A method for transporting high-bodied redfin bream fry

Abstract

The present invention discloses a method for transporting fry of a large-bodied croaker, belonging to the technical field of fry transportation. The method incorporates an anesthetic test for fry transportation, determining the appropriate type and concentration of anesthetic by studying four parameter indicators. This method reduces the mortality of released fry during transportation, particularly small, stress-prone fry, and has positive implications for the smooth implementation of stocking and reproduction.

Description

Technical Field

[0001] The invention relates to the technical field of fish fry transportation, in particular to a method for transporting high-bodied croaker fry. Background Art

[0002] Transporting fish fry is a crucial step in stocking and releasing fish in hydropower projects. During stocking and releasing, fry are typically packed in plastic bags, oxygenated, and sealed for transportation, offering convenient and efficient transport. The survival rate of fry is high during short-distance transportation. However, during long-distance transport, the enclosed conditions of the plastic bags can lead to contamination of the water inside by the fry's metabolism, resulting in varying degrees of mortality. In addition to the effects of deteriorating water quality, the fry's own behavioral characteristics can also affect survival rates. Highly stress-sensitive fry will violently impact the plastic bags or swim recklessly, inevitably resulting in injury and death during transportation. Therefore, a dose of anesthetic is used during fry transportation to reduce the fry's metabolism and stress response.

[0003] Fish fry anesthetics include MS-222 (ethyl m-aminobenzoate methanesulfonate), eugenol, quinaldine, and metoprolol. Among these anesthetics, MS-222 and eugenol are the most frequently used due to their excellent anesthetic effect, minimal residual drug residue, and safety to humans and animals. Anesthetics can suppress the fish's nervous system, prevent increases in plasma cortisol levels, lower ventricular contraction pressure, and alter gill hemodynamics, thereby reducing the fry's metabolic rate and improving the transport environment in film bags. Furthermore, the appropriate addition of anesthetics during transportation can reduce stress in the fry and prevent physical damage from violent impacts.

[0004] For example, the Chinese invention patent with publication number CN105325322A discloses a method for improving the survival rate of Mongolian croaker fry during transportation, comprising the following steps: (1) injecting clean water into a transport polyethylene film bag, with the volume accounting for 1 / 4 of the total volume; (2) placing Mongolian croaker fry in the bag at a density of 20 g fry per liter of water; (3) adding a quantitatively prepared anesthetic (eugenol 1‰ dilution) into the bag, with an anesthetic concentration of 5 mg eugenol dilution per liter of water; (4) injecting oxygen into the bag until it is fully expanded, and tying the bag mouth with a rubber band; (5) placing the film bag in a foam box for transportation for no more than 24 hours. This method has simple steps and is convenient and labor-saving when transporting a small amount of fry. However, this method does not establish a comparison system for conventional fish anesthetics. When implementing a large-scale release plan at a breeding and release station, or a large-scale release plan in a basin or region, each type of fry has different physiological habits, and direct transportation without preliminary testing has a high risk of mortality. Especially for the release of rare and endemic protected fish, the transport of fry is a critical step that must be carefully controlled. Only by selecting the appropriate transport method can mortality be minimized. Furthermore, this method has several technical flaws. The fry do not undergo a stress relief period before transport, and adding the anesthetic directly to the fry bag prevents the solution from being fully mixed, leading to fry mortality.

[0005] For example, the Chinese invention patent with publication number CN110463631A provides a method for improving the survival rate of commercial grass carp during high-density long-distance transportation. The method involves monitoring and regulating the water quality of the aquaculture water before catching, stopping the fish from feeding and temporarily raising them in water after catching, cooling and anesthesia, and slow-release oxygenation and water quality regulation during transportation. This method solves the problems of fish damage and high mortality caused by fish stress and deterioration of water quality during high-density long-distance transportation of commercial grass carp, thereby improving the density and survival rate of live grass carp during long-distance transportation. The method transports adult commercial grass carp. Adult fish have a significantly higher tolerance to water quality and hypoxia than fry. Therefore, the method has low guidance and adaptability for fry transportation. Fry transportation requires sophisticated operations, so more targeted method improvements are needed.

