Crayfish fast-growing new strain group subculture breeding method

Abstract

The invention relates to the technical field of crayfish breeding, and particularly discloses a rapid-growth new strain group subculture breeding method for crayfish, which takes growth performance as a breeding target, adopts a group subculture breeding method to improve and fix main selection characters generation by generation, evaluates breeding effect through whole group performance determination and genetic analysis, and is high in bred group uniformity and stable in character. By comparing the growth performance of the offspring, a parent combination with obvious offspring advantages is screened out, and the breeding performance of the crayfish population can be improved or recovered through population breeding, blood relationship hybridization updating and elimination of degenerated parents through breeding, separation and elimination.

Description

Technical Field

[0001] The invention relates to the technical field of crayfish breeding, and in particular to a method for successive breeding of a new fast-growing crayfish strain. Background Art

[0002] Crayfish, scientifically known as Procambarus clarkii, is an important freshwater shrimp species worldwide. Taxonomically, Procambarus clarkii belongs to the genus Procambarus in the phylum Arthropoda, class Crustacea, suborder Reptantia, family Cambaridae, kingdom Animalia. It is native to central and southern North America and northeastern Mexico. After being artificially introduced to Europe, the Nile River Basin, and China, its distribution range has expanded rapidly.

[0003] In 2022, 24 provinces in my country will breed crayfish, with a breeding area of ​​28 million mu and an output of 2.8907 million tons, up 7.69% and 9.76% year-on-year respectively; the comprehensive output value of crayfish is 458 billion yuan, of which the primary industry is 96 billion yuan, accounting for 20.96%, the secondary industry is 49.8 billion yuan, accounting for 10.87%, and the tertiary industry is 312.2 billion yuan, accounting for 68.17%. The output of crayfish farming ranks fourth among freshwater aquaculture varieties in my country, accounting for 8.79% of the total freshwater aquaculture output in the country. Hubei, Anhui, Hunan, Jiangsu, and Jiangxi are major aquaculture provinces, with a breeding output of 2.6374 million tons, accounting for 91.24% of the total aquaculture output in the country; the output of Sichuan, Shandong, Henan, Zhejiang, Chongqing, and Guangxi (municipalities and autonomous regions) exceeds 10,000 tons, with a breeding output of 239,000 tons, accounting for 8.27% of the total aquaculture output in the country.

[0004] In 2022, the area of ​​crayfish farming in Guangxi reached 172,900 mu, with a production of 11,000 tons, of which more than 90% was raised in rice fields. Guangxi currently has 24.41 million mu of water-retaining farmland, and the rice field farming rate of crayfish is less than 0.64%. There is great potential for the development of ecological cultivation of crayfish in rice fields.

[0005] Seed industry is the foundation and key of aquaculture, but the current crayfish breeding system is backward. In production, large-sized commercial shrimps are often caught in batches for sale, and small-sized shrimps after sale are left in the fields and ponds for self-breeding. After years of "catching the big and leaving the small" and the reverse selection of inbreeding for generations have caused the degradation of germplasm and poor production performance. "Catching the big and leaving the small, self-breeding" has led to a decrease in the growth rate and commercial rate of crayfish, and the disadvantages have become more and more significant year by year. Attempts to change the status quo by adopting factory breeding methods are difficult to promote due to the low emergence rate of artificial seedlings. Crayfish live in the bottom and caves. Female shrimps have a small number of eggs, lay eggs in batches, and have a long egg-holding period. The development of shrimp larvae is not synchronized and they kill each other. It is also not conducive to the use of factory breeding to produce large quantities of seedlings. The promotion of the "separation of breeding and rearing" production model urgently needs to solve the problems of seedling improvement and large-scale breeding and supply of improved varieties. Therefore, it is of great significance to cultivate crayfish varieties with excellent growth traits and stable genetics and establish a good breeding system for the healthy development of Guangxi's crayfish farming industry. Summary of the invention

[0006] The purpose of the present invention is to provide a method for successive breeding of a new fast-growing crayfish strain, to cultivate a crayfish variety with excellent growth traits and genetic stability, to establish a good seed breeding system, and to solve the problems of the current backward crayfish breeding system, the adverse selection of "catching the big and keeping the small" and cumulative inbreeding resulting in germplasm degeneration, poor production performance, and a decrease in crayfish growth rate and commercial rate of adult shrimp year by year.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A method for successive breeding of a new fast-growing crayfish strain.

