CATDOLL : CATDOLL: The scale of bream farming is getting bigger and bigger. What are the economic benefits of bream farming?

The scale of bream farming is getting bigger and bigger. What are the economic benefits of bream farming?

Qingyang County, Chizhou City, Anhui Province is densely covered with mountains, streams, rivers and well-developed water systems. It has become a major aquaculture county. Locals are used to raising grass carp. Due to the shortage of grass carp fry at the beginning of the year, the price once reached a high of 6.3 yuan/jin. Boss Zhang Xiaomao gave up grass carp and planned to raise carp. This year, the new rice fields were transformed into 72 mu of fish ponds and planting began on March 20, 2018. Parabramis 6-8 fish/jin, density 740 fish/mu, mainly silver carp. On October 28, Tangkou made a sample, the total weight of 16 Pekingese was 22.8 kg, and the average size was 1.42 kg/tail.

Cultivating parabolas in southern Anhui has obvious benefits. What are the regional advantages here? Cultivating parabolas in southern Anhui has obvious benefits. What are the regional advantages here?

Mr. Zhang believes that sole is different from grass carp, and there are certain differences in management. Before the grass carp pond was set up to breed parabolic fish, the anoxic pond was a parabolic fish. This year is the year of intensive breeding, so the density is low. The turtle has better liver and gallbladder disease than grass carp, and some Chinese herbal medicine is mixed and taken daily to protect the liver and gallbladder. Boss Zhang mentioned in the interview that this year he suffered a great loss in the treatment of parasites, and there were many diseases in the aquaculture process. The author has summarized some experiences based on the practice of Tangkou in recent years. In the process of bream breeding, when the water temperature reaches 18℃ in March every year, attention should be paid to insect inspection and medication. According to the specific situation of the parasites, insecticides can be selected from copper sulfate and ferrous sulfate mixture, trichlorfon, avermectin, etc. In the low temperature stage, use pyrethroids with caution or not.

Cultivating parabolas in southern Anhui has obvious benefits. What are the regional advantages here? In April, medication is given according to the specific types of tapeworms, ringworms, genoworms, trapworms and anchor fleas. In recent years, the prevention and control of tapeworms in the seeding stage of fish has received attention, and the infection rate has decreased. Killing anchor fleas has become easier due to the use of special insecticides. The infection rate of genoworms and oblique tubeworms is on the rise. Although the concentration of bream farming industry and the degree of production and marketing specialization in Anhui are not as good as those in Yiwu, Jiangsu, the local bream farming also has certain regional advantages.

very good

very good

very good

What are the management tasks for cage fish farming in winter?

Wintering in cages

In order to improve the specifications and quality of fish species released into large water surfaces and reduce the burden on wintering fish ponds, cages can be used for wintering.

All waters with good water quality, water depth of more than 3 meters, and relatively stable water level in winter can be used for wintering in cages. The cages used for wintering should be closed, with a mesh size of 2.0-2.5 cm. The size of the cage is 8×4×2 meters or 7×4×2 meters, and it can also be used with 2-year-old fish cages. The frame of the cage should be strong and durable, and maintain considerable buoyancy. If a wooden frame is used as a frame, a certain amount of plastic floats should be attached to prevent the wooden frame from being soaked in water for a long time and sinking. The sinker can be made of cast iron, ceramic, stone, etc. No matter what material is used to make the frame, float, and sinker, it must ensure that the cage has the correct net shape underwater, sufficient buoyancy, and appropriate water layer.

Fish species should be trained before entering the box. When caged fish species are transferred to the wintering box, they can be trained by a little denseness; pond-bred fish species should be trained by pulling the net more than twice. The fish species entering the box should be more than 2.5 inches in length to ensure a high survival rate. If the fish species entering the box are scratched, they are easily infected with Saprolegniasis and die, which is one of the main causes of death of wintering fish species. In order to avoid hurting the fish species, the operation should be careful and should be carried out at a low temperature of about 10℃.

