of the anchor head and corroded into a notch. When the fish was first invaded by the worm, it showed uneasiness and poor appetite, and then became thin and swam slowly.

This insect can invade the body surface of Changfeng crucian carp and other fish, which is particularly harmful to young fish and can cause death (mainly affecting the growth of large fish). The epidemic area of the disease is wide, and it has been found in various fish farming areas all over the country. it can be seen all the year round and can cause serious epidemics in summer and autumn.

Prevention and treatment methods:? Clean the pond with quicklime with water, the dosage is 200 million 250 mg / L. ? The fish fry were soaked in potassium permanganate for 15 minutes at the dosage of 10 mg / L and 20 mg / L. ? During the breeding season, the whole pool was sprinkled with trichlorfon (90%) at a dosage of 0.5 mg / L. Once every two weeks, two or three times in a row. Under the condition of thin water, ④ applied 400kg of rotten pig manure or cow manure to prevent and cure the disease every 667m2 of water surface and 1m water depth.

(4) rotifer: because rotifer parasites on the skin and Gill of fish to absorb nutrients, stimulate the tissue to secrete too much mucus, seriously affecting respiration. Mainly harm juvenile fish and fish species, a large number of infection when the fish body emaciation, blackening, swimming slow to death.

Prevention and cure method: clean the pond thoroughly with quicklime before releasing the fish in ①. ② soaked in 2% salt water for 2 minutes to disinfect the fish; sprinkle the whole pool with a net 0.5g per cubic meter wheel.

IV. Breeding and seedling supply units

(1) breeding units

1. Yangtze River Fisheries Research Institute, Chinese Academy of Fisheries Sciences

Address and zip code: No. 8 Wudayuan Road, Donghu New Technology Development Zone, Wuhan City, Hubei Province, 430223

Contact: Li Zhong

Tel: 1871 166312

Email:lizhong@yfi.ac.cn

two。 Institute of Hydrobiology, Chinese Academy of Sciences

Address and zip code: No. 7 East Hunan Road, Wuchang, Wuhan City, Hubei Province, 430071

(2) Seedling supply units

Yangtze River Fisheries Research Institute, Chinese Academy of Fisheries Sciences

[keywords]: freshwater diploid crucian carp yield aquaculture network