A fish breeding method that maintains genetic diversity

Abstract

The present invention relates to a method for breeding fish for maintaining genetic diversity, and belongs to the field of fishery science and application technology. The operation steps are as follows: (1) finding out the genetic background and selecting a basic population; (2) clarifying the breeding target and selecting the target individual, wherein the breeding target trait is one or more of growth rate, hypoxia tolerance, disease resistance, survival rate, and body color; (3) breeding parent grouping, after more than three generations of offspring screening and cultivation, the genetic diversity level of the breeding population reaches: the observed heterozygosity (Ho) of each generation is maintained above 0.5, the expected heterozygosity (He) is maintained above 0.5, and the number of alleles is maintained above 4. The present invention continuously selects individuals that meet the breeding target from a large population for breeding, so that the target trait-related genes are aggregated in the offspring, thereby obtaining a breeding population with significant target traits to meet the needs of industrial development; at the same time, because non-target populations are continuously eliminated during the breeding process, the breeding and conservation costs are greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of fishery science application, and in particular relates to a method for maintaining high genetic diversity during fish breeding and selection. Background Art

[0002] Under artificial breeding conditions, fish groups are kept in a closed state for a long time. With the increase of generations, inbreeding and non-directional artificial breeding cause a decrease in genetic diversity in the breeding group. The reduction of genetic diversity will reduce the adaptability of a species to environmental changes, reduce the richness of variation in the group, lead to germplasm decline, the disappearance of excellent traits, and ultimately affect breeding production and economic benefits.

[0003] Breeding companies need to carry out multiple generations of breeding and selection of selected varieties to ensure that the target traits of the bred varieties are improved. However, from the perspective of seed preservation costs and ease of management, companies often conserve a very limited number of parents, and the number of parents actually used for breeding is even smaller. With the increase in breeding generations, genetic diversity is bound to decline, and there is a risk of germplasm degradation and loss of excellent traits. Therefore, how to carry out seedling production and breeding of improved varieties with a small number of parents, while still maintaining a high genetic diversity of the breeding population, is a key technical problem that needs to be solved urgently. Summary of the invention

[0004] In order to solve the problem of reduced genetic diversity caused by continuous breeding of fish, the present invention provides a fish breeding method for maintaining genetic diversity.

[0005] A fish breeding operation to maintain genetic diversity follows these steps:

[0006] (1) Identify genetic background and select base population

[0007] (1.1) Selecting a population with high genetic diversity as a basic population, wherein the basic population comes from an aquatic breeding farm or natural waters;

[0008] (1.2) Use microsatellite molecular markers to evaluate the genetic diversity of the selected population, and select the population with observed heterozygosity (Ho) and expected heterozygosity (He) both higher than 0.5 and the number of genetic diversity index alleles not less than 4 as the basic population; and the number of individuals in the basic population shall not be less than 500;

[0009] (2) Clarify breeding goals and select target individuals

[0010] (2.1) Starting from the basic population, one or more economic traits are determined as the breeding target traits, wherein the economic traits are one or more of growth rate, hypoxia tolerance, disease resistance, survival rate, and body color;

[0011] (2.2) In each generation of summer flower fish fry, fingerlings, reserve parents, and parent fish, selection is carried out according to the breeding target traits, and finally the parents for breeding the next generation are obtained, with a total seed retention rate of less than 1%;

[0012] (3) Breeding parents are paired and offspring are raised in groups

[0013] (3.1) According to the breeding target traits, 30 to 40 sexually mature male and female individuals are selected from the parents of the next generation and divided into two groups, namely, primary generation group 1 (F0-1) and primary generation group 2 (F0-2); the number of each group is equal, with a male-female ratio of 1:1, and many-to-many artificial breeding is carried out within the group. The offspring obtained from the two groups are respectively referred to as first generation group 1 (F1-1) and first generation group 2 (F1-2), and are cultivated separately until sexual maturity;

[0014] (3.2) According to the breeding target traits, select 15 to 20 females and males with good gonad development, good vitality, no damage, and no deformity from the first generation group (F1-1);

[0015] Similarly, according to the breeding target traits, 15 to 20 females and males with good gonad development, good vitality, no damage, and no deformity are selected from the first generation two groups (F1-2);

[0016] (3.3) The female fish in F1-1 are mated with the male fish in F1-2 to carry out many-to-many artificial breeding. The obtained F2-1 progeny are recorded as F2-1. The F2-1 progeny are cultured separately until sexual maturity.

