Method for utilizing myriophyllum elatinoides to construct efficient ecological net cage to culture eels

Abstract

The invention discloses a method for constructing an efficient ecological net cage for culturing eels by using myriophyllum elatinoides. The method comprises the following steps: step 1, arranging the net cage; a plurality of net cages made of polyethylene materials are fixed in an aquaculture water area, the distance between the bottoms of the net cages and bottom mud in the water area is 30 cm, the tops of the net cages are 30 cm higher than the water surface, and arc-shaped attachment strips with the protruding height being 5 cm are arranged on the inner walls of the net cages Step 2, planting myriophyllum elatinoides; healthy myriophyllum elatinoides seedlings are transplanted in the water area in the net cage, so that the myriophyllum elatinoides covers 30% of the area of the water area in the net cage. According to the method for constructing the efficient ecological net cage to culture the eels by using the myriophyllum elatinoides, 30% of a net cage water area covered by the myriophyllum elatinoides is controlled, and the root system of the myriophyllum elatinoides can accurately absorb pollutants such as ammonia nitrogen and nitrite generated by excreta of the eels.

Description

Technical Field

[0001] This invention relates to the field of aquaculture technology, specifically a method for raising eels using green myriophyllum in high-efficiency ecological net cages. Background Technology

[0002] As a high-value freshwater aquatic product, eels are primarily farmed in net cages on a large scale. However, traditional net cage farming faces significant ecological and seedling challenges. On the one hand, the excrement and uneaten feed produced by eels easily lead to excessive levels of ammonia nitrogen and nitrite in the water. Traditional methods of control rely on frequent water changes or chemical purification agents, which not only consume water resources and damage the aquatic ecosystem but also may cause drug residues in eels. On the other hand, the pretreatment of seedlings is simple and lacks a temporary acclimatization period. In addition, the net cages lack a natural hiding environment, making eels susceptible to stress and disease, with a survival rate of only 60%-70%. Furthermore, the farming cycle is as long as 9-12 months, which is insufficient to meet the demands of high-efficiency farming.

[0003] Meanwhile, existing aquaculture practices suffer from low resource utilization and poor facility adaptability. Traditional feeds mainly consist of expensive fishmeal and soybean meal, accounting for over 50% of costs. Furthermore, the remaining parts of the aquatic plants grown in the cages are often discarded after pruning, failing to achieve resource recycling. In terms of cage design, the bottom tends to adhere closely to the bottom mud, leading to the spread of harmful substances. The lack of attachment structures on the inner walls increases the energy consumption of eels. The support structure is not deep enough, making it prone to tilting and escape during the flood season. Overall, it is difficult to form a "green and efficient" aquaculture system, and it cannot meet the current industry's demand for safe and low-cost aquaculture. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for constructing a high-efficiency ecological net cage for eel farming using *Myriophyllum spicatum*, comprising the following steps:

[0005] Step 1: Net cage setup;

[0006] Multiple polyethylene net cages are fixed in the aquaculture water area. The bottom of the net cage is 30-50cm away from the bottom mud of the water, and the top of the net cage is 20-30cm above the water surface. The inner wall of the net cage is equipped with arc-shaped attachment strips with a raised height of 5-8cm at intervals of 50cm.

[0007] Step 2: Cultivation of *Myriophyllum spicatum*;

[0008] Transplant healthy green foxtail grass seedlings into the water area inside the net cage, so that the green foxtail grass covers 30%-40% of the water area inside the net cage, and keep the root system of the green foxtail grass 10-15cm away from the bottom of the net cage.

[0009] By controlling the coverage of 30%-40% of the water in the net cages with green myriophyllum, its root system can precisely absorb pollutants such as ammonia nitrogen and nitrite produced by eel excrement.

[0010] Step 3: Release the eels;

[0011] Select healthy eel fry with a body length of 15-20cm and a weight of 20-30g. After disinfection, release them into the net cage at a density of 8-10 eels / m². The ratio of eel fry to green foxtail algae should be 1:1.5-2.

[0012] In the seedling stage, healthy eel fry measuring 15-20cm and 20-30g are carefully selected. They are disinfected with 3%-5% saline solution and temporarily raised for 2-3 days to reduce the risk of disease from the source.

[0013] Step 4: Aquaculture Management;

[0014] The aquaculture area is kept at a temperature of 22-28℃ and dissolved oxygen ≥5mg / L. Special feed is provided daily, water quality is monitored regularly, and debris in the net cages is cleaned up. Ecological aquaculture is achieved through the symbiotic structure of green myriophyllum and eel.

[0015] During the breeding process, the water temperature is controlled at 22-28℃ and the dissolved oxygen is ≥5mg / L. The feeding plan is dynamically adjusted according to the water temperature, and a nutritionally balanced special feed is used to enable the eels to reach the harvest standard of 35cm in length and 80g in weight in 6-8 months. The survival rate and growth rate are better than those of traditional breeding methods.

