Cultivation method for increasing survival rate of monopterus albus fries

Abstract

The invention relates to the technical field of monopterus albus fry breeding, and discloses a breeding method for improving the survival rate of monopterus albus fries, which comprises the following steps: (1) egg yolk breeding period: placing water hyacinth in a hatching frame, placing an air dispersing stone at the bottom of the frame, keeping a micro-flowing water state, breeding the monopterus albus fries in the hatching frame at 26-28 DEG C for 5-7 days after the monopterus albus fries are hatched out of membranes, after the egg yolk is completely absorbed, the larva fish later-stage cultivation is performed; (2) at the later stage of fry rearing, the fry are fed with zooplankter live bait for 2-3 days in an open mode; feeding the larva fish for domestication feeding for 3-5 days through tubificidae feeding after the larva fish is opened; (3) a cage culture period: firstly replacing the hatching frame with an indoor cage, continuing to feed with tubificidae for 7-10 days, and then transferring the larva fish into an outdoor cage to feed with tubificidae for 3-5 days; (4) a food conversion culture period: performing food conversion on the larva fish by using food conversion baits formed by mixed baits of tubificidae and micro-capsule materials; the feeding rate is 5-10%, and fish diseases are prevented and controlled daily. According to the scheme, the survival rate of ricefield eel fries is effectively increased to 70%, and the economic benefit of breeding is remarkably increased.

Description

Technical Field

[0001] The invention relates to the technical field of yellow eel fry breeding, and in particular to a breeding method for improving the survival rate of yellow eel fry. Background Art

[0002] Yellow field eel (Monopterus albus), commonly known as eel, is one of the important freshwater special economic fish in my country. It has huge market potential, high price, and basic output value of up to hundreds of billions of yuan. According to national transaction information in 2022, the average transaction price is 90 to 110 yuan per kilogram. Due to the shortage of commercial fish, it has been overfished for many years, and wild resources can no longer meet the demand of the market. Since the 1990s, the aquaculture industry has begun to develop gradually, and the demand for seedlings has also increased year by year. With the breakthrough of ecological reproduction and fully artificial reproduction technology, the aquaculture industry has ushered in rapid development. The annual demand for seedlings is more than 3 billion, and the wintering seedlings reach about 3 yuan / tail; however, the survival rate of yellow field eel seedlings, which are limited to the current seedling technology, is not high, so that yellow field eel seedlings are still in short supply.

[0003] At present, the conventional breeding method of yellow eel seed is generally to feed directly with chopped water earthworms after the yolk sac of indoor fry disappears basically, and then transfer to outdoor pond net cage cultivation after 3-5 days, and still feed water earthworms during the cultivation period. However, this yellow eel fry breeding method causes the survival rate of fry cultivation to be lower (generally only about 50%) because of the shortcomings such as the poor palatability of fry ingestion, high cost of fresh and live bait and carrying pathogens, and unsatisfactory disease prevention and control effects. For the fry that is currently in short supply, this breeding method cannot reach the fry demand far away, and also greatly reduces its promotion value.

[0004] In view of this, developing a breeding method for improving the survival rate of yellow eel fry can not only effectively make up for the shortcomings of the existing technology, but also effectively increase the output value and economic benefits of yellow eel fry farmers, which is of great significance to improving the market supply capacity of yellow eel. Summary of the invention

[0005] The present invention aims to provide a cultivation method for improving the survival rate of yellow eel fry, so as to solve the technical problem that the survival rate of yellow eel fry in the existing cultivation is low, resulting in a large gap in market supply.

[0006] To achieve the above object, the present invention adopts the following technical scheme: a cultivation method for improving the survival rate of yellow eel fry, comprising the following steps:

[0007] (I) Yolk cultivation period: Place water hyacinth in the hatching frame, place an air-dispersing stone at the bottom of the frame, maintain a micro-flowing water state, and cultivate the eel fry in the hatching frame at 26-28℃ for 5-7 days after the yolk is absorbed. Enter the late stage of fry cultivation;

[0008] (ii) Late stage of larval cultivation: saturation feeding of larvae with live zooplankton bait for 2-3 days; after opening, larvae are trained and fed with earthworm bait for 3-5 days;

[0009] (iii) Cage culture period: first replace the hatching frame with an indoor cage and continue to feed with water earthworm bait for 7 to 10 days; then transfer the fry to the outdoor cage and feed with water earthworm bait for 3 to 5 days; (iv) Transition culture period: Transition feed the fry by feeding with transition bait, with a feeding rate of 5 to 10%, and carry out daily fish disease prevention and control.

