A method for acclimatization and long-term breeding of xinjiang indigenous fish in saline-alkali water gradient

Abstract

The present application relates to the technical field of fish culture, in particular to a Xinjiang indigenous fish salinity-alkalinity water gradient acclimation and long-term culture method. In view of the problems of lack of salinity-alkalinity water acclimation method and long-term culture method of Xinjiang indigenous economic fish such as Ili percid, river perch and head river girella in the prior art, the present application provides a Xinjiang indigenous fish salinity-alkalinity water gradient acclimation and long-term culture method. After temporary culture of Ili percid, river perch or head river girella in fresh water, salinity acclimation or carbonate alkalinity acclimation is carried out. Sodium chloride is used for salinity acclimation, and sodium bicarbonate and sodium carbonate are used for alkalinity acclimation. The concentration of the new water is calculated according to the formula, so that the pool water reaches the target concentration after water change. Long-term culture is carried out after reaching the target concentration, and regular isosmotic water change is carried out. The method can reduce acclimation stress, improve survival rate and long-term culture stability.

Description

Technical Field

[0001] This invention relates to the field of fish farming technology, specifically to a method for the saline-alkali water gradient domestication and long-term farming of native fish species in Xinjiang. Background Technology

[0002] Saline-alkali water refers to natural water bodies with high salinity and carbonate alkalinity, widely distributed in Northwest, North, and Northeast my country. Xinjiang is rich in saline-alkali water resources, providing a resource base for developing saline-alkali water fisheries. However, due to the typically high salinity and carbonate alkalinity of saline-alkali water, it is difficult to use directly for conventional agricultural irrigation or drinking water for humans and livestock, resulting in long-standing problems of resource idleness and insufficient utilization. In recent years, utilizing saline-alkali water for aquaculture has gradually become an important direction for improving the utilization efficiency of saline-alkali water resources.

[0003] Currently, saline-alkali water aquaculture and domestication techniques are mostly focused on introduced or conventionally farmed species such as tilapia, California bass, whiteleg shrimp, largemouth bass, and silver carp. Ili perch, river perch, and Ertis River silver carp are all important native economic fish species in Xinjiang. Among them, the Ili perch (scientific name *Percaschrenkii*) is endemic to the Balkhash Lake-Ili River system and the Emin River-Ala Lake system; the river perch (scientific name *Percafluviatilis*, commonly known as the "Five-striped Black") is a major native fish species of the Ulungur River system and the Ertis River in my country; and the Ertis River silver carp (scientific name *Carassiusauratus gibelio*) is endemic to the Ertis River and Ulungur River systems in Xinjiang. While Ili perch, river perch, and Ertis River silver carp possess certain economic value and aquaculture development potential, different fish species exhibit varying tolerances to salinity and carbonate alkalinity, as well as differences in their suitable growth ranges. Existing saline-alkali water domestication methods developed for other fish species are difficult to directly apply to the aforementioned three native Xinjiang fish species. If they are raised directly in a saline-alkali water environment, they are prone to osmotic stress and acid-base regulation pressure, which can lead to decreased feeding, slow growth, increased stress, or even death.

[0004] Existing methods for acclimatizing fish to saline-alkaline water suffer from a lack of standardization in the acclimatization gradient and water exchange schedule. Some methods only vaguely disclose the gradual increase in salinity or alkalinity without specifying the daily increase rate, water exchange ratio, method of adjusting the concentration of the added water, or water quality stabilization measures. In practice, directly adding freshwater, solid salts, or high-concentration mother liquor to the aquaculture water can easily cause sudden changes in local salinity, carbonate alkalinity, or pH, affecting the fish's osmotic regulation and acid-base balance processes, reducing acclimatization survival rates and the reproducibility of the methods.

[0005] In addition, Xinjiang's natural saline water typically exhibits chloride-carbonate type water characteristics, with the main ions including Cl - HCO3 - and CO32- Current technologies often use sodium bicarbonate alone to adjust alkalinity. While this can increase the alkalinity of water, it is difficult to fully simulate the HCO3 content in natural saline-alkali water. - / CO3 2- The coexistence of carbonate systems leads to differences in ionic composition and pH buffering characteristics between artificially acclimatized water bodies and actual saline-alkali water bodies in Xinjiang, thus affecting the applicability of acclimatization results in actual aquaculture.

[0006] Meanwhile, existing studies mostly focus on short-term survival rates or acute tolerance during the acclimatization period, lacking growth assessments for long-term aquaculture at target salinity or carbonate alkalinity. Short-term survival does not indicate that fish can feed, grow, and be stably cultured in the corresponding saline-alkaline water environment in the long term, nor does it provide reliable species-concentration matching parameters for production practices. Summary of the Invention

[0007] To address the lack of existing methods for the saline-alkali water acclimatization and long-term aquaculture of native economic fish species in Xinjiang, such as the Ili perch, river perch, and Ertis silver carp, and the problems inherent in existing methods including unstable salinity increases, imprecise control of water concentration, significant differences in ionic composition between the alkalinity adjustment system and Xinjiang's natural saline-alkali water, and a lack of long-term aquaculture validation of acclimatization effects, this invention provides a method for the gradient acclimatization and long-term aquaculture of native Xinjiang fish species in saline-alkali water. This method unifies the initial state of the fish through freshwater temporary rearing, reduces acute saline-alkali stress by gradually increasing salinity or carbonate alkalinity daily, maintains stable water concentration during acclimatization by pre-mixing and controlling the concentration of the incoming water according to a formula, adjusts carbonate alkalinity using a mixture of sodium bicarbonate and sodium carbonate to simulate the carbonate system of Xinjiang's natural saline-alkali water, and allows for long-term aquaculture after reaching the target salinity or carbonate alkalinity. This improves the survival rate of acclimatized fish and the stability of long-term aquaculture, providing technical support for the development and utilization of native economic fish species in Xinjiang's saline-alkali water resources.

[0008] To achieve the above objectives, this invention provides a method for the saline-alkali water gradient acclimatization and long-term aquaculture of native fish species in Xinjiang, comprising the following steps:

[0009] The native fish species of Xinjiang to be domesticated were temporarily raised in freshwater to obtain the native fish species of Xinjiang to be domesticated after temporary rearing.

