New methods for creating large-sized, high-yield, and early-market Chinese mitten crab germplasm in cold regions

Abstract

This invention relates to the field of aquaculture technology and relates to a method for creating new germplasm of large-sized, high-yield, and early-marketing Chinese mitten crabs in cold regions. The method utilizes germplasm aggregation technology to self-pollinate or hybridize Chinese mitten crabs from the Liaohe and Yangtze River systems to obtain large-sized individuals capable of early market availability. This technology represents a significant breakthrough in the creation of new germplasm of large-sized, high-yield, and early-marketing Chinese mitten crabs in cold regions. This invention provides a method for creating new germplasm of large-sized, high-yield, and early-marketing Chinese mitten crabs in cold regions.

Description

Technical Field

[0001] This invention relates to the field of aquaculture technology, specifically to a method for creating new germplasm of large-sized, high-yield, and early-marketing Chinese mitten crab in cold regions. Background Technology

[0002] Chinese mitten crab ( Eriocheir sinensis Belonging to the phylum Arthropoda, class Crustacea, order Decapoda, and family Eriocheiridae, the Chinese mitten crab (Eriocheir sinensis) is one of the native crab species of East Asia with significant economic value. Wild populations are mainly distributed in rivers and lakes connected to the sea along the eastern coast of my country. As of January 2024, my country had artificially bred five new varieties of Chinese mitten crab from the Yangtze River system: "Yangtze No. 1," "Yangtze No. 2," "Jianghai 21," "Noah No. 1," and "Jinong No. 1," and one new variety from the Liaohe River system: "Guanghe No. 1." The breeding areas for these new varieties differ somewhat across river systems. For example, the Yangtze River mitten crab varieties are mainly bred in the Yangtze River basin, while the Liaohe River mitten crab variety "Guanghe No. 1" is mainly bred in parts of Northeast and North China.

[0003] Currently, Chinese mitten crabs farmed in cold-region ponds and rice paddies are small in size and of poor quality due to their short growth period and fewer molting cycles. Wang Shihui et al. (2021) showed that the average size of female Chinese mitten crabs farmed in rice paddies in the Liaohe River system in cold regions is around 60 g, and that of males is around 90 g; the average size in pond-farmed crabs is slightly higher, with females around 70 g and males around 100 g. However, compared to the large-sized Chinese mitten crabs required by the market, the current size of farmed Chinese mitten crabs is still too small. Furthermore, since northern Chinese mitten crabs are concentrated on the market before the Mid-Autumn Festival, and the date of the Mid-Autumn Festival varies each year, potentially falling between early and late September, the situation is further complicated by the fact that they are primarily available before the Mid-Autumn Festival.

[0004] Therefore, in order to address the situation where Chinese mitten crabs have poor gonad development when they are available in early September, it is particularly important to provide an innovative breeding method for a new breed of Chinese mitten crab that is large-sized, high-yielding, and available in cold regions and at an earlier time. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned technical problems and provide a method for creating new germplasm of large-sized, high-yield, and early-marketed Chinese mitten crab in cold regions.

[0006] The method for creating new germplasm of large-sized, high-yielding, and early-marketing Chinese mitten crab in cold regions is as follows:

[0007] Step 1: Germplasm collection and seedling propagation in the Liaohe and Yangtze River systems;

[0008] (1) At the end of September, large-sized female Chinese mitten crabs with intact limbs, strong activity and well-developed gonads were selected from two-year-old female Chinese mitten crabs raised in cold ponds in the Liaohe River system and transported to the estuary ponds for fattening; in mid-October, large-sized male Chinese mitten crabs with intact limbs, strong activity and well-developed gonads were selected from two-year-old male Chinese mitten crabs raised in ponds in the Yangtze River system and transported to the estuary ponds for fattening, and male and female mitten crabs were raised separately and fed with fresh fish during the breeding period;

[0009] (2) When the gonadal index of the female crab in step (1) reaches 8% or more and the gonadal index of the male crab reaches 3% or more, mating is carried out;

[0010] (3) After mating is completed, remove the male crabs; after the female crabs lay their eggs, put the berried crabs into the overwintering pond;

[0011] (4) Continue feeding the fish with fresh ice until mid-March of the following year;

[0012] (5) At the end of April, when the heartbeat of the fertilized eggs of the berried crabs exceeds 150 beats / min, the berried crabs are placed in the larval rearing pond to release the daphnia larvae; after all the berried crabs have released the daphnia larvae, the female crabs are removed.