The stocking density of overwintering fish varies with the dissolved oxygen in the water and the purpose of overwintering. If the lowest dissolved oxygen in the overwintering water layer is above 5 mg/L, the stocking density of fish in the cages set up in this water layer can be arranged at 8-20 kg/m3. If the purpose is to cultivate two-year-old fish or to raise adult fish, the density should be smaller. It is appropriate to stock the cages once in autumn and winter.

Wintering cages must not sink to the bottom and should be kept at least 0.5 meters away from the water bottom.

Cage fish farming is a scientific method of fish farming that has gradually developed on the basis of temporary breeding. It uses mesh to assemble a box of a certain shape, which is placed in a larger water body. The water inside and outside the cage is exchanged through the mesh, so that a living water environment suitable for fish is formed in the cage. Cages can be used to cultivate fish species at a high density or to intensively raise commercial fish. Cage fish farming has the characteristics of mobility, flexibility, simplicity, high yield, and wide adaptability to water areas. It has broad development prospects in my country's marine and freshwater aquaculture industry.

1. Characteristics and key points of cage fish farming

Juyouwan (I) Characteristics of cage fish farming

1. Cage fish farming can fully utilize natural water bodies such as rivers, lakes, and reservoirs and their bait to develop fish farming. It can not only cultivate fish species, but also raise adult fish. Especially in areas where there are no ponds, large water surfaces can be used to set up cages to cultivate fish species and raise adult fish on site, which has a positive effect on improving the survival rate and yield of fish farming.

2. Cage fish farming can be carried out at a high density and intensively, and the yield per unit area can be dozens or hundreds of times higher than that of ponds. The reason is that cage fish farming actually utilizes the superior natural conditions of a large water surface and combines small water bodies with intensive and intensive measures to achieve high yields. During the breeding process, the water inside and outside the cage is constantly exchanged, taking away the excrement of the fish in the cage and the residue of the feeding bait, bringing oxygen and plankton, so that the cage maintains a high level of dissolved oxygen. Therefore, even if the fish density in the cage is high, there will be no hypoxia and water quality deterioration, and it is guaranteed that the bait organisms required by the silver carp and bighead carp cultured in the cage are continuously supplied. In addition, the fish are kept in cages, which avoids the harm of harmful organisms, and can detect fish diseases in time, ensuring a high survival rate and an excellent recapture rate.

3. Cage fish farming has the advantages of being mobile and flexible, and can be invested in batches and developed gradually. It is also called nomadic fishery because it is easy to manage and catch fish, and the cages can be moved at any time if the water environment is not suitable.

2. Key points of cage fish farming

1. Choose a location with abundant natural bait and a certain amount of water flow to set up the cage.

2. Select the appropriate cage structure and installation method, including cage shape, size, arrangement and cage spacing.

3. Determine the stocking fish, size, density and polyculture ratio according to water conditions so as to give full play to the production potential of the water body.

4. Effectively carry out feeding, escape prevention, disease prevention, enemy prevention and other feeding and management work, especially keep the cage wall clean to prevent the mesh from being blocked and affecting water exchange.

2. Structure and device of cage

There are many structures and installation forms of fish cages. When selecting them, the principles of preventing fish from escaping, durability, saving labor and materials, facilitating water exchange, and easy management should be followed.

1. Structure of the cage

1. Cage composition

It consists of a box, a frame, a float, a sinker and fixing facilities.

(1) Box: It is made of mesh pieces stitched together according to a certain size. The most commonly used mesh is polyethylene, which has the advantages of high strength, corrosion resistance, low temperature resistance, and low price. There are four processing technologies for mesh: ① Hand-knitted mesh made of polyethylene twine. The advantages are good elasticity and durability. The disadvantages are that it has nodules, which can easily scratch the fish body, requires more materials, and has poor water filtration; ② Non-stretched nodule-free mesh. This process is fast to produce, saves materials, and is cheap, but has poor lateral tension and is easy to break; ③ Stretched nodule-free mesh. It has strong tensile strength, is soft, and is light in weight. It is 3/4 lower in cost than a nodule-free net box; ④ Polyethylene warp knitted mesh. It is smooth without knots and does not hurt the fish body. The mesh is fixed and does not distort. The box is soft and easy to sew. It is not easy to open holes for fish to escape, and the cost is low.