[0016] Preferably, in step one, the mesh size of the polyethylene net cage is 0.8-1.2cm, the specifications of a single net cage are 4-6m long, 2-3m wide, and 1.5-2m deep, the spacing between adjacent net cages is 1.5-2m, the net cage is fixed by bamboo poles or steel pipe supports, the supports are inserted into the bottom mud of the water area to a depth of ≥80cm, and the surface of the supports is covered with a silicone layer with a thickness of 2-3mm.

[0017] Preferably, in step two, the transplanting time of the green foxtail algae seedlings is 15-20 days before the release of eels. The seedling height is 25-35cm, and 15-20 seedlings are transplanted per square meter of water. When transplanting, the amount of moist soil attached to the roots of the green foxtail algae is 50-80g / seedling. For the first 3 days after transplanting, the water level in the net cage is kept stable at 80-100cm, and 0.1-0.2g / L of sodium bicarbonate solution is added to the water body daily.

[0018] Preferably, in step two, the *Myriophyllum spicatum* seedlings are pretreated before transplanting. The specific treatment method is as follows:

[0019] Soak the green foxtail seedlings in a 0.1%-0.2% carbendazim solution for 10-15 minutes. After removing them, let them air dry at a temperature of 25-28℃ and a humidity of 60%-70% until there are no obvious water droplets on the surface of the plants before transplanting. After pretreatment, the incidence of diseases and pests in the green foxtail seedlings is controlled to below 5%.

[0020] Preferably, the specific operation of the disinfection process in step three is as follows:

[0021] Soak the eel fry in a 3%-5% salt solution for 5-8 minutes, then rinse them 2-3 times with water from the aquaculture area, each rinse lasting 30-60 seconds.

[0022] Before releasing the eel fry, they need to be temporarily raised in net cages for 2-3 days. During the temporary raising period, the amount of tubifex worms fed to them daily is 1%-1.5% of the total weight of the eels. During the temporary raising period, the water volume should be changed by 1 / 5-1 / 4 per day.

[0023] Preferably, the water quality parameters of the aquaculture area in step four also meet the following requirements:

[0024] pH value 6.5-7.5, ammonia nitrogen content ≤0.5mg / L, nitrite content ≤0.1mg / L;

[0025] The biological regulation of green foxtail algae maintains a high-quality water environment with pH 6.5-7.5 and nitrite ≤0.1mg / L, reducing the use of exogenous substances such as pesticides and antibiotics throughout the process, ensuring that eel products are green and safe, and meet ecological aquaculture standards.

[0026] When the ammonia nitrogen content exceeds 0.5 mg / L, increase the amount of green foxtail grass replanted, which should be 10%-15% of the initial transplanted amount. After replanting, monitor the ammonia nitrogen content daily until it drops below 0.5 mg / L. When the ammonia nitrogen exceeds 0.5 mg / L, replanting 10%-15% green foxtail grass will allow for rapid degradation without relying on chemical purification agents.

[0027] Green foxtail algae provides a natural attachment environment for eels, reduces their stress response, forms a closed-loop symbiotic system, and significantly reduces pollution of external waters caused by aquaculture.

[0028] Preferably, in step four, the feeding is carried out twice a day, at 8:00-9:00 and 18:00-19:00 respectively, with a feeding amount of 3%-5% of the total weight of the eels. Uneaten feed should be removed within 1 hour after feeding. When the water temperature is below 20℃, the feeding amount is adjusted to 1%-2% of the total weight of the eels, the feeding time is adjusted to 10:00-11:00, and uneaten feed should be removed within 2 hours after feeding.

[0029] Preferably, the frequency of water quality monitoring in step four is once every 3 days. The monitoring indicators include water temperature, dissolved oxygen, pH value, ammonia nitrogen, and nitrite. Each time, three water samples are collected from different locations in the cage and mixed before testing.

[0030] The green foxtail algae in the net cages are pruned 1-2 times a month. When pruning, the green foxtail algae should be kept at a height of 20-30cm. The pruned green foxtail algae should be dried at 60-65℃ until the moisture content is ≤10%, and then crushed to a particle size of 100-120 mesh for use in the preparation of green foxtail algae powder in special feed.

[0031] After being dried at 60-65℃ and pulverized to 100-120 mesh, the trimmed green foxtail algae can be directly used as raw material for special feed. This not only solves the problem of processing trimmed green foxtail algae, but also replaces some high-priced feed ingredients, thus reducing feed costs.

[0032] Preferably, the special feed in step four consists of the following raw materials in parts by weight:

[0033] Fish meal 30%-45%, soybean meal 20%-30%, wheat bran 15%-25%, green foxtail algae powder 5%-15%, multivitamin premix 2%-5%, mineral additives 1%-5%;

[0034] The feed should be made into pellets with a diameter of 2-3 mm. Before feeding, soak the feed in warm water at 35-40℃ for 3-5 minutes. After soaking, the water absorption rate of the feed should be controlled at 20%-25%.

[0035] Preferably, the eel farming cycle is 6-8 months, and the eels are harvested when they reach a body length of 35cm or more and a weight of 80g or more.

