CATDOLL : CATDOLL: Wintering technology for barracuda farming

1. Artificial harbor aquaculture: Artificially dig ditches and build harbors at selected locations, build dams, sluices, and beaches, and build artificial fish farming harbors to transform those unproductive wastelands into productive fish harbors.

1. Building a dike

According to the terrain, dikes are built around the harbor. The height of the dikes should be more than 1 meter higher than the highest tidal level. The width of the dikes depends on specific needs, but should not be less than 1 meter at least. The slope is 15 to 70 degrees, so as to ensure the water level in the harbor and prevent fish and shrimp from escaping.

2. Digging trenches

Digging ditches is often limited by manpower and material resources, so too much digging is not possible, so a reasonable layout is required. Digging a number of ditches that connect vertically and horizontally is used to draw in tides and attract fry, and to store enough water in the harbor to create a suitable habitat and migratory growth place for fish and shrimp. The depth and width of the ditch depends on the height of the terrain, but it is better to be wide than narrow, and deep than shallow. There are generally four types of ditches: the central ditch faces the gate, draws in tides and brings in fry, and is the main channel for fish and shrimp fry to enter the port. The water surface should be wide and deep, generally 6 to 7 meters wide and 1.5 to 2 meters deep; the clear water ditch is parallel to the central ditch, located in the center of the port, with deep and clear water, 3 to 4 meters wide, 1.5 to 2 meters deep, with a stable water surface and relatively constant water temperature, which is a place for fish and shrimp to live, grow and shelter in high temperature seasons; the horizontal ditch branch ditches are divided from the central ditch to the sides of the small ditches, which are narrow and amorphous, and are all channels for fish and shrimp to swim freely, go to the beach to feed, and move around; the edge ditch is a small ditch around the fish port, which is used to drain the accumulated water and regulate the water volume. The central ditch and the edge ditch should have a certain slope to facilitate water intake and drainage.

3. Set up gates

There are large, medium and small gates. The large gate is also called the tide gate. It is located in the harbor where the water source is unobstructed, the terrain is low, and near the river end of the central ditch, so as to introduce tidal water to receive fish and shrimp fry. The medium gate is also called the dry gate, which is located in the higher terrain area in the harbor. It is used to introduce river water to regulate the water quality and water volume in the harbor after receiving fry. It is generally 1.5 meters high and 1.5 meters to 2 meters wide. The small gate is also called the backflow gate or the water release gate. It is 1 meter high and wide. It is built at the end of the edge ditch, with a lower terrain and connected to the edge ditch. It is used to remove the accumulated water in the harbor and introduce new water to enable the large gate to continue to receive fry, regulate water quality, and increase the fertility of the harbor water. In order to increase the amount of fry received during the frying period, some people add a large gate outside the small gate to carry out double-gate backflow frying. In production, in order to facilitate the emergence of fry and shrimp, a fish gate of similar size to the middle one is set near the Qingshui ditch at the lowest point in the harbor. It is called the foil gate. The foil is installed outside the gate to release water to catch fish and shrimp.

4. Beach opening

The fish breeding port is very large and cannot be completely ditched. There is a wide shallow beach outside the ditch, which will accumulate water after the tide and become a place for fish and shrimp to feed and move around, that is, a "pasture" for fish and shrimp. If manpower allows, it is best to clear the beach when building the port to create a better pasture.

5. Namiao

Since brackish water aquaculture is highly seasonal, whether it is natural harbor aquaculture or artificial harbor aquaculture, the general production cycle from stocking to harvest is only 4 to 4.5 months, and full preparation and planning must be made in advance. Before the end of April, a comprehensive inspection of the port facilities should be carried out, and the port ditch should be cleared. At high tide, all gates should be raised to release water into the port, and the water should be repeatedly filled and discharged 3 to 4 times to flush the salt and humus accumulated in the port. When the gates are opened to drain water, the large and small ditches should be flushed. Inducing fish and shrimp fry into the port is a highly technical job, and the skills of operating the gates must be mastered to achieve better results. From Grain in Ear to Lesser Heat is the stocking period, and fish and shrimp fry enter the port with the tide. Stocking can be divided into large-gate stocking, that is, when the large gate is raised at high tide, water flows into the port, and fish and shrimp fry flow downstream into the port. At this time, the flow rate must be greater than the swimming speed of the fish fry to prevent the fish and shrimp fry that have been received from escaping. In the middle stage of stocking, the number of fish and shrimp in the harbor increases, and they gradually grow up and their swimming ability also increases. Therefore, when the gate is raised to stock, the water level outside the gate must be higher than the water level in the harbor by more than 7 cm to ensure that fish and shrimp do not escape. In the late stage of stocking, the gate should be raised when it is 10 cm higher than the water level in the gate. At the same time, insert the eight-shaped foil inside the gate to reduce the possibility of fish and shrimp fry escaping. The opening size of the eight-shaped foil should be proportional to the flow rate of the incoming water. The small gate is used to lure the fry. When the tide is low, the large gate is closed and the small gate is raised to make the clear water in the harbor flow out. The temperature of the outflowing water is higher, which is conducive to the warm habit of pike against the current. The fry are introduced into the outer ditch of the small gate. At this time, some fry swim upstream into the harbor, and some fry are concentrated in the outer ditch. When the tide rises to a similar level as the water level in the harbor, the flow rate of the water discharged by the small gate slows down. At this time, all the small gates are raised. At this time, all the fry can enter the harbor through the gate, and then the small gate is closed. Because pike fry have the ability to swim upstream and love warmth, the number of pike fry received at small gates often exceeds that at large gates.