[0013] (6) Feed the daphnia larvae, specifically: the daphnia larvae in stages I-II are mainly fed with unicellular algae, the daphnia larvae in stages III-V are mainly fed with rotifers, and after the daphnia larvae grow into megalopa larvae, they are mainly fed with artemia.

[0014] (7) When the daphnia larvae grow to the megalopa larvae 2-4 days later, place the megalopa larvae in a disinfected desalination pond for rearing;

[0015] Step Two: Crab Farming and Overwintering Management;

[0016] 1) Select a cold-region aquaculture pond, disinfect it, fill it with clean water, and plant Elodea nuttallii;

[0017] 2) In mid-to-late May, apply well-rotted and fermented chicken manure around the pond;

[0018] 3) In early June, the megalopa larvae were transported to the ponds of the breeding base for rearing. They were initially fed crushed feed and later pelleted feed.

[0019] 4) From the end of September to the beginning of October, all juvenile crabs were caught, and the early-maturing crabs were removed. The normal juvenile crabs were put into the overwintering pond to overwinter.

[0020] Step 3: Adult crab farming;

[0021] ①In early April of the following year, select a cold-region aquaculture pond, disinfect the pond, and plant Elodea in the center of the pond;

[0022] ② In late April, release juvenile crab seedlings. In the early stage of breeding, feed them with compound feed containing 38-42% protein; in the middle stage of breeding, feed them with compound feed containing 34-38% protein; and in the later stage of breeding, feed them with compound feed containing 38-42% protein.

[0023] ③ From May to October, regularly monitor the growth of the Chinese mitten crab;

[0024] ④ From August to October, observe the gonadal development of Chinese mitten crabs. When the gonadal index of female crabs is above 3%, they can be sold on the market; when the gonadal index of male crabs is above 1.5%, they can be sold on the market.

[0025] The beneficial effects of this invention are:

[0026] (1) In order to address the situation that Chinese mitten crabs have poor gonad development when they are marketed in early September, this invention provides a method for creating new germplasm of large-sized, high-yield, and early-marketed Chinese mitten crabs in cold regions. Through germplasm aggregation technology, Chinese mitten crabs in the Liaohe and Yangtze River systems are self-crossed or crossbred and screened to obtain individuals with large size that can be marketed early. This technology will provide an important breakthrough for creating new germplasm of large-sized, high-yield, and early-marketed Chinese mitten crabs in cold regions.

[0027] (2) This invention creates a new germplasm of Chinese mitten crab, which improves the size, yield and market time of Chinese mitten crab raised in cold regions, and provides an important direction for the development of the Chinese mitten crab farming industry in cold regions.

[0028] This invention provides a method for creating new germplasm of large-sized, high-yield, and early-marketing Chinese mitten crabs in cold regions. Detailed Implementation

[0029] Specific Implementation Method 1: This implementation method for creating new germplasm of large-sized, high-yield, and early-marketing Chinese mitten crabs in cold regions is carried out according to the following steps:

[0030] Step 1: Germplasm collection and seedling propagation in the Liaohe and Yangtze River systems;

[0031] (1) At the end of September, large-sized female Chinese mitten crabs with intact limbs, strong activity and well-developed gonads were selected from two-year-old female Chinese mitten crabs raised in cold ponds in the Liaohe River system and transported to the estuary ponds in Panjin City, Liaoning Province for fattening; in mid-October, large-sized male Chinese mitten crabs with intact limbs, strong activity and well-developed gonads were selected from two-year-old male Chinese mitten crabs raised in ponds in the Yangtze River system and transported to the estuary ponds in Panjin City, Liaoning Province for fattening. Male and female mitten crabs were raised separately and fed with fresh fish during the breeding period.

[0032] (2) When the gonadal index (GSI) of the female breeding crab in step (1) reaches 8% or more and the gonadal index of the male breeding crab reaches 3% or more, mating is carried out;

[0033] (3) After mating is completed, drain the seawater from the mating pool and remove the male crabs; after the female crabs lay eggs, put the berried crabs into the overwintering pool; during the overwintering period, pay attention to clearing snow, improve the light transmittance of the water, and regularly monitor dissolved oxygen to ensure that the berried crabs can overwinter successfully.

