A screening method for comprehensive stress-resistant crabs

Abstract

The application discloses a kind of comprehensive stress-resistant crabs screening method, after preparing breeding system, monitoring breeding environment, after monitoring qualified, the crab to be screened is placed into breeding system temporary rearing, and ensure not to be stressed by outside world, after first round screening of crab is carried out to weight measurement and appearance characteristics, in turn, stress after feeding recovery speed, the screening of defense behavior, select high-quality breeding crab parent.The application is designed scientific and reasonable screening method by means of behavior physiology method, using crab growth state, stress after feeding recovery, defense behavior and individual environmental adaptability closely related, can simply, quickly and efficiently obtain strong appetite, healthy crab with strong stress resistance, and it has important significance for sustainable culture of crab.

Description

Technical Field

[0001] This invention belongs to the field of aquaculture technology, and specifically relates to a screening method for crabs with comprehensive stress resistance. Background Technology

[0002] In recent years, with the development and utilization of aquatic resources and space, the aquaculture ecosystem has continued to deteriorate, leading to frequent aquaculture disasters. Furthermore, the decline in germplasm resources has caused enormous losses to the aquaculture industry. Crabs are an important target for fishing and aquaculture in my country, providing humans with a large amount of high-quality protein. During normal crab farming, various environmental changes and human stresses are inevitable. The survival rate of farmed crabs has dropped from 80% to 20-40%. Weak or sub-healthy individuals in the farming population often exhibit anorexia and are the first to fall ill, infecting the entire population and causing large-scale disasters. Therefore, selecting and breeding robust and active populations can prevent aquaculture disasters. Robust populations also provide a population with strong stress resistance for further selection of quality and other traits, improving the rate of stress-resistant breeding and reducing farming costs. Summary of the Invention

[0003] To address the aforementioned problems, the purpose of this invention is to provide a comprehensive screening method for resilient crabs, which enables simple and efficient screening of crab health status. This method is suitable for providing high-quality breeding stock for crab apartment or cage farming and ecological aquaculture, thereby promoting the healthy and sustainable development of the crab farming industry.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] This invention provides a comprehensive method for screening stress-resistant crabs, comprising the following steps:

[0006] S1: The aquaculture system is first disinfected with disinfectant, then rinsed and soaked with fresh water, and then filled with fully aerated fresh water or natural seawater.

[0007] S2: Monitor the aquaculture environment of the aquaculture system until it meets the aquaculture indicator requirements and a qualified recirculating aquaculture system is obtained;

[0008] S3: Mark the carapace of the crabs, disinfect the adult crabs to be screened by soaking them in aquaculture water containing povidone-iodine, then rinse them with the prepared aquaculture water, and then put them into the qualified recirculating aquaculture system described in step S2.

[0009] S4: Select healthy individuals with high plumpness from the crabs of the same age in step S3;

[0010] S5: For the crabs screened in step S4, use the speed of appetite recovery after air exposure stress to screen healthy individuals with fast appetite recovery after stress, and let them recover for several hours.

[0011] S6: For the crabs selected in step S5, use the crabs' defensive behavior under attack conditions to select healthy and brave individuals that defend in place, thus completing the crab selection.

[0012] Preferably, the crab species include the Chinese mitten crab and the swimming crab (Portunus trituberculatus).

[0013] Preferably, in step S1, the disinfectant is bleaching powder, wherein the effective residual chlorine should be greater than 30 ppm; the number of fresh water rinsings is more than 3 times, and the fresh water soaking time is more than 1 day.

[0014] Preferably, in step S2, the pre-set environmental indicators for aquaculture are: water temperature of 15-25℃, daylight and darkness time of 12 hours each, pH value of 7.5-9.5, dissolved oxygen concentration ≥5mg / L, total ammonia nitrogen ≤0.5mg / L, and nitrite concentration ≤0.05mg / L.

[0015] Preferably, in step S3, the concentration of povidone-iodine is 20–40.0 mg / L, the dissolved oxygen concentration is ≥5 mg / L, and the soaking time is 20–30 min; the stocking density of crabs introduced into the aquaculture system is 5–10 crabs / m². 2 The water used for soaking is aquaculture water that has been aerated by an oxygen pump for more than two weeks, and the soaking time is 0.5 to 1 hour.