[0010] The principles and advantages of this solution are:

[0011] 1. Compared with the low survival rate of eel fry under the existing eel fry breeding technology, this plan effectively improves the survival rate of eel fry by optimizing the layout inside the hatchery, optimizing the hatching conditions, and adopting differentiated feeding methods with differentiated baits at different stages, thereby improving market supply capacity and economic benefits.

[0012] 2. This scheme places water hyacinth in the incubator to provide a shelter and other medium for the eel fry during the cultivation period, which is convenient for the attachment of fish eggs / small fry and prevents them from being carried away by running water. The water hyacinth root system is also convenient for feeding and placing bait, which is convenient for the fry to eat nearby, thereby increasing the utilization rate of bait during the opening period and accelerating the rapid adaptation of the fry to shorten the opening adaptation period. It not only helps to improve the survival rate of the eel fry, but also shortens the cultivation period and comprehensively improves the economic benefits.

[0013] 3. This scheme involves hatching the fry in an incubator and carrying out post-cultivation training to train them to eat. After they have basically adapted, they are transferred to cages for cultivation. During this process, it is convenient to keep the more fragile early seedlings warm and cultivate them, thereby initially ensuring the survival rate of the fry and avoiding a large number of deaths in the early stage of cultivation that would reduce their survival rate.

[0014] 4. This plan changes different cages for cultivation at different stages and feeds different baits to adapt to the feeding needs of seedlings at different growth stages, gradually increase the feeding amount of seedlings, and thus accelerate the growth rate of fry, shorten the time required for fry cultivation, improve cultivation efficiency and cultivation results, and improve benefits.

[0015] Preferably, as an improvement, during the (i) yolk incubation period, the density of yellow eel fry in the hatching frame is 1500-1800 / frame, the hatching frame size is 40x30x5 CM, the flow rate of the micro-flow water is 2-4 cm / s, and the dissolved oxygen is 6-8 mg / L.

[0016] Technical effect: This scheme adopts the above-mentioned setting to ensure that the yellow eel fry obtains sufficient oxygen and clean water quality, promoting their rapid growth and high survival rate.

[0017] Preferably, as an improvement, in the later stage of (ii) fry cultivation, the feeding amount of live zooplankton bait is 10-20 g / frame, and the live zooplankton bait is cladoceran zooplankton; the cultivation conditions in the hatching frame are: micro-flow water flow rate of 2-4 cm / s, dissolved oxygen 6-8 mg / L, and water temperature of 26-28°C.

[0018] Technical effect: This scheme adopts the above settings. Cladoceran zooplankton is a kind of microscopic zooplankton in the water. As bait, it has the advantages of rich nutrition, easy digestion, high biological activity, little impact on water quality and easy cultivation. It is generally a kind of bait for fish. This scheme makes reasonable use of cladoceran zooplankton to improve the growth rate and survival rate of yellow eel fry and ensure their healthy growth.

[0019] Preferably, as an improvement, during the feeding, indoor cage cultivation and outdoor cage cultivation, the bait is chopped water earthworm bait placed at the roots of water hyacinth and fed once in the morning and evening every day (i.e. 6-7 am and 6-7 pm, a total of two feedings per day), and the feces and bottom bait at the bottom of the frame / net are sucked out before each feeding; during the feeding training, the feeding amount is 20-30g / frame; during the indoor cage and outdoor cage cultivation, the feeding rate is 5-10%;

[0020] The method for processing the water earthworm bait is as follows: the live water earthworm bait is soaked in 2-3% salt water for 15-20 minutes in advance, washed twice with clean water, and then chopped and fed.

[0021] Technical effect: This scheme adopts the above-mentioned setting, which is convenient for feeding at the roots of water hyacinth, so that the fry can quickly obtain bait for consumption, avoid the accumulation of bait at the bottom of the pond, and the dead part of the bait will be cleaned up for consumption, which will cause waste. The accumulation at the bottom of the pond is also more likely to breed harmful microorganisms and endanger the health of the fry. In addition, this scheme uses salt water to soak the live bait of water earthworms. On the one hand, it effectively kills bacteria and parasites on the surface of water earthworms, reduces the spread of pathogens, and can inhibit the growth of bacteria and prolong the freshness of water earthworms; on the other hand, it can also improve the freshness of water earthworms, enhance the appetite of fry, soften the body wall of water earthworms, and help fry better digest and absorb nutrients. The applicant found through long-term experiments that if the concentration of salt water is too high or the soaking time is too long, it will cause the water earthworms to dehydrate and die, lose activity, and the nutrients in the body will be lost, reducing the nutritional value of the bait; and excessive salt may remain in the bait, which will not only pollute the water quality, but also affect the health of the fry. If the salt water concentration is too low or the soaking time is too short, the bacteria and parasites on the surface of the water earthworms cannot be effectively killed, increasing the risk of fish fry contracting diseases. In addition, if the feeding rate is too high, it will lead to water pollution, increased disease risk and rising economic costs; if the feeding rate is too low, it will lead to slow growth, physical weakness and economic losses. If the feeding frequency is too low, it will lead to slow growth, physical weakness and reduced economic benefits; if the feeding frequency is too high, it will lead to water pollution, growth inhibition and increased economic costs.