[0036] During harvest, the green foxtail algae in the net cage is first transferred to a spare net cage with the same environmental parameters as the original net cage. Then, the eels are caught using a combination of enclosure nets and hand nets. During the catching process, the net speed is controlled at 0.5-1m / min. The green foxtail algae is returned to the original net cage within 24 hours after harvest.

[0037] This invention provides a method for constructing efficient ecological net cages for eel farming using *Myriophyllum spicatum*, which has the following beneficial effects:

[0038] (I) The method of constructing a high-efficiency ecological net cage for eel farming using green foxtail algae involves controlling the coverage of the net cage water area to 30%-40%. Its root system can accurately absorb pollutants such as ammonia nitrogen and nitrite produced by eel excrement. When the ammonia nitrogen exceeds 0.5mg / L, replanting 10%-15% green foxtail algae can quickly degrade it without relying on chemical purification agents. At the same time, green foxtail algae provides a natural attachment environment for eels, reduces the stress response of eels, forms a closed-loop symbiotic system, and significantly reduces the pollution of external waters caused by aquaculture.

[0039] (II) The method of using green myriophyllum to construct high-efficiency ecological net cages for eel farming involves selecting healthy eel fry of 15-20cm and 20-30g in the seedling stage, disinfecting them with 3%-5% saline solution and temporarily raising them for 2-3 days to reduce the risk of disease from the source. During the farming process, the water temperature is controlled at 22-28℃ and the dissolved oxygen is ≥5mg / L. The feeding plan is dynamically adjusted according to the water temperature and a nutritionally balanced special feed is used. This allows the eels to reach the harvest standard of 35cm in length and 80g in weight in 6-8 months. The survival rate and growth rate are better than those of traditional farming methods.

[0040] (III) The method of using green myriophyllum to construct high-efficiency ecological cages for eel farming can effectively prevent eels from escaping and predators from invading through the details of cage design; water quality monitoring is carried out once every 3 days, covering key indicators such as water temperature, dissolved oxygen, and pH value; and the biological regulation of green myriophyllum maintains a high-quality water environment with pH 6.5-7.5 and nitrite ≤0.1mg / L, reducing the use of exogenous substances such as pesticides and antibiotics throughout the process, ensuring that the eel products are green and safe, and meet the standards of ecological farming.

[0041] (iv) The method of constructing an efficient ecological net cage for eel farming using green foxtail algae involves drying the trimmed green foxtail algae at 60-65℃ and crushing it to 100-120 mesh, which can then be used directly as raw material for special feed. This solves the problem of processing trimmed green foxtail algae and replaces some high-priced feed ingredients, reducing feed costs. At the same time, the pretreatment of green foxtail algae reduces the incidence of pests and diseases to ≤5%, reduces pesticide input, achieves resource recycling, and balances ecological and economic benefits. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Example 1: The present invention provides a technical solution:

[0044] A method for constructing efficient ecological cages for eel farming using *Myriophyllum spicatum* includes the following steps:

[0045] Step 1: Net cage setup;

[0046] Multiple polyethylene net cages are fixed in the aquaculture water area. The bottom of the net cage is 30cm away from the bottom mud of the water, the top of the net cage is 20cm above the water surface, and the inner wall of the net cage is equipped with arc-shaped attachment strips with a raised height of 5cm at intervals of 50cm.

[0047] The mesh size of the polyethylene net cage is 0.8cm. The specifications of a single net cage are 4m long, 2m wide and 1.5m deep. The spacing between adjacent net cages is 1.5m. The net cage is fixed by bamboo poles or steel pipe supports. The supports are inserted into the bottom mud of the water at a depth of ≥80cm and the surface of the supports is covered with a silicone layer with a thickness of 2mm.

[0048] Step 2: Cultivation of *Myriophyllum spicatum*;

[0049] Healthy green foxtail grass seedlings were transplanted into the water area inside the net cage, so that the green foxtail grass covered 30% of the water area inside the net cage, and the roots of the green foxtail grass were kept 10cm away from the bottom of the net cage.

[0050] By controlling the coverage of green myriophyllum to 30% of the water in the net cages, its root system can precisely absorb pollutants such as ammonia nitrogen and nitrite produced by eel excrement.

[0051] The transplanting time for the green foxtail algae seedlings is 15 days before the release of eels. The seedlings are 25cm tall, and 15 seedlings are transplanted per square meter of water. When transplanting, retain 50g of moist soil attached to the roots of each seedling. For the first 3 days after transplanting, keep the water level in the net cage stable at 80cm and add 0.1g / L of sodium bicarbonate solution to the water daily.

[0052] Before transplanting, the *Myriophyllum spicatum* seedlings should be pretreated. The specific treatment method is as follows:

[0053] Soak the green foxtail seedlings in a 0.1% carbendazim solution for 10 minutes. After removing them, let them air dry at a temperature of 25℃ and a humidity of 60% until there are no obvious water droplets on the surface of the plants before transplanting. After pretreatment, the incidence of diseases and pests in the green foxtail seedlings is controlled to below 5%.