[0016] Preferably, in step S4, healthy individuals with high plumpness are selected by weighing each crab of the same age to be screened in step S3, recording the weight and physical characteristics of the crabs, arranging the weight values ​​from largest to smallest, and selecting healthy individuals with the top third of weight that are vigorous, have intact legs, and no damage to their body surface for subsequent screening.

[0017] Preferably, in step S5, the method for screening the rate of appetite recovery after air exposure stress is as follows: the crabs are removed from the breeding system and exposed to the air for 10 minutes by netting; before feeding begins, food is placed on one side (long end) of a test tank (40cm long and 20cm wide), and the crabs are placed separately on the other side of the test tank. The time when the crabs first arrive at the food and begin feeding is measured, and the times are arranged from shortest to longest. The healthy individuals in the first third of the feeding time are selected for subsequent screening.

[0018] Preferably, in step S6, the method for screening the crab's defensive behavior under attack conditions is as follows: place the crab in the middle of the test box, fix the bionic crab to one end of a thin wooden stick and approach the crab to be tested from a distance or click on one end of the box to imitate the sound of footsteps approaching from a distance, and at the same time observe and record the crab's defensive behavior. Select healthy and brave individuals that defend in place with their claws forward and the claws open at an angle of more than 60° for more than 6 seconds, and discard sensitive and timid individuals that do not defend and move in the opposite direction with a distance greater than their body length. The screening is then completed.

[0019] The present invention adopts the above technical solution and has the following beneficial effects:

[0020] (1) This invention utilizes the characteristics of individual physiological behavior and environmental adaptability to screen crabs based on the principle that crabs with different health conditions, growth and development status, and stress recovery characteristics have different stress recovery times and stress coping methods after being subjected to various external environmental stimuli.

[0021] (2) By using the different stress response behaviors of crabs, individuals that are sensitive to stress, have difficulty recovering, and are physically weak can be separated from the crab population, thereby ensuring the crab population's resilience and achieving the goal of healthy breeding and promoting growth.

[0022] (3) The plumpness and external morphological characteristics of crab growth are used as the first indicator for crab stress resistance screening. The recovery of crab feeding after fishing, confined and bright space, and loneliness stress is used as the second indicator for crab stress resistance screening. The movement defense behavior of crabs when there are external threats is used as the third indicator for crab stress resistance screening.

[0023] (4) Crabs’ stress resistance and disease resistance are closely related. The selected healthy individuals can reduce the occurrence of diseases and improve the survival rate. The crabs selected in this invention have strong overall stress resistance.

[0024] (5) This invention selects healthy individuals that are resistant to stress, have a strong appetite and grow fast through multiple rounds of screening for breeding, which is conducive to optimizing the breeding structure and improving breeding efficiency. It is suitable for large-scale aquaculture.

[0025] (6) The equipment required by this invention is simple and easy to operate. The screening method used can be implemented in general crab farming sites. It is highly practical and especially suitable for providing high-quality breeding parents for crab apartments or cage farming and ecological farming.

[0026] In summary, this invention proposes a method for screening resilient and healthy crab individuals. Utilizing the principles that crab plumpness and morphological observation, appetite recovery after stress, and the close correlation between stress-induced movement and disease infection stress, this method employs multiple screenings and elimination of weak and inactive individuals to select resilient and appetite-rich crabs from a general crab population to establish a breeding parent population. This maintains the brave and healthy advantages of the offspring crab population, thereby increasing aquaculture yield and survival rate. Attached Figure Description

[0027] Figure 1 The results show the survival rate of offspring of *Eriocheir sinensis* that were screened in Example 1, exhibiting in-situ defense, positive active attack, and reverse escape.

[0028] Figure 2 The results show the average weight gain of offspring of *Eriocheir sinensis* that were screened in Example 1 for in-situ defense, positive active attack, and reverse escape.