[0022] Preferably, as an improvement, during the (iii) cage culture period, the size of the indoor cage is 40x30x15CM, and the pretreatment method of the indoor cage is: soak the cage in 8-12ppm potassium permanganate for 25-30min in advance, and then place it in clean water for 2-3d; when placing the cage, fix the four corners and put 1-3 pebbles in, so that the depth of the cage in the water is maintained at 10-15CM; transfer the water hyacinth and fry into the cage with water, continue to feed for 7-10d, and remove the bait on the bottom of the cage before each feeding. The size of the outdoor cage is 150x100x100CM, and the pretreatment method of the outdoor cage is: soak the cage with 8-12ppm potassium permanganate for 25-30min 30 days in advance, and then place it in the seedling cultivation pool; when placing the cage, fix the hanging objects at the four corners of the cage to make the cage fully unfold, adjust the water depth, and keep the net exposed to the water surface at 15-20CM; then transplant Alternanthera philoxeroides in the cage, and the transplanted area accounts for 1 / 2-2 / 3 of the cage area, and wait for use.

[0023] Technical effect: This scheme adopts the above settings, and potassium permanganate effectively disinfects the cages and reduces diseases; transplanting water hyacinth or water hyacinth in the cages and pressing the cages for sleep can help simulate the natural ecological environment of eels, thereby improving the growth effect and survival rate of eel fry.

[0024] Preferably, as an improvement, during the (iii) cage culture period, the fry are taken out from the indoor cages, placed in fry bags filled with raw water, filled with sufficient oxygen, and transported to the fry cultivation pond; the fry bags are placed in the cultivation pond until the water temperatures inside and outside the cultivation pond are basically the same, and then the fry are poured from the fry bags into a basin, an equal amount of pond water is added, and soaked in 2% salt for 5 minutes; the fry after soaking and sterilization are placed in the outdoor cages close to the water, and 1600±100 fish are placed in each box.

[0025] Technical effect: This scheme adopts the above-mentioned setting. After the fry adapt to the breeding pond environment, they are placed in the large water surface cage of the fish pond, which is convenient to reduce stimulation, help the fry adapt to the new environment, and thus improve the survival rate of the fry.

[0026] Preferably, as an improvement, in (iv) the transition feeding breeding period, the mixing method of the water earthworm and the microcapsule mixed bait in the transition feeding bait is as follows:

[0027] On the 1st to 3rd day of the transition feeding, the transition feeding bait is prepared by the following method: 400 g of water earthworms and 100 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0028] On the 4th to 6th day of transition feeding, the transition feeding bait is prepared by the following method: 350 g of water earthworms and 150 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0029] On the 7th to 9th day of transition feeding, the transition feeding bait is prepared by the following method: 300 g of water earthworms and 200 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0030] On the 10th to 12th day of the transition, the transition bait is prepared by the following method: 250 g of water earthworms and 250 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0031] On the 13th to 15th day of transition feeding, the transition feeding bait is prepared by the following method: 200 g of water earthworms and 300 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0032] On the 16th to 18th day of transition feeding, the transition feeding bait is prepared by the following method: 150 g of water earthworms and 350 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0033] On the 19th to 20th day of the transition feeding, the transition feeding bait is prepared by the following method: 100 g of water earthworms and 400 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0034] On the 21st day of feeding, the fish were fed directly with microencapsulated mixed feed.

[0035] Technical effect: This scheme adopts the above-mentioned setting, which is convenient for gradually switching to microcapsule mixed bait until the eel fry are fully adapted to it, and it is convenient for the fry to adapt to the subsequent full feed breeding.