[0034] (4) Continue to feed fresh fish until mid-March of the following year to help the berried crabs recover their physical condition as soon as possible. During this period, microecological preparations can be used to regulate water quality.

[0035] (5) At the end of April, when the heartbeat of the fertilized crab eggs exceeds 150 beats / min, the larvae can be placed in cages. Each cage should contain 25-30 berried crabs, and the nursery should contain 50 kg / mu of megalopa larvae. About 3 days after hanging the cages, the berried crabs will have basically all expelled the zoea larvae. Then, the cages can be removed, and the female crabs can be removed.

[0036] Note: The nursery workers place the berried crabs into net cages and put them into the larval rearing pond, a process called "hanging cages". At night, the berried crabs release the hatched larvae into the water, a process called "seedling distribution".

[0037] (6) Feed the daphnia larvae, specifically: the daphnia larvae in stages I-II are mainly fed with unicellular algae, the daphnia larvae in stages III-V are mainly fed with rotifers, and after the daphnia larvae grow to the megalopa larvae dilution stage, they are mainly fed with artemia.

[0038] (7) When the daphnia larvae grow to the megalopa larvae 2-4 days after birth, they can be captured by netting or nighttime light trapping. The megalopa larvae are then placed in a disinfected desalination pond for further rearing.

[0039] Note: According to the growth stages, daphnia larvae are divided into five stages: stage I, stage II, stage III, stage IV, and stage V. After metamorphosis, stage V daphnia larvae become megalopa larvae.

[0040] Step Two: Crab Farming and Overwintering Management;

[0041] 1) Select outdoor aquaculture ponds in cold regions. Set up 30 cm high escape-proof netting around the ponds to prevent the experimental crabs from climbing and escaping. Disinfect the ponds with quicklime (75 kg / mu), then fill them with clean water. One week later, plant *Elodea nuttallii* (a type of algae). Elodea Nuttallii ), to provide cover and food for megalopa larvae;

[0042] 2) In mid-to-late May, apply well-rotted and fermented chicken manure around the pond to fertilize the water;

[0043] 3) In early June, the megalopa larvae of female Liaohe crabs and male Yangtze crabs were transported from the breeding base in Panjin, Liaoning to the aquaculture experimental base via cold chain to carry out crab juvenile farming experiments. They were fed crushed feed in the early stage and pellet feed in the later stage.

[0044] 4) From the end of September to the beginning of October, all the juvenile crabs in the pond were caught using the method of "ground traps + draining and catching". The early-maturing crabs were removed and the normal juvenile crabs were put into the overwintering pond for overwintering.

[0045] Step 3: Adult crab farming;

[0046] ① In early April of the following year, outdoor aquaculture ponds in cold regions were selected. A 30 cm high escape-proof net was installed around the pond to prevent the experimental crabs from climbing and escaping. The ponds were also surrounded by a 30-40 cm high escape-proof net, with the bottom of the net buried 20 cm in the soil. In early April, the experimental ponds were disinfected with quicklime (75 kg / mu). Two weeks later, *Elodea nuttallii* (…) was introduced… Elodea Nuttallii Planted on a platform in the center of the pond, Elodea can provide a hiding place for Chinese mitten crabs to molt, and it is also an important plant food and can purify the water.

[0047] ② In late April, release juvenile crab seedlings. In the early stage of breeding, feed them with a compound feed with a protein content of 38-42% to help the Chinese mitten crabs recover their strength quickly. In the middle stage of breeding, feed them with a compound feed with a protein content of 34-38%. In the later stage of breeding, since it involves fattening the Chinese mitten crabs, it is recommended to feed them with a compound feed with a protein content of 38-42%.

[0048] ③ From May to October, regularly monitor the growth of the Chinese mitten crab;

[0049] ④ From August to October, observe the gonadal development of Chinese mitten crabs. When the gonadal index of female crabs is above 3%, they can be sold on the market; when the gonadal index of male crabs is above 1.5%, they can be sold on the market.

[0050] The beneficial effects of this implementation method are:

[0051] (1) In order to address the situation that Chinese mitten crabs have poor gonad development when they are marketed in early September, this embodiment provides a method for creating a new germplasm of large-sized, high-yield, and early-marketed Chinese mitten crabs in cold regions. Through germplasm aggregation technology, Chinese mitten crabs in the Liaohe and Yangtze River systems are self-crossed or crossbred and screened to obtain individuals with large size that can be marketed early. This technology will provide an important breakthrough for creating a new germplasm of large-sized, high-yield, and early-marketed Chinese mitten crabs in cold regions.

