Fry transportation method

Abstract

The invention discloses a fry transportation method, and belongs to the technical field of fry transportation. According to the fry transportation method, a fry transportation anesthesia test is introduced, the appropriate anesthetic type and concentration are determined through research of four parameter indexes, the death rate of released fries, especially small-size and stress-prone fries in the transportation process is reduced, and the method has positive significance on smooth enhancement and release.

Description

Technical Field

[0001] The invention relates to the technical field of fish fry transportation, and in particular to a fish fry transportation method. Background Art

[0002] The transportation of fry is one of the important links in the proliferation and release of water conservancy and hydropower projects. During the proliferation and release, the fry are generally loaded in film bags and sealed for transportation after oxygenation, which has the characteristics of convenient and efficient transportation. The survival rate of fry is higher during short-distance transportation. However, for the long-distance transportation of fry, under the closed conditions of the film bags, the metabolism of the fry will pollute the water quality in the film bags, which will cause the death of the fry to varying degrees. In addition to the impact of water quality deterioration, the habit characteristics of the fry themselves will also affect the survival rate. Fry with strong stress will violently hit the film bag or swim repeatedly, and will inevitably be injured and killed during the transportation process. Therefore, a certain dose of anesthetics is used in the transportation of fry to reduce the metabolism and stress habits of the fry.

[0003] Anesthetics for fish fry include MS-222 (ethyl m-aminobenzoate methanesulfonate), eugenol, quinaldine, metoprolol, etc. Among these anesthetics, MS-222 and eugenol have the characteristics of good anesthetic effect, small drug residue and no harm to human and animal health, and are the most frequently used anesthetics. Anesthetics can inhibit the nervous system of fish, prevent the increase of plasma cortisol concentration, reduce the contraction pressure of the ventricle and change the blood power of the fish gills, thereby reducing the metabolic rate of fish fry and improving the transportation environment of the film bag carrier. In addition, adding an appropriate amount of anesthetics during transportation can also reduce the stress of fish fry and avoid physical damage caused by violent impact.

[0004] For example, the Chinese invention patent with publication number CN105325322A discloses a method for improving the survival rate of Mongolian carp fry during transportation, comprising the following steps: (1) injecting clean water into the transport polyethylene film bag, the volume of which accounts for 1 / 4 of the total volume; (2) placing Mongolian carp fry in the bag, with 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. The steps of this method are simple and have the effect of saving trouble and effort when transporting a small amount of fry. However, this method has not established 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 river basin or region, each type of fry has different physiological habits, and direct transportation without preliminary testing has a high risk of death. Especially for the release of rare and endemic protected fish, the transportation of fry is one of the key links that must be controlled. Only by choosing the appropriate transportation method can the mortality rate be reduced to the greatest extent. In addition, there are still some technical defects in this method. The fry do not have a stress relief stage before transportation, and the anesthetic is directly added to the fry loading bag, which will cause the solution to not be repeatedly mixed, resulting in the death of the fry.

[0005] For another 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, through the steps of monitoring and regulating the water quality of the aquaculture water before catching, stopping feeding and temporarily raising the fish in water after catching, cooling and anesthesia treatment, slow-release oxygenation and water quality regulation during transportation, etc., to solve the problems of fish damage and high mortality caused by fish stress and deterioration of transportation water quality during high-density long-distance transportation of commercial grass carp, and improve the density and survival rate of live grass carp during long-distance transportation. The transportation object of this method is adult commercial grass carp, and the tolerance of adult fish to water quality and hypoxia is significantly higher than that of fry. Therefore, this method has low guidance and adaptability to the transportation of fry, and the transportation of fry requires refined operation, so more targeted method improvements are needed.