[0029] Figure 3 The results show the survival rate of the offspring of *Portunus trituberculatus* selected in Example 2—those exhibiting in-situ defense, forward active attack, and reverse escape—at a salinity of 8. Detailed Implementation

[0030] The technical solution of the present invention will be further illustrated below through embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other implementation methods obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] This invention utilizes the correlation between individual physiological and behavioral responses and environmental adaptability. Based on the principle that crabs with different health conditions, growth and development stages, and stress recovery characteristics exhibit varying recovery times and stress responses to different external stimuli, multiple screening methods are employed to select crabs. Healthy and courageous crabs, after exposure to air, recover quickly and begin feeding within a short time, adopting a defensive posture when faced with external threats. Conversely, crabs with poor health and low activity levels, after severe exposure to air, do not recover quickly, do not begin feeding for a short period, and adopt an escape defense strategy when faced with external threats. The screening process employs scientifically sound testing methods, avoiding crab deaths due to excessive screening intensity while accurately selecting healthy and active crabs.

[0032] The invention will be explained and illustrated below with reference to implementation examples.

[0033] Example 1

[0034] This embodiment provides a comprehensive screening method for the Chinese mitten crab with strong resistance, the steps of which are as follows:

[0035] S1. After disinfecting the aquaculture system with bleaching powder disinfectant with residual chlorine of 30ppm, rinse with fresh water and soak for 1 day, rinse with fresh water 3 times, and then inject fully aerated fresh water.

[0036] S2. Monitor the aquaculture environment of the aquaculture system to ensure that it meets the preset environmental indicators: water temperature 18-25℃, daylight and darkness time 12h each, pH value 7.5-9.5, dissolved oxygen concentration ≥6mg / L, total ammonia nitrogen ≤0.2mg / L, and nitrite concentration ≤0.01mg / L.

[0037] S3. After marking the carapace of the Chinese mitten crab, the adult Chinese mitten crabs to be screened are disinfected by soaking in aquaculture water containing 30.0 mg / L povidone-iodine for 30 minutes, then rinsed in aquaculture water that has been aerated for more than two weeks with an oxygen pump for 0.5 hours, and then placed into the qualified aquaculture system in step S2; wherein the dissolved oxygen concentration of the aquaculture water containing 30.0 mg / L povidone-iodine is 6 mg / L, and the stocking density of the Chinese mitten crabs introduced into the aquaculture system is 5-10 crabs / m². 2 .

[0038] S4. Weigh each of the same-age Chinese mitten crabs to be screened in step S3, record their weight and physical characteristics, arrange the weight values ​​from largest to smallest, and screen out healthy individuals that are in the top third of the weight, are vigorous, have intact legs, and have no damage to their body surface.

[0039] S5. For the Chinese mitten crabs screened in step S4, select active and healthy individuals with fast appetite recovery after air exposure stress by using the speed of appetite recovery after stress. Then allow them to recover for several hours. At the beginning, remove the Chinese mitten crabs from the breeding system by netting and expose them to air for 10 minutes. Place them in a test tank to measure the feeding recovery speed. Before feeding begins, place the food on one side (long end) of the test tank (40cm long and 20cm wide) and place the Chinese mitten crabs on the other side of the test tank. Measure the time when the Chinese mitten crabs first reach the food and start feeding. Arrange the times from shortest to longest and select the first third of healthy individuals for subsequent screening.

[0040] S6. For the Chinese mitten crabs selected in step S5, use the defensive behavior of Chinese mitten crabs under attack conditions to select healthy and brave individuals that defend in place, and then allow them to recover for several hours. At the beginning, take the Chinese mitten crabs out of the breeding system and place them in the middle of the test box. Fix the bionic crab to one end of a thin wooden stick and approach the Chinese mitten crab to be tested from a distance or click on one end of the box to imitate the sound of footsteps approaching from a distance. At the same time, observe and record the defensive behavior of the Chinese mitten crabs. Select healthy individuals that defend in place with their claws forward and the claws open at an angle of more than 60° for more than 8 seconds. Discard sensitive individuals that move in the opposite direction and escape at a distance greater than their body length. The selection is now complete.

[0041] Example 2

[0042] This embodiment provides a comprehensive screening method for the resilient swimming crab *Portunus trituberculatus*, the steps of which are as follows:

[0043] S1. After disinfecting the aquaculture system with bleaching powder disinfectant with residual chlorine of 30 ppm, rinse with fresh water and soak for 1 day, rinse with fresh water 3 times, and then inject fully aerated natural seawater.