[0036] Preferably, as an improvement, the microcapsule mixed bait is prepared from the following raw materials in parts by weight: 75-85 parts of protein source raw materials, 11-23 parts of fat source raw materials, 0.5-1 parts of complex vitamins, 0.5-1 parts of complex minerals, 0.5-1 parts of tributyrin, and 0.5-1 parts of rattan tea flavonoids; the protein source raw materials are ultrafinely ground into 350-400 mesh micropowders, and then fully mixed with the fat source raw materials, complex vitamins, complex minerals, tributyrin, and rattan tea flavonoids; after adding water to adjust the slurry, emulsify for 10-20 minutes, and homogenize under 10-20 MPa; spray, dry, sieve, and cool to obtain the microcapsule opening material.

[0037] Technical effect: This scheme adopts the above-mentioned setting, which is convenient for not adding any additional capsule wall materials (such as starch or gelatin, etc.), but relying on the collagen in the protein source raw materials to wrap other raw materials to form microcapsule particles, thereby reducing adverse reactions after fry consumption and further improving the survival rate of fry.

[0038] Preferably, as an improvement, during the (iv) transitional feeding breeding period, the transitional feeding feed is gradually concentrated in the place where the aquatic plants in the cage are abundant, with an initial feeding rate of 10%, which is reduced by 1% every 7 days until it is fed at 5%; the initial feeding frequency is once in the morning and once in the evening (i.e., 6-7 a.m. and 6-7 p.m., a total of two feedings per day), and in the later stage, according to the development of the fry, the feeding frequency is changed to once a night, and the particle diameter of the bait is gradually increased.

[0039] Technical effect: This scheme adopts the above-mentioned setting, which is convenient for domesticating fry to gradually adapt to the time and space of centralized feeding, helps to simplify the subsequent feeding methods of fry and improve feeding efficiency.

[0040] Preferably, as an improvement, fish disease prevention and control are included in both (iii) the cage culture period and (iv) the feed culture period, and the method is as follows:

[0041] S1. Detection: During fish disease prevention and control, 5 fry are randomly selected from each box for fish disease inspection once a week. When the disease occurs, timely treatment is given and the whole box of eels is moved to a blank place;

[0042] S2. Disinfection of the breeding environment once every half month, including the following:

[0043] (a) Use 0.1ml / m3 of compound iodine for aquaculture 3 The water body is diluted and sprayed throughout the pond to prevent external injuries or bacterial diseases on the body surface;

[0044] (b) Sprinkle 2% salt water around the cage to prevent and treat surface parasites;

[0045] (c) Add 1g of floxacin, 2g of three yellow powder and 2g of electrolytic multivitamin to every kilogram of bait to prevent and control bacterial diseases. Use it continuously for 2 days.

[0046] Technical effect: This plan adopts the above-mentioned settings, which facilitates regular disinfection of the breeding environment, helps reduce diseases, and further improves the survival rate of eel fry. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of indoor cultivation of yellow eel fry in Example 1 of the present invention.

[0048] Figure 2 This is a schematic diagram of the temporary rearing of the hatching frame for the eel fry that has emerged from the film in Example 1 of the present invention (without the addition of water hyacinth).

[0049] Figure 3 This is a schematic diagram of the temporary rearing of the hatching frame for the eel fry that has emerged from the membrane in Example 1 of the present invention (the eel fry hides at the roots of the water hyacinth).

[0050] Figure 4 This is a schematic diagram of the indoor cage temporary culture in Example 1 of the present invention.

[0051] Figure 5 This is a schematic diagram of placing yellow eel fry into an outdoor cage for cultivation in Example 1 of the present invention.

[0052] Figure 6 This is a schematic diagram of the outdoor cage cultivation of yellow eel fry in Example 1 of the present invention. DETAILED DESCRIPTION

[0053] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following examples and experimental examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used can be obtained from commercial sources.

[0054] Example 1

[0055] This scheme provides a cultivation method for improving the survival rate of yellow eel fry, comprising the following steps:

[0056] (I) Yolk cultivation period: Place water hyacinth in the hatching frame, place an air-dispersing stone at the bottom of the frame, maintain a micro-flow state, and cultivate the eel fry in the hatching frame at a temperature of 26-28°C, a flow rate of 2-4 cm / s, and a dissolved oxygen of 6-8 mg / L for 5-7 days after the yolk is absorbed. Enter the late stage of fry cultivation;

[0057] As a reference, the hatching box size is 40x30x5 CM, and the density of yellow eel fry in the hatching box is 1500-1800 per frame. Figures 1 to 3 .

