How to raise Xiangyun crucian carp? Breeding technology for the crucian carp variety Xiangyun crucian carp

Xiangyun crucian carp is a triploid crucian carp successfully bred by Professor Liu Yun and others from the Biology Department of Hunan Normal University, in collaboration with the Xiangyin Donghu Fish Farm, using a combination of cell engineering technology and sexual hybridization. Its male parent is a tetraploid fish, referred to as the "gene pool fish," and its female parent is the Japanese white crucian carp (Carassius cuvieri). Xiangyun crucian carp is a high-tech product of bioengineering, and its theoretical significance and application value are at a leading level both domestically and internationally.
　　
I. Seed production technology for Xiangyun crucian carp
The production and seed production process for Xiangyun crucian carp is as follows:
2N cell engineering technology 4N (gene pool fish) × 2N (Japanese white crucian carp) male parent sexual hybridization female parent 3N (Xiangyun crucian carp). Xiangyun crucian carp has excellent traits such as self-sterility, fast growth speed, wide feeding habits, strong disease resistance, tolerance to low oxygen and low temperature, and easy harvesting. Its flesh is tender and delicious, suitable for angling. This fish is suitable for farming in ponds, lakes, reservoirs, rice fields and cages. Under general pond conditions, polyculture can yield 60-100 kg per mu, and monoculture can yield 500-800 kg per mu. Cage farming can yield a net production of 50-90 kg per square meter.
　　
II. Biological characteristics: Xiangyun crucian carp has a completely crucian carp body shape. Tests using LDH and EST isozymes and mtDNA analysis indicate that Xiangyun crucian carp leans toward maternal inheritance but also has gene expression from Xiangjiang wild carp, Jing crucian carp, Xiang crucian carp, tetraploid fish and others, so it differs from ordinary crucian carp in the following ways:
1. External differences between Xiangyun crucian carp and other crucian carp. The appearance of Xiangyun crucian carp is similar to ordinary white crucian carp, but its body shape is superior to other varieties. Because it is sterile, its gonads are small in proportion, so it has fewer internal organs, a smaller belly than other crucian carp, thicker back muscle, and a more "slender" body shape than other crucian carp varieties. The scale arrangement on the back of Xiangyun crucian carp is often somewhat irregular (other crucian carp rarely show this phenomenon), and the lateral line scales are generally in the range of 30-32.
2. The gonadal development of Xiangyun crucian carp is abnormal, and it cannot reproduce on its own: Xiangyun crucian carp is a triploid crucian carp, cannot reproduce offspring, and does not exhibit sexual chasing behavior, so it can be stocked in any aquaculture water body without causing mixing of other crucian carp variety resources, and there will be no decline in commercial fish quality due to excessive reproduction.
3. Xiangyun crucian carp grows fast, and its growth is not limited by sexual maturity. General crucian carp varieties are affected in growth speed by early sexual maturity, which limits individual growth. Xiangyun crucian carp not only has obvious hybrid growth advantage, but also, because it is sterile, the nutrients it takes in are completely used for growth, and individual growth is not limited by sexual maturity. According to controlled growth tests in the same pond, the growth speed of Xiangyun crucian carp exceeds that of its female parent (Japanese white crucian carp) by 1 times, and is 3-5 times that of ordinary crucian carp. The largest body weight of the same-year fry can reach 0.5 kg. Spring fingerlings raised to market size generally can reach 0.5-1 kg per individual, and the largest individual can reach 1.5 kg.
4. Xiangyun crucian carp has strong stress resistance. The hybrid advantage of Xiangyun crucian carp is also shown in its strong resistance to harsh natural environments, mainly in the following aspects:
(1) Strong disease resistance and wide adaptability. After years of promotion, it has been farmed in 20 provinces and cities in China, and can adapt to local environments. There have been no reports of major losses caused by infectious diseases.
(2) Strong tolerance to low oxygen. It can still grow well under conditions of high stocking density and small water bodies (for example, cage farming with 200 fish per square meter, with a yield of 57 kg per square meter). When pond farming experiences "pond suffocation" due to oxygen deficiency, grass carp, silver carp, bighead carp and other four major Chinese carps all show varying degrees of death, while Xiangyun crucian carp rarely dies.
(3) Good low-temperature tolerance. In the Hunan region, it can feed year-round. When the water temperature is 10°C (the four major Chinese carps have all stopped feeding), it can still feed and grow.
5. Wide feeding habits and low feed conversion ratio. Xiangyun crucian carp not only has wide feeding habits and tolerance for coarse feed, but also retains the characteristic of its female parent, the Japanese white crucian carp, of being able to feed on some plankton. In addition, the nutrients it consumes are completely used for growth, so its feed utilization rate is higher than that of other crucian carp.