[0006] In summary, providing a method for transporting fry can reduce the mortality of fry, especially small-sized fry that are susceptible to stress, 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 with high survival rate and strong guidance is provided, comprising the following steps: (1) Select healthy juvenile fish with a total length of 4-5 cm, complete body scales and fins, and basic adult characteristics as the fry for release; (2) Releasing fish fry for temporary rearing and cultivation to provide them with an adaptation period from artificial aquaculture waters to natural waters; (3) Establish an anesthetic test for fry transportation. Based on the mortality results 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. Stop feeding the fry before the test; set a predetermined gradient of anesthetic concentration according to the type of anesthetic selected in the test, prepare anesthetic solutions respectively, and adjust the pH thereof to be neutral to form several treatment groups; b. Determine the oxygen consumption rate of fry, determine the loading density of fry in the container, and reduce the error of the test caused by oxygen consumption when the fry density is too high; c. The total length and weight of the test fry were counted; anesthetics were added and mixed in the water container according to the setting of each treatment group, and then the loading operation was performed, the fry were loaded based on the loading density, and the container was closed after oxygenation; a group without adding anesthetics and the rest of the operations were the same as the control group; d. According to the actual simulation requirements of the fry release and transportation time, the duration of the anesthesia test was controlled within 20 hours. During the anesthesia test, the water physicochemical indicators of each treatment group and control group were measured every 3-5 hours, and the mortality rate of fry in each group was counted. The type and concentration of anesthetics used in the fry transportation link were determined based on the mortality results. Among them, the water physicochemical indicators were dissolved oxygen, pH, ammonia nitrogen content, and non-ionic 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.

[0008] The second generation of artificially bred fish from wild parents can be produced in large quantities under controlled conditions. By selecting different parents for pairing and avoiding inbreeding, the genetic diversity of the population can be maintained or increased. The fish can grow under pathogen-free conditions, reducing the spread of disease, improving the health of the seedlings, 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 fish population in natural waters.

[0009] Preferably, in step (1), the fry are the first generation of artificial reproduction of wild parents, have no injuries or diseases in appearance, are bright in color, have uniform sizes, swim in groups, are active, and have the ability to swim against the current.

[0010] The low deformity rate of fry means that the released fry are in good health and can better adapt to the natural environment, thus improving the survival rate and growth rate after release. Healthy fry reduce the environmental pressure caused by sick and weak fry, and can more effectively play their ecological functions in natural waters, such as filtering plankton and improving water quality, which helps to restore the aquatic ecosystem and maintain biodiversity.

[0011] 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%.

[0012] The water area 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. The open water area without shelter is conducive to the natural flow and exchange of water bodies, improves the dissolved oxygen level, reduces the accumulation of harmful substances, and provides a better living environment for the temporary rearing of fry.

[0013] Preferably, in step (2), the temporary culture is carried out in a water area with a water 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.

[0014] 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 breeding period. Such natural baits usually contain high-quality protein, essential amino acids, fatty acids, vitamins and minerals, which are helpful for 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 to the experiment.

[0015] Preferably, in step (2), the fry are fed with small wild fish, shrimp, insects, cladocerans and copepods during the temporary rearing period.

[0016] Preferably, in step (3) a, the types of anesthetics used are MS-222 and eugenol.

[0017] 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.

[0018] Film bags are commonly used containers for transporting fry, and the containers simulate the scene of normal fry transportation. Based on the specifications of the fry of the present invention, a film bag with a volume of 20 L is a suitable loading size, and the appropriate loading density can ensure that the fry have sufficient living space while reducing the damage caused by bumps and pressure changes during transportation or testing, thereby improving the survival rate of the fry.

[0019] Preferably, in step (3) b, the container is a film bag with a volume of 20 L; and the loading density of the fry is 50 g / bag.

[0020] The appropriate ratio of water to oxygen in the container is 1:3-4, which helps ensure that the selected size of fry has sufficient dissolved oxygen during transportation. This ratio helps maintain the gas balance in the water body and reduces the accumulation of carbon dioxide, thereby reducing the risk of death of fry due to lack of oxygen or carbon dioxide poisoning. The appropriate oxygen level also helps stabilize the water environment and reduce stress reactions caused by lack of oxygen.

[0021] Preferably, in step (3) c, the ratio of water to oxygen in the container is 1:3-4.

[0022] Using water from temporary water bodies is beneficial for fry to adapt to the test or transportation environment and reduce the stress response of fry during the above process. It is also beneficial to reduce mortality during the test and transportation and help improve the accuracy of the test.

[0023] 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.

[0024] 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; 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.

[0025] The present invention specifically designs the above technical scheme for the transportation of fry based on the needs of the proliferation and release of water conservancy and hydropower projects. Compared with fry released in rivers, lakes and reservoirs, fry released in other water types or adult fish are smaller in size and more sensitive to anesthesia. The larger the size of the released fish species, the stronger their ability to adapt to the environment and avoid harmful organisms, and the higher their survival rate. However, the larger the size of the fish species, the higher the breeding cost, and the more production facilities are required.

