Method for saltwater to freshwater acclimation of a salt-tolerant fish

Abstract

The application discloses a method for salinization domestication of euryhaline fish, and aims to solve the technical problems of long domestication period and weak adaptability of the euryhaline fish, and relates to the technical field of aquaculture.The method comprises the following steps: 3-5 days in advance, the heat shock protein inducer and the medium-short chain fatty acid are mixed and fed to the fish to be domesticated; the mixed feeding amount of the heat shock protein inducer is 200 mg-400 mg per kg of feed; the mixed feeding amount of the medium-short chain fatty acid is 200 mg-500 mg per kg of feed; then, the gradient high-salt feed and the gradient salt water are mixed and fed; the salt content of the feed is increased by 1% per day to 5%, the salinity of the water is increased by 5‰ per day to 15-25‰, the mixed feeding is continuously carried out for 4-5 days, and the target domestication salinity is maintained for 2-3 days.

Description

Technical Field

[0001] This application relates to the field of animal husbandry technology, and in particular to a method for the salinization and domestication of euryhaline fish. Background Technology

[0002] Euryhaline fish are those fish that can adapt to living in waters with a wide range of salinity variations. These fish typically exhibit great tolerance to slow changes in salinity, such as tilapia, mullet, anchovies, anchovies, and rainbow trout. Some species, such as mullet, barracuda, barracuda, spotted sea bass, and yellowfin seabream, can even be domesticated in freshwater with gradually decreasing salinity and raised in pure freshwater.

[0003] Saline aquaculture is a method to increase the economic value of euryhaline fish. Through saline conditioning, the muscle elasticity of farmed fish can be increased, and the content of flavor-enhancing amino acids can be improved, resulting in a more delicious taste. It is particularly effective in removing the muddy taste of fish farmed in freshwater environments, thereby improving product quality and market competitiveness. This not only provides consumers with high-quality aquatic products but also enriches the variety of marine aquaculture fish in my country.

[0004] When fish adapt to high-salt environments, their physiological structures undergo a series of changes. For example, their gill structure becomes more developed to meet the needs of absorbing oxygen and excreting excess salt from the high salinity. Specifically, the number of gill chlorinating cells increases, and the reticulum and saccular duct systems become more developed to enhance their ability to regulate salt levels. Fish also adjust their metabolic activities in high-salt environments. To maintain osmotic balance, fish increase water absorption and reduce water excretion, while adjusting the amount and concentration of urine to minimize salt loss.

[0005] Currently, the most common method for salinization training of fish is the gradual salinity increase method. First, euryhaline fish are placed in water with lower salinity, and then the salinity is gradually increased until the target salinity is reached. During the salinity increase, the rate and magnitude of increase need to be controlled to avoid causing excessive stress to the fish. Furthermore, the control of the training environment and the nutritional management of the fish can also affect their physiological state and the effectiveness of the training. However, currently, practitioners only focus on salinity control and have not yet considered comprehensive measures. Therefore, the long salinization training cycle and low adaptability of euryhaline fish remain key issues restricting their salinization aquaculture. Summary of the Invention

[0006] This application provides a method for the salinization and domestication of euryhaline fish, aiming to solve the technical problems of long salinization and domestication cycles and low adaptability of existing euryhaline fish.

[0007] To address the aforementioned technical problems, this application provides a method for the salinization and domestication of euryhaline fish, comprising the following steps:

[0008] For domesticated fish, heat shock protein inducer and medium- and short-chain fatty acids should be mixed and fed for 3-5 days in advance; the amount of heat shock protein inducer should be 200mg-400mg / kg of feed; the amount of medium- and short-chain fatty acids should be 200mg-500mg / kg of feed.

[0009] Then, mix in a gradient of high-salt feed and a gradient of salinity in the water. The salt content of the feed is increased by 1% to 5% per day, and the salinity of the water is increased by 5‰ to 15-25‰ per day. Continue this process for 4-5 days, and maintain the target salinity for 2-3 days after the target salinity has been reached.

[0010] As some optional embodiments of this application, the heat shock protein inducer is teprenone or cactus extract, and the medium- and short-chain fatty acids are glyceryl tartrate or glyceryl monolaurate.

[0011] As some alternative embodiments of this application, the fish to be domesticated are freshwater or low-salinity cultured red tilapia or juvenile Chinese perch.

[0012] As some optional embodiments of this application, the fish to be domesticated is a juvenile red tilapia with a body length of 13±0.7cm and a weight of 105±14.6g.

[0013] As some optional embodiments of this application, the salinization acclimatization pond is an indoor cement pond of 4m×4m×1.2m, the salinization acclimatization density is 1000 fish / pond, during the salinization acclimatization period, tilapia-specific compound feed is fed twice a day, 20% of the water is changed daily, the temperature is maintained at 28±1℃, and dissolved oxygen is maintained at ≥5.0mg / L and pH 7.5-8.0 by air stone aeration throughout the day.