[0010] Salinity or alkalinity acclimatization was carried out on native Xinjiang fish species that were temporarily held and awaiting domestication.

[0011] The salinity acclimatization process involves adding sodium chloride to fresh water to prepare new water A. This new water A is then gradually introduced at a daily gradient of 0.2-0.8‰ to increase the salinity of the aquaculture water until the salinity reaches the target salinity of 3-7‰.

[0012] Alkalinity acclimatization involves adding sodium bicarbonate and sodium carbonate to fresh water to prepare new water B. This new water B is then gradually introduced at a daily gradient of 1.5-2.5 mmol / L to increase the carbonate alkalinity of the aquaculture water until a target carbonate alkalinity of 30-50 mmol / L is reached. The molar ratio of sodium bicarbonate to sodium carbonate is 8:2 to 9.5:0.5.

[0013] During salinity or alkalinity acclimatization, the concentration of new water A or new water B added should be calculated using the following formula to ensure that the concentration of the aquaculture water after the water exchange and mixing reaches the target concentration for the day:

[0014] The concentration of new water = the target concentration for the day + (the target concentration for the day - the current concentration of water in the pool) × (the proportion of old water volume / the proportion of new water volume).

[0015] When salinity acclimatization is performed, the target concentration for the day and the current concentration in the pond water refer to the target salinity for the day and the current concentration in the pond water, respectively, and the new water introduced is called new water A; when alkalinity acclimatization is performed, the target concentration for the day and the current concentration in the pond water refer to the target carbonate alkalinity for the day and the current carbonate alkalinity in the pond water, respectively, and the new water introduced is called new water B; the proportion of new water volume is the ratio of the volume of new water A or new water B introduced to the total volume of the aquaculture water after the water change, and the proportion of old water volume is the ratio of the remaining water volume after deducting the volume of new water A or new water B from the total volume of the aquaculture water after the water change;

[0016] Once the aquaculture water reaches the target salinity or target carbonate alkalinity, the salinity or carbonate alkalinity is no longer increased. The domesticated Xinjiang native fish are then cultured at the target salinity or target carbonate alkalinity for a long period of time. During the long-term culture period, the corresponding new water A or new water B is periodically introduced, and the salinity of new water A is consistent with the target salinity, and the carbonate alkalinity of new water B is consistent with the target carbonate alkalinity.

[0017] Optionally, temporarily raising the fish species to be domesticated in freshwater includes: temporarily raising the Xinjiang native fish species to be domesticated in freshwater for 7 days, during which the salinity of the freshwater is less than 0.5‰, the carbonate alkalinity is 1-2 mmol / L, the water temperature is 22-26℃, the dissolved oxygen is ≥5 mg / L, and unhealthy individuals are removed, to obtain the Xinjiang native fish species to be domesticated after temporary rearing.

[0018] Optionally, during salinity acclimatization, the target salinity is any one of 3‰, 5‰, and 7‰, and the daily increase in salinity is 0.5‰.

[0019] Optionally, during alkalinity acclimatization, the target carbonate alkalinity is any one of 30 mmol / L, 40 mmol / L, and 50 mmol / L, and the daily increase in carbonate alkalinity is 2 mmol / L.

[0020] Optionally, the native fish species of Xinjiang is the Erhe River silver carp. The target salinity for salinity acclimatization is 3-7‰, and the target carbonate alkalinity for alkalinity acclimatization is ≤40 mmol / L.

[0021] The native fish species of Xinjiang is the Ili perch. The target salinity for salinity acclimatization is 3-5‰, and the target carbonate alkalinity for alkalinity acclimatization is ≤30 mmol / L.

[0022] The native fish species of Xinjiang is the perch. Instead of salinity acclimatization, only alkalinity acclimatization will be carried out, with a target carbonate alkalinity ≤30mmol / L.

[0023] Optionally, the molar ratio of sodium bicarbonate to sodium carbonate is 9:1.

[0024] Optionally, during the salinity or alkalinity acclimatization period, the daily volume of new water A or new water B is 1 / 5 to 1 / 2 of the total volume of the aquaculture water body, and an equal volume of the original pond water is discharged; wherein, new water A or new water B is slowly injected into the aquaculture water body.

[0025] Optionally, during salinity or alkalinity acclimatization, if fish exhibit stress symptoms such as lying on their side or refusing to eat, the increase in salinity or carbonate alkalinity should be paused for 1-2 days. During the pause, water should be exchanged daily at the same concentration as during the salinity or alkalinity acclimatization period. Gradual acclimatization should continue after the fish resume normal activity and feeding.

[0026] Optionally, during salinity or alkalinity acclimatization, the water temperature should be controlled at 18-22℃, dissolved oxygen ≥5mg / L, and formulated feed should be given twice a day at a rate of 2%-3% of the fish's body weight. During salinity acclimatization, the pH should be controlled at 7.5-8.0; during alkalinity acclimatization, the pH should be controlled at 8.0-8.5, and should not exceed 8.8.

[0027] Optionally, the long-term aquaculture period is 60 days. During the long-term aquaculture period, the water is changed every 2-4 days, and the amount of water changed each time is 1 / 4-1 / 2 of the total volume of the aquaculture water. The water temperature is controlled at 18-26℃, dissolved oxygen ≥5mg / L, ammonia nitrogen concentration less than 0.2mg / L, nitrite nitrogen concentration less than 0.1mg / L, and alkalinity group pH ≤8.8.

[0028] Compared with existing technologies, the present invention provides a method for the gradient domestication and long-term aquaculture of native fish species in saline-alkali water, which brings the following significant effects:

[0029] 1. This invention establishes a salinity or carbonate alkalinity gradient acclimatization process for native Xinjiang fish species, namely, Ili perch, river perch, and Erhe silver carp. Through freshwater temporary rearing, daily small increases in target concentration, and stress suspension treatment, the fish gradually complete osmotic regulation and acid-base adaptation, avoiding direct entry into high salinity and alkalinity water bodies that would cause acute stress. The survival rate of the three fish species during the acclimatization process can reach over 95%, indicating that this method can effectively improve the safety and survival rate of acclimatization.