[0026] The release of fry in this method is based on the formation of scales. The eyes, fins, mouth and digestive tract functions of the fry are fully formed. From the perspective of their life history, they belong to the juvenile stage and have formed their own inherent lifestyle. After the formation of scales, the various functions of the skin on the body surface have become perfect. The mucus secreted by the skin can reduce the resistance of the water body to the fish body, ensure the swimming speed of the fish body in the water, and enable the fish to prey more efficiently and better avoid predation by other fish; the mucus secreted by the skin forms a protective film outside the body, which can effectively resist the invasion of various bacteria in the water body and maintain the health of the body; the mucus can also accelerate the precipitation of suspended matter in the water body around the fish body and maintain the stability of the water body in which it is located. In addition, after the formation of scales, the pigments of most fish epidermal cells have been formed and adapted to the background of the water body in which they are located, so that the fish can better hide themselves in the water environment, so that they can more effectively prey and avoid predation by other fish. The release specifications can be diversified according to the adaptability of each fish.

[0027] In addition to the above-mentioned individual characteristics of selected released fry, the present invention also establishes a fry transportation anesthesia test to determine the type and concentration of suitable anesthetics to reduce the mortality rate of fry. When designing the method, the inventor considered that the mortality rate of fry increases with the increase of transportation time, corresponding to the continuous deterioration of water quality. When carrying out the fry transportation operation, whether the dissolved oxygen in the transportation water can be maintained to be sufficient 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 the establishment of the anesthesia test. The technical difficulty that the present invention needs to overcome is how to select as few parameters as possible from a large number of reference indicators to establish representative indicators, avoid interference from other factors, so as to accurately and intuitively reflect the type and concentration of anesthetics on the mortality rate and the connection between them, and achieve the above-mentioned convenience and accuracy requirements. The pH value, ammonia nitrogen and non-ionic ammonia content level of the transportation water have an important influence on the survival rate of fry transportation. High concentrations of ammonia nitrogen will cause an increase in the ammonia nitrogen and pH content of the fry's blood, thereby destroying red blood cells and gill cells, further affecting the fry's osmotic pressure regulation and increasing the fry's demand for dissolved oxygen. Non-ionic ammonia is a substance that is highly toxic to fry. As presented in the embodiments of the present invention, the selection and analysis of the above parameters can accurately reflect the effect of anesthetics on mortality, which has a good guiding effect on the actual release and transportation process.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention provides a fry transportation method, introduces a fry transportation anesthesia test, determines the appropriate anesthetic type and concentration through the study of four parameter indicators, reduces the mortality rate of released fry during transportation, especially small-sized fry that are easily stressed, and has positive significance for the smooth progress of proliferation and release. DETAILED DESCRIPTION