[0006] In summary, a method for transporting high-bodied fry of redfin croaker is provided to reduce the mortality of fry, especially small-sized fry that are easily stressed, which has positive significance for the smooth implementation of reproduction and release. Summary of the Invention

[0007] In view of the above-mentioned defects of the prior art, in a first aspect of the present invention, a method for transporting fry of red croaker with high survival rate and strong guidance is provided, comprising the following steps:

[0008] (1) Select healthy juvenile breccia with a total length of 4-5 cm, complete body scales and fins, and the appearance of adults as the released fry;

[0009] (2) Releasing fry for temporary rearing and cultivation to provide them with an adaptation period from artificial aquaculture waters to natural water bodies;

[0010] (3) Establish an anesthesia test for fry transportation. Based on the mortality of fry in each treatment group at different time periods, determine the type and concentration of anesthetics in the fry transportation process. The method is as follows:

[0011] a. Prior to the test, the fry were deprived of food; a predetermined gradient of anesthetic concentrations was set according to the type of anesthetic selected for the test, and anesthetic solutions were prepared and adjusted to a neutral pH to form several treatment groups;

[0012] b. Measure the oxygen consumption rate of the fry, determine the loading density of the fry in the container, and reduce the error of the test caused by the oxygen consumption when the fry density is too high;

[0013] C, the full length and body weight of the statistical test fry; according to the arrangement of each treatment group, anesthetics were added and mixed in the container of water, and then the loading operation was carried out. The fry were loaded based on the loading density and the container was closed after oxygenation; a group without adding anesthetics and with the same operation as the control group was used;

[0014] d. Based on the actual simulated fry release and transportation time requirements, the duration of the anesthesia test was controlled within 20 hours. During the anesthesia test, the water physical and chemical parameters of each treatment group and control group were measured every 3-5 hours, and the mortality rate of fry in each group was calculated. The type and concentration of anesthetic used in the fry transportation process were determined based on the mortality results. The water physical and chemical parameters included dissolved oxygen, pH, ammonia nitrogen content, and non-ionized ammonia content.

[0015] (4) The type and concentration of anesthetics determined in the fry transport anesthesia test shall be applied to the transportation of released fry, and the fry shall be packaged using the same containers, water and loading operations as those used in the fry transport anesthesia test. The fry shall be disinfected when transported to the release site to prevent bacterial diseases in the transported fish.

[0016] The second generation of artificially bred fry from wild parents can be produced in large quantities under controlled conditions. By selecting different broodstock for pairing, inbreeding can be avoided, thereby maintaining or increasing the genetic diversity of the population. They can also grow under pathogen-free conditions, reducing the spread of disease, improving the health of the fry, and enabling the fry to adapt to the natural environment more quickly, thereby improving the efficiency and success rate of release and helping to restore and increase the number of fish populations in natural waters.

[0017] Preferably, in step (1), the fry are the first generation artificially bred from wild parents, have no injuries or diseases on the outside, are bright in color, have uniform sizes, swim in groups, are active, and have the ability to swim against the current.

[0018] A low deformity rate indicates that the released fry are in good health, better able to adapt to the natural environment, and have a higher survival rate and growth rate after release. Healthy fry reduce the environmental pressure caused by sick and weak fry, and can more effectively perform their ecological functions in natural waters, such as filtering plankton and improving water quality, thereby contributing to the recovery of aquatic ecosystems and maintaining biodiversity.

[0019] Preferably, in step (1), the deformity rate of the fry (the percentage of individuals with irregular shapes to the total number of fry) is less than 3%.

[0020] Waters with a depth of 1.5-2 meters can provide relatively stable water temperature and good water quality conditions for the fry selected by the present invention. Open and unobstructed waters are conducive to the natural flow and exchange of water bodies, increase dissolved oxygen levels, reduce the accumulation of harmful substances, and provide a better living environment for temporarily rearing fry.