[0030] 2. During the acclimatization period, the present invention adopts the method of pre-mixing and replacing the water with new water and determining the concentration of the replacement water according to the formula, so that the pool water after the replacement water is mixed can accurately reach the target concentration of the day. This avoids the sudden changes in local salinity, alkalinity or pH caused by directly adding fresh water, solid salts or high-concentration mother liquor, thereby reducing repeated stress and human operation errors, and improving the standardization, repeatability and production controllability of the acclimatization process.

[0031] 3. This invention uses sodium chloride to adjust salinity and sodium bicarbonate and sodium carbonate in combination to adjust carbonate alkalinity, making the acclimatized water more similar to the natural saline-alkali water in Xinjiang. Cl - HCO3 - and CO3 2- The coexisting ionic composition is conducive to the formation of a more stable carbonate buffer environment, reducing the differences in water quality caused by a single alkalinity reagent, improving the consistency between the acclimatization environment and the actual saline-alkali water aquaculture environment, and making the acclimatization results more suitable for subsequent actual aquaculture applications.

[0032] 4. This invention allows for long-term aquaculture after reaching the target salinity or carbonate alkalinity, with regular replacement of water with fresh water of the same concentration to maintain water stability. This enables the evaluation of fish's sustained feeding and growth performance under target salinity and alkalinity conditions. After 60 days of aquaculture verification, the weight gain rate of the Eerhe River silver carp reached 157.6% at a salinity of 3‰ and 153.7% at a carbonate alkalinity of 30 mmol / L; the weight gain rate of the Ili perch reached 132.0% at a salinity of 5‰, higher than the 112.9% of the freshwater control group; and the weight gain rate of the river perch reached 95.6% at a carbonate alkalinity of 30 mmol / L, higher than the 70.4% of the freshwater control group. These results demonstrate that this invention can screen suitable salinity or carbonate alkalinity conditions for different fish species, providing parameter basis for large-scale aquaculture. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a flowchart illustrating the saline-alkali acclimatization process of native Xinjiang fish (Ili perch, river perch, and Erhe silver carp) according to the present invention.

[0035] Figure 2 A photograph of the Ili perch of this invention;

[0036] Figure 3 This is a photograph of the Erhe silver carp of the present invention;

[0037] Figure 4 A photograph of the perch of this invention;

[0038] Figure 5 This is a diagram showing the culture status of the Erhe silver carp in a breeding pond according to the present invention;

[0039] Figure 6 This is a diagram showing the group state of the Erhe silver carp during the domestication process of the present invention;

[0040] Figure 7 This is a photograph of the water quality measurement work for the aquaculture of silver carp in the Erhe River during this invention.

[0041] Figure 8 This is a photograph of the feeding process for the silver carp of the E'he River according to the present invention;

[0042] Figure 9 This is a diagram showing the culture status of perch in a culture pond according to the present invention;

[0043] Figure 10 This is a diagram showing the population state of the perch during the domestication process of the present invention.

[0044] Figure 11 This is a photograph of the salinity detection work in the perch farming water of this invention;

[0045] Figure 12 This is a photograph of the perch feeding process according to the present invention;

[0046] Figure 13 This is a diagram showing the culture status of the Ili perch in a culture pond according to the present invention;

[0047] Figure 14 This is a photograph of the water change process for the Ili perch of this invention;

[0048] Figure 15 This is a photograph of the salinity detection work in the water used for Ili perch farming according to the present invention;

[0049] Figure 16 This is a photograph of the feeding process for the Ili perch according to the present invention;

[0050] Figure 17 This is a diagram showing the population state of the Ili perch during the domestication process of this invention. Detailed Implementation

[0051] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0052] This invention relates to a method for the gradual acclimatization and long-term aquaculture of native Xinjiang fish species in saline-alkali water, based on simulating the ionic composition of natural saline-alkali water in Xinjiang. The native Xinjiang fish species include one or more of the following: Ili perch, river perch, and Ertis silver carp. The method comprises three stages: initial temporary rearing, gradual acclimatization, and long-term aquaculture at the target concentration. Gradual acclimatization includes either salinity acclimatization or alkalinity acclimatization. Salinity acclimatization primarily regulates water salinity, while alkalinity acclimatization primarily regulates water carbonate alkalinity.

[0053] Example 1: Preparation of temporary acclimatization and salinity adjustment reagents

[0054] This example illustrates the temporary acclimatization process of fish species to be domesticated before entering salinity or alkalinity domestication.

[0055] (1) Preparation of breeding pond: A square ceramic tile breeding pond with a volume of 1024L is used. Before use, the breeding pond is thoroughly disinfected with a 20mg / L potassium permanganate solution, soaked for 24 hours, and then rinsed with clean water.

[0056] (2) Fish selection: Select juvenile Ili perch, river perch or Erhe silver carp with no injuries on their bodies and uniform size. Among them, Ili perch, river perch and Erhe silver carp are important native economic fish in Xinjiang. They have the advantages of delicious meat, fast growth and strong resistance, and are ideal species for saline-alkali water aquaculture.

[0057] Its specific biological characteristics are described below:

[0058] 1) Ili perch

[0059] The Ili perch (scientific name *Percaschrenkii*) is an endemic fish species distributed in the Lake Balkhash-Ili River system and the Emin River-Ala Lake system, belonging to the genus *Percas* of the family Perciformes. Historically, it was an important economic fish, with an average annual yield of 564.3 tons in Lake Balkhash during the 1950s and 60s. However, its population declined sharply due to invasive species, ecological degradation, and overfishing. Adult Ili perch primarily inhabit slow-flowing environments such as river floodplains. Juveniles feed on planktonic crustaceans, while adults become carnivorous. This species can inhabit both freshwater and brackish water, and studies have shown that it has good tolerance potential to chloride-based saline water, with a 96-hour acute salinity tolerance higher than that of freshwater populations of the same genus, the river perch. Currently, the Ili perch has not yet entered the stage of large-scale commercial aquaculture and remains in the "germination conservation and breeding + small-scale trial farming" stage.