2. Breeding management

During the breeding period, the water quality, water temperature, and water volume in the harbor must be adjusted to be suitable for the growth of fish and shrimp. Adjusting the water quality in the harbor is the main management work of harbor breeding. Frequent water changes can maintain good water quality. At the same time, replacing fresh water can bring in live biological bait and increase the fertility of the water. The phosphate content in the harbor is one of the main conditions that determine the fatness of the water quality. The river water contains sufficient phosphates. After the sluice gates are closed, the phosphorus content in the harbor decreases day by day. When it drops to below 3 mg/L to 4 mg/L, it will affect the growth of swimming organisms. Therefore, some river water should be added appropriately. Fertilization is a measure to increase phosphorus, nitrogen and other substances in the harbor to make the water fertile. The fermented human and animal manure is piled up in the shallow water of the harbor or put into a basket and thrown into the ditch. After a few days, plankton can reproduce in large quantities. This is an effective measure. During the entire breeding period, the water quality in the harbor remains fresh and fertile, with a pH of 7.6-8.5, a specific gravity of 1.008-1.010, a dissolved oxygen content of 5 mg/L-7 mg/L, a nitrogen content of 4 mg/L-5 mg/L, and a phosphorus content of 0.4 mg/L-0.8 mg/L, which is ideal for the growth of fish and shrimp. During the more than 4 months of breeding, it is the rainy season, so attention must be paid to flood prevention, and dike repair and embankment repair and dike gate inspection work must be done in advance.

3. Harvest

The harvest season should not be later than Bailu, because the weather is changeable after Bailu, and the fish and shrimps are slow to move and should not be concentrated. If the weather is cold, the fish cannot be caught completely, and the fish and shrimps are easy to freeze to death in the harbor, which makes fishing difficult and causes losses. Common fishing gear for harvesting includes drift foil, set-up and some other nets. Drift foil is a kind of fishing gear made of two layers of reed foil in the shape of a dustpan. The bottom layer is coarse and sparse, and the upper layer is fine and dense. The open end is placed at the gate of the drift foil facing the water source. The drift foil should be placed on a wooden frame that has been pre-made with wooden stakes. When the embankment is pulled up and the water is released, the fish and shrimps flow into the drift foil with the water. This fishing gear and fishing method mainly catches pike and white shrimps of the year. Set-up is also called "calling the tide" and "the maze". When the harbor water gradually drains and becomes shallower, and the fish and shrimps can no longer enter the foil, it is necessary to use set-up. This fishing method is composed of more than ten reed foils, which are set at the mouth of the clear water ditch. First, a small gap is inserted in the mud with a guide board, and the reed foil goes down along the gap to form a fish swirl that is easy to enter but difficult to exit. During production, the fish gate is opened to lead the tide into the harbor. When the fish encounter the fresh water, they swim upstream and mistakenly enter the trap. At this time, we must pay attention to controlling the size and speed of the tide entering, and adjust it until the water is dry and clear. This fishing gear mainly catches pike and a few miscellaneous fish and shrimp. Other effective fishing gear and methods include digging trenches, digging pits, and using cone bag nets, wire nets and rotary nets on the gates.

4. Pond farming

There are two forms: one is to raise freshwater fish as the main species and mix with 10% to 20% pike; the other is to raise pike as the main species and mix with freshwater fish. The former has been widely adopted and has good economic benefits; the latter is not popular among the masses because of its low yield and low income.

The main food of pike is benthic diatoms and organic debris. They do not compete with domestic fish for food when mixed with them, and can also use grass carp feces as bait. In the adult stage, in addition to feeding certain commercial baits according to conditions, applying manure, green manure or treated sewage and fertilizer water can achieve good production results. Generally, 10% to 20% or 100 to 150 pike fry of the year are mixed with each acre of fish pond, and they can grow to a weight of 300 to 400 grams by the end of the year. Without increasing the feeding and affecting the output of other farmed fish, the average output can be increased by 25 to 75 kilograms. The mixed breeding ratio for an output of 250 kg per mu is: 200 one-year-old pike, 100-200 two-year-old pike, 100 silver carp, 50 bighead carp, and 450 small tilapia; the mixed breeding ratio for an output of 500 kg per mu is: 300 one-year-old pike, 500 two-year-old pike, 240 silver carp, 150 grass carp, 150 bream, and 40 carp.