[0017] Similarly, the male fish in the first generation group (F1-1) and the female fish in the first generation group (F1-2) were mated to carry out many-to-many artificial breeding, and the obtained second generation group two offspring were recorded as second generation group two (F2-2), and the second generation group two offspring were cultivated separately to sexual maturity;

[0018] (3.4) According to the breeding target traits, select 15 to 20 females and males with good gonad development, good vitality, no damage, and no deformity from the second generation group (F2-1);

[0019] Similarly, according to the breeding target traits, 15 to 20 females and males with good gonad development, good vitality, no damage, and no deformity were selected from the second generation and second group (F2-2);

[0020] (3.5) The female fish in the second generation group (F2-1) are mated with the male fish in the second generation group (F2-2) to carry out many-to-many artificial breeding. The obtained three-generation group offspring are recorded as three-generation group (F3-1). The three-generation group offspring are raised separately until sexual maturity;

[0021] Similarly, the male fish in the second generation group one (F2-1) was mated with the female fish in the second generation group two (F2-2) to carry out many-to-many artificial breeding, and the obtained third generation group two offspring was recorded as third generation group two (F3-2), and the third generation group two offspring were cultivated separately to sexual maturity;

[0022] (3.6) Produce four generations of one group (F4-1) and four generations of two groups (F4-2) according to the above method, and cultivate them to sexual maturity; then reproduce five generations of one group (F5-1) and five generations of two groups (F5-2), and so on in this order;

[0023] Through the above steps, the genetic diversity level of the breeding population is maintained: the observed heterozygosity (Ho) of each generation is maintained above 0.5, the expected heterozygosity (He) is maintained above 0.5, and the number of alleles is maintained above 4.

[0024] The further technical solution is as follows:

[0025] In step (1.1), the natural waters are large rivers, lakes and other water bodies, such as the Yangtze River, Huaihe River, Chaohu Lake and Poyang Lake.

[0026] In step (2.2), the specific operations are as follows:

[0027] (2.2.1) The first screening is at the summer flower seedling stage, and individuals with obvious target traits, good vitality and no deformities are selected as the breeding group. The number of the selected group is less than 1 / 2 to 2 / 3 of the total number;

[0028] (2.2.2) The second screening is at the fingerling stage, and individuals with obvious target traits, good vitality and no deformities are selected as the breeding group. The number of the selected group is less than 1 / 5 to 1 / 4 of the total number;

[0029] (2.2.3) The third screening is at the reserve parent stage. Individuals with obvious target traits, good vitality and no deformities are selected as the breeding group. The number of the selected group is less than 1 / 5 to 1 / 4 of the total number;

[0030] (2.2.4) The fourth screening is at the broodstock stage, where individuals with obvious target traits, good vitality and no deformities are selected as the breeding group. The number of the selected group is less than 1 / 5 to 1 / 4 of the total number.

[0031] The beneficial technical effects of the present invention are embodied in the following aspects:

[0032] (1) The present invention continuously selects individuals that meet the breeding goals from a large population for reproduction, so that the target trait-associated genes are aggregated in the offspring, thereby obtaining a breeding population with significant target traits to meet the needs of industrial development.

[0033] (2) The present invention effectively avoids inbreeding due to the parent grouping and cross-combination design, the reasonable number of parents, and the separate cultivation of offspring, so that the observed heterozygosity (Ho) and expected heterozygosity (He) of each generation are maintained above 0.5, and the number of alleles is above 4, ensuring that the germplasm is not degraded and the production performance is not reduced.

[0034] (3) The present invention selects target populations at each generation of summer flowers, fish species, reserve parents, and parents, greatly improving breeding efficiency. In addition, since non-target populations are continuously eliminated during the breeding process, breeding and conservation costs are greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a diagram showing the selection of parent groups for the base group. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below through examples.