[0058] (ii) Late stage of fry cultivation: Feed the fry with live zooplankton bait (as a reference, the live zooplankton bait is cladoceran zooplankton) at a feeding rate of 10-20 g / frame, and let the fry open their mouths for 2-3 days; after the fry open their mouths, feed them with chopped earthworm bait placed at the roots of water hyacinth for 3-5 days, once in the morning and once in the evening (i.e. 6-7 am and 6-7 pm, a total of two times a day), with a feeding rate of 20-30 g / frame, and suck out the feces and residual bait at the bottom of the frame / net before each feeding;

[0059] This stage is still completed in the incubation frame, and the cultivation conditions in the incubation frame maintain a micro-flow water flow rate of 2-4 cm / s, dissolved oxygen 6-8 mg / L, and a water temperature of 26-28°C.

[0060] Among them, the processing method of water earthworm bait is: prepare water earthworm bait as follows: soak the live water earthworm bait in 2-3% salt water for 15-20 minutes in advance, wash it with clean water twice, and then chop it up and feed it (no need to chop it up during the subsequent cage culture period).

[0061] (III) Cage culture period: first replace the hatching frame with an indoor cage and continue to feed the above-mentioned water earthworm bait (no need to chop) for 7 to 10 days, then transfer the fry to the outdoor cage and continue to feed the above-mentioned water earthworm bait (no need to chop) for 3 to 5 days; when cultivating in indoor and outdoor cages, the feeding rate is 5 to 10%, and fish disease prevention and control is carried out on a daily basis.

[0062] As a reference, the indoor cage is a 60-mesh cage (40x30x15CM). The pretreatment method for the indoor cage is: soak the cage in 8-12ppm potassium permanganate for 25-30min in advance, and then place it in clean water for 2-3 days; when placing the cage, fix the four corners and put 1-3 pebbles in to keep the cage in the water at a depth of 10-15CM; transfer the water hyacinth and fry into the cage with water, and continue to feed for 7-10 days. Before each feeding, remove the bait residue and feces at the bottom of the cage; see the temporary breeding status in the indoor cage for details. Figure 4 .

[0063] The outdoor cage is a 40-mesh cage (150x100x100CM). The pretreatment method of the outdoor cage is: soak the cage with 8-12ppm potassium permanganate for 25-30min 30 days in advance, and then place it in the seedling cultivation pool; when placing the cage, fix hanging objects at the four corners of the cage to make the cage fully unfold, adjust the water immersion depth, and keep the net exposed to the water surface at 15-20CM; then transplant Alternanthera philoxeroides in the cage, and the transplanted area accounts for 1 / 2-2 / 3 of the cage area, and stand by.

[0064] Afterwards, the fry were removed from the indoor cages, placed in fry bags filled with raw water, filled with sufficient oxygen, and transferred to the fry culture pool; the fry bags were placed in the culture pool until the water temperature inside and outside was basically the same, and then the fry were poured from the fry bags into a basin, an equal amount of pool water was added, and soaked in 2% salt for 5 minutes; the fry after soaking and sterilization were placed in the outdoor cages, with 1600±100 fish in each box. For details on the status of outdoor cage culture, see Figures 5-6 .

[0065] (IV) Transition feeding period: The fry are fed with a transition feed consisting of a mixture of earthworms and microcapsule feed at a feeding rate of 5-10%, and fish disease prevention and control is carried out on a daily basis. Specifically, the feeding of the transition feed is gradually concentrated in the place where the water plants are abundant in the cage, with an initial feeding rate of 10%, and the feeding rate is reduced by 1% every 7 days until it is fed at 5%; the initial feeding frequency is 6-7 am and 6-7 pm every day, that is, feeding once at sunrise and sunset, and a total of 2 times for the whole. In the later stage, according to the development of the fry, the feeding frequency is changed to once a night (i.e., feeding once at 6-7 pm), and the particle diameter of the bait is gradually increased.

[0066] As a reference, microcapsule mixed bait can be purchased on the market (such as Yuequn Dongwan Microcapsule Open-ended Feed No. 2), or it can be made by yourself. When making it yourself, the microcapsule mixed bait is prepared from the following raw materials in parts by weight: 75-85 parts of protein source raw material, 11-23 parts of fat source raw material, 0.5-1 part of complex vitamins, 0.5-1 part of complex minerals, 0.5-1 part of tributyrin, and 0.5-1 part of rattan tea flavonoids; the protein source raw material is ultrafinely ground into 350-400 mesh micropowder, and then fully mixed with the fat source raw material, complex vitamins, complex minerals, tributyrin, and rattan tea flavonoids; after adding water to adjust the slurry, emulsify for 10-20 minutes, and homogenize under 10-20MPa; spray, dry, sieve, and cool to obtain the microcapsule open-ended feed.