[0029] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0030] Example 1 A method for transporting fry, the steps are as follows: (1) During the transportation of fry, breams are highly susceptible to stress and are well representative as test subjects. Therefore, this example uses Erythroculter bream as the test subject; healthy Erythroculter breams with a total length of 4-5 cm, complete body scales and fins, and an appearance that has the basic characteristics of adults are selected as the released fry; The fry of the red bream came from a hydropower station. They were the first generation of artificial reproduction of wild parents. The fry had no injuries or diseases, bright color, uniform size, swam in groups, were active, and had the ability to swim against the current. The overall deformity rate was 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 should be carried out in the bay of the hydropower station, with a water depth of 1.5-2 m, and no buildings or tall trees around to provide shade or wind protection. Fry cages or enclosures should be set up for temporary rearing and cultivation. The temporary rearing and cultivation period is 5-10 days; during the temporary rearing and cultivation period, small wild fish, shrimp, insects, cladocerans, and copepods should be fed to allow 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; (3) Establish an anesthetic test for fry transportation. Based on the mortality results 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. Depriving the fry of food for 24 hours before the test is beneficial to reduce the excretion during the transportation of the fry. Otherwise, feeding will increase excretion, which will cause the water quality of the transport bag to deteriorate; The anesthetics used in the experiment were MS-222 and eugenol. The 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 different anesthetic concentrations were set for the two anesthetics. Three anesthetic concentrations were set in this experiment, MS-222: 10 mg / L, 20 mg / L and 40 mg / L, respectively referred to as 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 Ding-2 anesthesia group, Ding-5 anesthesia group and Ding-10 anesthesia group; 3 replicates were set for each group. b. The oxygen consumption rate of the fry of the high-bodied red carp was determined through preliminary experiments. The loading density of the fry was set to 50 g / bag and the number of fry was set to 65-72 / bag, which is conducive to reducing the oxygen consumption after the fry density is too high; the volume of the film bag used to load the fry is 20 L, length × width: 60 cm × 45 cm; c. After the fry were taken out of the pond, the total length and weight were measured first. The total length was 43.57 ± 0.87 mm (mean ± standard deviation), and the weight was 0.72 ± 0.21 g (mean ± standard deviation). Then, according to the settings of each treatment group, anesthetics were added to the water from temporary cultivation (water temperature was 28 ℃, dissolved oxygen in the water was ≥ 6.5 mg / L, pH was 7.5, conductivity was 330 us / cm, and ammonia nitrogen content was ≤ 0.45 mg / L). After fully mixing, the water was put into a film bag, and then the fry was put in. The film bag was oxygenated and tied tightly. The volume ratio of water and oxygen in each film bag was controlled at 1:3. The group without adding anesthetics and the other operations were the same was used as the control group, and it was transported to the laboratory. The transportation time was controlled within 2 hours. d. The duration of the fry transport anesthesia test was controlled at 20 h. The dissolved oxygen, pH, ammonia nitrogen content, and non-ionic ammonia content in the film bag carrier of each group were measured every 5 h, and the mortality rate of fry in each film bag was counted (mortality rate = (number of deaths / total number) × 100%); dissolved oxygen and pH indexes were measured by electrochemical probe method and glass electrode method respectively; ammonia nitrogen index was measured by Nessler's reagent colorimetry; based on the measured ammonia nitrogen, water temperature and pH index, the non-ionic ammonia concentration was calculated according to the Fishery Water Quality Standard (GB 11607-89) to obtain its content; Anesthetic concentration determination: The above-mentioned dissolved oxygen, pH, ammonia nitrogen content, non-ionized ammonia content and mortality rate were expressed as "mean ± standard deviation". One-way analysis of variance 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 multiple groups with different anesthetic concentrations). P < 0.05 was considered statistically significant. The dissolved oxygen content test results are shown in Table 1; Table 1: Dissolved oxygen content test results (unit: average value, mg / L; different letters indicate significant differences at the same time point, p<0.05)

[0031] From the results analysis in Table 1, it can be seen that at the beginning of the experiment (0 h), the dissolved oxygen content of the 7 treatment groups was about 15 mg / L, with no significant difference; at the 10th hour after the start of the experiment, the dissolved oxygen content of the 7 treatment groups was greater than 13 mg / L, and still maintained at a high level; at the 15th and 20th hours of the experiment, the dissolved oxygen of the 7 treatment groups showed a downward trend, and the rate of decline of dissolved oxygen in the 3 anesthesia groups of MS-222 was significantly slower than that of the other 4 groups, indicating that the MS-222 anesthetic can maintain dissolved oxygen for a longer period of time; through one-way ANOVA LSD multiple comparison, at the 15th and 20th hours, the dissolved oxygen content of the 3 anesthesia groups of MS-222 was significantly higher than that of the control group and the 3 anesthesia groups of eugenol (p<0.05); The pH test results are shown in Table 2; Table 2: pH test results (different letters at the same time point indicate significant differences, p<0.05)

[0032] From the results in Table 2, it can be seen that the pH of the seven treatment groups decreased rapidly during the test period, which was most obvious in the first 5 hours, from 7.8 at the beginning to 7.4, and there was no significant difference among the treatment groups; at the 10th hour of the test, except for the MS-40 anesthesia group, the pH value was significantly higher than that of the control group (p<0.05), and there was no significant difference between the other anesthesia groups and the control group; at the 15th and 20th hours of the test, the pH values ​​of the three MS-222 anesthesia groups were significantly higher than those of the control group (p<0.05), and there was no significant difference between the three eugenol anesthesia groups and the control group; at the end of the test, the pH value of the control group was 6.92 ± 0.04, the highest pH value of the MS-40 anesthesia group was 7.04 ± 0.02, and the lowest pH value of the eugenol-10 anesthesia group was 6.81 ± 0.02; The ammonia nitrogen test results are shown in Table 3; Table 3: Ammonia nitrogen test results (unit: average value, mg / L; different letters at the same time point indicate significant differences, p<0.05)