[0009] Step 1: Select the Egyptian population, the Hunan Yueyang population, the Shanglin population, the Hubei Jingzhou population, the Jiangxi Hukou population and the Hubei Qianjiang population as the breeding base population according to the growth performance of crayfish;

[0010] Step 2: Select individuals from the breeding base group according to their weight and gender to form a breeding core group for successive generations of breeding.

[0011] As a limitation of the present invention, in step 1, the growth performance of crayfish includes: individual weight, body length, carapace length, carapace width, and abdominal segment length.

[0012] As a limitation of the present invention, when forming the breeding core group, the weight of the selected individuals is more than 15% greater than the average weight of the breeding basic group of the same sex.

[0013] As a limitation of the present invention, in the breeding core group formed, the body length of male shrimps is ≥8.5 cm, the body length of female shrimps is ≥8.0 cm, and the ratio of male to female individuals is 2:1.

[0014] As a limitation of the present invention, when forming the breeding core group, the stocking amount of crayfish is 20-40 kg / mu, and the number of individuals in the core group is not less than 1,200.

[0015] As a limitation of the present invention, during the successive breeding, selection is made based on individual weight, and the weight of individuals selected in each generation is more than 15% greater than the average weight of the same generation and same sex group.

[0016] As a limitation of the present invention, during the successive breeding and cultivation, the breeding pond area is 1 to 2 mu / mouth, the broodstock are released at a density of 20 to 40 kg / mu, the ratio of male to female individuals is (2 to 3):1, and the offspring breeding time is 135 to 165 days.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention proposes a method for successive breeding of a new fast-growing crayfish strain, which takes growth performance as the breeding target and adopts a group successive breeding method to improve and fix the main selected traits from generation to generation. The bred population has high uniformity and stable traits. The breeding performance of the crayfish population can be improved or restored through group selection, blood hybridization and renewal, and separation of breeding and rearing to eliminate degraded parents. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The weight distribution diagram of each generation of the Egyptian strain at 150 days of age in Example 2;

[0020] Figure 2 The figure is the weight distribution diagram of each generation of Hunan Yueyang strain at 150 days of age in Example 2;

[0021] Figure 3 This is the body weight distribution diagram of each generation of the Hubei Qianjiang strain at 150 days of age in Example 2. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1: Establishing a basic group and a core group for crayfish breeding

[0024] 1.1 Selection of breeding base population

[0025] Six crayfish groups were selected from Egypt, Yueyang, Hunan, Shanglin, Guangxi, Jingzhou, Hubei, Hukou, Jiangxi and Qianjiang, Hubei, and were cultured in the aquarium laboratory of Guangxi Fisheries Research Institute. The breeding pond was 3m×1.5m long and wide, with a water depth of 1m. The specifications of the shrimp fry used for breeding were 5-6g in weight and 4-5cm in length. After one week of temporary breeding in the pond, the shrimp fry with strong body and sound appendages were selected for growth performance test, and no growth phenotypic indicators were selected. There were 300 shrimp fry in each group, and the breeding time was from March 15 to May 14, 2021. After 60 days of breeding, the growth indicators such as body length and weight of each group were measured and statistically analyzed. See Table 1 for details.

[0026] Table 1: 60-day production performance of different types of crayfish populations

[0027] group Average weight (g) Average body length (cm) Growth rate (g / d) Survival rate Egypt <![CDATA[35.77±5.46 a ]]> 7.83±0.38 0.512 73.8％ Yueyang <![CDATA[33.61±6.25 b ]]> 7.73±0.41 0.477 74.5％ Shanglin <![CDATA[32.38±7.53 b ]]> 7.60±0.38 0.456 73.1％ Jingzhou <![CDATA[32.60±6.53 b ]]> 7.61±0.39 0.460 72.5％ Lake Mouth <![CDATA[31.94±7.62 b ]]> 7.57±0.44 0.449 71.9％ Qianjiang <![CDATA[32.91±6.19 b ]]> 7.65±0.35 0.465 73.4％