[0021] Preferably, in step (2), the temporary culture is carried out in waters with a depth of 1.5-2 m, with no shelters around to provide shade or wind protection, and a fry cage or enclosure is set up for temporary culture, and the temporary culture time is 5-10 days.

[0022] In view of the physiological characteristics of small-sized fry, small wild fish, shrimp, insects, cladocerans and copepods are used for feeding during the temporary rearing period. Such natural baits usually contain high-quality protein, essential amino acids, fatty acids, vitamins and minerals, which are conducive to the growth of fry and the development of the immune system, enhance the disease resistance of fry and reduce the occurrence of diseases; the natural movement and smell of natural baits can also stimulate the feeding instinct of fry, promote their active foraging, enable fry to adapt to the fish pond environment, reduce stress and avoid errors caused by experiments.

[0023] Preferably, in step (2), the fry are fed with small wild fish, shrimp, insects, cladocerans, and copepods during the temporary rearing period.

[0024] Preferably, in step (3) a, the anesthetics used are MS-222 and eugenol.

[0025] Further preferably, the anesthetic concentration of the MS-222 is set to 10 mg / L, 20 mg / L, and 40 mg / L; the anesthetic concentration of the eugenol is set to 2 mg / L, 5 mg / L, and 10 mg / L.

[0026] Film bags are commonly used for transporting fry, and they simulate normal fry transport conditions. Based on the specifications of the fry in this invention, a 20-liter film bag is an appropriate loading size. The appropriate loading density ensures sufficient living space for the fry while minimizing damage caused by jolts and pressure fluctuations during transportation or testing, thereby improving the fry's survival rate.

[0027] Preferably, in step (3) b, the container is a film bag with a volume of 20 L; the loading density of the fry is 50 g / bag.

[0028] A suitable ratio of 1:3-4 water to oxygen in the container helps ensure that the selected fry size has sufficient dissolved oxygen during transportation. This ratio helps maintain the gas balance in the water column and reduces the accumulation of carbon dioxide, thereby reducing the risk of fish mortality from hypoxia or carbon dioxide poisoning. The appropriate oxygen level also helps stabilize the water environment and reduce stress reactions caused by hypoxia.

[0029] Preferably, in step (3) c, the ratio of water to oxygen in the container is 1:3-4.

[0030] Using water from temporary holding bodies helps fry adapt to the testing or transportation environment, reduces stress during the process, reduces mortality during testing and transportation, and helps improve test accuracy.

[0031] Preferably, in step (3) c, the water comes from the water body where the temporary cultivation is located; the water temperature is 20-28 ° C, the dissolved oxygen in the water is ≥6.5 mg / L, the pH is 7.2-7.5, the conductivity is 320-330 us / cm, and the ammonia nitrogen content is ≤0.45 mg / L.

[0032] Preferably, in step (3) d, dissolved oxygen is measured by an electrochemical probe method; pH is measured by a glass electrode method; ammonia nitrogen content is measured by Nessler's reagent colorimetry; and non-ionic ammonia concentration is calculated according to GB 11607-89 based on the measured ammonia nitrogen content, water temperature and pH, to measure the non-ionic ammonia content.

[0033] The present invention specifically designs the above technical solution for fish fry transportation based on the needs of fish breeding and release in water conservancy and hydropower projects. Compared to fry released from rivers, lakes, and reservoirs, fry from other water types or adult fish are smaller and more sensitive to anesthesia. Larger fish species are released, and their ability to adapt to the environment and avoid predators increases their survival rate. However, larger fish species increase the cost of breeding and require more production facilities.