[0054] Step 3: Release the eels;

[0055] Healthy eel fry with a body length of 15cm and a weight of 20g were selected, disinfected, and then released into the net cage at a stocking density of 8 eels / m², with a stocking ratio of eel fry to green foxtail algae of 1:1.5.

[0056] In the seedling stage, healthy eel fry measuring 15cm and 20g are carefully selected, disinfected with 3% saline solution, and temporarily raised for 2 days to reduce the risk of disease from the source.

[0057] The specific procedures for disinfection are as follows:

[0058] Soak the eel fry in a 3% salt solution for 5 minutes, then rinse them twice with water from the breeding area, each rinse lasting 30 seconds.

[0059] Before releasing the eel fry, they need to be temporarily kept in the net cage for 2 days. During the temporary keeping period, the amount of tubifex worms fed to them daily is 1% of the total weight of the eels, and the water volume changed during the temporary keeping period is 1 / 5 of the daily volume.

[0060] During the breeding process, the water temperature is controlled at 22℃ and the dissolved oxygen is ≥5mg / L. The feeding plan is dynamically adjusted according to the water temperature and a nutritionally balanced special feed is used to enable the eels to reach the harvest standard of 35cm in length and 80g in weight in 6 months. The survival rate and growth rate are better than those of traditional breeding methods.

[0061] Step 4: Aquaculture Management;

[0062] The aquaculture area is kept at a water temperature of 22℃ and dissolved oxygen ≥5mg / L. Special feed is provided daily, water quality is monitored regularly, and debris in the net cages is cleaned up. Ecological aquaculture is achieved through the symbiotic structure of green myriophyllum and eel.

[0063] The special feed consists of the following ingredients in parts by weight:

[0064] Fish meal 40%, soybean meal 25%, wheat bran 20%, green foxtail algae powder 10%, multivitamin premix 3%, mineral additives 2%;

[0065] The feed is made into pellets with a diameter of 2mm. Before feeding, it is soaked in warm water at 35℃ for 3 minutes. After soaking, the water absorption rate of the feed is controlled at 20%.

[0066] The water quality parameters of the aquaculture area also meet the following requirements:

[0067] pH value 6.5, ammonia nitrogen content ≤0.5mg / L, nitrite content ≤0.1mg / L;

[0068] The biological regulation of green foxtail algae maintains a high-quality water environment with pH 6.5 and nitrite ≤0.1mg / L, reducing the use of exogenous substances such as pesticides and antibiotics throughout the process, ensuring that eel products are green and safe, and meet ecological aquaculture standards.

[0069] When the ammonia nitrogen content exceeds 0.5 mg / L, increase the replanting amount of green foxtail grass to 10% of the initial transplanting amount. After replanting, monitor the ammonia nitrogen content daily until it drops below 0.5 mg / L. When the ammonia nitrogen exceeds 0.5 mg / L, replanting 10% green foxtail grass will allow for rapid degradation without relying on chemical purification agents.

[0070] Green foxtail algae provides a natural attachment environment for eels, reduces their stress response, forms a closed-loop symbiotic system, and significantly reduces pollution of external waters caused by aquaculture.

[0071] Feeding is conducted twice daily, at 8:00 AM and 6:00 PM, with a feed amount equal to 3% of the total eel weight. Uneaten feed is removed within one hour after feeding. When the water temperature is below 20℃, the feed amount is adjusted to 1% of the total eel weight, and the feeding time is adjusted to 10:00 AM. Uneaten feed is removed within two hours after feeding. Water quality is monitored every three days, including water temperature, dissolved oxygen, pH, ammonia nitrogen, and nitrite. Three water samples are collected from different locations within the cage for each monitoring session and then mixed before testing.

[0072] The green foxtail algae in the net cages are pruned once a month, with the algae remaining at a height of 20cm. The pruned algae are dried at 60℃ until the moisture content is ≤10%, and then crushed to a particle size of 100 mesh for use in the preparation of green foxtail algae powder in special feed.

[0073] After being dried at 60℃ and pulverized to 100 mesh, the trimmed green foxtail algae can be used directly as raw material for special feed. This not only solves the problem of processing trimmed green foxtail algae, but also replaces some high-priced feed ingredients, thus reducing feed costs.

[0074] The eel farming cycle is 6 months, and they are harvested when they reach a length of 35cm or more and a weight of 80g or more.

[0075] During harvest, the green foxtail algae in the net cage is first transferred to a spare net cage with the same environmental parameters as the original net cage. Then, the eels are caught using a combination of enclosure nets and hand nets. During the catching process, the net speed is controlled at 0.5 m / min. The green foxtail algae is returned to the original net cage within 24 hours after harvest.

[0076] Example 2: According to Example 1, the present invention provides a technical solution:

[0077] A method for constructing efficient ecological cages for eel farming using *Myriophyllum spicatum* includes the following steps:

[0078] Step 1: Net cage setup;

[0079] Multiple polyethylene net cages are fixed in the aquaculture water area. The bottom of the net cage is 50cm away from the bottom mud of the water area, and the top of the net cage is 30cm above the water surface. The inner wall of the net cage is equipped with arc-shaped attachment strips with a raised height of 8cm at intervals of 50cm.