[0037] Example 1

[0038] This embodiment 1 takes the conservation and breeding of Pelteobagrus vachelli as an example.

[0039] A breeding operation of Pelteobagrus vachelli to maintain genetic diversity is as follows:

[0040] (1) Identify the genetic background and select the base population.

[0041] Pelteobagrus vachelli was collected from six breeding farms in Guangdong, Sichuan, Zhejiang and Anhui to carry out genetic diversity testing. The specific operations are as follows:

[0042] (1.1) After preliminary experiments, 8 pairs of microsatellite primers that can stably amplify, have a large number of alleles, and have good polymorphism were screened out as shown in Table 1:

[0043] Table 1 Microsatellite primers of Pelteobagrus vachelli

[0044]

[0045] Table 2 Genetic diversity information of eight microsatellite loci in Pelteobagrus vachelli

[0046]

[0047] As shown in Table 2, the 8 microsatellite loci have high genetic diversity in the population of P. vachelli, meeting the standard of high genetic diversity of microsatellites, among which the size range and average value of the number of alleles are greater than 4; the size range and average value of the observed heterozygosity (Ho), expected heterozygosity (He) and polymorphic information content (PIC) are greater than 0.5. This indicates that the selected microsatellite loci are suitable for the study of genetic diversity of the population of P. vachelli.

[0048] (1.2) Based on the verification of the reliability of the selected molecular markers, the test results are as shown in Table 3:

[0049] Table 3 Comparison of genetic diversity information among six populations of P. vachelli

[0050] Population Sample number n Allele number Na Observed heterozygosity Ho Expected heterozygosity He Polymorphic Information Content (PIC) Guangdong GD 30 8.125 0.825 0.767 0.717 Sichuan SC 22 6.500 0.869 0.731 0.672 Zhejiang ZJ 30 8.250 0.842 0.806 0.762 Huainan HN 30 7.125 0.758 0.734 0.686 Lu'an LA 26 6.750 0.808 0.729 0.673 Fengtai FT 30 7.625 0.825 0.766 0.718 All samplesTotal 168 11.000 0.819 0.811 0.705

[0051] As shown in Table 3, the genetic diversity index Na among the populations of P. vachelli was 6.500-8.250, which was greater than 4; Ho was 0.758-0.869, He was 0.729-0.806, and PIC was 0.672-0.762, which were all greater than the high polymorphism standard of 0.5. Therefore, it was considered that the six populations of P. vachelli had high genetic diversity and similar genetic diversity levels. Based on this, according to the actual production needs, the populations in Huainan, Anhui and Zhejiang were selected as the basic populations, and 1,000 P. vachelli with good vitality, no damage, and no deformity were selected as the basic population.

[0052] (2) Clarify breeding goals and select target individuals

[0053] (2.1) Starting from the basic population, one or more economic traits are determined as the breeding target traits. In this Example 1, growth rate is used as the breeding target trait of Pelteobagrus vachelli.

[0054] (2.2) In each generation, summer flower fry, one-year-old fingerlings, two-year-old fingerlings, and even the parent stage, selection is carried out according to the growth rate as the breeding target trait, and the total seed retention rate of each generation is about 0.4%. Figure 1 , as follows:

[0055] (2.2.1) The first screening is conducted about one month after the emergence of the film, i.e. the summer flower seedling stage, and individuals with large size, good vitality and no deformity are selected as the breeding group. The number of the selected group is less than 1 / 2 of the total number, about 50,000.

[0056] (2.2.2) The second screening is when the fish size is about 50-100g / tail (1 year old), and individuals with large size, good vitality and no deformity are selected as the breeding group. The number of selected groups is less than 1 / 5 of the total number, about 10,000 fish.

[0057] (2.2.3) The third screening is conducted at the reserve broodstock stage when the fish are about 150-250g / tail (2 years old). Individuals with large size, good vitality and no deformity are selected as the breeding group. The number of the selected group is less than 1 / 5 of the total number, about 2,000 fish.