[0014] As some optional embodiments of this application, after being raised in saline acclimatization for 28 days, the survival rate of juvenile fish reached 99.2%, and the weight gain rate of juvenile fish was 102.5%.

[0015] As some optional embodiments of this application, the fish to be domesticated is a juvenile spotted bass with a body length of 15±1.4cm and a weight of 118±19.9g.

[0016] As some optional embodiments of this application, the salinization and acclimatization pond is an indoor cement pond of 4m×4m×1.2m, the salinization and acclimatization density is 500 fish / pond, during the salinization and acclimatization period, tilapia-specific compound feed is fed twice a day, 20% of the water is changed daily, the temperature is maintained at 28±1℃, and dissolved oxygen is maintained at ≥5.0mg / L and pH 7.5-8.0 by air stone aeration throughout the day.

[0017] As some optional embodiments of this application, after being raised in saline acclimatization for 28 days, the survival rate of juvenile fish reached 89.5%, and the weight gain rate of juvenile fish was 74.5%.

[0018] Existing methods for salinization training of fish mostly employ a gradual increase in water salinity, which is relatively simplistic and does not consider the weakening of fish's immunity and stress damage caused by salinity stress. Therefore, these methods suffer from long training times and low survival rates. Compared to existing technologies, the salinization training method for euryhaline fish described in this application involves feeding the fish with heat shock protein inducers such as teprenone and medium-to-short chain fatty acids such as glyceryl tartrate or laurate monoglyceride for 3-5 days before salinization training to improve the stress tolerance and intestinal immunity of the fish to be trained. During the salinization training process, a combination of feeding a gradient of high-salt feed and a gradient increase in water salinity achieves comprehensive salinization training for euryhaline fish. That is, strengthening stress tolerance and intestinal nutrition and immunity before salinization training improves the body's tolerance to the high-intensity stress brought about by subsequent salinization, reduces stress damage, maintains intestinal tissue homeostasis, enhances the fish's adaptability to salinity changes, and increases the success rate of training. By combining the feeding of gradient high-salt feed with the gradient salinity of the water, the internal physiological response of the organism and the adaptation to the external environment are coordinated, thereby improving domestication efficiency and shortening the domestication time. Detailed Implementation

[0019] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] Current methods for salinization and domestication of fish mainly employ a gradual increase in water salinity, which is relatively simplistic and does not consider the weakening of fish's immunity and stress damage caused by salinity stress. As a result, there are problems such as long domestication time and low survival rate.

[0021] To address the above issues, this application has implemented the following technological innovations:

[0022] 1) Pretreatment for salinization: Feed the fish with heat shock protein inducers such as teprenone (200-400 mg / kg feed) and medium- and short-chain fatty acids such as tretinoin (200-500 mg / kg feed) for 3-5 days to improve their stress tolerance and intestinal immunity. This synergistic effect reduces the stress damage caused by increased salinity, enhances environmental adaptability, and improves the success rate of subsequent salinization.

[0023] 2) Saline acclimatization process: Comprehensive saline acclimatization of euryhaline fish is achieved by combining the feeding of gradient high-salt feed with the gradual increase of salinity in the water. The high-salt feed is prepared with concentrated seawater or sea salt, and the salt content of the feed is gradually increased by 1% per day to 5%, while the salinity of the water is gradually increased by 5‰ per day until the salinity of the water reaches 15-25‰.

[0024] The method described in this application will be explained in detail below with reference to specific embodiments:

[0025] Example 1:

[0026] Juvenile red tilapia (Oreochromis mossambicus × ​​O. niloticus) were used for salinization acclimation. The fish measured 13±0.7 cm in length and 105±14.6 g in weight. A treatment group and a control group were established, with three replicates in each group, for a total of six indoor cement ponds (4m×4m×1.2m). The salinization acclimation density was 1000 fish / pond. During the acclimation period, the fish were fed twice daily with a 20% water change, the temperature was maintained at 28±1℃, and dissolved oxygen was maintained at ≥5.0 mg / L with air stones throughout the day, and the pH was maintained at 7.5-8.0. Before salinization, the juvenile fish in the treatment group were fed a combination of teprenone and tributyric acid at 200 mg and 300 mg per kilogram of feed, respectively, using purified water as the drug solvent, for three consecutive days. The control group underwent the same feed preparation as the treatment group, except that the same amount of purified water was mixed into the feed. During the salinization acclimatization phase, the treatment group was fed a gradient of high-salt feed combined with a gradient increase in water salinity. The feed salinity was gradually increased by 1% daily to 5%, and the high-salt feed was prepared with seawater salt. The water salinity was gradually increased by 5‰ daily until it reached 20‰. The control group was not fed high-salt feed, and the water salinity was gradually increased by 5‰ daily until it reached 20‰. After acclimatization, both groups of fish were maintained in a 20‰ salinity environment for 28 days. Survival rate and weight gain were recorded. Data for the experimental group are shown in Table 1, and data for the control group are shown in Table 2.