[0052] (2) This implementation method creates a new germplasm of Chinese mitten crab, improves the size and yield of Chinese mitten crabs raised in cold regions and advances the market time, providing an important direction for the development of the Chinese mitten crab farming industry in cold regions.

[0053] Specific implementation method two: The difference between this implementation method and specific implementation method one is that the feeding dosage of fresh fish in steps (1) and (4) is 1 to 5% of the body weight of the broodstock crab.

[0054] The other steps are the same as in Specific Implementation Method 1.

[0055] Specific implementation method three: The difference between this implementation method and specific implementation method one or two is that: in step (2), before mating, the water in the breeding pond is drained, the male breeding crabs are moved into the pond of the female breeding crabs, and filtered seawater is added to a water depth of 1~1.2 m. The salinity of the seawater is 25~30 ppt. The average water temperature during mating is 8~10℃, the ratio of female breeding crabs to male breeding crabs is 2:1, and mating and egg-carrying can be completed in 7~10 days.

[0056] The other steps are the same as in Specific Implementation Method 1 or 2.

[0057] Specific implementation method four: The difference between this implementation method and specific implementation methods one to three is that the water depth of the overwintering pond in step (3) is 2~2.5 m, and the density of berried crabs is controlled at 1000~1500 crabs / mu; the dissolved oxygen in the overwintering pond is monitored regularly during the overwintering period.

[0058] The other steps are the same as those in Specific Implementation Methods One to Three.

[0059] Specific implementation method five: The difference between this implementation method and specific implementation methods one to four is that: in step (5), the dissolved oxygen in the larval rearing pond is not less than 5 mg / L and the pH does not exceed 9.0; in step (6), the daphnia larvae in stages I to V are fed once in the morning and once in the evening (08:00 and 17:00), and the feeding dose each time is 5 to 10% of the daphnia larvae's body weight.

[0060] The other steps are the same as those in Specific Implementation Methods One through Four.

[0061] Specific implementation method six: The difference between this implementation method and specific implementation methods one to five is that the desalination tank in step (7) undergoes desalination 4 to 6 times until the salinity of the water body drops to below 3 ppt.

[0062] The other steps are the same as those in Specific Implementation Methods 1 to 5.

[0063] Specific Implementation Method Seven: The difference between this implementation method and Specific Implementation Methods One through Six is ​​that: in step 3), megalopa larvae are fed at a density of 750-1000 g / mu, the particle size of the pelleted feed is 1.0 mm, and the feeding dosage is 1-5% of the megalopa larvae's body weight; during the breeding period, the water depth is 70-80 cm in June and 0.8-1 m from July to September, and adjusted in a timely manner according to the air temperature; during the breeding period, the water pH is maintained at 7.0-8.5, and the ammonia nitrogen is less than 0.4 mg / L. Water is changed or microbial preparations are added appropriately according to the pond water quality to maintain good water quality and allow the juvenile crabs to grow normally.

[0064] The other steps are the same as those in Specific Implementation Methods 1 to 6.

[0065] Specific Implementation Method Eight: The difference between this implementation method and Specific Implementation Methods One to Seven is that in step 4), the density of juvenile crabs during the overwintering period is 400~500 kg / mu, and the water depth is controlled to be above 2.5 m.

[0066] The other steps are the same as those in Specific Implementation Methods 1 to 7.

[0067] Specific Implementation Method Nine: The difference between this implementation method and Specific Implementation Methods One to Eight is that the planting distance of Elodea in Step 1) and Step ① is 1~2 m and the row spacing is 2~3 m.

[0068] The other steps are the same as those in Specific Implementation Methods 1 to 8.

[0069] Specific Implementation Method 10: The difference between this implementation method and Specific Implementation Methods 1 to 9 is that: in step ②, the stocking density of juvenile crab seedlings is 1000~1200 per mu; water quality control products such as microecological preparations are used regularly, and the physicochemical indicators of pond water quality are monitored regularly throughout the process to ensure that ammonia nitrogen is less than 1 mg / L and the pH of the water body is 7.0~8.5.

[0070] The other steps are the same as those in Specific Implementation Methods 1 to 9.