[0058] (2.2.4) The fourth screening is when the broodstock weigh about 300-500g / tail (3 years old), and the individuals with large size, good vitality and no deformity are selected as the breeding group. The number of the selected group is less than 1 / 5 of the total number, about 400 tails, and they are temporarily placed in the broodstock pond. According to the production and breeding needs, select the appropriate amount of parents for breeding.

[0059] According to the number of parents selected above, each group and each generation of Pelteobagrus vachelli can obtain about 100,000 offspring, which can be bred separately.

[0060] (3) Breeding parent combination, offspring screening and cultivation

[0061] (3.1) 30 sexually mature male and female fish were selected from the basic population of Pelteobagrus vachelli and divided into two groups, each with 15 male and female fish, respectively recorded as primary generation group 1 (F0-1) and primary generation group 2 (F0-2). Many-to-many artificial breeding was carried out within the two groups. The offspring obtained from the two groups were respectively recorded as first generation group 1 (F1-1) and first generation group 2 (F1-2). They were cultivated separately and screened at different growth stages according to the method of (2.2) until they reached sexual maturity.

[0062] (3.2) Select 15 females and 15 males with good gonad development, good vitality, no damage, and no deformity from the first generation group (F1-1); then select 15 females and 15 males with good gonad development, good vitality, no damage, and no deformity from the second generation group (F1-2).

[0063] (3.3) The female fish in the first generation group (F1-1) are mated with the male fish in the first generation group (F1-2) to carry out many-to-many artificial breeding. The offspring obtained are recorded as the second generation group (F2-1), which are cultivated separately and screened at different growth stages according to the method of (2.2) until they reach sexual maturity; the male fish in the first generation group (F1-1) are mated with the female fish in the first generation group (F1-2) to carry out many-to-many artificial breeding. The offspring obtained are recorded as the second generation group (F2-2), which are cultivated separately and screened at different growth stages according to the method of (2.2) until they reach sexual maturity.

[0064] (3.4) According to the method of step (3.2), female fish and male fish with good gonad development, good vitality, no damage and no deformity are selected from the second generation group (F2-1) and the second generation group (F2-2) as broodstock, and then group breeding is carried out according to step (3.3) to obtain the next generation, which is recorded as the third generation group (F3-1) and the third generation group (F3-2).

[0065] (4) Genetic diversity testing after breeding

[0066] The above method has been used to select and breed P. vachelli for three consecutive generations, and the F1 to F3 generation populations have been obtained. The genetic diversity of the three generations has been tested, and its genetic diversity remains at a high level, which is in line with expectations. The details are as follows:

[0067] (4.1) After preliminary experiments, 8 pairs of microsatellite primers that can stably amplify, have a large number of alleles and good polymorphism were screened. The primers listed in Table 1 are selected here to ensure the consistency of the comparison scale.

[0068] Table 4 Genetic information of three consecutive generations of breeding populations of P. vachelli based on microsatellite markers

[0069]

[0070]

[0071] As shown in Table 4, the eight microsatellite loci have high genetic diversity in the P. vachelli population, meeting the standard of high genetic diversity of microsatellites.

[0072] (4.2) On the basis of confirming that the selected molecular markers are reliable, the test results are as follows: The comparison of genetic information of the breeding population for three consecutive generations is shown in Table 5;

[0073] Table 5 Comparison of genetic information of three consecutive generations of breeding populations of Pelteobagrus vachelli

[0074]

[0075] As shown in Table 5, the overall genetic diversity of the three populations was high (Ho = 0.7672-0.8250, He = 0.6323-0.7663, PIC = 0.5754-0.7183), all higher than 0.5. The number of observed alleles (Na) was higher than 4. The results proved that this method effectively maintained genetic diversity at a high level, which was conducive to the continuous development of seed conservation and breeding.

[0076] Example 2

[0077] This embodiment 2 takes the breeding of smooth-lipped fish as an example.

[0078] A breeding operation step of smooth lip fish maintaining genetic diversity is as follows:

[0079] (1) Identify the genetic background and select the base population.