[0028] 1.2 Establishment of breeding base population

[0029] According to the genetic diversity of the population and the growth performance test results shown in Table 1, three populations from Egypt, Yueyang, Hunan, and Qianjiang, Hubei were selected as breeding materials, and germplasm was introduced for breeding through trade and other means. The introduction information is shown in Table 2. The breeding site is located in a crayfish base in Liangqing District, Nanning City. The base has clean water sources and complete breeding facilities. The breeding pond area is 1.5 to 10 mu and the water depth is 1.0 to 2.0 m. Aquatic plants are planted in the pond, and each breeding pond is equipped with an independent escape prevention net.

[0030] Table 2: Introduction information

[0031] serial number Weight Body length cm Introduction time Egypt 30.2±5.51 7.6±0.4 2021.04.22 Yueyang, Hunan 25.3±6.23 7.0±0.6 2021.10.08 Qianjiang, Hubei 10.6±3.54 5.7±0.4 2023.04.19

[0032] After temporary rearing, the introduced population was eliminated of weak individuals, and individuals with strong bodies and healthy appendages were selected to establish breeding basic groups according to their provenance. They were cultured in breeding ponds with a stocking rate of 30 kg / mu. When the average body weight reached more than 30 g, the body weight of the individuals in the basic group was measured. See Table 3 for details.

[0033] Table 3: Results of breeding population statistics

[0034]

[0035] 1.3 Establishing a breeding core group

[0036] According to the mean and standard deviation of the basic group body weight shown in Table 3, the selection of individuals for group building is estimated.The cutoff point was selected, and robust individuals with sound appendages were selected from the basic group according to the cutoff point and gender to form a breeding core group (F0). The weight of the selected individuals was more than 15% greater than the average weight of the basic group of the same gender, and the selection intensity was indirectly controlled. The male shrimps in the selected core group were required to be ≥8.5cm in length, and the female shrimps were ≥8.0cm in length. The number of core group individuals was not less than 1200, and the male-to-female ratio was 2:1. After the breeding core group was established, the selected core group individuals were stocked at a density of 30kg / mu. After the average weight of the core group individuals reached more than 40g, the weight of the core group individuals was measured. The results are shown in Table 4.

[0037] Table 4: Results of re-statistics of breeding core population

[0038]

[0039] Example 2: Method for successive breeding of a new fast-growing crayfish strain

[0040] 2.1 Cultivation of succession breeding population

[0041] From the breeding core group established in Example 1, a new generation of breeding groups was formed with strong shrimp bodies, sound appendages, and a body weight exceeding 15% of the group mean. The Egyptian and Hunan Yueyang strains were selected for 3 generations of successive breeding, which were recorded as F1, F2, and F3 generations, respectively. The Hubei Qianjiang strain was selected for 1 generation of successive breeding, which was recorded as F1. The successive breeding was carried out in a crayfish base in Liangqing District, Nanning City. The breeding pond area was about 1.5 mu / mouth, and the parent shrimp was placed at a density of 30 kg / mu, with a male-female ratio of 2:1, 520 female shrimps / mu, 260 male shrimps / mu, and the culture age was 150d. The pond culture was carried out according to the T / QJCIPA 001-2022 standard. The individuals in the control group also came from the breeding core group, but no weight index selection was performed. The differences in growth traits between different groups were compared by one-way analysis of variance (ANOVA), and multiple comparisons between groups were performed by the SNK method. All statistical analyses were performed using SPSS 19.0 analysis software, with a significance level of P < 0.05. After statistical analysis, the standard selection response (SR), realized heritability (h2R), and genetic gain (GG) were calculated.