[0034] The release of fry in this method is based on the formation of scales. The fry's eyes, fins, mouth, and digestive tract are fully developed, marking their life cycle as juveniles, with their established lifestyles. After scales are formed, the various functions of the skin are fully developed. The mucus secreted by the skin reduces water resistance on the fish, ensuring its swimming speed, allowing it to more efficiently hunt and avoid predators. The mucus secreted by the skin forms a protective film on the outside of the body, effectively resisting the invasion of various bacteria in the water and maintaining its health. The mucus also accelerates the sedimentation of suspended matter in the surrounding water, maintaining the stability of the water. Furthermore, after scales are formed, the pigmentation of most fish's epidermal cells has developed and adapted to the background of the water, allowing the fish to better conceal itself in the aquatic environment, thereby more effectively hunting and avoiding predators. Release specifications can be varied based on the adaptability of each fish.

[0035] In addition to the above-mentioned individual characteristics of selected released fry, the present invention also established a fry transport anesthesia test to determine the type and concentration of suitable anesthetics to reduce the mortality rate of fry. When designing the method, the inventors took into account that the mortality rate of fry increases with the increase of transportation time, corresponding to the continuous deterioration of water quality. When carrying out fry transportation operations, whether the transport water body can maintain sufficient dissolved oxygen is an important factor in determining the success of the operation. It should be noted that the factors affecting the mortality rate of fry are extensive and diverse, and the selection of different indicators will greatly affect the convenience and accuracy of establishing the anesthesia test. The technical difficulty that the present invention needs to overcome is how to select as few parameters as possible from the numerous indicators available for reference to establish representative indicators, avoid interference from other factors, and thus accurately and intuitively reflect the effects of the type and concentration of anesthetics on mortality and the connection between them, and achieve the above-mentioned convenience and accuracy requirements. The pH value, ammonia nitrogen and non-ionic ammonia content levels of the transport water body have an important impact on the survival rate of fry transportation. High concentrations of ammonia nitrogen can increase blood ammonia nitrogen and pH levels in fry, damaging red blood cells and gill cells, affecting the fry's osmotic pressure regulation and increasing their demand for dissolved oxygen. Non-ionic ammonia is highly toxic to fry. As demonstrated in the examples of the present invention, the selection and analysis of the above parameters can accurately reflect the impact of anesthetics on mortality, providing valuable guidance for the actual release and transportation process.

[0036] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0037] The present invention provides a method for transporting fry of greater erythroculter, introduces an anesthesia test for transporting fry of greater erythroculter, determines the appropriate type and concentration of anesthetic through the study of four parameter indicators, reduces the mortality rate of fry of greater erythroculter during transportation, and has positive significance for the smooth implementation of reproduction and release. DETAILED DESCRIPTION

[0038] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0039] Example 1

[0040] A method for transporting fry of high-bodied redfin bream comprises the following steps:

[0041] (1) During the transportation of fry, croakers are highly susceptible to stress and are therefore well-represented as experimental subjects. Therefore, this example uses Erythroculter bream as the subject; healthy Erythroculter bream juveniles with a total length of 4-5 cm, complete body scales and fins, and an appearance that already possesses the basic characteristics of adults are selected as the released fry;

[0042] The fry, sourced from a hydropower station's stocking and release station, are the first generation of artificially bred wild fry. They are free of injuries and disease, have a bright color, are uniform in size, swim in clusters, are active, and are able to swim against currents. Their overall deformity rate is less than 3%.

[0043] (2) Release the fry for temporary rearing and cultivation to provide them with an adaptation period from artificial aquaculture water bodies to natural water bodies; temporary rearing and cultivation should be carried out in the bay of the hydropower station, with a water depth of 1.5-2 m, without buildings or tall trees around to provide shade or wind protection, and fish cages or enclosures should be set up for temporary rearing and cultivation. The temporary rearing and cultivation time is 5-10 days; during the temporary rearing and cultivation period, small wild fish, shrimp, insects, cladocerans, and copepods should be fed to enable the fry to adapt to the fish pond environment, reduce the stress of the fry during transportation, and help reduce the mortality of the fry;

[0044] (3) Establish an anesthesia test for fry transportation. Based on the mortality of fry in each treatment group at different time periods, determine the type and concentration of anesthetics in the fry transportation process. The method is as follows:

[0045] a. Depriving the fry of food for 24 hours before the experiment is beneficial to reduce excretion during fry transportation. Otherwise, feeding will increase excretion, which will cause the water quality in the transport bag to deteriorate.