[0080] Wild mullets were collected from the Yangtze River and Xin'an River systems to conduct genetic diversity testing. The specific operations are as follows:

[0081] (1.1) After preliminary experiments, 8 pairs of microsatellite primers that can stably amplify, have a large number of alleles, and have good polymorphism were screened out as shown in Table 1:

[0082] Table 1 Microsatellite primers for Glechoma glabripennis

[0083]

[0084] Table 2 Genetic diversity information of eight microsatellite loci of Glechoma glabrescens

[0085] Location Allele number Na Observed heterozygosity Ho Expected heterozygosity He Polymorphic Information Content (PIC) HCC21 18 0.660 0.743 0.702 HCE64 4 0.223 0.231 0.176 HCG81 15 0.894 0.844 0.824 HCC34 12 0.872 0.703 0.665 HCD114 16 0.617 0.902 0.899 HCC14 12 0.617 0.853 0.829 HCC33 10 0.702 0.817 0.788 HCG111 4 0.670 0.637 0.561 average 11.38 0.657 0.716 0.690

[0086] As shown in Table 2, the eight microsatellite loci have high genetic diversity in the Glechoma glabrescens population, meeting the standard of high genetic diversity of microsatellites, among which the size range and average value of the number of alleles are greater than 4; the size range and average value of the observed heterozygosity (Ho), expected heterozygosity (He) and polymorphic information content (PIC) are greater than 0.5. This indicates that the selected microsatellite loci are suitable for the study of genetic diversity of the Glechoma glabrescens population.

[0087] (1.2) Based on the verification of the reliability of the selected molecular markers, the test results are shown in Table 3 below.

[0088] Table 3 Comparison of genetic diversity information of six populations of Glechoma glabrescens

[0089] group Sample number n Allele number Na Observed heterozygosity Ho Expected heterozygosity He Polymorphic Information Content (PIC) Bicun 30 8.474 0.57 0.69 0.633 Qizili 30 8.151 0.52 0.63 0.614 Nantang 30 7.572 0.50 0.69 0.636 Shangfeng 30 5.655 0.51 0.61 0.611 North Shore 30 6.279 0.61 0.71 0.667 Zhujiakeng 30 7.175 0.56 0.64 0.685

[0090] As shown in Table 3, the genetic diversity index Na among the groups of sphenanthera was 5.655-8.474, which was greater than 4; Ho was 0.50-0.61, He was 0.61-0.71, and PIC was 0.611-0.685, which were all greater than the high polymorphism standard of 0.5. Therefore, it was considered that the six groups of sphenanthera had high genetic diversity and similar genetic diversity levels. Based on this, according to the actual production needs, the group in Zhujiakeng was selected as the basic group, and 600 sphenanthera with good vitality, no damage, and no deformity were selected as the basic group.

[0091] (2) Clarify breeding objectives and select target individuals.

[0092] (2.1) Starting from the base population, growth rate was determined as the target trait for the selection of smooth-lipped fish.

[0093] (2.2) In each generation of summer flower fry, fingerlings, reserve parents, and parent stage, selection is carried out according to the growth rate as the breeding target trait, and the total seed retention rate of each generation is about 0.4%. The details are as follows:

[0094] (2.2.1) The first screening is conducted about one month after the emergence of the film, i.e. the summer flower seedling stage, and individuals with large size, good vitality and no deformity are selected as the breeding group. The number of the selected group is less than 1 / 2 of the total number, about 30,000.

[0095] (2.2.2) The second screening is when the fish size is about 5-10g / tail, and individuals with large size, good vitality and no deformity are selected as the breeding group. The number of the selected group is less than 1 / 5 of the total number, about 6,000 fish.

[0096] (2.2.3) The third screening is at the reserve broodstock stage when the fish weigh about 50-75g / tail. Individuals with large size, good vitality and no deformity are selected as the breeding group. The number of the selected group is less than 1 / 5 of the total number, about 1,200 fish.

[0097] (2.2.4) The fourth screening is when the broodstock weigh about 100-150g / tail. Individuals with large size, good vitality and no deformity are selected as the breeding group. The number of the selected group is less than 1 / 5 of the total number, about 300 tails, and they are temporarily placed in the broodstock pond. According to the production and breeding needs, select the appropriate number of parents for breeding.