[0060] 2) River perch

[0061] The Chinese perch (scientific name *Percafluviatilis*, commonly known as the five-striped black perch) is widely distributed in the water systems of Europe, the Black Sea, the Caspian Sea, and the Aral Sea. It is a major native fish species of the Ulungur River system and the Irtysh River in my country. The Chinese perch is a valuable carnivorous, cold-temperate freshwater fish belonging to the genus *Perca* of the family Perciformes. It was introduced to Bosten Lake in Xinjiang in the late 1960s. After the 1990s, due to overfishing, habitat destruction, and invasive species, the catch of Chinese perch in various natural waters of Xinjiang declined sharply, but its economic value increased year by year. Chinese perch is now farmed on a large scale and is one of the main economic fish species in Xinjiang. While primarily living in freshwater, Chinese perch can also be found in brackish water, with an optimal rearing temperature of 10-22℃.

[0062] 3) Erhe Silver Carp

[0063] The Ertis River Silver Carp (scientific name *Carassius auratus gibelio*) is a unique fish species endemic to the Ertis River and Ulungur River systems in Xinjiang, belonging to the genus *Carassius* of the family Cyprinidae. This species inhabits slow-moving waters such as lakes and river bends, and is omnivorous, with plankton making up a large proportion of its diet. The Ertis River Silver Carp is a eurythermal cold-water fish, exhibiting strong adaptability to low temperatures and rapid growth, and is highly tolerant of adverse environments. In recent years, with the increasing maturity of artificial breeding and seedling cultivation techniques, the Ertis River Silver Carp has gradually become a new species for pond aquaculture and is a high-quality economic fish with significant development potential. In 2023, the artificial breeding volume of the Ertis River Silver Carp reached 51 million individuals.

[0064] (3) Temporary holding: The fish were temporarily held in freshwater (salinity <0.5‰, carbonate alkalinity 1-2 mmol / L) for 7 days at a water temperature of 22-26℃. Continuous aeration was maintained to ensure dissolved oxygen ≥5 mg / L. The fish were fed normally every day. During the temporary holding period, the fish's activity, feeding, and body condition were observed. Unhealthy individuals that swam slowly, swarmed alone, had congested body surface, fin rot, or refused to eat were promptly removed and culled. After the temporary holding period, the fish were obtained as acclimatized fry. The water quality and fish condition records during the temporary holding period are shown in Table 1.

[0065] Table 1. Summary of water quality and fish condition during temporary rearing of three native Xinjiang fish species.

[0066]

[0067] Table 1 shows that during the 7-day temporary rearing period, the water temperature for each fish species was maintained at 22.8-25.3℃, dissolved oxygen at 5.6-6.5 mg / L, and pH at 7.5-7.8, all meeting the requirements for temporary rearing. Specifically, the water quality of the Ili perch remained stable during the temporary rearing period; any individuals exhibiting abnormal behavior, such as swimming alone, were promptly removed, while the remaining individuals showed normal activity and feeding. A small number of abnormal or dead individuals appeared in the early stages of the temporary rearing of the river perch, but their condition stabilized later, and the remaining individuals showed normal activity and feeding. For the Ertis silver carp, unhealthy individuals exhibiting abnormal behavior, such as swimming alone, were removed in the early stages of the temporary rearing; their condition stabilized later, and the remaining individuals showed normal activity and feeding. Temporary rearing and the removal of unhealthy individuals can reduce the impact of transportation, transfer to other ponds, and individual health differences on the subsequent salinity or alkalinity acclimatization results.

[0068] (4) Preparation of salt and alkali adjustment reagents: analytical grade sodium chloride (NaCl) is used for salinity adjustment; a mixture of sodium bicarbonate (NaHCO3) and sodium carbonate (Na2CO3) is used for alkalinity adjustment, with a molar ratio of 9:1.

[0069] The above temporary rearing steps allow the fish to gradually adapt to the culture pond environment, reducing the impact of transportation, transfer to another pond, and individual health differences on the subsequent salinity or alkalinity acclimatization results.

[0070] Example 2: Salinity gradient acclimatization

[0071] This embodiment illustrates the salinity gradient acclimatization method for Ili perch, river perch, or Ertis carp.

[0072] Acclimation groups: One freshwater control group and three salinity acclimation groups were set up, with target salinity values ​​of 3‰, 5‰ and 7‰, respectively.

[0073] Adjustment reagent: analytical grade sodium chloride (NaCl).

[0074] Preparation of salt water for replacement: Before changing the water each day, take an equal volume of fresh water to be replaced, add the calculated amount of NaCl, dissolve it completely, and prepare the salt water for replacement.

[0075] The salinity of the added salt water is calculated using the following formula:

[0076] Salinity of incoming water = Target salinity for the day + (Target salinity for the day - Current pool water salinity) × (Percentage of old water / Percentage of new water)

[0077] If the water exchange volume is 1 / 3 (i.e., new water accounts for 1 / 3 and old water accounts for 2 / 3), then: the salinity of the exchanged water = the target salinity for the day + (the target salinity for the day - the current salinity of the pool water) × 2

[0078] Example: If the current pool water salinity is 3.0‰ and the target salinity for the day is 3.5‰, then the salinity of the incoming water should be adjusted to: 3.5 + (3.5 - 3.0) × 2 = 3.5 + 1.0 = 4.5‰.

[0079] The prepared 4.5‰ saline solution is slowly injected into the aquaculture pond from the bottom along the pond wall. Simultaneously, an equal volume of old water is discharged through drains located in the middle or upper part of the pond. Continuous aeration or water circulation promotes uniform mixing of the new and old water, ensuring that the total volume of the aquaculture water remains constant after the water change. After mixing, the overall salinity of the pond reaches 3.5‰, achieving a uniform increase of 0.5‰ per day. This algorithm is applicable to the gradient increase phase of all salinity groups.

[0080] Gradient Enhancement: Increase by 0.5‰ daily. By slowly and continuously injecting the prepared brine (according to the above formula) into the aquaculture pond while simultaneously draining an equal volume of old water, one-third of the water volume is replaced, allowing the pond water salinity to rise steadily and evenly to the target salinity for the day. This synchronized water exchange method avoids the water level drop and sudden reduction in fish activity space caused by draining old water first, and also avoids the instantaneous increase in pond water concentration or secondary fluctuations in water volume caused by adding new water first, thereby reducing stress responses in the fish.