6. Easy to catch. Xiangyun crucian carp farmed in ponds does not "burrow into mud," and the net capture rate can reach about 80%. Unlike ordinary crucian carp, it does not require "draining the pond" for market harvest.
7. Excellent quality. Xiangyun crucian carp has tender flesh and delicious meat, retaining the flavor of crucian carp, while also having fewer small bones, fewer internal organs, more edible parts, and a larger individual size. The glutamic acid content in its muscle is relatively high, giving it better taste than ordinary crucian carp, and it is well received by consumers.
　　
III. Fry and fingerling rearing
1. Summer fry rearing: Although Xiangyun crucian carp has obvious hybrid advantages, the summer fry rearing stage happens to fall in the low-temperature, rainy, and relatively poor climate period from April to early May, which brings considerable difficulty to fry production. In addition to strictly following conventional rearing procedures, special attention should be paid to the following points:
(1) Strict pond clearing and disinfection. Fry ponds for stocking Xiangyun crucian carp must be thoroughly cleared and disinfected to remove wild miscellaneous fish and harmful organisms. The incoming water must also be strictly filtered to prevent new harmful organisms from entering. Because the temperature is low, fry growth is relatively slow, while wild miscellaneous fish and harmful organisms reproduce very quickly. A small number of wild miscellaneous fish that escape, such as topmouth gudgeon, wild crucian carp, grass shrimp, etc., will rapidly reproduce and seriously threaten the survival rate of Xiangyun crucian carp fry, sometimes even causing total loss. At the same time, in low-temperature weather, the toxicity of pond-clearing drugs dissipates slowly, so the pond water toxicity must also be carefully tested before stocking fry.
(2) Insist on stocking fry in fertilized water. Because Xiangyun crucian carp has strong low-oxygen tolerance, pre-fertilizing a pond of "good water" has a significant effect on improving summer fry survival rate, avoiding the disadvantage that fry cannot fully feed because plankton reproduce slowly due to low temperature and rain after stocking. Water fertilization should be kept "fertile but fresh," preventing the appearance of "old water" or "white water" caused by mass reproduction of large Daphnia.
(3) Mainly monoculture, with appropriate density. Xiangyun crucian carp summer fry should not be polycultured with other fry. The stocking density should be sparse rather than dense, with 80,000-100,000 fry per mu. Sparse stocking is best, with 40,000-60,000 per mu being suitable. In about 15 days, summer fry of about 3 cm can be raised, and then the pond can be freed to raise summer fry of the four major Chinese carps, improving the utilization rate of the fry pond. Under special circumstances, if the stocking density must be increased, the pond should also be divided in time after 8-10 days.
(4) Timely supplement concentrated feed. In the early stage, Xiangyun crucian carp fry feed on plankton, so as long as fertilization maintains water color, it is sufficient. After 8-12 days in the pond, the feeding habits of the fry begin to differentiate. When the fry begin to "show full bellies," rice bran, rapeseed cake powder and other concentrated feed should be supplemented in time. If fry are found swimming frantically in groups along the pond edge without stopping, this indicates a lack of concentrated feed, and more concentrated feed should be spread along the pond edge; otherwise, the survival rate will be seriously affected.
As long as attention is paid to the characteristics of Xiangyun crucian carp fry and management is careful, no serious diseases will occur during the summer fry stage, and the survival rate can reach over 80%.
2. Fingerling rearing. In addition to directly using summer fry to raise market fish, Xiangyun crucian carp summer fry are generally further raised into 40-50 g fingerlings, to be used in winter or the following spring for market fish farming. This can make full use of the advantage that the growth of Xiangyun crucian carp is not affected by sexual maturity. Fingerling rearing mainly includes the following methods.
(1) Monoculture. Monoculture ponds for Xiangyun crucian carp should not exceed 15 mu, with water depth in the range of 1.5-2.5 m and convenient drainage and irrigation. Before stocking, the pond must be strictly cleared and disinfected. The stocking amount depends on pond conditions, with 6,000-10,000 fish per mu, and can be mixed with 1,000 summer fry of silver carp and bighead carp, or 200 spring fingerlings, and about 5% grass carp and bream fingerlings may be stocked as appropriate. In addition to adhering to timed and quantitative feeding every day, new water should be added frequently to keep the pond water oxygen content at a normal level (4-6 mg/L), and attention should be paid to preventing fingerlings from escaping (Xiangyun crucian carp has a habit of swimming against the current). After 6 months of rearing, they can reach 40-60 g per fish. Generally, the yield per mu can reach 300-350 kg, and ponds with good management conditions can reach 500 kg.