[0046] The anesthetics used in the experiment were MS-222 and eugenol. These two anesthetics were prepared into dilute solutions, and the pH of the anesthetic solutions was adjusted to neutral (pH = 7.0) with sodium bicarbonate solution. The concentration effects of the two anesthetics were preliminarily screened, and multiple anesthetic concentrations were set for each anesthetic. This experiment set three anesthetic concentrations: MS-222: 10 mg / L, 20 mg / L, and 40 mg / L, respectively referred to as the MS-10 anesthesia group, MS-20 anesthesia group, and MS-40 anesthesia group; eugenol: 2 mg / L, 5 mg / L, and 10 mg / L, respectively referred to as the Ding-2 anesthesia group, Ding-5 anesthesia group, and Ding-10 anesthesia group. Three replicates were set for each group.

[0047] b. Preliminary tests were conducted to determine the oxygen consumption rate of fry. The fry loading density was set at 50 g / bag, with a fry count of 65-72 fry / bag, which is beneficial for reducing oxygen consumption when the fry density is too high. The film bag used to load the fry had a volume of 20 L and a length × width of 60 cm × 45 cm.

[0048] c. After the fry were removed from the pond, their total length and weight were measured, resulting in a total length of 43.57 ± 0.87 mm (mean ± SD) and a weight of 0.72 ± 0.21 g (mean ± SD). Anesthetics were then added to the water from the temporary aquarium (water temperature 28°C, dissolved oxygen ≥ 6.5 mg / L, pH 7.5, conductivity 330 μS / cm, and ammonia nitrogen content ≤ 0.45 mg / L) according to the settings of each treatment group. After thorough mixing, the fry were placed in film bags, and the fry were placed in the bags. The bags were then oxygenated and tied securely, with the volume ratio of water to oxygen in each bag set at 1:3. A control group, which did not receive anesthetics and underwent the same procedures, was used as the control group and transported to the laboratory within 2 h.

[0049] The fry transport anesthesia experiment lasted 20 hours. Dissolved oxygen, pH, ammonia nitrogen, and non-ionized ammonia content in the film bag carriers of each group were measured every 5 hours, and the mortality rate of fry in each film bag was calculated (mortality rate = (number of deaths / total number) × 100%). Dissolved oxygen and pH were measured using the electrochemical probe method and the glass electrode method, respectively; ammonia nitrogen was measured using the Nessler reagent colorimetric method. Based on the measured ammonia nitrogen, water temperature, and pH, the non-ionized ammonia concentration was calculated according to the Fishery Water Quality Standard (GB 11607-89).

[0050] Anesthetic concentration determination:

[0051] The above-mentioned dissolved oxygen, pH, ammonia nitrogen content, non-ionized ammonia content, and mortality rates are expressed as "mean ± standard deviation". One-way analysis of variance with LSD multiple comparison was used to analyze the differences in water quality and fry mortality among the treatment groups (i.e., the control group and the groups with different anesthetic concentrations). Statistical significance was considered when p < 0.05.

[0052] The dissolved oxygen content test results are shown in Table 1;

[0053] Table 1: Dissolved oxygen content test results (unit: average, mg / L; different letters indicate significant differences at the same time point, p<0.05)

[0054]

[0055] The results in Table 1 show that at the beginning of the experiment (hour 0), the dissolved oxygen content of the seven treatment groups was approximately 15 mg / L, with no significant difference. At hour 10 after the start of the experiment, the dissolved oxygen content of the seven treatment groups was greater than 13 mg / L, and remained at a high level. At hour 15 and hour 20, the dissolved oxygen content of the seven treatment groups showed a downward trend, and the rate of decline of dissolved oxygen in the three MS-222 anesthesia groups was significantly slower than that in the other four groups, indicating that the MS-222 anesthetic can maintain dissolved oxygen for a longer period of time. By one-way analysis of variance (ANOVA) with LSD multiple comparisons, the dissolved oxygen content of the three MS-222 anesthesia groups was significantly higher than that of the control group and the three eugenol anesthesia groups at hour 15 and hour 20 (p < 0.05).