[0080] The polyethylene net cage has a mesh size of 1.2cm, and the specifications of a single net cage are 6m long, 3m wide, and 2m deep. The spacing between adjacent net cages is 2m. The net cage is fixed by bamboo poles or steel pipe supports. The supports are inserted into the bottom mud of the water area to a depth of ≥80cm, and the surface of the supports is covered with a silicone layer with a thickness of 3mm.

[0081] Step 2: Cultivation of *Myriophyllum spicatum*;

[0082] Healthy green foxtail grass seedlings were transplanted into the water area inside the net cage, so that the green foxtail grass covered 40% of the water area inside the net cage, and the roots of the green foxtail grass were kept 15cm away from the bottom of the net cage.

[0083] By controlling the coverage of green foxtail algae in 40% of the net cage water area, its root system can precisely absorb pollutants such as ammonia nitrogen and nitrite produced by eel excrement.

[0084] The transplanting time for the green foxtail algae seedlings is 20 days before the release of eels. The seedlings are 35cm tall, and 20 seedlings are transplanted per square meter of water. When transplanting, retain 80g of moist soil attached to the roots of each seedling. For the first 3 days after transplanting, keep the water level in the net cage stable at 100cm and add 0.2g / L of sodium bicarbonate solution to the water daily.

[0085] Before transplanting, the *Myriophyllum spicatum* seedlings should be pretreated. The specific treatment method is as follows:

[0086] Soak the green foxtail seedlings in a 0.2% carbendazim solution for 10-15 minutes. After removing them, air dry the surface moisture in an environment with a temperature of 28℃ and a humidity of 70% until there are no obvious water droplets on the plant surface before transplanting. After pretreatment, the incidence of diseases and pests in the green foxtail seedlings is controlled to below 5%.

[0087] Step 3: Release the eels;

[0088] Healthy eel fry with a body length of 20cm and a weight of 30g were selected, disinfected, and then released into the net cage at a density of 10 eels / m². The ratio of eel fry to green foxtail algae was 1:2.

[0089] In the seedling stage, healthy eel fry measuring 20cm and 30g are carefully selected, disinfected with 5% saline solution, and temporarily raised for 3 days to reduce the risk of disease from the source.

[0090] The specific procedures for disinfection are as follows:

[0091] Soak the eel fry in a 5% salt solution for 8 minutes, then rinse them three times with water from the aquaculture area, each rinse lasting 60 seconds.

[0092] Among them, the eel fry need to be temporarily raised in the net cage for 3 days before being released. During the temporary raising period, the amount of tubifex worms fed to them daily is 1.5% of the total weight of the eels, and the water volume changed during the temporary raising period is 1 / 4 of the daily volume.

[0093] Step 4: Aquaculture Management;

[0094] The aquaculture area is kept at a water temperature of 28℃ and dissolved oxygen level of ≥5mg / L. Special feed is provided daily, and water quality is monitored regularly and debris in the net cages is cleaned up. Ecological aquaculture is achieved through the symbiotic structure of green myriophyllum and eel.

[0095] During the breeding process, the water temperature is controlled at 28℃ and the dissolved oxygen is ≥5mg / L. The feeding plan is dynamically adjusted according to the water temperature and a nutritionally balanced special feed is used to enable the eels to reach the harvest standard of 35cm in length and 80g in weight in 8 months. The survival rate and growth rate are better than those of traditional breeding methods.

[0096] The water quality parameters of the aquaculture area also meet the following requirements:

[0097] pH value 7.5, ammonia nitrogen content ≤0.5mg / L, nitrite content ≤0.1mg / L;

[0098] The biological regulation of green foxtail algae maintains a high-quality water environment with pH 7.5 and nitrite ≤0.1mg / L, reducing the use of exogenous substances such as pesticides and antibiotics throughout the process, ensuring that eel products are green and safe, and meet ecological aquaculture standards.

[0099] When the ammonia nitrogen content exceeds 0.5 mg / L, increase the replanting amount of green foxtail grass to 15% of the initial transplanting amount. After replanting, monitor the ammonia nitrogen content daily until it drops below 0.5 mg / L. When the ammonia nitrogen exceeds 0.5 mg / L, replanting 15% green foxtail grass will allow for rapid degradation without relying on chemical purification agents.

[0100] Green foxtail algae provides a natural attachment environment for eels, reduces their stress response, forms a closed-loop symbiotic system, and significantly reduces pollution of external waters caused by aquaculture.

[0101] Feed twice a day, at 9:00 and 19:00, at a rate of 5% of the total weight of the eels. Remove any uneaten feed within one hour after feeding. When the water temperature is below 20℃, adjust the feeding rate to 2% of the total weight of the eels and adjust the feeding time to 11:00. Remove any uneaten feed within two hours after feeding.

[0102] The water quality is monitored regularly every 3 days. The monitoring indicators include water temperature, dissolved oxygen, pH value, ammonia nitrogen, and nitrite. Each time, three water samples are collected from different locations in the cage and mixed before testing.