[0071] The beneficial effects of the present invention are verified using the following embodiments:

[0072] Example 1:

[0073] On September 16, 2021, the applicant collected large-sized, high-quality Chinese mitten crabs from the Liaohe River system, including 2,500 females with an average weight of (101.57±3.16) g and 1,500 males with an average weight of (135.86±2.15) g. On October 15, 2021, the applicant collected large-sized, high-quality Chinese mitten crabs from the Yangtze River system, including 1,000 females with an average weight of (153.70±2.86) g and 500 males with an average weight of (210.90±4.66) g.

[0074] After conducting juvenile crab farming in 2022 and adult crab farming in 2023, we have reached the following conclusions:

[0075] (1) Specifications: The average weight of self-bred female crabs from the Liaohe River was (80.64±1.75)g, and that of male crabs was (110.23±0.73)g. The proportion of female crabs with an average weight ≥80g was 49.53%. The average weight of self-bred female crabs from the Yangtze River was (79.99±1.56)g, and that of male crabs was (107.33±3.99)g. The proportion of female crabs with an average weight ≥80g was 48.47%. The average weight of female crabs hybridized from the Liaohe River and the Yangtze River was (84.13±2.10)g, and that of male crabs was (113.85±3.02)g. The proportion of female crabs with an average weight ≥80g was 61.42%.

[0076] (2) Survival rate and yield: The survival rates of self-bred crabs from the Liaohe River, self-bred crabs from the Yangtze River, and hybrid crabs from the Liaohe River and the Yangtze River were (43.89±0.94)%, (58.36±2.53)%, and (60.82±2.00)%, respectively. Among them, the survival rates of hybrid crabs and self-bred crabs from the Yangtze River were significantly higher than those of self-bred crabs from the Liaohe River. P <0.05; the yields were (660.20±15.40) kg / hm². 2 (919.63±17.69) kg / hm 2 and (1063.18±84.61) kg / hm 2 Among them, the yield of hybrid crabs and Yangtze River self-crossing crabs was significantly higher than that of Liaohe River self-crossing crabs. P <0.05).

[0077] (3) Gonadal Development (Market Time): The gonadal indices of self-bred crabs from the Liaohe River, self-bred crabs from the Yangtze River, and hybrid crabs from the Liaohe River and the Yangtze River are shown in Table 1. On September 10, the gonadal index of the female hybrid crabs from the Liaohe River and the Yangtze River was (4.84±0.43)%, significantly higher than that of self-bred crabs from the Liaohe River and the Yangtze River. P The value <0.05 indicates that the hybrid crabs have better gonadal development and can be marketed earlier. In conclusion, by hybridizing female crabs from the Liao River with male crabs from the Yangtze River, the megalopa larvae bred in Panjin City, Liaoning Province, can be transported to the cold regions of Heilongjiang Province for aquaculture, achieving the goal of producing large-sized, high-yield, and early-marketed commercial crabs.

[0078] Table 1 shows the comparative values ​​of gonadal index at different stages of adult crab farming;

[0079] Table 1

[0080]

[0081] Note: Superscripts in the same row data contain different letters to indicate significant differences. P <0.05).