[0056] The pH test results are shown in Table 2;

[0057] Table 2: pH test results (different letters indicate significant differences at the same time point, p<0.05)

[0058]

[0059] The results in Table 2 show that the pH values of all seven treatment groups decreased rapidly during the experimental period, with the most significant decrease in the first 5 hours, from 7.8 at the beginning to 7.4, with no significant differences among the treatment groups. At the 10th hour of the experiment, except for the MS-40 anesthesia group, the pH value was significantly higher than that of the control group (p < 0.05), there were no significant differences between the other anesthesia groups and the control group. At the 15th and 20th hours of the experiment, the pH values of the three MS-222 anesthesia groups were significantly higher than those of the control group (p < 0.05), while there were no significant differences between the three eugenol anesthesia groups and the control group. At the end of the experiment, the pH value of the control group was 6.92 ± 0.04, the highest pH value was 7.04 ± 0.02 in the MS-40 anesthesia group, and the lowest pH value was 6.81 ± 0.02 in the eugenol-10 anesthesia group.

[0060] The ammonia nitrogen test results are shown in Table 3;

[0061] Table 3: Ammonia nitrogen test results (unit: average value, mg / L; different letters indicate significant differences at the same time point, p<0.05)

[0062]

[0063] The results in Table 3 show that at the beginning of the experiment (hour 0), the ammonia nitrogen content in all seven treatment groups was 0.47 mg / L. After the experiment began, the ammonia nitrogen content increased rapidly. At hour 5, there was no significant difference in the ammonia nitrogen content among the seven treatment groups. Starting from hour 10, the ammonia nitrogen content in the control group increased rapidly. Ten hours after the experiment, the ammonia nitrogen content in the six anesthesia groups was significantly lower than that in the control group (p < 0.05). At the end of the experiment, the ammonia nitrogen content in the control group was 11.05 ± 0.23 mg / L, the highest was 8.43 ± 0.52 mg / L in MS-10, and the lowest was 4.78 ± 0.43 mg / L in Ding-5.

[0064] The test results of non-ionic ammonia content are shown in Table 4;

[0065] Table 4: Non-ionized ammonia content test (unit: average value, mg / L; different letters indicate significant differences at the same time point, p<0.05)

[0066]

[0067] The results in Table 4 show that the change pattern of non-ionized ammonia during the experiment was inconsistent with that of ammonia nitrogen. The non-ionized ammonia content in the control group showed a linear upward trend (slope of approximately 1), while the six anesthesia groups showed a trend of first increasing and then decreasing. In addition, the non-ionized ammonia content in the control group was lower than that in the six anesthesia groups 10 hours before the experiment, but was higher than that in the six anesthesia groups 10 hours after the experiment (p < 0.05). When comparing the treatment effects of the two anesthetics, there was no significant difference between the two in the 10 hours before the experiment. However, 10 hours after the experiment, the non-ionized ammonia content in the three eugenol anesthesia groups was significantly higher than that in the three MS-222 anesthesia groups (p < 0.05).

[0068] The statistical results of fry mortality are shown in Table 5;

[0069] Table 5: Statistical results of fry mortality (different letters indicate significant differences at the same time point, p<0.05)

[0070]

[0071] The statistical results in Table 5 show that the cumulative mortality of fry showed an increasing trend during the experiment. At the 5th hour, the control group (34.04% ± 15.4%), which had the highest cumulative mortality, was significantly higher than the six anesthesia groups (p < 0.05). Although there were no significant differences in water quality (dissolved oxygen, pH, ammonia nitrogen, and non-ionized ammonia) between the control group and the six anesthesia groups, anesthetics can reduce the stress of fry, inhibit their mobility, and prevent physical damage. Compared with the six anesthesia groups, the fry in the control group had a stronger stress response, with red gills and behaviors such as colliding with the bag wall. At the 10th hour, the cumulative mortality did not increase significantly compared with the 5th hour. At the 15th hour, the cumulative mortality of fry in the control group increased significantly, while the increase in the six anesthesia groups was not significant. Therefore, the cumulative mortality of the control group at this time point was significantly higher than that in the six anesthesia groups (p < 0.05). At the end of the experiment, the cumulative mortality of fry in the control group was 45.87% ± 15.6%, which was significantly higher than that in the six anesthesia groups.