[0044] S2. Monitor the aquaculture environment of the aquaculture system to ensure that it meets the preset environmental indicators: water temperature 20-25℃, daylight and darkness time 12h each, pH value 7.8-8.5, dissolved oxygen concentration ≥6mg / L, total ammonia nitrogen ≤0.3mg / L, and nitrite concentration ≤0.01mg / L.

[0045] S3. After marking the carapace of the three-spined swimming crab, the adult three-spined swimming crabs to be screened are disinfected by soaking in aquaculture water containing 30.0 mg / L povidone-iodine for 30 minutes, then soaked in aquaculture water that has been aerated for more than two weeks with an oxygen pump for 0.5 hours, and then placed into the qualified aquaculture system in step S2; wherein, the dissolved oxygen concentration of the aquaculture water containing 30.0 mg / L povidone-iodine is 6 mg / L, and the stocking density of the three-spined swimming crabs introduced into the aquaculture system is 5-10 crabs / m².

[0046] S4. Weigh each of the three-spined swimming crabs of the same age to be screened in step S3, record their weight and physical characteristics, arrange the weight values ​​from largest to smallest, and screen out healthy individuals that are in the top third of the weight, are vigorous, have intact legs, and have no damage to their body surface.

[0047] S5. For the three-spined swimming crabs selected in step S4, the fast recovery rate of appetite after air exposure stress is used to select active and healthy individuals with fast recovery of appetite after stress, and then they are allowed to recover for several hours. At the beginning, the three-spined swimming crabs are taken out of the breeding system by netting and exposed to the air for 10 minutes, and then placed in a test tank to measure the feeding recovery rate. Before feeding begins, food is placed on one side (long end) of the test tank (40cm long and 20cm wide), and the three-spined swimming crabs are placed alone on the other side of the test tank. The time when the three-spined swimming crabs first reach the food and start feeding is measured. The times are arranged from smallest to largest, and the healthy individuals in the first third of the feeding time are selected for subsequent screening.

[0048] S6. For the three-spined swimming crabs selected in step S5, use their defensive behavior under attack conditions to select healthy and brave individuals that defend themselves in place, and then allow them to recover for several hours. At the beginning, take the three-spined swimming crabs out of the breeding system and place them in the middle of the test box. Fix the bionic crab to one end of a thin wooden stick and approach the three-spined swimming crabs to be tested from a distance or click on one end of the box to imitate the sound of footsteps approaching from a distance. At the same time, observe and record the defensive behavior of the three-spined swimming crabs. Select healthy individuals that defend themselves in place with their claws forward and the claws open at an angle of more than 60° for more than 6 seconds. Discard sensitive individuals that move in the opposite direction and escape at a distance greater than their body length. The selection is now complete.

[0049] Test Results

[0050] Using Example 1 as the test sample, the effects of other examples are similar to those of Example 1.

[0051] Using the comprehensive stress-resistant crab screening method of this invention, individuals of Chinese mitten crabs exhibiting in-situ defense, positive active attack (attack defense), and reverse escape (escape defense), as well as their offspring, were selected. Sixteen individuals from each group were then selected for stress resistance testing.

[0052] (1) Survival rate test of Chinese mitten crab offspring selected from those exhibiting in-situ defense, forward active attack, and reverse escape.

[0053] Test results are as follows Figure 1 As shown, the offspring of the Chinese mitten crab that were selected to defend in place have a stronger survival ability.

[0054] (2) Average weight gain rate test of the selected offspring of Chinese mitten crabs exhibiting in-situ defense, positive active attack, and reverse escape.

[0055] Test results are as follows Figure 2 As shown, the offspring of the Chinese mitten crab that adopted in-situ defense had a higher average weight gain rate than the offspring of the Chinese mitten crab that actively attacked in the front and fled in the back.

[0056] Using Example 2 as the test sample, the effects of other examples are similar to those of Example 2.