[0103] The green foxtail algae in the net cages are pruned twice a month. During pruning, the green foxtail algae are kept to a height of 30cm. The pruned green foxtail algae are dried at 65℃ until the moisture content is ≤10%, and then crushed to a particle size of 120 mesh for use in the preparation of green foxtail algae powder in special feed.

[0104] After being dried at 65℃ and pulverized to 120 mesh, the trimmed green foxtail algae can be used directly as raw material for special feed. This not only solves the problem of processing trimmed green foxtail algae, but also replaces some high-priced feed ingredients, thus reducing feed costs.

[0105] The special feed consists of the following ingredients in parts by weight:

[0106] Fish meal 45%, soybean meal 20%, wheat bran 20%, green foxtail algae powder 8%, multivitamin premix 4%, mineral additives 3%;

[0107] The feed is made into pellets with a diameter of 3mm. Before feeding, it is soaked in warm water at 40℃ for 5 minutes. After soaking, the water absorption rate of the feed is controlled at 25%.

[0108] The eel farming cycle is 8 months, and they are harvested when they reach a length of 35cm or more and a weight of 80g or more.

[0109] During harvest, the green foxtail algae in the net cage is first transferred to a spare net cage with the same environmental parameters as the original net cage. Then, the eels are caught using a combination of enclosure nets and hand nets. During the catching process, the nets are moved at a speed of 1 m / min. The green foxtail algae is returned to the original net cage within 24 hours after harvest.

[0110] Example 3: Based on Examples 1 and 2, the present invention provides a technical solution:

[0111] A method for constructing efficient ecological cages for eel farming using *Myriophyllum spicatum* includes the following steps:

[0112] Step 1: Net cage setup;

[0113] Multiple polyethylene net cages are fixed in the aquaculture water area. The bottom of the net cage is 40cm away from the bottom mud of the water area, and the top of the net cage is 25cm above the water surface. The inner wall of the net cage is equipped with arc-shaped attachment strips with a raised height of 6cm at intervals of 50cm.

[0114] The mesh size of the polyethylene net cage is 1.2cm. The specifications of a single net cage are 5m long, 2.5m wide, and 1.75m deep. The spacing between adjacent net cages is 1.5m. The net cages are fixed by bamboo poles or steel pipe supports. The supports are inserted into the bottom mud of the water area to a depth of ≥80cm, and the surface of the supports is covered with a silicone layer with a thickness of 2.5mm.

[0115] Step 2: Cultivation of *Myriophyllum spicatum*;

[0116] Healthy green foxtail grass seedlings were transplanted into the water area inside the net cage, so that the green foxtail grass covered 35% of the water area inside the net cage, and the roots of the green foxtail grass were kept 12.5cm away from the bottom of the net cage.

[0117] By controlling the coverage of green myriophyllum to 32% of the water in the net cages, its root system can precisely absorb pollutants such as ammonia nitrogen and nitrite produced by eel excrement.

[0118] The transplanting time for the green foxtail algae seedlings is 20 days before the release of eels. The seedlings are 30cm tall, and 16 seedlings are transplanted per square meter of water. When transplanting, retain 75g of moist soil attached to the roots of each seedling. For the first 3 days after transplanting, keep the water level in the net cage stable at 90cm and add 0.15g / L of sodium bicarbonate solution to the water daily.

[0119] Before transplanting, the *Myriophyllum spicatum* seedlings should be pretreated. The specific treatment method is as follows:

[0120] Soak the green foxtail seedlings in a 0.15% carbendazim solution for 12.5 minutes. After removing them, air dry the surface moisture in an environment with a temperature of 26℃ and a humidity of 65% until there are no obvious water droplets on the plant surface before transplanting. After pretreatment, the incidence of diseases and pests in the green foxtail seedlings is controlled to below 5%.

[0121] Step 3: Release the eels;

[0122] Healthy eel fry with a body length of 16cm and a weight of 25g were selected, disinfected, and then released into the net cage at a stocking density of 9 eels / m², with a stocking ratio of eel fry to green foxtail algae of 1:1.7.

[0123] In the seedling stage, healthy eel fry measuring 16cm and weighing 25g are carefully selected. They are disinfected with 4% saline solution and temporarily raised for 3 days to reduce the risk of disease from the source.

[0124] The specific procedures for disinfection are as follows:

[0125] Soak the eel fry in a 4% salt solution for 7 minutes, then rinse them twice with water from the aquaculture area, each rinse lasting 45 seconds.

[0126] Before releasing the eel fry, they need to be temporarily kept in the net cage for 2 days. During the temporary keeping period, the amount of tubifex worms fed to them daily is 1.5% of the total weight of the eels, and the water volume changed during the temporary keeping period is 1 / 4 per day.

[0127] Step 4: Aquaculture Management;

[0128] The aquaculture area is kept at a water temperature of 25℃ and dissolved oxygen ≥5mg / L. Special feed is provided daily, water quality is monitored regularly, and debris in the net cages is cleaned up. Ecological aquaculture is achieved through the symbiotic structure of green myriophyllum and eel.