(2) Frame: It is a bracket used to hang the box, usually made of bamboo, wood, steel pipe, plastic pipe, etc. The box is fixed on the frame to keep it open and in shape.

(3) Float: It is a device used to make the cage float on the water. Floats are usually made of foam plastics and hard blow molding, or glass balls or iron barrels tied to the frame. Bamboo or wooden frames not only support the cage, but also act as floats.

(4) Sinkers: These are devices that sink the bottom of the cage into the water. Porcelain sinkers are generally used, but stones, cement blocks, etc. can also be used. If conditions permit, a steel pipe with a diameter of 2-2.5 cm can be used, which can both support the bottom net and serve as a sinker.

In addition, the position of the cage should be fixed with iron anchors, or the cage should be supported and fixed with cement piles or bamboo piles.

2. The shape of the cage

There are rectangular, square, cylindrical, octagonal and other shapes. At present, the most commonly used in production is rectangular, followed by square, because it is easy to operate, has a large water flow area, and is easy to make. 3. Size of the cage

The smallest cage area is about 1 square meter. Usually, the cage area of ​​1-15 square meters is a small cage. The cage area of ​​15-60 square meters is a medium-sized cage. The large cage area is 60-100 square meters, and the larger ones are 500-600 square meters. Generally speaking, the area of ​​the cage should not be too large. If it is too large, it will be inconvenient to operate and have poor wind resistance. However, although the output of a cage that is too small is high, the cost is high. At present, most cages with a size of 10-30 square meters are used, that is, 7×4 meters, 5×3 meters, 3×3 meters, 3×4 meters and other specifications.

4. Cage height

The height of the cage is determined by the depth of the water and the vertical distribution of plankton. Currently, cages between 1.5 and 2.5 meters are mostly used. Cages of 2 to 4 meters can also be used in deep waters. However, the distance between the bottom of the cage and the bottom of the water must be at least 0.5 meters to allow waste from the bottom to be discharged from the cage.

5. Mesh size

The size of the cage mesh should be determined according to the aquaculture object, in order to save materials as much as possible and achieve the highest exchange rate of cage water. If the mesh is too small, it will not only increase the cost of the cage, but also affect the exchange and renewal of water flow; if the mesh is too large, fish will escape. Usually, 4 cm summer flower fingerlings are raised in cages with a mesh of 1.1 cm; 11-13 cm one-year-old fingerlings are raised in cages with a mesh of 2.5-3 cm; and cages for fish are raised in cages with a mesh of 3-5 cm. In order to ensure smooth water exchange and reduce the number of cage flushing, it is best to switch to cages with larger meshes as the fish grow.

(II) Installation of cages

1. Type of cage device

There are currently three methods of cage installation in my country, depending on water conditions, breeding objects and cage types.

(1) Floating cage

The upper mesh of the box is tied around a frame made of bamboo, sinkers are tied around the lower mesh, both ends of the frame are tied to the anchor with ropes, the top is sealed with a mesh, and the frame is tied with a float, floating on the water.

The cage has a simple structure, uses less materials, has strong wind resistance, and can float freely with water level, wind direction, and current. It is usually set up in open waters with unstable water levels and few ships.

There are two types of cages: single-cage floating type and multi-cage floating type. The single-cage floating type is a single cage set up in one location, fixed with a single or double anchor. It has good water exchange, convenient for cage transfer and cleaning, but poor wind resistance. The multi-cage floating type is to connect 3-5 cages in series in a row, fixed at both ends with anchors, and the distance between cages in each row should be greater than 50 meters. This method occupies less water surface, relatively centralized management, and is suitable for large-scale development, but the production effect is not as good as the single-cage floating type.