[0042] 2.2 Progress in Egyptian strain selection and breeding

[0043] The weight of crayfish cultured for 150 days was measured, and the weight, coefficient of variation, selection intensity, selection response, genetic gain and actual heritability of each group were analyzed and calculated. The results are shown in Table 5. The average weight of the F0 generation breeding group of the Egyptian strain was 47.70±10.73g, with a coefficient of variation of 0.23; the average weight of the F1 generation breeding group was 51.93±11.27g, with a coefficient of variation of 0.22, and the average weight of the control group was 47.49±11.33g, with a coefficient of variation of 0.24; the average weight of the F2 generation breeding group was 55.77±10.96g, with a coefficient of variation of 0.20, and the average weight of the control group was 49.22±9.94g, with a coefficient of variation of 0.20; the average weight of the F3 breeding population was 58.39±11.40g, with a coefficient of variation of 0.19, and the average weight of the control group was 46.96±10.30g, with a coefficient of variation of 0.22; the selection intensities calculated for the F1, F2 and F3 generations were 2.06, 2.39 and 1.69, respectively; the actual heritability was 0.1731, 0.1409 and 0.1374; the genetic progress was 8.86%, 7.4% and 4.70%, respectively, and the total genetic progress from F0 to F3 was 22.41%. After multiple comparisons, such as Figure 1 As shown, the weight gain levels of F1, F2 and F3 generations after selection were significantly different from those of F0 generation.

[0044] Table 5: Progress in breeding of Egyptian strains

[0045]

[0046]

[0047] 2.3 Progress in the selection and breeding of Hunan Yueyang strains

[0048] The body weights of 150-day-old crayfish were measured, and the body weight, coefficient of variation, selection intensity, selection response, genetic gain and realized heritability of each group were analyzed and calculated. The results are shown in Table 6. The average body weight of the F0 generation breeding population of Yueyang strain was 45.62±12.32g, with a coefficient of variation of 0.27; the average body weight of the F1 generation breeding population was 49.01±12.25g, with a coefficient of variation of 0.25, and the average body weight of the control group was 45.40±16.67g, with a coefficient of variation of 0.37; the average body weight of the F2 generation breeding population was 52.79±12.67g, with a coefficient of variation of 0.24, and the average body weight of the control group was 44.76±12.45g, with a coefficient of variation of 0.28; the average body weight of the F3 generation breeding population was 55.67±12.80g, with a coefficient of variation of 0.23, and the average body weight of the control group was 48.2±16.81g, with a coefficient of variation of 0.35; The selection intensity, selection response, genetic gain and realized heritability of each generation of Hunan Yueyang strain at 150 days of age. The selection intensities calculated for the F1, F2, and F3 generations were 2.11, 2.47, and 2.63, respectively, and the actual heritabilities were 0.1224, 0.1303, and 0.1177. The genetic progress was 7.43%, 7.87%, and 6.50%, respectively, and the total genetic progress from F0 to F3 was 21.38%. After multiple comparisons, Figure 2 As shown, the weight gain levels of F1, F2 and F3 generations after selection were significantly different from those of F0 generation.

[0049] Table 6: Progress in breeding of Hunan Yueyang strains

[0050]

[0051]

[0052] 2.4 Progress in Breeding of Hubei Qianjiang Line

[0053] The weight of crayfish at 150 days of culture was measured, and the weight, coefficient of variation, selection intensity, selection response, genetic gain and realized heritability of each group were analyzed and calculated. The results are shown in Table 7. The average weight of the F0 generation breeding group in Qianjiang group was 42.91±10.23g, with a coefficient of variation of 0.24; the average weight of the F1 generation breeding group was 46.70±9.59g, with a coefficient of variation of 0.21; the average weight of the control group was 42.06±10.13g, with a coefficient of variation of 0.24; the selection intensity, selection response, genetic gain and realized heritability of each generation of Hubei Qianjiang strain at 150 days of age. The selection intensity, genetic gain and realized heritability calculated for the F1 generation were 2.11, 9.771% and 0.1764, respectively. After multiple comparisons, such as Figure 3 As shown, the weight gain level of the F1 generation after selection was significantly different from that of the F0 generation.

[0054] Table 7: Progress of breeding of Qianjiang population in Hubei

[0055]

[0056] 2.5 Analysis of population growth rate and uniformity

[0057] The body weight of the introduced Egyptian population, Hunan Yueyang population and Hubei Qianjiang population at 150 days of age was measured. The results showed that the average body weight of the three introduced populations at 150 days of age were 47.7±10.73g, 45.62±13.15g and 42.91±10.23g, respectively. The Egyptian population had the fastest growth rate, which was 4.56% and 11.16% faster than the Hunan Yueyang population and Hubei Qianjiang population, respectively.