[0067] As a reference, the mixing method of earthworms and microencapsulated mixed bait in the conversion bait is as follows:

[0068] On the 1st to 3rd day of the transition feeding, the transition feeding bait is prepared by the following method: 400 g of water earthworms and 100 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0069] On the 4th to 6th day of transition feeding, the transition feeding bait is prepared by the following method: 350 g of water earthworms and 150 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0070] On the 7th to 9th day of transition feeding, the transition feeding bait is prepared by the following method: 300 g of water earthworms and 200 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0071] On the 10th to 12th day of the transition, the transition bait is prepared by the following method: 250 g of water earthworms and 250 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0072] On the 13th to 15th day of transition feeding, the transition feeding bait is prepared by the following method: 200 g of water earthworms and 300 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0073] On the 16th to 18th day of transition feeding, the transition feeding bait is prepared by the following method: 150 g of water earthworms and 350 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0074] On the 19th to 20th day of the transition feeding, the transition feeding bait is prepared by the following method: 100 g of water earthworms and 400 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait;

[0075] On the 21st day of feeding, the fish were fed directly with microencapsulated mixed feed.

[0076] In addition, as a reference, the prevention and control of fish diseases during the aforementioned (iii) cage culture period and (iv) feed culture period can be carried out with reference to the following methods:

[0077] S1. Detection: During fish disease prevention and control, 5 fry are randomly selected from each box for fish disease inspection once a week. When the disease occurs, timely treatment is given and the whole box of eels is moved to a blank place;

[0078] S2. Disinfection of the breeding environment once every half month, including the following:

[0079] (a) Use 0.1ml / m3 of compound iodine for aquaculture 3 The water body is diluted and sprayed throughout the pond to prevent external injuries or bacterial diseases on the body surface;

[0080] (b) Sprinkle 2% salt water around the cage to prevent and treat surface parasites;

[0081] (c) Add 1g of floxacin, 2g of three yellow powder and 2g of electrolytic multivitamin to every kilogram of bait to prevent and control bacterial diseases. Use it continuously for 2 days.

[0082] Finally, during the entire breeding process, after the eel cage fry is put into the pond, bird-proof nets are set up on the cages; at the same time, all eel production tools should be disinfected in time, and the eel's eating situation should be paid attention to in time, and the white transparent foam in the water plants in the cage should be carefully observed. If there is any, the entire cage and several attached cages should be moved in time for isolation observation or the eel should be fished out. At the same time, the eel is a scaleless carnivorous fish. When feeding compound feed, attention should be paid to the protein, fat and fish meal quality in its feed, and fish health products such as liver and gallbladder protection should be added every 3 days during the feeding process. Feed residues should be removed in time after 1 hour of each feeding.

[0083] From May 20, 2023 to June 7, 2023, a total of 339,000 newly hatched eel fry were bred in 6 batches. According to the above method, they were cultivated until November 20, 2023, and 243,700 eel fry were obtained before wintering, with an average survival rate of 71.89%.

[0084] Table 1 Results of eel fry cultivation in 2023

[0085] batch First batch Second batch The third batch The fourth batch The fifth batch The sixth batch Initial quantity / 10,000 4.2 5.4 6.8 6 6.4 5.1 Final quantity / 10,000 2.99 3.98 4.97 4.37 4.52 3.54 Survival rate% 71.23 73.61 73.09 72.83 70.63 69.44

[0086] Comparative Example 1

[0087] Before mass cultivation, some yellow eel fry were selected for comparative experiments. Three experimental groups were cultivated using this method, while the control group was fed with chopped water earthworms for 3 to 5 days after the yolk sac of the fry disappeared, and then transferred to outdoor pond cages for cultivation, and continued to be fed with water earthworms during the cultivation period.

[0088] Table 2 Comparative test results

[0089]

[0090] Experimental data show that the method for cultivating yellow eel fry of this scheme has the following advantages:

[0091] 1. This scheme significantly improves the survival rate of fry by training fry to start eating, prolonging indoor temporary rearing, changing feed in advance and preventing and controlling fish diseases, and effectively solves the problems of low survival rate of fry, high cost of fresh bait, and poor effect of fish disease prevention and control in the prior art.

[0092] 2. In order to improve the palatability of the bait for fry, the inventor explored the following three methods: first, the use of zooplankton is consistent with the fry's natural environment in the wild; second, zooplankton is used as the opening bait, which is more palatable than the conventional earthworms; third, cladocerans are used as the opening bait, with an opening rate of 100%, which is more than 20% higher than the traditional method. This scheme uses the third method, which significantly improves the opening rate of fry, thereby improving the survival rate of seedlings.