(1) Fixed cage

Generally, it is an open cage, which is connected by piles and cross bars to form a frame. The cage is suspended on the frame, and there is no float on the upper line. The upper and lower four corners of the cage are connected to the upper and lower iron rings or pulleys of the piles, which is convenient for adjusting the cage lifting and washing, fishing, etc. The net body is 0.7-1 meters above the water surface, and the net body is 1.5-2.5 meters underwater. Usually, the cage cannot be raised or lowered with the rise and fall of the water level. This method is only suitable for shallow lakes and plain reservoirs with small water level changes. The advantages are low cost, convenient operation, easy management, and strong wind resistance. The disadvantages are that it cannot be moved and is difficult to set up in deep water areas. In addition, the habitat of the fish in the cage often changes with the water level. If you do not pay attention to timely adjustment, it will affect the breeding effect.

(3) Sunken cage

The entire cage is submerged at a predetermined depth underwater. The net body is not affected by water level changes, the mesh has few attachments, and is less affected by wind, waves, and currents. It is suitable for seawater cage fish farming and places with strong winds and waves. It is often used in northern my country for wintering of fish species. The disadvantages are inconvenient operation, low fish growth rate and low production level.

2. Cage arrangement and density

The cage arrangement method should take into account the principle of ensuring that each cage can have good water exchange and convenient management. The cages should be arranged as sparsely as possible in a finished product shape.

The density of cages should be determined according to water quality and management conditions. For silver carp and bighead carp, cages can occupy 1% of the water surface in rich waters with abundant bait, and 0.5% in poor waters. For carnivorous fish, the density should be determined according to the water flow, water fertility, and dissolved oxygen content of the water. If the water flow is good, the fertility is moderate, and the dissolved oxygen is high, more cages can be set up, otherwise fewer cages can be set up.

3. Water layer for cage setting

The depth of the cage is generally no more than 3 meters, because the distribution of plankton accounts for 58.7% in the water layer within 2 meters, and 41.3% in the 2-4.2 meters. Especially in water bodies with low transparency, phytoplankton is most abundant, and the number of zooplankton in the water layer within 1 meter is less than that in the water layer of 1-2 meters, especially at 2-3 meters. Therefore, in waters with rich water quality and rich phytoplankton, cages should be set in shallower water layers, but the bottom of the cage should be more than 0.5 meters from the bottom of the water. In waters with poor water quality, or cages mainly for raising bighead carp, cages can be set in deeper water layers as appropriate, but not too deep.

3. Selection of cage location

Cage fish farming relies on the exchange of water inside and outside the cage to maintain a good ecological environment inside the cage. Therefore, the environmental conditions of the location where the cage is set up are crucial to the success or failure of cage fish farming.

The location for setting up cages should meet the following conditions: ① wide water surface, stable water level, leeward and sunny, high water temperature, 3-7 meters deep, quiet environment, fresh water quality, no pollution, and neutral to alkaline waters are preferred; ② choose water bodies with self-flowing water or tides. The water flow rate is generally best to be 0.05-0.2 m/s to ensure the supply of oxygen. If the water flow is too fast, the fish in the cage will often swim against the current, consuming their physical strength and affecting their growth; ③ cages mainly for raising silver carp and bighead carp should be selected with fertile water, rich plankton (generally, 2 million or more phytoplankton and 3,000 or more zooplankton per liter of water are considered fertile water), 30-50 cm of transparency, and less mud and impurities in the water. Turbid water is not conducive to the growth of plankton.

4. Fish stocking

Cage fish farming mainly depends on water quality and feed sources. In water bodies with richer water quality and more natural bait, silver carp and bighead carp should be mainly farmed. In water bodies with thinner water quality, transparency of more than 50 cm, and light water color, silver carp and bighead carp are not suitable for farming. Instead, it is better to farm fish that are fed with feed, such as grass carp, carp, tilapia, California perch, sweet-scented fish and other grazing fish.

1. Preparation before putting the fish into the box

Before the cage is put into the water, holes and cracks should be carefully checked. The cage should be installed 3-5 days in advance before the fish are put into the cage and placed in the breeding waters. After the net is soaked and attached with algae, the cage can be fully expanded and the fish body can be avoided from being scratched.