5. Mixed culture of marine fish and shrimp

Mixing and interbreeding fish in shrimp ponds can increase the output and economic benefits of shrimp ponds. The fish suitable for mixed breeding in shrimp ponds are mainly pike, mullet and tilapia. Mixing and interbreeding pike in shrimp ponds can increase the yield of 25 kg of pike per mu without increasing the amount of feed and affecting the yield of shrimp. However, pike fry should generally be released into shrimp ponds when the shrimp is more than 4 cm to 5 cm in length. The size is about 10 cm, and 100 to 200 per mu.

6. Salt field breeding

That is, "salt pond" farming. Shrimp are raised in salt field storage ponds, and pike accounts for 40% to 60% of the production in this type of farming. Salt field farming does not require the construction of facilities and fish ponds, so the cost is low and easy to promote, but the contradiction between fishery and salt production is difficult to resolve.

7. Disease prevention and control

1. Oriental mullet

The infection rate of marine pike fry is extremely high. Oriental mullet is a kind of copepod that parasitizes in seawater, but it is not suitable for living in brackish water. If it is found in waters with high salinity, fresh water can be introduced to reduce the salinity. The mullet will fall off and die if living in brackish water. In addition, polychaete larvae, originally the main food for shrimp, will drill into the gill cavity of pike when they reproduce excessively in summer, and gather densely between the gill rakers, resembling fly maggots, causing the pike to suffocate and die. This pest often appears in harbor aquaculture.

2. Chrysophyte

It is the most harmful disease to pike species and adult fish. If the small whip golden algae is found in the fish pond, the whole pond of farmed pike can be destroyed in a few days. The small whip golden algae is a typical brackish water flagellate algae. The pond where the disease occurs has a "splash" of small whip golden algae, and the cell density in the pond can reach 8×105/ml.

The treatment method can be to use copper sulfate with a concentration of (2~3)×10-6 or liquid ammonia with a concentration of (10~15)×10-6 to spray the entire pond. Spraying the entire pond with yellow mud water also has good results.

3. Saprolegnia and Chytrid

Saprolegniasis, also known as skin mold disease, commonly known as "white hair disease", is more common in spring and summer. It is mainly caused by injuries, scales falling off, and infection with Saprolegnias during fishing and artificial breeding. The infected area grows fluffy white mold hyphae. The sick fish lose their appetite, move slowly, become increasingly emaciated until death.

Treatment methods should be carefully operated to avoid hurting the fish. Apply red mercury or gentian violet to the place where the scales fall off in time, and seal it with vaseline. At the same time, it is best to keep the pool water flowing frequently. If the fish has been infected with water mold, 0.1% potassium permanganate solution can be used to bathe the sick fish for 5 to 10 minutes to achieve a certain effect.

Chytrid fungus mainly infects eggs during the hatching process of fertilized eggs. Therefore, during the hatching process, dead eggs should be removed in time to prevent the water quality from deteriorating, and new water should be replaced and antibiotics should be added to inhibit the reproduction of microorganisms.

1. Seedling cultivation

1. Pond conditions The area of ​​the pike seedling cultivation pond is generally between 1 and 5 mu, with a water depth of 1.0 to 1.5 meters, a muddy sandy soil structure, a flat pond bottom, good water retention performance, and a complete pond water inlet and outlet system to facilitate pond water exchange. The aquaculture water is required to be pollution-free, clear, with a pH value of 7.2 to 8.5 and dissolved oxygen above 4 mg/L.

2. Preparations before stocking The stocking time of fry is generally in the first and middle ten days of May. According to the stocking time, the nursery pond should be cleaned and disinfected 20 days in advance. The first choice of disinfectant is quicklime. Use dry disinfection method, use 120-150 kg of quicklime per mu, and evenly sprinkle the whole pond to kill harmful organisms and pathogens in the pond. Drain the pond water after 7 days, and then add 40-50 cm of water. Use 60-80 mesh polyethylene or nylon yarn to filter the water.

3. Cultivation of water quality in the nursery pond After the nursery pond is filled with water, water fertilization and water quality cultivation should be carried out immediately. Fermented cow dung and chicken dung and other organic fertilizers can be placed on the sunny side of the pond, with a dosage of 150-200 kg per mu, to facilitate the rapid reproduction of plankton in the water body. If the water quality is poor, the amount of fertilizer can be appropriately increased to keep the transparency of the pond water at 25-30 cm, and the water color is preferably green-blue.