Claims

1. A method for creating a new germplasm of Eriocheir sinensis in cold regions with large size, high yield and early market, characterized in that The method is carried out according to the following steps: Step one: germplasm collection and seedling breeding of Liaohe and Yangtze River systems (1) In late September, female Eriocheir sinensis of the second year of the Liaohe River system, which are large in size, have perfect limbs, strong activity and perfect gonadal development, are selected from ponds in cold areas, and are transported to estuary ponds for fattening; in mid-October, male Eriocheir sinensis of the second year of the Yangtze River system, which are large in size, have perfect limbs, strong activity and perfect gonadal development, are selected from ponds in the Yangtze River basin, and are transported to estuary ponds for fattening, and the male and female species crabs are bred separately, and fresh fish is fed during breeding; (2) When the gonadal index of the female species crabs in step (1) reaches more than 8%, and the gonadal index of the male species crabs reaches more than 3%, mating is carried out; In step (2), the water in the breeding pond is discharged before mating, and the male species crabs are moved into the pond of the female species crabs, filtered seawater is added to a water depth of 1-1.2 m, and the salinity of the seawater is 25-30 ppt; the average water temperature during mating is 8-10℃, and the ratio of female species crabs to male species crabs is 2:1; (3) After mating is completed, the male crabs are removed; after the female crabs lay eggs, the egg-carrying crabs are placed in the overwintering pond; (4) In mid-March of the following year, fresh fish is continued to be fed; (5) In late April, when the fertilized egg heartbeat of the egg-carrying crabs exceeds 150 times / min, the egg-carrying crabs are placed in the larva cultivation pond to discharge the lamellibranchiate larvae; after the egg-carrying crabs discharge the lamellibranchiate larvae, the female crabs are removed; (6) The lamellibranchiate larvae are fed, specifically: the lamellibranchiate larvae in stages I-II are mainly fed with Chlorella, the lamellibranchiate larvae in stages III-V are mainly fed with rotifers, and after the lamellibranchiate larvae grow into large-eyed larvae, they are mainly fed with Artemia; (7) When the lamellibranchiate larvae grow into large-eyed larvae for 2-4 days, the large-eyed larvae are placed in a disinfected desalination pond for breeding; Step two: crab breeding and overwintering management 1) Select a pond in a cold area, disinfect it, and then inject clean water and plant Elodea canadensis; 2) In mid-to-late May, apply fermented chicken manure around the pond; 3) In early June, the large-eyed larvae are transported to the ponds in the breeding base for breeding, and broken feed is fed in the early stage and pellet feed is fed in the later stage; In step 3), the large-eyed larvae are released at a density of 750-1000 g / mu, the particle size of the pellet feed is 1.0 mm, and the feeding dose is 1-5% of the body weight of the large-eyed larvae; during breeding, the water depth is 70-80 cm in June, and 0.8-1 m in July-September; during breeding, the water pH is guaranteed to be 7.0-8.5, and the ammonia nitrogen is less than 0.4 mg / L; 4) From late September to early October, all the crabs are captured, and the precocious crabs are removed, and the normal crabs are placed in the overwintering pond for overwintering; Step three: adult crab breeding ① In early April of the following year, a pond in a cold area is selected, the pond is disinfected, and Elodea canadensis is planted in the center of the pond; ② In late April, the crab seedlings are released, and in the early stage of breeding, the compound feed with a protein content of 38-42% is fed, in the middle stage of breeding, the compound feed with a protein content of 34-38% is fed, and in the later stage of breeding, the compound feed with a protein content of 38-42% is fed; ③ From May to October, the growth of E. sinensis was regularly monitored; ④ From August to October, the gonadal development of E. sinensis was observed, and the female crab with gonadal index of more than 3% and the male crab with gonadal index of more than 1.5% could be sold.

2. The method for creating a new germplasm of large-sized high-yield early market Chinese mitten crab in cold regions according to claim 1, characterized in that The feeding dose of ice-fresh fish in step (1) and step (4) was 1-5% of the body weight of the crab.

3. The method for creating a new germplasm of large-sized high-yield early market Chinese mitten crab in cold regions according to claim 1, characterized in that The water depth of the overwintering pond in step (3) was 2-2.5 m, and the density of the egg-carrying crab was controlled at 1000-1500 per mu; the dissolved oxygen in the overwintering pond was regularly monitored during the overwintering period.

4. The method for creating a new germplasm of large-sized high-yield early market Chinese mitten crab in cold regions according to claim 1, characterized in that The dissolved oxygen in the larva cultivation pond in step (5) was not less than 5 mg / L, and the pH was not more than 9.0; the leech-like larva in steps (6) was fed twice a day, and the feeding dose was 5-10% of the body weight of the leech-like larva.

5. The method for creating a new germplasm of large-sized high-yield early market Chinese mitten crab in cold regions according to claim 1, characterized in that The desalination pond in step (7) was desalinated for 4-6 times, and the water salinity was reduced to less than 3 ppt.

6. The method for creating a new germplasm of large-sized high-yield early market Chinese mitten crab in cold regions according to claim 1, characterized in that The density of the overwintering crab in step 4) was 400-500 kg per mu, and the water depth was controlled at more than 2.5 m.

7. The method for creating a new germplasm of large-scale high-yield early market Chinese mitten crab in cold regions according to claim 1, characterized in that The planting distance of the Elodea canadensis in steps 1) and ① was 1-2 m, and the row spacing was 2-3 m.

8. The method for creating a new germplasm of large-sized high-yield early market Chinese mitten crab in cold regions according to claim 1, characterized in that The stocking density of the crab fry in step ② was 1000-1200 per mu, and the ammonia nitrogen was controlled at less than 1 mg / L, and the water pH was 7.0-8.5.

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