Ten days before the summer flowers are put into the box, they are trained by pulling nets in the original pond for no less than three times. The intensive training time should be extended successively. This is one of the key measures to ensure the survival rate of the fish. When the fry need to be transported over long distances, after three trainings, the fry to be transported are placed in a cloth pool set up in another pond with fresh water. After hanging water for one night, they are transported the next morning to improve the survival rate of the fish.

2. Fish stocking

1. Stocking of silver carp and bighead carp

(1) Stocking varieties and proportions

When raising silver carp and bighead carp in cages in lakes, ditches, reservoirs, etc., the stocking ratio varies due to the different natural bait compositions in the waters. In waters with richer water quality, lower transparency, and more phytoplankton, silver carp should be the main species, with bighead carp as a supplement. In waters with more zooplankton and higher transparency, bighead carp should be the main species, with silver carp as a supplement. In addition, about 5% of omnivorous and scraping fish such as tilapia, crucian carp, carp, silver carp, or bighead carp should be appropriately added to remove algae attached to the net wall.

(2) Stocking specifications

For general fish cages, the stocking specifications for summer flowers are required to be more than 3 cm, and larger is better than smaller. The specifications should be uniform, the body color should be bright, the physique should be strong, and the body surface should be free of damage.

(3) Stocking density

Cage fish breeding is a high-density breeding. The stocking density should be determined according to the amount of plankton in the water body, the amount of water exchange in the cage, and the level of feeding and management technology. In general waters, 50-200 summer flowers are stocked per cubic meter. In relatively fertile waters, 200-400 can be stocked. In particularly fertile waters, 500-600 can be stocked. The size of the box is about 13 cm. When breeding two-year-old fish, generally 20-60 10-13 cm fish are stocked per cubic meter.

In fact, within a certain density range, increasing stocking density can increase the production of fish populations, but the individual size of fish leaving the box is smaller. Appropriately reducing the density can correspondingly increase the size of fish leaving the box.

The level of management technology is related to the survival rate of fish species. At present, the survival rate of fish species with a higher level of management technology can reach more than 80%, while most units are around 60%. In production, the death of fish species in cages mainly occurs in the early stage of entering the cage. The main reason for death is that the fish are injured due to careless operation during exercise and transportation. Therefore, strict body surface disinfection should be carried out when the fish species enter the cage, and they should be checked once a week after entering the cage and supplemented. It is best to put enough fish species at one time.

Based on our judgment of production potential and the box specifications we require to be achieved, and referring to the survival rate index, the stocking density can be calculated using the following formula.

Number of fish per square meter = production capacity per square meter × number of fish per kilogram ÷ survival rate of fish

2. Fish feeding in cages

The cage-raised fish requires fresh water with low fertility, sufficient dissolved oxygen (5 mg oxygen/L), and a water flow rate of about 0.2 m/s.

The stocking density of fed fish fingerlings can be much higher than that of silver carp and bighead carp fingerlings, which mainly depends on the water exchange volume, the level of dissolved oxygen, the supply of feed and the species of culture. The stocking density can reach 1,000 per square meter when the water flow is large, the flow rate is about 0.2 m/s, the water quality is good, the dissolved oxygen is high, and the feed is sufficient. In waters with small water exchange volume and rich water quality, the stocking density should not be too large.

When breeding fish in cages, it is best to change cages of different sizes in time as the fish grow. Generally, three sizes of cages are used from fingerlings to grow-out fish. For example, fish of summer flowers and above are bred in cages with a mesh of 1.1 cm; 8 cm fish are bred in cages with a mesh of 2 cm; one-year-old fish of 11-13 cm are bred in cages with a mesh of 2.5-3 cm; fish of 20 cm and above are bred in cages with a mesh of 5-6 cm. In this way, not only can the water exchange in the cages be improved, but also the cost of the cages can be saved.

5. Feeding and management of cage fish farming

Cage fish farming is a high-density fish farming method, and strict feeding and management are the fundamental guarantee for success.