[0081] Target salinity achieved: Once the pond water salinity reaches the target salinity (3‰, 5‰, or 7‰), the increase is stopped, and the long-term aquaculture phase begins. During this phase, when changing 1 / 3 of the water every 3 days, the salinity of the new water is precisely equal to the target salinity for that group, achieving equal concentration replacement and maintaining constant salinity. During water changes in the long-term aquaculture phase, the same method of slowly adding new water while simultaneously draining an equal volume of old water is used to maintain stable water volume and salinity.

[0082] Stress management: If the fish show signs of severe stress such as lying on their side or refusing to eat, stop increasing the salt concentration for 1-2 days. During this period, change 1 / 3 of the salt solution daily and perform equal volume water changes as described above. Continue the process after the fish recovers.

[0083] Management during acclimatization: During acclimatization, maintain water temperature between 18-22℃, dissolved oxygen above 5mg / L, and pH between 7.5-8.0. Feed twice daily with formulated feed, at a rate of 2%-3% of the fish's body weight. Observe the fish's activity and feeding behavior daily, promptly removing and recording any dead fish.

[0084] Example 3: Alkalinity gradient acclimatization

[0085] This embodiment illustrates the carbonate alkalinity gradient acclimatization method for Ili perch, river perch, or Ertis carp.

[0086] Acclimation groups: One freshwater control group and three alkalinity acclimation groups were set up, with target alkalinity values ​​of 30 mmol / L, 40 mmol / L and 50 mmol / L, respectively.

[0087] Adjustment reagents: Analytical grade sodium bicarbonate (NaHCO3) and sodium carbonate (Na2CO3) are mixed at a molar ratio of 9:1.

[0088] Preparation of Alkaline Solution: Before changing the water daily, take an equal volume of fresh water to be replaced, weigh out the reagents according to a NaHCO3 to Na2CO3 molar ratio of 9:1, and dissolve them thoroughly to prepare the alkaline solution. The carbonate alkalinity of the alkaline solution is calculated using the following formula:

[0089] The alkalinity of carbonates in the replaced alkaline water is calculated using the following formula:

[0090] Alkalinity of incoming water = Daily target alkalinity + (Daily target alkalinity - Current pool water alkalinity) × 2

[0091] Example: If the current alkalinity of the pool water is 10 mmol / L and the target alkalinity for the day is 12 mmol / L, then the alkalinity of the incoming water should be adjusted to: 12 + (12 - 10) × 2 = 12 + 4 = 16 mmol / L.

[0092] Weigh the reagents according to a NaHCO3 to Na2CO3 molar ratio of 9:1, dissolve them in an equal volume of fresh water to be replaced, and prepare an alkaline solution with an alkalinity of 16 mmol / L. Slowly inject the prepared alkaline solution into the aquaculture pond from the bottom along the pond wall, while simultaneously draining an equal volume of old water through a drain outlet located in the middle or upper part of the aquaculture pond. Promote the uniform mixing of the alkaline solution and the original pond water through continuous aeration or water circulation, so that the total volume of the aquaculture water remains unchanged after the water change. After mixing, the overall carbonate alkalinity of the pond reaches 12 mmol / L, completing the daily increase of 2 mmol / L.

[0093] Enhancing the gradient: Increase carbonate alkalinity by 2 mmol / L daily. This is achieved by slowly and continuously injecting the prepared alkaline water (according to the above formula) into the aquaculture pond while simultaneously draining an equal volume of old water, thus replacing 1 / 3 of the water volume. This allows the pond water's carbonate alkalinity to rise steadily and evenly to the daily target level. This synchronized water exchange method avoids the water level drop and sudden reduction in fish activity space caused by draining old water first, and also avoids the instantaneous increase in alkalinity or pH caused by adding new water first, thereby reducing stress on the fish.

[0094] Target alkalinity achievement: Once the pool water alkalinity reaches the target alkalinity (30, 40, or 50 mmol / L), further increases should be stopped. During long-term aquaculture, when changing 1 / 3 of the water every 3 days, the alkalinity of the new water should be precisely equal to the target alkalinity for that group, achieving equal concentration replacement and maintaining constant alkalinity. During water changes in long-term aquaculture, the same method of slowly adding new water while simultaneously draining an equal volume of old water should be used to maintain stable aquaculture water volume, carbonate alkalinity, and pH.

[0095] pH control: Because the compound reagent affects the pH, it is necessary to monitor it daily throughout the acclimatization process and strictly control the pH of the water body to ≤8.8 through means such as enhanced aeration.

[0096] Management during acclimatization: During acclimatization, maintain water temperature at 18-22℃, dissolved oxygen above 5mg / L, and pH at 8.0-8.5. Feed twice daily with formulated feed, at a rate of 2%-3% of the fish's body weight. Observe the fish's activity and feeding behavior daily, promptly removing and recording any dead fish.

[0097] Example 4: Long-term culture at target concentration

[0098] This embodiment illustrates the long-term aquaculture management and growth evaluation method under target salinity or target carbonate alkalinity after completing salinity gradient acclimatization or alkalinity gradient acclimatization.

[0099] Aquaculture facilities: Each treatment group and the freshwater control group were placed independently in a 1024L square ceramic tile aquaculture tank.

[0100] Feeding management: Feed the fish twice a day, at 9:00 am and 6:00 pm, at a rate of 3%-5% of the fish's body weight, and adjust the amount according to the fish's feeding behavior.

[0101] Water quality management:

[0102] Salinity and alkalinity monitoring: Salinity and alkalinity are measured once daily at 8:00 AM and 5:00 PM. Salinity is measured using a salinity meter, and total alkalinity is measured using acid-base titration. When salinity or alkalinity deviates from the target value by ±0.2‰ or ±1 mmol / L, it is adjusted using fresh water pre-adjusted to the corresponding salinity or carbonate alkalinity.

[0103] Water change frequency: Change the water every 3 days, replacing 1 / 3 of the water volume each time. When changing the water, the salinity and alkalinity of the new water should be consistent with the water volume to avoid stress to the fish caused by water quality fluctuations.