[0093] 3. The fry bred in this scheme have stronger adaptability. Specifically, this scheme prolongs the indoor cage bred time, so that the fry have stronger adaptability to the environment and disease resistance when transferred to outdoor cage bred, which can effectively improve the survival rate in the pond.

[0094] 4. This program effectively reduces the incidence of fry during the feeding stage: using compound iodine to prevent and treat fish diseases once every three days avoids the occurrence of saprolegniasis, and reduces the incidence and mortality of rhabdovirus by more than 80%.

[0095] 5. The bait for the fry in this scheme is easy to obtain after the food is switched: compared with the conventional cultivation using fresh water earthworms to feed until the next year, the commercial feed fed after the early food switching is easier to buy and preserve, and the bait cost is reduced by more than 30%.

[0096] 6. The disease prevention and control effect of fry in this scheme is better: first, compared with the conventional cultivation using fresh water earthworms for feeding, the commercial feed reduces the introduction of pathogens; second, the disease prevention and control method of the present invention adopts a combination of oral and external use to comprehensively prevent and control common parasitic, bacterial and other diseases, which can effectively reduce the incidence loss by 30-50%.

[0097] 7. The fry of this scheme grows faster: compared with the earthworms used in conventional cultivation, the commercial feed is more nutritionally comprehensive and the growth rate is increased by 15-20%.

[0098] In summary, compared with conventional breeding, the fry bred in this scheme grows faster, has uniform specifications, and has a better physique, enhanced disease resistance, and a fry survival rate that is increased by more than 20%. When the fry are cultivated to the wintering period, the fry survival rate can still reach 70-80% during actual large-scale breeding, which significantly improves the survival rate of the fry and thus improves production efficiency.

[0099] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for raising the survival rate of yellow eel fry, characterized in that: The steps include: (I) Yolk cultivation period: Place water hyacinth in the hatching frame, place an air-dispersing stone at the bottom of the frame, maintain a micro-flowing water state, and cultivate the eel fry in the hatching frame at 26-28℃ for 5-7 days after the yolk is absorbed. Enter the late stage of fry cultivation; (ii) Late stage of larval cultivation: saturation feeding of larvae with live zooplankton bait for 2-3 days; after opening, larvae are trained and fed with earthworm bait for 3-5 days; (III) Cage culture period: First, replace the hatching frame with an indoor cage and continue to feed with water earthworms for 7 to 10 days, then transfer the fry to an outdoor cage and feed with water earthworms for 3 to 5 days; (IV) Transition feeding period: The fry are fed with a transition feed consisting of a mixture of earthworms and microcapsule feed; the feeding rate is 5-10%, and fish disease prevention and control is carried out on a daily basis.

2. A method for cultivating a fry according to claim 1, characterized in that: During the (i) yolk incubation period, the density of yellow eel fry in the hatching frame is 1500-1800 / frame, the size of the hatching frame is 40x30x5 CM, the flow rate of the micro-flow water is 2-4 cm / s, and the dissolved oxygen is 6-8 mg / L.

3. A method for cultivating a fry according to claim 1, characterized in that: In (ii) the late stage of fry cultivation, the feeding amount of live zooplankton bait is 10-20 g / frame, and the live zooplankton bait is cladoceran zooplankton; the cultivation conditions in the hatching frame are: micro-flow water velocity is 2-4 cm / s, dissolved oxygen is 6-8 mg / L, and water temperature is 26-28°C.

4. A method for cultivating a fry according to claim 1, characterized in that: During the feeding training, indoor cage cultivation and outdoor cage cultivation, the bait is chopped water earthworm bait placed at the roots of water hyacinth and fed once in the morning and evening every day, and the feces and residual bait at the bottom of the frame / net are sucked out before each feeding; during the feeding training, the feeding amount is 20-30g / frame; during indoor cage and outdoor cage cultivation, the feeding rate is 5-10%; The method for processing the water earthworm bait is as follows: the live water earthworm bait is soaked in 2-3% salt water for 15-20 minutes in advance, washed twice with clean water, and then chopped and fed.

5. A method for cultivating a fry of yellow eel according to claim 1, characterized in that: During the (III) cage culture period, the size of the indoor cage is 40x30x15CM. The pretreatment method of the indoor cage is: soak the cage in 8-12ppm potassium permanganate for 25-30min in advance, and then place it in clean water for 2-3d; when placing the cage, fix the four corners and put 1-3 pebbles in, so that the water depth of the cage is maintained at 10-15CM; transfer the water hyacinth and fry into the cage with water, continue to feed for 7-10d, and remove the bait residue and feces at the bottom of the cage before each feeding. The size of the outdoor net cage is 150x100x100CM, and the pretreatment method of the outdoor net cage is: 30 days in advance, the net cage is soaked in 8-12ppm potassium permanganate for 25-30min, and then placed in a seedling cultivation pool; when placing the net cage, hanging objects are fixed at the four corners of the net cage to fully unfold the net cage, and the water entry depth is adjusted, and the net exposed to the water surface is maintained at 15-20CM; then, Alternanthera philoxeroides is transplanted in the net cage, and the transplanted area accounts for 1 / 2-2 / 3 of the net cage area, and it is ready for use.