[0058] As shown in Table 8, the coefficients of variation of the F0, F1, F2, and F3 generations of the Egyptian strain were 0.2250, 0.2170, 0.1965, and 0.1907, respectively, and the coefficient of variation of the bred F3 generation was 15.24% lower than that before breeding (F0); the coefficients of variation of the F0, F1, F2, and F3 generations of the Hunan Yueyang strain were 0.2722, 0.2512, 0.2419, and 0.2402, respectively, and the coefficient of variation of the bred F3 generation was 11.76% lower than that before breeding (F0); the coefficients of variation of the F0 and F1 generations of the Hubei Qianjiang strain were 0.2370 and 0.2030, respectively, and the coefficient of variation of the F1 generation was 14.35% lower than that before breeding (F0).

[0059] Table 8: Mean body weight and coefficient of variation of each generation at 150 days of age in the breeding population

[0060]

[0061]

[0062] The three fast-growing crayfish selected were compared in groups, and the results are shown in Table 9. The fast-growing new strain selected from the Egyptian population performed best, with a growth rate 36.08% and 27.99% faster than that of the Hubei Qianjiang population and the Hunan Yueyang population before breeding; 25.03% and 4.89% faster than that of the Hubei Qianjiang population (F1) and the Hunan Yueyang population (F3) after breeding; the weight variation coefficient was 12.50% and 27.59% lower than that of the Hubei Qianjiang population and the Hunan Yueyang population before breeding, and 0% and 27.59% lower than that of the Hubei Qianjiang population (F1) and the Hunan Yueyang population (F3) after breeding.

[0063] Table 9: Comparison of growth rate and population uniformity of new strains among populations

[0064]

[0065]

[0066] 2.6 Genetic diversity of breeding populations

[0067] The number of alleles at 12 microsatellite loci in the three breeding populations of Egypt, Yueyang and Qianjiang ranged from 6 to 16 (an average of 11.083), the number of effective alleles ranged from 3.102 to 6.291 (an average of 4.790), the observed heterozygosity ranged from 0.189 to 0.800, the expected heterozygosity ranged from 0.678 to 0.841, and the polymorphic information content ranged from 0.655 to 0.821. All 12 microsatellite loci are highly polymorphic loci (PIC>0.5) and can be used to analyze the genetic structure of crayfish.

[0068] The genetic diversity parameters of the three newly bred lines in Egypt, Yueyang, Hunan, and Qianjiang, Hubei are shown in Table 10. The average number of alleles in the three populations ranged from 7.083 to 9.250, the average number of effective alleles ranged from 4.025 to 4.830, the average observed heterozygosity values ​​ranged from 0.567 to 0.631, the average expected heterozygosity values ​​ranged from 0.743 to 0.779, and the average PIC values ​​ranged from 0.708 to 0.751. The results showed that the three populations had high genetic diversity, as shown in the following table: Egypt > Qianjiang, Hubei > Yueyang, Hunan; compared with the pre-breeding period (F0), the average polymorphic information content PIC was improved.

[0069] Table 10: Genetic diversity of the selected strain population based on 12 microsatellite loci

[0070]

[0071] As shown in Table 11, population genetic differentiation analysis showed that there were different degrees of differentiation among the three crayfish populations. Among them, the fixation index (Fst) between the Qianjiang population in Hubei and the Yueyang population in Hunan was the smallest (0.036), followed by the Egypt and Yueyang populations in Hunan (0.046), both of which were at a slight differentiation level (Fst < 0.05), while the Egypt and Qianjiang populations in Hubei had the largest index (0.123), which were at a moderate differentiation level (0.05 < Fst < 0.15). The gene flow between populations was 8.751-30.145, indicating that there was extensive gene exchange between populations.

[0072] Table 11: Interpopulation differentiation index Fst (below the diagonal) and gene flow Nm (on the diagonal)

[0073]

[0074]

[0075] As shown in Table 12, the results of AMOVA showed that 2% of the genetic variation came from among populations, and 98% came from within populations. The UPGMA clustering tree constructed based on Nei's genetic distance showed that the populations from Yueyang, Hunan and Qianjiang, Hubei clustered into one branch, and the Egyptian population formed a separate branch.