[0104] Other water quality indicators: Water temperature, dissolved oxygen, pH, ammonia nitrogen, and nitrite nitrogen are measured weekly. Water temperature is controlled between 18-22℃, dissolved oxygen is maintained above 5 mg / L, pH is controlled between 7.5-8.5 (salinity group) or 8.0-9.0 (alkalinity group), ammonia nitrogen concentration is controlled below 0.2 mg / L, and nitrite nitrogen concentration is controlled below 0.1 mg / L.

[0105] Routine water change: Change 1 / 3 of the water every 3 days. The new water must be precisely prepared beforehand with the corresponding reagent to achieve the exact same target salinity (NaCl) or target alkalinity (NaHCO3 + Na2CO3 9:1) as the target water in the tank, so as to achieve equal concentration replacement and ensure environmental stability.

[0106] Water quality control thresholds: Maintain water temperature at 22-26℃ throughout the process; dissolved oxygen ≥5mg / L; salinity or alkalinity fluctuations within ±5% of the target value; ammonia nitrogen <0.2mg / L; nitrite nitrogen <0.1mg / L; alkalinity group pH ≤8.8.

[0107] Rearing and Evaluation: Rearing for 60 days. Weighing was performed on days 0, 30, 45, and 60 to calculate the weight gain and specific growth rate (SGR).

[0108] SGR (% / day) = [ln(final body weight) - ln(initial body weight)] / number of days of rearing × 100%.

[0109] The above scheme was used to conduct verification experiments, and some growth results are as follows:

[0110] Erhe silver carp: At 60 days, the final body weight of the salinity 3‰ group was 26.33g, with a weight gain rate of 157.6%, which was much higher than that of the freshwater control group (20.87g, 106.2%); the weight gain of the alkalinity 30mmol / L group was 25.93g (153.7%), which also significantly promoted growth.

[0111] Ili perch: The final body weight of the 5‰ salinity group was 21.25g (weight gain rate 132.0%), which was the highest among all salinity groups and better than the control (19.42g, 112.9%); the 30mmol / L alkalinity group could grow normally (20.58g), but the 40mmol / L group (16.52g) had been inhibited.

[0112] River perch: The final body weight of the 30 mmol / L alkalinity group reached 30.05 g (weight gain rate 95.6%), which was not only higher than the control (26.12 g, 70.4%), but also far exceeded all salinity groups; growth was significantly inhibited when the salinity was above 5‰.

[0113] Based on the above long-term aquaculture results, when the fish species to be domesticated is the Equator silver carp, the target salinity is 3-7‰ and the target carbonate alkalinity is no higher than 40 mmol / L; when the fish species to be domesticated is the Ili perch, the target salinity is 3-5‰ and the target carbonate alkalinity is no higher than 30 mmol / L; when the fish species to be domesticated is the river perch, alkalinity domestication is adopted, salinity domestication is not carried out, and the target carbonate alkalinity is no higher than 30 mmol / L.

[0114] Experimental results

[0115] The growth performance of the three fish species under different salinity and alkalinity conditions is shown in the table below:

[0116] Table 2. Growth performance (g) of Ehe silver carp under different salinity and alkalinity conditions.

[0117]

[0118] Table 3. Growth performance of Ili perch under different salinity and alkalinity conditions (g)

[0119]

[0120] Table 4. Growth performance of perch under different salinity and alkalinity conditions (g)

[0121]

[0122] To evaluate the survival of different treatment groups throughout the entire process of temporary holding, domestication, and long-term breeding, the initial number of tails, the number of deaths during the temporary holding period, the number of tails removed during the temporary holding period, the number of deaths during the domestication period, the number of deaths during the long-term breeding period, and the final number of survivors were recorded for each treatment group. The results are shown in Table 5.

[0123] Among them, individuals removed during the temporary holding period are those that are unhealthy, such as those that swim slowly, swim alone, have congested skin, have fin rot, or refuse to eat; the cumulative reduction is the sum of the number of deaths during the temporary holding period, the number of individuals removed during the temporary holding period, the number of individuals that died during the domestication period, and the number of individuals that died during the long-term breeding period.

[0124] Domestication survival rate is used to evaluate the survival of fish during the gradient domestication stage, and is calculated according to the following formula:

[0125] Domestication survival rate (%) = (Initial number of tails - Number of deaths during temporary holding period - Number of tails removed during temporary holding period - Number of tails killed during domestication period) / (Initial number of tails - Number of deaths during temporary holding period - Number of tails removed during temporary holding period) * 100%;

[0126] Overall survival rate is used to evaluate the overall survival of fish from temporary holding and gradual acclimatization to the end of long-term aquaculture, and is calculated according to the following formula:

[0127] Overall survival rate (%): final number of survivors / initial number of survivors * 100%.

[0128] Table 5. Mortality and Survival Rate Statistics

[0129]

[0130] Example 5: Alternative Implementation

[0131] Based on the above embodiments, the present invention may also include the following alternative embodiments.

[0132] Alternative Option 1 (Accustomed Growth Gradient Alternative Option): The daily increase in salinity can be 0.2-0.8‰, and the daily increase in alkalinity can fluctuate within the range of 1.5-2.5 mmol / L, with minor adjustments based on the condition of the fish.

[0133] Alternative Option Two (Water Exchange Alternative): During the acclimatization period, the daily water exchange volume can be adjusted based on the stocking density, the water body's self-purification capacity, and water quality monitoring results. The water exchange volume can be 1 / 5 to 1 / 2 of the total water volume, with 1 / 3 being optimal. Experiments have verified that when 1 / 3 of the water is exchanged daily, ammonia nitrogen in the water can be stably controlled at 0.1-0.15 mg / L, nitrite nitrogen is below 0.05 mg / L, fish show no obvious stress response, the acclimatization survival rate can reach over 95%, and the energy consumption for water exchange is moderate. When the daily water exchange volume is 1 / 5, ammonia nitrogen easily accumulates to over 0.3 mg / L, leading to a decrease in fish feeding. When the daily water exchange volume is 1 / 2, although the water quality is relatively clean, the water body is more disturbed, and the energy consumption for water exchange increases, reducing production economics.