[0027] Table 1:

[0028]

[0029] Table 2:

[0030]

[0031] It can be seen that after 28 days of saline acclimatization and rearing, the survival rate of juvenile fish in the treatment group reached 99.2%, which was significantly higher than that of the control group (83.3%) (P<0.01); the weight gain rate of juvenile fish in the treatment group was 102.5%, which was significantly higher than that of the control group (78.6%) (P<0.01); the fish in the treatment group were robust and had a strong appetite, while the fish in the control group had poor appetite and developed varying degrees of bacterial infection and enteritis during the period, which recovered after drug treatment.

[0032] Example 2:

[0033] Juvenile Chinese sea bass (Lateolabrax maculatus) with a body length of 15±1.4cm and a weight of 118±19.9g were used for salinization acclimation. A treatment group and a control group were established, with three replicates in each group, for a total of six indoor cement ponds (4m×4m×1.2m). The salinization acclimation density was 500 fish / pond. During the acclimation period, the fish were fed twice daily with a sea bass-specific formulated feed, with 20% water exchanged daily. The temperature was maintained at 28±1℃, and dissolved oxygen was maintained at ≥5.0mg / L with air stones throughout the day, and the pH was maintained at 7.5-8.0. Before salinization, the juvenile fish in the treatment group were fed a combination of teprenone and tributyrate at 250mg and 400mg per kilogram of feed, respectively, using purified water as the drug solvent, for three consecutive days. The control group underwent the same feed preparation as the treatment group, except that the same weight of purified water was used in the feed preparation. During the salinization acclimatization phase, the treatment group was fed a gradient of high-salt feed combined with a gradient increase in water salinity. The feed salinity was gradually increased by 1% daily to 5%, and the high-salt feed was prepared with seawater salt. The water salinity was gradually increased by 5‰ daily until it reached 25‰. The control group was not fed high-salt feed, and the water salinity was gradually increased by 5‰ daily until it reached 25‰. After acclimatization, both groups of fish were maintained in a 25‰ salinity environment for 28 days. Survival rate and weight gain were recorded. Data for the experimental group are shown in Table 3, and data for the control group are shown in Table 4.

[0034] Table 3:

[0035]

[0036] Table 4:

[0037]

[0038] It can be seen that after 28 days of saline acclimatization and rearing, the survival rate of juvenile fish in the treatment group reached 89.5%, which was significantly higher than that of the control group (64.4%) (P<0.01); the weight gain rate of juvenile fish in the treatment group was 74.5%, which was significantly higher than that of the control group (52.4%) (P<0.01); the fish in the treatment group were robust and had a strong appetite, while the fish in the control group had poor appetite and developed varying degrees of bacterial infection and enteritis during the period, which recovered after drug treatment.

[0039] Na in chloride cells + / K +ATPase enzymes play a crucial role in osmotic pressure regulation, responding to changes in environmental salinity and adjusting the osmotic pressure balance within and outside the fish's body. One of the technological innovations of this application is that a gradient high-salt diet can simulate the gradual increase in salinity in the natural environment, allowing fish to gradually adapt to a high-salt environment during feeding. This adaptation process involves adjustments to physiological structure and changes in metabolic activity. The combination of gradient high-salt feeding and a gradual increase in water salinity helps the organism better adapt to a high-salt environment, improving salinization efficiency and shortening salinization time. Furthermore, appropriate salt intake can stimulate the fish's immune system and enhance its resistance. This helps fish reduce disease incidence and maintain a healthy state in high-salt environments.

[0040] During salinization and domestication, fish undergo a series of high-intensity stresses, including pond transfer, transportation, adaptation to new aquatic environments, and overcoming changes in salinity. When fish are subjected to stress, their bodies undergo a series of physiological changes to cope with this adverse environment. Stress triggers responses in the fish's nervous and endocrine systems, leading to the release of stress hormones such as adrenaline and noradrenaline. These hormones can regulate the body's metabolism and immune function, but they can also damage organs such as the intestines.

[0041] The gut is a vital organ for nutrient absorption and immunity in fish, and gut health is closely related to the gut microenvironment. Gut microbiota homeostasis is crucial for maintaining fish health. Under stress, fish immune function is impaired, leading to reduced immune cell activity and decreased secretion of immune factors. This makes fish more susceptible to pathogens, resulting in intestinal inflammation and damage. Furthermore, stress directly affects the structure and function of the fish gut, such as impairing the intestinal barrier and causing gut microbiota imbalance.