[0072] Based on the above analysis, when transporting redfin bream fry in film bags with oxygenation and anesthetic, the water quality in the bags showed an increase in ammonia nitrogen and non-ionized ammonia content, and a decrease in dissolved oxygen content and pH level. The water quality continued to deteriorate during transportation, and the degree of deterioration increased with the extension of transportation time.

[0073] Eugenol and MS-222 anesthetics can effectively improve fry survival, improve transportation water quality, maintain a good transportation environment, and reduce fry mortality. Based on the fry mortality of each treatment group at different time periods, the type and concentration of anesthetics in the fry transportation process were determined and applied to the fry transportation process at the fish breeding and release station; for short-term transportation (within 5 hours), eugenol anesthetic concentration of 5 mg / L was used; for medium-term transportation (5-15 hours), eugenol anesthetic concentration of 2-10 mg / L and MS-222 anesthetic concentration of 20-40 mg / L were used; for long-term transportation (15-20 hours), eugenol anesthetic concentration of 5 mg / L and MS-222 anesthetic concentration of 10-40 mg / L were used;

[0074] (4) The guiding types and concentrations of anesthetics determined in the fry transport anesthesia test are applied to the transportation of released fry, and the fry are packaged using the same film bags, water and loading operations as in the fry transport anesthesia test; the impact on the fish body during the transportation of fry is mainly abrasions on the fish body, and the fry are disinfected with bleach solution when they arrive at the release site to prevent bacterial diseases in the transported fish.

[0075] In summary, the release of fry of the croaker bream in this method, based on the formation of scales, indicates that the fry's eyes, fins, mouth, and digestive tract are fully developed, marking them as juveniles in their life history and establishing their own unique lifestyle. After scales are formed, the various functions of the skin are fully developed. The mucus secreted by the skin reduces water resistance on the fish, ensuring its swimming speed, enabling it to more efficiently hunt and avoid predators. The mucus secreted by the skin forms a protective film on the outside of the body, effectively resisting the invasion of various bacteria in the water and maintaining its health. The mucus also accelerates the sedimentation of suspended matter in the surrounding water, maintaining the stability of the water. Furthermore, after scales are formed, the pigmentation of most fish's epidermal cells has developed and adapted to the background of the water, allowing the fish to better conceal itself in the aquatic environment, thereby more effectively hunting and avoiding predators. Release specifications can be varied based on the adaptability of each fish.

[0076] In addition to the above-mentioned individual characteristics of selected fry for release, the present invention establishes an anesthesia test for transport of fry of greater californicus to determine the type and concentration of suitable anesthetics to reduce the mortality rate of fry. When designing the method, since the mortality rate of fry increases with the increase of transportation time, it corresponds to the continuous deterioration of water quality. Therefore, when carrying out the transportation operation of greater californicus fry, whether the transportation water body can maintain sufficient dissolved oxygen is an important factor in determining the success of the operation. However, the factors affecting the mortality rate of fry are extensive and diverse, and the selection of different indicators will greatly affect the convenience and accuracy of establishing the anesthesia test. The present invention overcomes the technical difficulties of how to select as few parameters as possible from a large number of reference indicators to establish representative indicators and avoid interference from other factors, accurately and intuitively reflects the influence of the type and concentration of anesthetics on mortality and the relationship between them, and achieves the above-mentioned convenience and accuracy requirements. The pH value, ammonia nitrogen and non-ionic ammonia content level of the transportation water body have an important influence on the survival rate of fry transportation. High concentrations of ammonia nitrogen can increase blood ammonia nitrogen and pH levels in redfin fry, damaging red blood cells and gill cells, affecting the fry's osmotic pressure regulation and increasing their dissolved oxygen requirement. Non-ionic ammonia is highly toxic to fry. The selection and analysis of the above parameters accurately reflects the impact of anesthetics on mortality, providing valuable guidance for actual release and transportation.