[0098] According to the number of parents selected above, each group and each generation of smooth-lipped fish can obtain about 80,000 offspring, which can be bred individually.

[0099] (3) Pairing of breeding parents and screening and breeding of offspring.

[0100] (3.1) 30 sexually mature male and female fish were selected from the basic population of smooth lipped fish and divided into two groups, with 15 male and female fish in each group, respectively recorded as primary generation group 1 (F0-1) and primary generation group 2 (F0-2). Many-to-many artificial breeding was carried out within the groups. The offspring obtained from the two groups were respectively recorded as first generation group 1 (F1-1) and first generation group 2 (F1-2). They were cultivated separately and screened at different growth stages according to the method of (2.2) until they reached sexual maturity.

[0101] (3.2) Select 15 females and 15 males with good gonad development, good vitality, no damage, and no deformity from the first generation group (F1-1); then select 15 females and 15 males with good gonad development, good vitality, no damage, and no deformity from the second generation group (F1-2).

[0102] (3.3) The female fish in the first generation group (F1-1) are mated with the male fish in the first generation group (F1-2) to carry out many-to-many artificial breeding. The offspring obtained are recorded as the second generation group (F2-1), which are cultivated separately and screened at different growth stages according to the method of (2.2) until they reach sexual maturity; the male fish in the first generation group (F1-1) are mated with the female fish in the first generation group (F1-2) to carry out many-to-many artificial breeding. The offspring obtained are recorded as the second generation group (F2-2), which are cultivated separately and screened at different growth stages according to the method of (2.2) until they reach sexual maturity.

[0103] (3.4) According to the method of step (3.2), female fish and male fish with good gonad development, good vitality, no damage and no deformity are selected from the second generation group (F2-1) and the second generation group (F2-2) as broodstock, and then group breeding is carried out according to step (3.3) to obtain the next generation, which is recorded as the third generation group (F3-1) and the third generation group (F3-2).

[0104] (4) Post-selection genetics and diversity testing

[0105] The above method has been used to select and breed the smooth-lipped fish for three consecutive generations, and the F1 to F3 generation populations have been obtained. The genetic diversity of the three generations has been tested, and its genetic diversity remains at a high level, which is in line with expectations. The details are as follows:

[0106] (4.1) After preliminary experiments, 8 pairs of microsatellite primers that can stably amplify, have a large number of alleles and good polymorphism were screened. The primers listed in Table 1 are selected here to ensure the consistency of the comparison scale.

[0107] Table 4 Genetic information of three consecutive generations of breeding populations of P. vachelli based on microsatellite markers

[0108]

[0109]

[0110] As shown in Table 4, the eight microsatellite loci have high genetic diversity in the Glaucus glabripennis population, meeting the standard of high genetic diversity of microsatellites.

[0111] (4.2) On the basis of confirming that the selected molecular markers are reliable, the test results are as follows: The comparison of genetic information of the breeding population for three consecutive generations is shown in Table 5;

[0112] Table 5 Comparison of genetic information of three consecutive generations of breeding populations of smooth-lipped fish

[0113]

[0114] As shown in Table 5, the overall genetic diversity of the three populations was high (Ho = 0.8213 ~ 0.7205, He = 0.7849 ~ 0.6713, PIC = 0.7301 ~ 0.6493), all higher than 0.5. The number of observed alleles (Na) was higher than 4. The results proved that this method effectively maintained genetic diversity at a high level, which was conducive to the continuous development of seed conservation and breeding.