[0134] The required water exchange volume is related to the stocking density, the water body's self-purification capacity, and the rate of pollutant accumulation. When the stocking density is low and the water body's self-purification capacity is strong, a lower water exchange volume can be used; when the stocking density is high or pollutants accumulate rapidly, a higher water exchange volume is needed. Experiments have shown that when the stocking density is below 5 kg / m³, a daily water exchange of 1 / 5 is sufficient to maintain stable water quality; when the stocking density is above 15 kg / m³, the daily water exchange volume needs to be increased to 1 / 2 to control ammonia nitrogen below 0.2 mg / L.

[0135] Water exchange methods can be changed from slow introduction to drip addition, as long as small-scale, high-frequency, equal-concentration replacements are achieved. During long-term aquaculture, the water exchange frequency can be adjusted appropriately based on stocking density and water quality. When the stocking density is low, water can be changed every 4 days; when the stocking density is high, water can be changed every 2 days. Each water exchange should maintain a volume between 1 / 4 and 1 / 2 of the aquaculture water volume.

[0136] Alternative Solution 3 (Alternative to Aquaculture Pond): The 1024L square ceramic tile aquaculture pond used in the above embodiments is only one specific implementation method. The aquaculture facilities of the present invention are not limited to this. Cement ponds, fiberglass water tanks, canvas ponds, recirculating aquaculture ponds, and other facilities can also be used. Under the condition that the target salinity or target carbonate alkalinity can be maintained stably, other aquaculture facilities such as net cages can also be used.

[0137] Alternative Solution Four (Fish Size Alternative): The domestication method of this invention is also applicable to Ili perch, river perch, and Ertis silver carp of different sizes, including fry, fingerlings, and adults. For larger fish, the rate of increase in salinity or alkalinity can be appropriately accelerated to shorten the domestication time. When adjusting the rate of increase in salinity or carbonate alkalinity, the fish's activity, feeding, and stress response should be used as the basis for judgment.

[0138] Alternative Option 5 (Fine-tuning of alkalinity blending ratio):

[0139] In the above embodiments, NaHCO3 and Na2CO3 are mixed in a molar ratio of 9:1, which is a preferred embodiment of the present invention. HCO3 in Xinjiang natural chloride-carbonate type saline-alkali water. - / CO3 2- The molar ratio is approximately 8:1 to 10:1, corresponding to a water pH range of approximately 8.0-8.8. This is to simulate the HCO3 content in natural saline-alkali water in Xinjiang. - and CO3 2- In this invention, a coexisting carbonate buffer system is constructed by using a mixture of NaHCO3 and Na2CO3 to adjust the alkalinity of the carbonate.

[0140] Screening experiments based on compound ratios showed that when the molar ratio of NaHCO3 to Na2CO3 was 7:3, the pH of the water easily rose to 8.9-9.3, exceeding the upper limit of fish tolerance. The survival rate after 60 days was 82%, and the weight gain rate after 60 days was 68.5%, indicating a weak buffering capacity. When the molar ratio of NaHCO3 to Na2CO3 was 10:0, i.e., NaHCO3 was used alone to adjust alkalinity, the pH of the water was 7.8-8.6. Under aeration conditions, the pH fluctuated greatly, and the survival rate after 60 days was 91%, with a weight gain rate of 132.5% after 60 days, also indicating a weak buffering capacity.

[0141] When the molar ratio of NaHCO3 to Na2CO3 is between 8:2 and 9.5:0.5, the pH of the water can be stably maintained within the range of 8.0-8.8, resulting in high fish survival and weight gain rates. Specifically, at an 8:2 ratio, the water pH is 8.4-8.7, with a 60-day survival rate of 96% and a 60-day weight gain rate of 148.2%; at a 9:1 ratio, the water pH is 8.2-8.5, with a 60-day survival rate of 98% and a 60-day weight gain rate of 153.7%, demonstrating the strongest buffering capacity and the most stable pH; at a 9.5:0.5 ratio, the water pH is 8.0-8.3, with a 60-day survival rate of 97% and a 60-day weight gain rate of 151.4%. Therefore, the molar ratio of NaHCO3 to Na2CO3 can be adjusted between 8:2 and 9.5:0.5, and can be further adjusted to 9:1.

[0142] Alternative Option Six (Equivalent Reagent Replacement): For salinity adjustment, natural seawater or underground brine can be used to replace NaCl; for alkalinity adjustment, sodium salts can be partially replaced by potassium salts, as long as the core is HCO3-. - / CO3 2- Compound system.

[0143] Terminology and Principle Explanation:

[0144] To facilitate understanding of this invention, the relevant terms and technical principles are further explained below.

[0145] (1) Standardized Terminology

[0146] Ili perch: scientific name Percas chrenkii, referred to as "Ili perch" throughout this article.

[0147] River perch: scientific name Perca fluviatilis, commonly known as five-striped black perch, will be referred to as "river perch" throughout this article.

[0148] Erhe Silver Carp: scientific name Carassius auratus gibelio, referred to as "Erhe Silver Carp" throughout this article.

[0149] Salinity: expressed in parts per thousand (‰), adjusted with NaCl.

[0150] Alkalinity: refers to the alkalinity of carbonates, expressed in millimoles per liter (mmol / L), and adjusted by mixing NaHCO3 and Na2CO3 in a molar ratio of 9:1.

[0151] Water change: The operation of draining some of the old water and adding an equal amount of new water. The amount of water changed is expressed as a fraction of the total water volume used for aquaculture.

[0152] SGR (Specific Growth Rate): (% / day) = (ln final body weight - ln initial body weight) / number of days × 100%.

[0153] (2) Characteristics of ionic composition of saline-alkali water resources in Xinjiang

[0154] The basis for choosing NaCl to adjust salt content and NaHCO3 + Na2CO3 to adjust alkali content is that the natural saline water in Xinjiang is of the chloride-carbonate type. Cl - HCO3 - CO3 2- The dominant ion is HCO3-. A 9:1 molar ratio is used to achieve the desired HCO3- concentration within the target pH range of ≤8.8. - With CO3 2- The optimal ratio, which closely approximates the measured values ​​in natural water bodies, can form a stable buffer system, avoiding drastic pH fluctuations caused by a single NaHCO3.

[0155] (3) Physiological mechanisms of salt and alkali stress in fish

[0156] Fish in saline-alkali environments primarily face osmotic pressure stress and acid-base balance stress. Increased salinity leads to water loss, requiring fish to regulate ion transport in their gills to maintain osmotic pressure balance; increased alkalinity raises the pH of their blood, necessitating regulation of respiration and kidney function to maintain acid-base balance. The step-by-step gradient acclimatization method of this invention enables fish to gradually adapt to these physiological changes, reducing stress responses.