(2) Polyculture. Generally, as long as other carp or crucian carp varieties are not polycultured, spring fingerling ponds can all be polycultured with Xiangyun crucian carp summer fry. Generally, 300-500 fish are stocked per mu. In addition to feeding according to conventional farming methods, concentrated feed should be appropriately supplemented at the turn of autumn and winter to meet the feed needs of Xiangyun crucian carp. This can increase the yield of Xiangyun crucian carp by 50-70 kg per mu.
(3) Cage farming. When there is a large demand for Xiangyun crucian carp spring fingerlings but fish ponds are lacking, cage farming of Xiangyun crucian carp can be carried out effectively by taking advantage of its filter-feeding ability, tolerance to dense stocking, disease resistance, and suitability for commercial feed. Cages should be placed in eutrophic large water bodies with slight flowing water and shelter from wind and sun, such as reservoir bays and lake inlets, and the mesh size should match the fingerling size. Adhere to daily feeding and cage cleaning, and pay attention to preventing parasitic diseases. Stock 400-500 summer fry (one-inch fry) per square meter. After 4-6 months, they can reach 40-60 g fingerling size, with a survival rate of up to 90%. At the same time, using cages to raise adult Xiangyun crucian carp also gives better results than raising grass carp or other carp. Generally, a 28 sq m cage is stocked with about 3,000 fingerlings of 50 g size. After 6 months of rearing, they can reach 400-600 g adult fish size. The net profit per cage can reach about 4,000 yuan, and management is convenient.
　　
IV. Adult fish farming technology
1. Farming situation of Xiangyun crucian carp in the Beijing suburbs:
In 1998, adult fish farming trials were conducted at 4 fish farms in Tongzhou, Pinggu, Haidian and other districts and counties in the Beijing suburbs. From May 10-20, 1998, 153,000 Xiangyun crucian carp summer fry were purchased from the Xiangyun crucian carp Changsha pilot test base of the Hunan Provincial Science and Technology Commission, and were harvested from the ponds in mid-October. The adult fish trial area was 26.7 mu, with a total yield of 13,435 kg and an average yield of 503 kg per mu, of which Xiangyun crucian carp was 440 kg and silver carp and bighead carp were 63 kg. The survival rate of Xiangyun crucian carp was 93.6%, the average size was 193 g per fish, the feed conversion ratio was 1.28, and the input-output ratio was 1:1.26. Through the 1998 farming trials, Xiangyun crucian carp showed the following characteristics:
(1) Obvious growth advantage. Xiangyun crucian carp has a relatively fast growth speed, more than 1.5 times faster than ordinary crucian carp.
(2) Low feed conversion ratio. During the farming period, the feed conversion ratio averaged 1.2-1.5.
(3) Strong disease resistance and low-oxygen tolerance. During the farming period, none of the participating units found any large-scale fish disease outbreaks. For example, the Liangjiadian Fish Farm in Haidian District reached a stocking density of 8,600 fish per mu, with no fish disease occurring, and during the farming period the aerator was only run for a few days in the high-temperature season, indicating that this fish has strong low-oxygen tolerance.
(4) Low-temperature tolerance. According to Beijing farming patterns, ordinary crucian carp and bream generally stop feeding around mid-October, while this fish can still feed in late October when the temperature is relatively low, extending the growth period.
2. Several issues that should be noted during the farming of Xiangyun crucian carp
(1) Intensive farming of Xiangyun crucian carp is beneficial for its intensive aquaculture, but attention should be paid to the proportion of silver carp and bighead carp mixed in. Generally, 250-300 silver carp and 25-30 bighead carp are stocked per mu, with the ratio of silver carp to bighead carp basically controlled at 10:1. During farming, never mix in grass carp, common carp or other fish with strong food competition ability, so as not to affect the feeding and growth of the main farmed fish.
(2) Xiangyun crucian carp has the characteristics of fast food grabbing, large area and short time when feeding, so the number of feedings and the feeding area can be appropriately increased each day. In the high-temperature season, feed 5-6 times per day (specifically depending on water temperature and weather conditions). Fish farms with conditions can use automatic feeders to increase the feeding area.
(3) Strengthen feeding management in the early stocking period. Xiangyun crucian carp has a strong ability to feed in groups. The key to forming this feeding habit lies in the domestication work within one month after stocking, and the method of first concentrating and then dividing into ponds should be followed. For example, the Liangjiadian Fish Farm in Haidian District raised a total of 60,000 summer fry. They were first placed in a 5-mu pond and fed with crushed feed. When they grew to 25 g per fish, the pond was divided. After pond division, the density decreased but this did not affect the group feeding of Xiangyun crucian carp.
(4) Stocking density. According to reports from various farming units, in adult fish farming of Xiangyun crucian carp, the smaller the density, the slower they float up to grab food. Therefore, the appropriate adult fish stocking density is 3,000-3,500 fish per mu.