[0129] During the breeding process, the water temperature is controlled at 25℃ and the dissolved oxygen is ≥5mg / L. The feeding plan is dynamically adjusted according to the water temperature and a nutritionally balanced special feed is used to enable the eels to reach the harvest standard of 35cm in length and 80g in weight in 7 months. The survival rate and growth rate are better than those of traditional breeding methods.

[0130] The water quality parameters of the aquaculture area also meet the following requirements:

[0131] pH value 7.5, ammonia nitrogen content ≤0.5mg / L, nitrite content ≤0.1mg / L;

[0132] The biological regulation of green foxtail algae maintains a high-quality water environment with pH 7.5 and nitrite ≤0.1mg / L, reducing the use of exogenous substances such as pesticides and antibiotics throughout the process, ensuring that eel products are green and safe, and meet ecological aquaculture standards.

[0133] When the ammonia nitrogen content exceeds 0.5 mg / L, increase the replanting amount of green foxtail grass to 15% of the initial transplanting amount. After replanting, monitor the ammonia nitrogen content daily until it drops below 0.5 mg / L. When the ammonia nitrogen exceeds 0.5 mg / L, replanting 15% green foxtail grass will allow for rapid degradation without relying on chemical purification agents.

[0134] Green foxtail algae provides a natural attachment environment for eels, reduces their stress response, forms a closed-loop symbiotic system, and significantly reduces pollution of external waters caused by aquaculture.

[0135] Feed twice a day, at 8:30 and 18:30, at a rate of 4% of the total weight of the eels. Remove any uneaten feed within one hour after feeding. When the water temperature is below 20℃, adjust the feeding rate to 1.5% of the total weight of the eels and adjust the feeding time to 10:30. Remove any uneaten feed within two hours after feeding.

[0136] The water quality is monitored regularly every 3 days. The monitoring indicators include water temperature, dissolved oxygen, pH value, ammonia nitrogen, and nitrite. Each time, three water samples are collected from different locations in the cage and mixed before testing.

[0137] The green foxtail algae in the net cages are pruned twice a month. During pruning, the green foxtail algae are kept to a height of 30cm. The pruned green foxtail algae are dried at 65℃ until the moisture content is ≤10%, and then crushed to a particle size of 100 mesh for use in the preparation of green foxtail algae powder in special feed.

[0138] After being dried at 65℃ and pulverized to 100 mesh, the trimmed green foxtail algae can be used directly as raw material for special feed. This not only solves the problem of processing trimmed green foxtail algae, but also replaces some high-priced feed ingredients, thus reducing feed costs.

[0139] The special feed consists of the following ingredients in parts by weight:

[0140] Fish meal 43.2%, soybean meal 21.2%, wheat bran 18.7%, green myriophyllum powder 10.9%, multivitamin premix 4.2%, mineral additives 1.8%;

[0141] The feed is made into pellets with a diameter of 2.5 mm. Before feeding, it is soaked in warm water at 38°C for 4 minutes. After soaking, the water absorption rate of the feed is controlled at 22%.

[0142] The eel farming cycle is 7 months. The eels are harvested when they reach a length of 35cm or more and a weight of 80g or more.

[0143] During harvest, the green foxtail algae in the net cage is first transferred to a spare net cage with the same environmental parameters as the original net cage. Then, the eels are caught using a combination of enclosure nets and hand nets. During the catching process, the nets are moved at a speed of 1 m / min. The green foxtail algae is returned to the original net cage within 24 hours after harvest.

[0144] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0145] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for constructing efficient ecological net cages for eel farming using *Myriophyllum spicatum*, characterized in that... Includes the following steps: Step 1: Net cage setup; Multiple polyethylene net cages are fixed in the aquaculture water area. The bottom of the net cage is 30-50cm away from the bottom mud of the water, and the top of the net cage is 20-30cm above the water surface. The inner wall of the net cage is equipped with arc-shaped attachment strips with a raised height of 5-8cm at intervals of 50cm. Step 2: Cultivation of *Myriophyllum spicatum*; Transplant healthy green foxtail grass seedlings into the water area inside the net cage, so that the green foxtail grass covers 30%-40% of the water area inside the net cage, and keep the root system of the green foxtail grass 10-15cm away from the bottom of the net cage. Step 3: Release the eels; Select healthy eel fry with a body length of 15-20cm and a weight of 20-30g. After disinfection, release them into the net cage at a density of 8-10 eels / m². The ratio of eel fry to green foxtail algae should be 1:1.5-2. Step 4: Aquaculture Management; The aquaculture area is kept at a temperature of 22-28℃ and dissolved oxygen ≥5mg / L. Special feed is provided daily, water quality is monitored regularly, and debris in the net cages is cleaned up. Ecological aquaculture is achieved through the symbiotic structure of green myriophyllum and eel.

2. The method for constructing an efficient ecological net cage for eel farming using *Myriophyllum spicatum* as described in claim 1, characterized in that: In step one, the mesh size of the polyethylene net cage is 0.8-1.2cm, the specifications of a single net cage are 4-6m long, 2-3m wide, and 1.5-2m deep, the spacing between adjacent net cages is 1.5-2m, the net cage is fixed by bamboo poles or steel pipe supports, the supports are inserted into the bottom mud of the water area to a depth of ≥80cm, and the surface of the supports is covered with a silicone layer with a thickness of 2-3mm.