1. Daily management

The daily management of cage fish farming should be carried out around disease prevention, escape prevention, and enemy prevention. There should be a dedicated person responsible for regular inspections to observe the fish's eating and activities, and timely treatment of fish diseases. In the season of fish disease epidemics, it is necessary to focus on prevention. The cages should be checked regularly for damage in combination with cleaning. It is necessary to pay attention to whether there are holes bitten by water rats. If there are any damages, they should be repaired immediately. During the flood season and typhoon season, preventive measures should be strengthened to ensure the safety of the cages. The deformation or displacement of the cages caused by strong winds should be sorted out in time to ensure the effective space in the cages and the reasonable distance between the cages. When the water level drops, it should be displaced in time to avoid mud on the bottom of the cage. It is necessary to check whether the cages have been drilled into harmful fish frequently, and if conditions permit, a net should be set up to prevent enemy damage. Open cages should prevent bird damage, and the fish bodies should be checked regularly to understand the growth of fish, analyze existing problems, and take corresponding measures in time. Keep a cage fish farming diary, accumulate experience, make plans, and improve technical level.

2. Feeding feed properly

At present, cage fish farming has shifted from mainly breeding silver carp and bighead carp using natural bait to developing a breeding method that mainly uses carnivorous fish, which requires feeding natural bait or artificial bait.

The feed and feeding amount of caged fish should be different according to the different sizes, density, growth conditions, water quality, climate conditions, etc. of the farmed fish. At present, most farmed fish are mainly fed with artificial compound pellet feed, and other natural baits such as grass, fish, shrimp, mollusk meat, etc. A few carnivorous fish are fed with fish meat or live fish, shrimp, etc.

The composition and dosage ratio of pellet feed vary with the different farmed fish, so the feed formula should be studied. Under normal circumstances, the daily feeding amount is 3-5% of the total weight of the fish, divided into 2-4 feedings, and each feeding should be completed within 30 minutes. It is best to set up a feeding table in the cage to prevent feed loss and facilitate the cleaning of residues.

(III) Cleaning the cage

After the cage is put into the water, a lot of dirt will be attached after 3-5 days, and then some algae or other organisms will attach to it, which is called green mud moss. In serious cases, the mesh will be blocked, affecting the exchange of water inside and outside the cage. The richer the water quality, the more attachments there are; the smaller the mesh, the more serious the attachment. Generally, the most is within the 1-meter water layer. If it is not cleaned in time, it is easy to cause the water quality in the cage to deteriorate, lack of oxygen and bait, and affect the growth of fish. Therefore, cleaning the cage is one of the important measures in breeding management.

There are several ways to clean the cages.

1. Manual cleaning

Scattered net cages are often cleaned manually. The nets are lifted up every 5 days or so and scrubbed and beaten with brooms, branches, brushes, etc.

2. Mechanical cleaning

When working on a large area, lift one side of the cage and rinse it with a high-pressure water gun to remove dirt from the cage.

3. Biological removal

Fish that eat attached algae are mixed in the box, such as bream, tilapia, carp, etc. This method not only saves labor and money, but also increases the fish production per unit area.

4. Sun exposure

Expose half of the net above the water surface and expose it to the sun. When the temperature is 37-38℃, expose the net for about 55 minutes, and when the temperature is 30-31℃, expose it for 85 minutes to kill the filamentous algae and other organisms attached to the net cage. Then switch to the other half of the cage. Or replace the cage with more attachments, expose it in the sun to kill the attached organisms, and then beat it to remove them. Polyethylene is prone to aging if it is exposed to the sun frequently, so it is not suitable to be exposed to the sun frequently.

5. Caisson method

The closed cage is sunk 3-5 meters underwater so that the algae will die and fall off due to insufficient photosynthesis in the weak light environment.

6. Drug elimination method

Expose the mesh of each part of the cage to the water surface in turn, sprinkle lime water or plant ash on it to prevent the attached organisms from getting sunlight and dying. Sprinkle 0.7-1.0ppm copper sulfate solution on the mesh, which has a certain effect on killing filamentous algae.

(IV) Fish fingerlings shipped out of the box

When the fingerlings are raised to a certain size, they can be released from the box and put into lakes and reservoirs. Generally, they are released from the box in autumn and winter. It is better to release them earlier and put them into the ponds and reservoirs earlier. The fingerlings should be properly and intensively exercised before being released from the box to avoid casualties during the acceptance and counting. The acceptance includes weight, size, survival rate, qualified rate, yield, etc. The counting adopts the weight method, and the sampling is not less than 2 times, 2-2.5 kg each time.