[0076] Table 12: Analysis of Molecular Variance (AMOVA)

[0077] Sources of variation Degrees of Freedom sum of squares Variance components percentage(%) Intergroup 2 18.033 0.072 2％ In-group 177 826.850 4.671 98％ total 179 844.883 4.744 100％

[0078] 2.7 Conclusions on the Genetic Diversity Analysis of the Selected Populations

[0079] The results showed that 12 loci showed high polymorphism (0.748 < PIC < 0.768) in the three populations of Egypt, Yueyang, Hunan and Qianjiang, Hubei, meeting the requirements for the genetic diversity analysis of crayfish; the average expected heterozygosity of 12 microsatellite loci was 0.782, indicating a relatively high level of population heterozygosity. The three crayfish populations all had a high level of genetic diversity (0.700 < He < 0.729, 0.748 < PIC < 0.768). The average expected heterozygosity of the three populations was much higher than the average observed heterozygosity, indicating that there was a phenomenon of heterozygote loss in the three crayfish populations. This may be due to the relatively small population size and the occurrence of bottleneck effects, resulting in genetic drift and other reasons, leading to the loss of alleles.

[0080] In summary, the method for successive selection of the fast-growing new strain population of crayfish proposed by the present invention uses growth performance as the breeding goal, adopts the method of successive selection of populations to gradually improve and fix the main selected traits, and uses the whole population performance measurement and genetic analysis to evaluate the breeding effect. Two fast-growing new strains of crayfish with high population uniformity, stable traits and relatively high genetic diversity were developed. Among them, the growth rate of the Egyptian strain F3 increased by 22.41% compared with the F0 generation, and the coefficient of variation of body weight decreased by 17.39% compared with the F0 generation. The expected heterozygosity and polymorphic information content were 0.779 and 0.751 respectively; the growth rate of the Yueyang, Hunan strain F3 increased by 22.03% compared with the F0 generation, and the coefficient of variation of body weight decreased by 11.11% compared with the F0 generation. The expected heterozygosity and polymorphic information content were 0.774 and 0.708 respectively. By population selection, blood hybridization and renewal, and elimination of degenerate parents through breeding and separation, the aquaculture performance of the crayfish population can be improved or restored.

[0081] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A method for successive breeding of a new fast-growing crayfish strain, characterized in that: Specifically: Step 1: Select the Egyptian population, the Hunan Yueyang population, the Shanglin population, the Hubei Jingzhou population, the Jiangxi Hukou population and the Hubei Qianjiang population as the breeding base population according to the growth performance of crayfish; Step 2: Select individuals from the breeding base group according to their weight and gender to form a breeding core group for successive generations of breeding.

2. The method for successive breeding of a new fast-growing crayfish strain according to claim 1, characterized in that: In step 1, the growth performance of crayfish includes: individual weight, body length, carapace length, carapace width, and abdominal segment length.

3. The method for successive breeding of a new fast-growing crayfish strain according to claim 1, characterized in that: When forming a breeding core group, the selected individuals have a weight that is more than 15% greater than the average weight of the breeding base group of the same sex.

4. The method for successive breeding of a new fast-growing crayfish strain according to claim 1, characterized in that: In the breeding core group formed, the body length of male shrimps is ≥8.5cm, the body length of female shrimps is ≥8.0cm, and the ratio of male to female individuals is 2:

1.

5. The method for successive breeding of a new fast-growing crayfish strain according to claim 1, characterized in that: When forming a core breeding group, the stocking rate of crayfish is 20-40 kg / mu, and the number of individuals in the core group is not less than 1,200.

6. The method for selecting and breeding a new fast-growing crayfish strain according to claim 1, characterized in that: During successive breeding, selection is made based on individual weight, and the weight of individuals selected in each generation should be at least 15% greater than the average weight of the same generation and same sex group.

7. The method for successive breeding of a new fast-growing crayfish strain according to claim 1, characterized in that: During successive breeding and cultivation, the breeding pond area is 1 to 2 mu / mouth, the broodstock are released at a density of 20 to 40 kg / mu, the ratio of male to female individuals is (2 to 3):1, and the offspring breeding time is 135 to 165 days.

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