[0042] Heat shock proteins (HSPs) are a class of endogenous protective proteins synthesized by cells in response to various stress conditions (such as high temperature, hypoxia, and DNA damage). They play an important role in maintaining cellular homeostasis, promoting cell survival, and adapting to the external environment. Heat shock protein inducers are substances or drugs that can induce increased expression of HSPs; teprenone is a potent inducer of HSP expression. Medium- and short-chain fatty acids such as tributyrate have multifaceted protective effects on the fish gut, including improving intestinal morphology, enhancing intestinal barrier function, improving immunity, and promoting nutrient utilization. One of the technological innovations of this application is to improve the body's tolerance to subsequent high-intensity stress and reduce stress damage by strengthening nutritional immunity and stress tolerance before salinization, thereby maintaining intestinal tissue homeostasis; and to achieve rapid and stable balance of the intestinal environment through stress protection and intestinal nutritional health regulation during salinization, thereby improving salinization adaptability and ensuring the body's health.

[0043] It can be seen that the method described in this application has the following advantages:

[0044] Strengthening stress tolerance and intestinal nutrition and immunity before salinization improves the body's tolerance to the high-intensity stress brought about by subsequent salinization, reduces stress damage, maintains intestinal tissue homeostasis, enhances the fish's adaptability to salinity changes, and increases the success rate of acclimatization. By combining a gradient of high-salt feed with a gradient increase in water salinity, the body's internal physiological response and external environmental adaptation are coordinated, improving acclimatization efficiency and shortening the acclimatization time. Specifically, by feeding heat shock protein inducers such as teprenone and medium- and short-chain fatty acids such as tretinoin and lauric acid monoglycerides for 3-5 days before salinization, the stress tolerance and intestinal immunity of the fish to be acclimatized are improved. During salinization, the comprehensive salinization acclimatization of euryhaline fish is achieved by combining a gradient of high-salt feed with a gradient increase in water salinity.

[0045] Furthermore, strengthening stress tolerance and intestinal nutrition and immunity before salinization enhances the body's tolerance to the high-intensity stress brought about by subsequent salinization, reduces stress damage, maintains intestinal tissue homeostasis, enhances the fish's adaptability to salinity changes, and improves the success rate of acclimatization. By combining the feeding of gradient high-salt feed with the gradient increase of salinity in the water, the internal physiological response of the body and the adaptation to the external environment are coordinated, improving acclimatization efficiency and shortening the acclimatization time.

[0046] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for the salinization and domestication of euryhaline fish, characterized in that, Includes the following steps: For domesticated fish, heat shock protein inducer and medium- and short-chain fatty acids should be mixed and fed for 3-5 days in advance; the amount of heat shock protein inducer should be 200mg-400mg / kg of feed; the amount of medium- and short-chain fatty acids should be 200mg-500mg / kg of feed. Then mix in a gradient of high-salt feed and a gradient of salinity in the water; the salt content of the feed is increased by 1% to 5% per day, and the salinity of the water is increased by 5‰ to 15-25‰ per day. Continue this mixing for 4-5 days, and maintain the salinity for 2-3 days after the desired salinity has been achieved. The heat shock protein inducer is teprenone or cactus extract, and the medium- and short-chain fatty acids are glyceryl tribaniate or glyceryl monolaurate. The fish to be domesticated were juvenile spotted bass, with a body length of 15±1.4cm and a weight of 118±19.9g.

2. The method for salinization and domestication of euryhaline fish according to claim 1, characterized in that, The salinization and acclimatization pond is an indoor cement pond measuring 4m×4m×1.2m. The salinization and acclimatization density is 1000 tilapia per pond. During the salinization and acclimatization period, tilapia are fed twice a day with special formulated feed, 20% of the water is changed daily, the temperature is maintained at 28±1℃, and dissolved oxygen is maintained at ≥5.0mg / L with air stones throughout the day, and the pH is 7.5-8.

0.

3. The method for salinization and domestication of euryhaline fish according to claim 2, characterized in that, After being raised in saline conditions for 28 days, the survival rate of the juvenile fish reached 99.2%, and the weight gain rate of the juvenile fish was 102.5%.

4. The method for salinization and domestication of euryhaline fish according to claim 1, characterized in that, The salinization and acclimatization pond is an indoor cement pond measuring 4m×4m×1.2m. The salinization and acclimatization density is 500 fish / pond. During the salinization and acclimatization period, tilapia are fed twice a day with special compound feed, 20% of the water is changed daily, the temperature is maintained at 28±1℃, and dissolved oxygen is maintained at ≥5.0mg / L with air stones throughout the day, and the pH is 7.5-8.

0.

5. The method for salinization and domestication of euryhaline fish according to claim 4, characterized in that, After being raised in saline conditions for 28 days, the survival rate of the juvenile fish reached 89.5%, and the weight gain rate of the juvenile fish was 74.5%.

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