[0033] From the results in Table 3, we can see that at the beginning of the experiment (0 h), the ammonia nitrogen content of the 7 treatment groups was 0.47 mg / L; after the experiment started, the ammonia nitrogen content increased rapidly, and there was no significant difference in the ammonia nitrogen content of the 7 treatment groups at the 5th h. The ammonia nitrogen content of the control group increased rapidly from the 10th h; 10 h after the experiment, the ammonia nitrogen content of the 6 anesthesia groups was significantly lower than that of the control group (p<0.05); at the end of the experiment, the ammonia nitrogen content of 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; The test results of non-ionic ammonia content are shown in Table 4; Table 4: Non-ionized ammonia content test (unit: average value, mg / L; different letters at the same time point indicate significant differences, p<0.05)

[0034] From the results in Table 4, we can see that during the experiment, the change pattern of non-ionized ammonia was not consistent with that of ammonia nitrogen; the non-ionized ammonia content of the control group showed a linear upward trend (slope of about 1), and the 6 anesthesia groups showed a trend of first increasing and then decreasing; in addition, the non-ionized ammonia content of the control group was lower than that of the 6 anesthesia groups 10 hours before the experiment, but higher than that of the 6 anesthesia groups 10 hours after the experiment (p<0.05); comparing the treatment effects of the two anesthetics, there was no significant difference between the two 10 hours before the experiment; but 10 hours after the experiment, the non-ionized ammonia content of the three eugenol anesthesia groups was significantly higher than that of the three MS-222 anesthesia groups (p<0.05); The statistical results of fry mortality are shown in Table 5; Table 5: Statistical results of fry mortality (different letters at the same time point indicate significant differences, p<0.05)

[0035] From the statistical results in Table 5, it can be seen that during the experiment, the cumulative mortality rate of fry showed an upward trend; at the 5th hour of the experiment, the control group with the highest cumulative mortality rate (34.04% ± 15.4%) was significantly higher than the 6 anesthesia groups (p<0.05); although there was no significant difference in water quality (dissolved oxygen, pH, ammonia nitrogen, non-ionized ammonia) between the control group and the 6 anesthesia groups, anesthetics can reduce the stress of fry, inhibit the activity of fry, and avoid physical damage; compared with the 6 anesthesia groups, the fry in the control group had a stronger stress response, with red gills and behaviors of colliding with the bag wall; at the 10th hour, the cumulative mortality rate was not significantly increased compared with the 5th hour; at the 15th hour, the cumulative mortality rate of fry in the control group increased significantly, while the increase in the 6 anesthesia groups was not obvious, so the cumulative mortality rate of the control group at this time point was significantly higher than that of the 6 anesthesia groups (p<0.05); at the end of the experiment, the cumulative mortality rate of fry in the control group was 45.87% ±15.6%, which was significantly higher than that in the 6 anesthesia groups; Based on the above analysis, when the fry of the red bream were transported in film bags filled with oxygen and anesthetics, the ammonia nitrogen and non-ion ammonia content in the water increased, and the dissolved oxygen content and pH level decreased. The water quality continued to deteriorate during transportation, and the degree of deterioration increased with the extension of transportation time. Eugenol and MS-222 anesthetics can effectively improve the survival of fry, improve the water quality of transportation, maintain a good transportation environment, and reduce the mortality of fry. The types and concentrations of anesthetics in the fry transportation process were determined by the mortality of fry in each treatment group at different time periods, and applied to the fry transportation process of fish breeding and release stations; in short-term transportation (within 5 hours), eugenol anesthetic concentration of 5 mg / L was used; in 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; in 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; (4) The guiding types and concentrations of anesthetics determined in the fry transport anesthesia test shall be applied to the transportation of released fry, and the fry shall be packed using the same film bags, water and loading operations as in the fry transport anesthesia test; the main impact on the fish body during the transportation of fry is abrasions on the fish body. When the fry are transported to the release site, they shall be disinfected with bleach solution to prevent bacterial diseases in the transported fish.

[0036] In summary, the release of fry in this method is based on the formation of scales. The eyes, fins, mouths and digestive tract functions of the fry are fully formed. From the perspective of their life history, they belong to the juvenile stage and have formed their own inherent lifestyle. After the formation of scales, the various functions of the skin on the body surface have become perfect. The mucus secreted by the skin can reduce the resistance of the water body to the fish body, ensure the swimming speed of the fish body in the water, and enable the fish to prey more efficiently and better avoid predation by other fish; the mucus secreted by the skin forms a protective film outside the body, which can effectively resist the invasion of various bacteria in the water body and maintain the health of the body; the mucus can also accelerate the precipitation of suspended matter in the water body around the fish body and maintain the stability of the water body in which it is located. In addition, after the formation of scales, the pigments of most fish epidermal cells have been formed and adapted to the background of the water body in which they are located, so that the fish can better hide themselves in the water environment, so that they can prey more effectively and avoid predation by other fish. The release specifications can be diversified according to the adaptability of each fish.