[0157] The above terms and principles are used to aid in understanding the present invention and should not be construed as limiting the scope of protection of the present invention.

[0158] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention, enabling those skilled in the art to understand and apply it. However, it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to the present invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention.

Claims

1. A method for the gradual domestication and long-term aquaculture of native fish species in saline-alkali water in Xinjiang, characterized in that, Includes the following steps: The native fish species of Xinjiang to be domesticated were temporarily raised in freshwater to obtain the native fish species of Xinjiang to be domesticated after temporary rearing. Salinity or alkalinity acclimatization was carried out on native Xinjiang fish species that were temporarily held and awaiting domestication. The salinity acclimatization process involves adding sodium chloride to fresh water to prepare new water A. This new water A is then gradually introduced at a daily gradient of 0.2-0.8‰ to increase the salinity of the aquaculture water until the salinity reaches the target salinity of 3-7‰. Alkalinity acclimatization involves adding sodium bicarbonate and sodium carbonate to fresh water to prepare new water B. This new water B is then gradually introduced at a daily gradient of 1.5-2.5 mmol / L to increase the carbonate alkalinity of the aquaculture water until a target carbonate alkalinity of 30-50 mmol / L is reached. The molar ratio of sodium bicarbonate to sodium carbonate is 8:2 to 9.5:0.

5. During salinity or alkalinity acclimatization, the concentration of new water A or new water B added should be calculated using the following formula to ensure that the concentration of the aquaculture water after the water exchange and mixing reaches the target concentration for the day: The concentration of new water = the target concentration for the day + (the target concentration for the day - the current concentration of water in the pool) × (the proportion of old water volume / the proportion of new water volume). Specifically, when salinity acclimatization is performed, the target concentration for the day and the current concentration of the pool water are the target salinity for the day and the current concentration of the pool water, respectively, and the new water introduced is called new water A; when alkalinity acclimatization is performed, the target concentration for the day and the current concentration of the pool water are the target carbonate alkalinity for the day and the current carbonate alkalinity of the pool water, respectively, and the new water introduced is called new water B; the proportion of new water volume is the ratio of the volume of new water A or new water B introduced to the total volume of the aquaculture water after the water exchange, and the proportion of old water volume is the ratio of the remaining water volume after deducting the volume of new water A or new water B from the total volume of the aquaculture water after the water exchange. Once the aquaculture water reaches the target salinity or target carbonate alkalinity, the salinity or carbonate alkalinity is no longer increased. The domesticated Xinjiang native fish are then cultured at the target salinity or target carbonate alkalinity for a long period of time. During the long-term culture period, the corresponding new water A or new water B is periodically introduced, and the salinity of new water A is consistent with the target salinity, and the carbonate alkalinity of new water B is consistent with the target carbonate alkalinity.

2. The method according to claim 1, characterized in that, The native Xinjiang fish species to be domesticated were temporarily held in freshwater for 7 days. During the holding period, the salinity of the freshwater was less than 0.5‰, the carbonate alkalinity was 1-2 mmol / L, the water temperature was 22-26℃, and the dissolved oxygen was ≥5mg / L. Unhealthy individuals were removed to obtain the domesticated native Xinjiang fish species after temporary holding.

3. The method according to claim 1, characterized in that, During salinity acclimatization, the target salinity is any one of 3‰, 5‰, and 7‰, and the daily increase in salinity is 0.5‰.

4. The method according to claim 3, characterized in that, During alkalinity acclimatization, the target carbonate alkalinity is any one of 30 mmol / L, 40 mmol / L, and 50 mmol / L, and the daily increase in carbonate alkalinity is 2 mmol / L.

5. The method according to claim 1, characterized in that: The native fish species of Xinjiang is the Erhe silver carp. The target salinity for salinity acclimatization is 3-7‰, and the target carbonate alkalinity for alkalinity acclimatization is ≤40 mmol / L. The native fish species of Xinjiang is the Ili perch. The target salinity for salinity acclimatization is 3-5‰, and the target carbonate alkalinity for alkalinity acclimatization is ≤30 mmol / L. The native fish species of Xinjiang is the perch. Instead of salinity acclimatization, only alkalinity acclimatization will be carried out, with a target carbonate alkalinity ≤30 mmol / L.

6. The method according to claim 1, characterized in that, The molar ratio of sodium bicarbonate to sodium carbonate is 9:

1.

7. The method according to claim 1, characterized in that, During the salinity or alkalinity acclimatization period, the daily volume of new water A or new water B should be 1 / 5 to 1 / 2 of the total volume of the aquaculture water body, and an equal volume of the original pond water should be discharged; among them, new water A or new water B should be slowly injected into the aquaculture water body.

8. The method according to claim 7, characterized in that, During salinity or alkalinity acclimatization, if fish exhibit stress symptoms such as lying on their side or refusing to eat, suspend the increase of salinity or carbonate alkalinity for 1-2 days. During the suspension period, perform daily water changes at the same concentration as during the salinity or alkalinity acclimatization period. Once the fish resume normal activity and feeding, continue the gradient acclimatization process.

9. The method according to claim 8, characterized in that, During salinity or alkalinity acclimatization, the water temperature should be controlled at 18-22℃, dissolved oxygen ≥5mg / L, and formulated feed should be given twice a day at a rate of 2%-3% of the fish's body weight. During salinity acclimatization, the pH should be controlled at 7.5-8.0; during alkalinity acclimatization, the pH should be controlled at 8.0-8.5, and should not exceed 8.

8.

10. The method according to claim 1, characterized in that, The long-term breeding period is 60 days. During the long-term breeding period, the water should be changed every 2-4 days, and the amount of water changed each time should be 1 / 4-1 / 2 of the total volume of the breeding water. The water temperature should be controlled at 18-26℃, dissolved oxygen ≥5mg / L, ammonia nitrogen concentration ≤0.2mg / L, nitrite nitrogen concentration ≤0.1mg / L, and alkalinity group pH≤8.8.

Images