[0057] Using the comprehensive stress-resistant crab screening method of this invention, individuals of the three-spined swimming crab that defend in place, individuals of the three-spined swimming crab that actively attack in the positive direction (attack defense) and individuals of the three-spined swimming crab that escape in the reverse direction (escape defense), as well as their offspring, were selected, and sixteen of each were selected for stress resistance testing.

[0058] (3) Survival rate test of selected offspring of *Portunus trituberculatus* exhibiting in-situ defense, forward active attack, and reverse escape at a salinity of 8.

[0059] Test results are as follows Figure 3 As shown, the selected offspring of the three-spined swimming crab that adopted in-situ defense showed stronger salinity tolerance than the offspring of the three-spined swimming crab that were more sensitive and actively attacked or fled in the opposite direction.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A comprehensive screening method for stress-resistant crabs, characterized in that, Includes the following steps: S1: The aquaculture system is first disinfected with disinfectant, then rinsed and soaked with fresh water, and then filled with fully aerated fresh water or natural seawater. S2: Monitor the aquaculture environment of the aquaculture system until it meets the aquaculture indicator requirements and a qualified recirculating aquaculture system is obtained; S3: Mark the carapace of the crabs, disinfect the adult crabs to be screened by soaking them in aquaculture water containing povidone-iodine, then rinse them with the prepared aquaculture water, and then put them into the qualified recirculating aquaculture system described in step S2. S4: Select healthy individuals with high plumpness from the crabs of the same age in step S3; S5: For the crabs screened in step S4, use the speed of appetite recovery after air exposure stress to screen healthy individuals with fast appetite recovery after stress, and let them recover for several hours. S6: For the crabs selected in step S5, use the crabs' defensive behavior under attack conditions to select healthy and brave individuals that defend in place, thus completing the selection of crabs. The crab species mentioned include the Chinese mitten crab and the swimming crab (Portunus trituberculatus). In step S4, healthy individuals with high plumpness are selected by weighing each crab of the same age to be screened in step S3, recording the weight and appearance of the crabs, arranging the weight values ​​from largest to smallest, and selecting the top third of healthy individuals with high vitality, intact legs, and no damage to the body surface for subsequent screening. In step S5, the screening method for the rate of appetite recovery after air exposure stress is as follows: crabs are removed from the breeding system and netted and exposed to air for 10 minutes; before feeding begins, food is placed on one side of the long end of the test tank, and crabs are placed separately on the other side of the test tank. The time when the crabs first arrive at the food and start feeding is measured, and the times are arranged from shortest to longest. The first third of healthy individuals are selected for subsequent screening. In step S6, the method for screening crab defensive behavior under attack conditions is as follows: Place the crab in the middle of the test box, fix the bionic crab to one end of a thin wooden stick and approach the crab to be tested from a distance, or click on one end of the box to imitate the sound of footsteps approaching from a distance. At the same time, observe and record the crab's defensive behavior. Select healthy and brave individuals that defend in place with their claws forward and the claws open at an angle of more than 60° for more than 6 seconds. Discard sensitive and timid individuals that do not defend and move away in the opposite direction with a distance greater than their body length. The screening is then completed.

2. The screening method for comprehensively resilient crabs according to claim 1, characterized in that, In step S1, the disinfectant is bleaching powder, in which the effective residual chlorine should be greater than 30 ppm; the number of fresh water rinses is more than 3 times, and the fresh water soaking time is more than 1 day.

3. The screening method for comprehensively resilient crabs according to claim 1, characterized in that, In step S2, the pre-set environmental indicators for aquaculture are: water temperature of 15~25℃, daylight and darkness time of 12 hours each, pH value of 7.5~9.5, dissolved oxygen concentration ≥5mg / L, total ammonia nitrogen ≤0.5mg / L, and nitrite concentration ≤0.05mg / L.

4. The screening method for comprehensively resilient crabs according to claim 1, characterized in that, In step S3, the concentration of povidone-iodine is 20-40.0 mg / L, the dissolved oxygen concentration is ≥5 mg / L, and the soaking time is 20-30 min; the stocking density of crabs introduced into the aquaculture system is 5-10 crabs / m². 2 The water used for soaking is aquaculture water that has been aerated by an oxygen pump for more than two weeks, and the soaking time is 0.5 to 1 hour.

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