[0077] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for transporting fry of high-bodied red croaker, characterized in that: The steps include: (1) Select healthy juvenile breccia with a total length of 4-5 cm, complete body scales and fins, and the appearance of adults as the released fry; The fry are the offspring of wild parents artificially bred, with no injuries or diseases, bright color, uniform size, swimming in groups, active movements, and the ability to swim against the current; the deformity rate of the fry is less than 3%; (2) Release the fry for temporary rearing and cultivation to provide them with an adaptation period from artificial aquaculture water bodies to natural water bodies; temporary rearing and cultivation is carried out in waters with a depth of 1.5-2 m, without any shelter from the sun or wind, and with fry cages or enclosures for temporary rearing and cultivation. The temporary rearing and cultivation period is 5-10 days; during the temporary rearing and cultivation period, the fry are fed with small wild fish, shrimp, insects, cladocerans, and copepods; (3) Establish an anesthesia test for fry transportation. Based on the mortality of fry in each treatment group at different time periods, determine the type and concentration of anesthetics in the fry transportation process. The method is as follows: a. The fry were fasted before the experiment; a predetermined gradient of anesthetic concentrations was set according to the type of anesthetic selected for the experiment, and anesthetic solutions were prepared respectively, and their pH was adjusted to be neutral to form several treatment groups; the types of anesthetics used were MS-222 and eugenol; the anesthetic concentrations of MS-222 were set to 10 mg / L, 20 mg / L, and 40 mg / L; the anesthetic concentrations of the eugenol were set to 2 mg / L, 5 mg / L, and 10 mg / L; B, measure the oxygen consumption rate of fry, determine the loading density of fry in the container, reduce the error of oxygen consumption after the fry density is too high to the test; The container adopts a film bag with a volume of 20 L; The loading density of the described fry is 50 g / bag; c. Statistically measure the total length and weight of the experimental fry; add an anesthetic to a water container according to the settings of each treatment group and mix, then perform a loading operation, load the fry based on the loading density, oxygenate, and seal the container; a group without the addition of an anesthetic and subject to the same other procedures served as a control group; the ratio of water to oxygenated oxygen in the container was 1:3-4, and the water was obtained from the water body where the temporary cultivation was located; the water temperature was 20-28°C, the dissolved oxygen in the water was ≥6.5 mg / L, the pH was 7.2-7.5, the conductivity was 320-330 μS / cm, and the ammonia nitrogen content was ≤0.45 mg / L; d. Based on the actual simulated fry release and transportation time requirements, the duration of the anesthesia test was controlled within 20 hours. During the anesthesia test, the water physical and chemical parameters of each treatment group and control group were measured every 3-5 hours, and the mortality rate of fry in each group was calculated. The type and concentration of anesthetic used in the fry transportation process were determined based on the mortality results. The water physical and chemical parameters included dissolved oxygen, pH, ammonia nitrogen content, and non-ionized ammonia content. (4) The type and concentration of anesthetics determined in the fry transport anesthesia test shall be applied to the transportation of released fry, and the fry shall be packaged using the same containers, water and loading operations as those used in the fry transport anesthesia test. The fry shall be disinfected when transported to the release site to prevent bacterial diseases in the transported fish.

2. The method for transporting fry of greater erythroculter according to claim 1, wherein: In the step (3) d, dissolved oxygen is measured by an electrochemical probe method; pH is measured by a glass electrode method; ammonia nitrogen content is measured by Nessler's reagent colorimetry; based on the measured ammonia nitrogen content, water temperature and pH, the non-ionic ammonia concentration is calculated according to GB 11607-89 to measure the non-ionic ammonia content.

Images