[0037] In addition to the above-mentioned individual characteristics of selected released fry, the present invention establishes 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, 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 fry transportation operation, whether the dissolved oxygen in the transport water can be maintained sufficiently is an important factor in determining whether the operation is successful or not. 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 the establishment of 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 effects of the types and concentrations of anesthetics on mortality and the connection between them, and realizes the above-mentioned convenience and accuracy requirements. The pH value, ammonia nitrogen and non-ionic ammonia content level of the transport water body have an important influence on the survival rate of fry transportation. High concentrations of ammonia nitrogen will cause an increase in the ammonia nitrogen and pH content of fry blood, thereby destroying red blood cells and gill cells, thereby affecting the osmotic pressure regulation of fry and increasing the demand for dissolved oxygen by fry. Non-ionic ammonia is a substance that is highly toxic to fish fry. The selection and analysis of the above parameters accurately reflect the effect of anesthetics on mortality, which has a good guiding effect on the actual release and transportation process.

[0038] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for transporting fry, characterized in that: The steps include: (1) Select healthy juvenile fish with a total length of 4-5 cm, complete body scales and fins, and basic adult characteristics as the fry for release; (2) Releasing fish fry for temporary rearing and cultivation to provide them with an adaptation period from artificial aquaculture waters to natural waters; (3) Establish an anesthetic test for fry transportation. Based on the mortality results 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. Stop feeding the fry before the test; set a predetermined gradient of anesthetic concentration according to the type of anesthetic selected in the test, prepare anesthetic solutions respectively, and adjust the pH thereof to be neutral to form several treatment groups; b. Determine the oxygen consumption rate of fry, determine the loading density of fry in the container, and reduce the error of the test caused by oxygen consumption when the fry density is too high; c. The total length and weight of the test fry were counted; anesthetics were added and mixed in the water container according to the setting of each treatment group, and then the loading operation was performed, the fry were loaded based on the loading density, and the container was closed after oxygenation; a group without adding anesthetics and the rest of the operations were the same as the control group; d. According to the actual simulation requirements of the fry release and transportation time, the duration of the anesthesia test was controlled within 20 hours. During the anesthesia test, the water physicochemical indicators of each treatment group and control group were measured every 3-5 hours, and the mortality rate of fry in each group was counted. The type and concentration of anesthetics used in the fry transportation link were determined based on the mortality results. Among them, the water physicochemical indicators were dissolved oxygen, pH, ammonia nitrogen content, and non-ionic 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 according to claim 1, characterized in that: The fry are the offspring of artificially bred wild parents. They have no injuries or diseases on the outside, are bright in color, have uniform sizes, swim in groups, are lively, and have the ability to swim against the current.

3. The method for transporting fry according to claim 1, characterized in that: In the step (1), the deformity rate of the fry is less than 3%.

4. The method for transporting fry according to claim 1, characterized in that: In the step (2), the temporary culture is carried out in a water area with a water depth of 1.5-2 m, with no shelters around to provide shade or wind protection, and a fish fry cage or enclosure is set up for temporary culture. The temporary culture period is 5-10 days.

5. The method for transporting fry according to claim 1, characterized in that: In the step (2), the fry are fed with small wild fish, shrimp, insects, cladocerans and copepods during the temporary rearing period.

6. The method for transporting fry according to claim 1, characterized in that: In step (3) a, the types of anesthetics used are MS-222 and eugenol; the anesthetic concentrations of MS-222 are set to 10 mg / L, 20 mg / L, and 40 mg / L; the anesthetic concentrations of eugenol are set to 2 mg / L, 5 mg / L, and 10 mg / L.

7. The method for transporting fry according to claim 1, characterized in that: 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.

8. The method for transporting fry according to claim 1, characterized in that: In step (3) c, the ratio of water to oxygen in the container is 1:3-4.

9. The method for transporting fry according to claim 1, characterized in that: 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.

10. The method for transporting fry according to claim 1, characterized in that: 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 colorimetric method; 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.

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