When the water temperature drops to about 10℃, the fish have basically stopped eating. At this time, they should not be released or sold. They can be sorted according to different species and specifications and stored in boxes. The storage density is 1.5-2.5 kg of fingerlings per cubic meter.

(V) Wintering in cages

In order to improve the specifications and quality of fish species released into large water surfaces and reduce the burden on wintering fish ponds, cages can be used for wintering.

Cages can be used for wintering in waters with good water quality, a water depth of more than 3 meters, and relatively stable water levels in winter. The cages used for wintering should be closed, with a mesh size of 2.0-2.5 cm. The size of the cage is 8×4×2 meters or 7×4×2 meters, and it can also be used with 2-year-old fish cages. The frame of the cage should be strong and durable, and maintain considerable buoyancy. If a wooden frame is used as a frame, a certain amount of plastic floats should be attached to prevent the wooden frame from being soaked in water for a long time and sinking. The sinker can be made of cast iron, ceramics, stones, etc. No matter what material is used to make the frame, float, and sinker, it must ensure that the cage has the correct net shape underwater, sufficient buoyancy, and an appropriate water layer.

Fish fingerlings should be trained before entering the box. When cage-reared fish fingerlings are transferred to the wintering box, they can be trained by a little dense gathering; pond-reared fish fingerlings should be trained by pulling the net more than twice. The fish fingerlings entering the box should be more than 2.5 inches to ensure a higher survival rate. After the fish fingerlings entering the box are scratched, they are easily infected with Saprolegniasis and die, which is one of the main causes of death of wintering fish fingerlings. In order to avoid hurting the fish fingerlings, the movements should be careful during operation and the operation should be carried out at a low temperature of about 10℃.

The stocking density of overwintering fish varies with the dissolved oxygen in the water and the purpose of overwintering. If the lowest dissolved oxygen in the overwintering water layer is above 5 mg/L, the stocking density of fish in the cages set up in this water layer can be arranged at 8-20 kg/m3. If the purpose is to cultivate two-year-old fish or to raise adult fish, the density should be smaller. It is appropriate to stock the cages once in autumn and winter.

Wintering cages must not sink to the bottom and should be kept at least 0.5 meters away from the water bottom.

6. Cage fish farming

1. How to grow fish in cages

Cage fish farming is a simple, convenient, low-investment, and fast-acting farming method. In recent years, cage farming of commercial fish has developed rapidly throughout the country with good economic benefits. Currently, there are several ways to grow fish in cages:

1. Choose waters with fertile water, rich plankton and current to set up cages, mainly breeding filter-feeding silver carp and bighead carp, with 5-10% tilapia and other scraping fish, without feeding or with little artificial bait;

2. Choose areas with particularly fertile water or areas with suburban domestic sewage to set up cages, mainly raising tilapia at high density and feeding them appropriately;

3. Set up cages in waters with good water quality, mainly stocking grass carp, bream, carp, California bass, forktail catfish, sweet-scented fish and other high-quality fish, with tilapia, silver carp and bighead carp. The stocking specifications should be large, and the stocking quantity should be determined according to the water quality, fish species source, bait conditions and breeding technology level, with 20-200 fish per cubic meter. It is entirely dependent on artificial feeding of fine and rough feed, and the fine and rough feed must be combined according to nutritional requirements and processed into granular feed for feeding.

2. Feed formula for fish grown in cages

The formula of compound pellet feed contains 25-50% protein, 20-40% carbohydrate and 5-10% fat. It is necessary to reasonably arrange the balance between essential amino acids, vitamins, inorganic substances and various nutrients in the formula ingredients, and make the compound feed have enough energy. Due to the different types of cage farming, the feed formula used is also different. The same kind of feed raw materials from different origins also contain different nutrients. Feed formulas are often local, so feeding tests must be carried out and the formula adjusted according to the test results.

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