3. The method for constructing a high-efficiency ecological net cage for eel farming using *Myriophyllum spicatum* as described in claim 1, characterized in that: In step two, the transplanting time for the green foxtail algae seedlings is 15-20 days before the release of eels. The seedlings should be 25-35cm tall, with 15-20 seedlings transplanted per square meter of water. When transplanting, retain 50-80g of moist soil attached to the roots of each seedling. For the first 3 days after transplanting, keep the water level in the net cage stable at 80-100cm and add 0.1-0.2g / L of sodium bicarbonate solution to the water daily.

4. The method for constructing an efficient ecological net cage for eel farming using *Myriophyllum spicatum* as described in claim 3, characterized in that... In step two, the *Myriophyllum spicatum* seedlings are pretreated before transplanting. The specific treatment method is as follows: Soak the green foxtail seedlings in a 0.1%-0.2% carbendazim solution for 10-15 minutes. After removing them, let them air dry at a temperature of 25-28℃ and a humidity of 60%-70% until there are no obvious water droplets on the surface of the plants before transplanting. After pretreatment, the incidence of diseases and pests in the green foxtail seedlings is controlled to below 5%.

5. The method for constructing a high-efficiency ecological net cage for eel farming using *Myriophyllum spicatum* as described in claim 1, characterized in that... The specific procedures for disinfection in step three are as follows: Soak the eel fry in a 3%-5% salt solution for 5-8 minutes, then rinse them 2-3 times with water from the aquaculture area, each rinse lasting 30-60 seconds. Before releasing the eel fry, they need to be temporarily raised in net cages for 2-3 days. During the temporary raising period, the amount of tubifex worms fed to them daily is 1%-1.5% of the total weight of the eels. During the temporary raising period, the water volume should be changed by 1 / 5-1 / 4 per day.

6. The method for constructing an efficient ecological net cage for eel farming using *Myriophyllum spicatum* as described in claim 1, characterized in that... The water quality parameters of the aquaculture area in step four also meet the following requirements: pH value 6.5-7.5, ammonia nitrogen content ≤0.5mg / L, nitrite content ≤0.1mg / L; When the ammonia nitrogen content is detected to exceed 0.5 mg / L, increase the amount of green foxtail grass replanted. The replanting amount should be 10%-15% of the initial transplanting amount. After replanting, monitor the ammonia nitrogen content daily until the ammonia nitrogen content drops below 0.5 mg / L.

7. A method for constructing an efficient ecological net cage for eel farming using *Myriophyllum spicatum* as described in claim 6, characterized in that: In step four, feeding is conducted twice daily, at 8:00-9:00 and 18:00-19:00, with a feeding amount of 3%-5% of the total weight of the eels. Uneaten feed should be removed within one hour after feeding. When the water temperature is below 20℃, the feeding amount is adjusted to 1%-2% of the total weight of the eels, and the feeding time is adjusted to 10:00-11:

00. Uneaten feed should be removed within two hours after feeding.

8. A method for constructing an efficient ecological net cage for eel farming using *Myriophyllum spicatum* as described in claim 7, characterized in that: In step four, the water quality is monitored regularly once every three days. The monitoring indicators include water temperature, dissolved oxygen, pH value, ammonia nitrogen, and nitrite. Each time, three water samples are collected from different locations in the cage and mixed before testing. The green foxtail algae in the net cages are pruned 1-2 times a month. When pruning, the green foxtail algae should be kept at a height of 20-30cm. The pruned green foxtail algae should be dried at 60-65℃ until the moisture content is ≤10%, and then crushed to a particle size of 100-120 mesh for use in the preparation of green foxtail algae powder in special feed.

9. A method for constructing an efficient ecological net cage for eel farming using *Myriophyllum spicatum* as described in claim 1, characterized in that: The special feed in step four consists of the following raw materials in parts by weight: Fish meal 30%-40%, soybean meal 20%-25%, wheat bran 15%-20%, green foxtail algae powder 5%-10%, multivitamin premix 2%-3%, mineral additives 1%-2%; The feed should be made into pellets with a diameter of 2-3 mm. Before feeding, soak the feed in warm water at 35-40℃ for 3-5 minutes. After soaking, the water absorption rate of the feed should be controlled at 20%-25%.

10. A method for constructing an efficient ecological net cage for eel farming using *Myriophyllum spicatum* as described in claim 1, characterized in that: The eel farming cycle is 6-8 months, and they are harvested when they reach a length of 35cm or more and a weight of 80g or more. During harvest, the green foxtail algae in the net cage is first transferred to a spare net cage with the same environmental parameters as the original net cage. Then, the eels are caught using a combination of enclosure nets and hand nets. During the catching process, the net speed is controlled at 0.5-1m / min. The green foxtail algae is returned to the original net cage within 24 hours after harvest.