6. A method for cultivating yellow eel fry for improving survival rate according to claim 5, characterized in that: During the (III) cage culture period, the fry are taken out from the indoor cages, placed in fry bags filled with raw water, filled with sufficient oxygen, and transferred to the fry breeding pond; the fry bags are placed in the breeding pond until the water temperature inside and outside the breeding pond is basically the same, and then the fry are poured from the fry bags into a basin, an equal amount of pond water is added, and soaked in 2% salt for 5 minutes; the fry after soaking and sterilization are placed in the outdoor cages close to the water, and 1600±100 fish are placed in each box.

7. A method for cultivating yellow eel fry for improving survival rate according to claim 1, characterized in that: During the (iv) transition feeding breeding period, the mixing method of the water earthworm and the microcapsule mixed bait in the transition feeding bait is as follows: On the 1st to 3rd day of the transition feeding, the transition feeding bait is prepared by the following method: 400 g of water earthworms and 100 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait; On the 4th to 6th day of the transition, the transition bait is prepared by the following method: 350 g of water earthworms and 150 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait; On the 7th to 9th day of transition feeding, the transition feeding bait is prepared by the following method: 300 g of water earthworms and 200 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait; On the 10th to 12th day of the transition, the transition bait is prepared by the following method: 250 g of water earthworms and 250 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait; On the 13th to 15th day of transition feeding, the transition feeding bait is prepared by the following method: 200 g of water earthworms and 300 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait; On the 16th to 18th day of transition feeding, the transition feeding bait is prepared by the following method: 150 g of water earthworms and 350 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait; On the 19th to 20th day of the transition feeding, the transition feeding bait is prepared by the following method: 100 g of water earthworms and 400 g of microcapsule mixed bait are stirred and mixed into a mass to obtain the bait; On the 21st day of feeding, the fish were fed directly with microencapsulated mixed feed.

8. A method for cultivating yellow eel fry for improving survival rate according to claim 7, characterized in that: The microcapsule mixed bait is prepared from the following raw materials in parts by weight: 75-85 parts of protein source raw materials, 11-23 parts of fat source raw materials, 0.5-1 parts of complex vitamins, 0.5-1 parts of complex minerals, 0.5-1 parts of tributyrin, and 0.5-1 parts of rattan tea flavonoids; the protein source raw materials are ultrafinely ground into micropowders of 350-400 meshes, and then fully mixed with the fat source raw materials, complex vitamins, complex minerals, tributyrin, and rattan tea flavonoids; water is added to adjust the slurry, and the mixture is emulsified for 10-20 minutes, and homogenized under the condition of 10-20 MPa; after spraying, drying, sieving, and cooling, the microcapsule open material is obtained.

9. A method for cultivating yellow eel fry for improving survival rate according to claim 8, characterized in that: During (iv) the transitional feeding period, the feeding of the transitional feed is gradually concentrated in the place with abundant aquatic plants in the cage, with an initial feeding rate of 10%, which is reduced by 1% every 7 days until it is fed at 5%; the initial feeding frequency is once in the morning and once in the evening, and in the later stage, according to the development of the fry, the feeding frequency is changed to once a night, and the particle diameter of the feed is gradually increased.

10. A method for raising the survival rate of yellow eel fry according to claim 1, characterized in that: Fish disease prevention and control are included in both the (iii) cage culture period and the (iv) feed culture period. The methods are as follows: S1. Detection: During fish disease prevention and control, 5 fry are randomly selected from each box for fish disease inspection once a week. When the disease occurs, timely treatment is given and the whole box of eels is moved to a blank place; S2. Disinfection of the breeding environment once every half month, including the following: (a) Use 0.1ml / m3 of compound iodine for aquaculture 3 The water body is diluted and sprayed throughout the pond to prevent external injuries or bacterial diseases on the body surface; (b) Sprinkle 2% salt water around the cage to prevent and treat surface parasites; (c) Add 1g of floxacin, 2g of three yellow powder and 2g of electrolytic multivitamin to every kilogram of bait to prevent and control bacterial diseases. Use it continuously for 2 days.

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