[0115] It will be easily understood by those skilled in the art that the above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for breeding fish to maintain genetic diversity, characterized in that: The steps are as follows: (1) Determine the genetic background and select the base population (1.1) Selecting a population with high genetic diversity as the basic population, the basic population comes from an aquatic breeding farm or natural waters; (1.2) Use microsatellite molecular markers to evaluate the genetic diversity of the selected population and select the observed heterozygosity ( Ho ), expected heterozygosity ( He ) are all higher than 0.5, and the number of alleles in the genetic diversity index is not less than 4 as the basic population; and the number of individuals in the basic population is not less than 500; (2) Clarify breeding goals and select target individuals (2.1) Starting from the basic population, one or more economic traits are determined as the target traits for breeding, and the economic traits are one or more of growth rate, hypoxia tolerance, disease resistance, survival rate, and body color; (2.2) In each generation of summer flower fish fry, fingerlings, reserve parents, and parent fish, selection is carried out according to the breeding target traits, and finally the parents for breeding the next generation are obtained, with a total seed retention rate of less than 1%; (3) Breeding parents are paired and offspring are raised in groups (3.1) According to the breeding target traits, 30 to 40 sexually mature male and female individuals are selected from the parents of the next generation and divided into two groups, namely, primary generation group 1 (F0-1) and primary generation group 2 (F0-2); the number of each group is equal, with a male-female ratio of 1:1, and many-to-many artificial breeding is carried out within the group. The offspring obtained from the two groups are respectively referred to as first generation group 1 (F1-1) and first generation group 2 (F1-2), and are cultured separately until sexual maturity; (3.2) According to the breeding target traits, select 15 to 20 females and males with good gonad development, good vitality, no damage, and no deformity from the first generation group (F1-1); Similarly, according to the breeding target traits, 15 to 20 females and males with good gonad development, good vitality, no damage, and no deformity are selected from the first generation two groups (F1-2); (3.3) The female fish in F1-1 are mated with the male fish in F1-2 to carry out many-to-many artificial breeding. The obtained F2-1 offspring are recorded as F2-1. The F2-1 offspring are raised separately until sexual maturity. Similarly, the male fish in the first generation group (F1-1) were mated with the female fish in the first generation group (F1-2) to carry out many-to-many artificial breeding, and the obtained second generation group two offspring were recorded as second generation group two (F2-2), and the second generation group two offspring were raised separately to sexual maturity; (3.4) According to the breeding target traits, select 15 to 20 females and males with good gonad development, good vitality, no damage, and no deformity from the second generation group (F2-1); Similarly, according to the breeding target traits, 15 to 20 females and males with good gonad development, good vitality, no damage, and no deformity were selected from the second generation and second group (F2-2); (3.5) The female fish in the second generation group (F2-1) are mated with the male fish in the second generation group (F2-2) to carry out many-to-many artificial breeding. The three generations of offspring obtained are recorded as three generations of offspring (F3-1). The three generations of offspring are raised separately until sexual maturity; Similarly, the male fish in the second generation group one (F2-1) was mated with the female fish in the second generation group two (F2-2) to carry out many-to-many artificial breeding, and the obtained third generation group two offspring was recorded as third generation group two (F3-2), and the third generation group two offspring were raised separately to sexual maturity; (3.6) Produce four generations of one group (F4-1) and four generations of two groups (F4-2) according to the above method, and cultivate them to sexual maturity; then reproduce five generations of one group (F5-1) and five generations of two groups (F5-2), and so on in this order; Through the above steps, the genetic diversity level of the breeding population: the observed heterozygosity of each generation ( Ho ) remains above 0.5, and the expected heterozygosity ( He ) remains above 0.5 and the number of alleles remains above 4.

2. A method for breeding fish for maintaining genetic diversity according to claim 1, characterized in that: In step (1.1), the natural waters are large rivers, lakes, and lakes.

3. A method for breeding fish for maintaining genetic diversity according to claim 1, characterized in that: In step (2.2), the specific operations are as follows: (2.2.1) The first screening is at the summer flower seedling stage, and individuals with obvious target traits, good vitality and no deformities are selected as the breeding group. The number of the selected group is less than 1 / 2 to 2 / 3 of the total number; (2.2.2) The second screening is at the fingerling stage, and individuals with obvious target traits, good vitality and no deformities are selected as the breeding group. The number of the selected group is less than 1 / 5 to 1 / 4 of the total number; (2.2.3) The third screening is to select individuals with obvious target traits, good vitality and no deformity as the breeding group at the reserve parent stage. The number of the selected group is less than 1 / 5 to 1 / 4 of the total number; (2.2.4) The fourth screening is carried out at the broodstock stage, and individuals with obvious target traits, good vitality and no deformities are selected as the breeding group. The number of the selected group is less than 1 / 5 to 1 / 4 of the total number.

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