4. Stocking density

(1) Cultivation of summer flower fish: The fry should be selected from artificially bred fish that are healthy, disease-free, uniform in size, and have been diluted. 100,000 to 150,000 fish should be stocked per mu. After 20 to 30 days of cultivation, when the summer flower fish of pike reach 2.5 to 3 cm, they can be trained by pulling nets and removed from the pond in time for fish seed cultivation.

(2) Fish fingerling cultivation: 3,000 to 5,000 summer flower fish fingerlings of 2.5 to 3 cm in size are released per mu, and they can be cultivated into fish fingerlings of about 12 cm in size within the same year.

5. Breeding management

(1) Bait management:

In the fry cultivation stage, fertilization and soybean milk are mainly used in the early stage, and soybean cake slurry or rice bran is fed in the later stage. The daily feeding amount is 10% to 15% of body weight. In the fish fingerling cultivation stage, try to feed as much as possible, and feed according to the feed with high silicon and cellulose content that pike likes, such as soybean cake, bran, vegetable cake, rice bran, peanut cake or distiller's grains, etc. The daily feeding amount is 8% to 10% of body weight, and then gradually decreases as the individual grows. At the same time, the feeding amount should be controlled according to weather changes. Under normal circumstances, feed twice a day, usually at 8:00-9:00 in the morning and 4:00-5:00 in the afternoon. Feed a little more when the weather is fine, feed less when it is rainy, and do not feed in heavy rain, thunderstorm, and low air pressure.

(2) Water quality management:

After the fry are put into the pond, the water transparency is maintained at 25 to 30 cm. The abundance of biological bait is maintained by fertilizing, spraying soybean milk and feeding. New water is added to the pond every 5 to 7 days, 10 cm each time, and finally the pond water is maintained at about 1 meter. During the fish seed cultivation period, the pond water is controlled between 1.2 and 1.5 meters. In the hot season, in order to prevent fish from floating and prevent water quality from aging, new water is added in time, and the exchange volume each time is controlled at 10% to 15% of the pond water.

2. Fish breeding

1. Pond conditions The area of ​​the pike culture pond is generally 5 to 20 mu, with a water depth of 1.5 to 2.0 meters. The fish pond should be selected in a place with sufficient water source, aquaculture water that meets the fishery water standards, and convenient transportation and electricity. The pond shape is preferably rectangular, with long light hours, muddy and sandy soil structure, and a certain inclination of the pond bottom toward the drain outlet to facilitate draining the pond water. The pond water inlet and outlet system is complete. At the same time, each pond is equipped with a 0.75-1.5 kilowatt aerator according to the size of the area.

2. Pond cleaning, disinfection and water quality cultivation 20 days before stocking fish fingerlings, the pond must be thoroughly cleaned and disinfected (refer to the disinfection method of seedling cultivation pond). After the pond is disinfected, wait for the drug properties to disappear, and then fill the pond with water. When filling the water, use 80-mesh nylon yarn or polyethylene net to filter. Then pile fermented organic fertilizer (chicken manure, pig manure, cow manure, etc.) at the four corners of the pond, with an amount of 100 to 200 kilograms per mu. The seeped fertilizer water can cultivate water quality after entering the pond. Fertilization is treated differently according to the different conditions of newly built ponds and old ponds. The amount of fertilizer applied to newly built ponds is appropriately increased due to the thin bottom quality, while that applied to old ponds is reduced accordingly.

3. Fish fingerlings should be free of injury and disease, healthy and of uniform size. In general conventional breeding, 800 to 1,000 fish fingerlings of about 12 cm in size are released per mu, and the expected output is 400 to 500 kg.

4. Feeding and management

(1) Feeding: Pike is an omnivorous fish that prefers plants. It feeds a wide range of foods, such as bean cake, vegetable cake, rice bran, bran, distiller's grains, wheat, corn, etc. The feeding rate is calculated based on 3% to 5% of the fish's body weight. As the fish grows, the feeding rate can be appropriately reduced, depending on the weather, water quality, and fish activity of the day. Feeding is done twice a day, at 8:00-9:00 a.m. and 4:00-5:00 p.m.

(2) Water quality adjustment: First, the water quality of the pool should be kept fertile and fresh, but not too concentrated. Timely water exchange is very important to prevent the occurrence of floating heads. The amount of water exchanged each time is 20% to 30% of the total pool water volume, so that the transparency of the pool water is maintained at 30 to 40 cm.

(3) Disease prevention: When the stocking density of pike is low, the probability of disease occurrence is low. Common diseases include enteritis and saprolegniasis. It is very important to do a good job of prevention.

First, be careful when stocking and catching fish to avoid scratching the fish;

Second, water disinfection should be carried out by regularly spraying the entire pond with dibromocyanine disinfectant at a concentration of 0.2 g/m3 (according to experimental observations, bleaching powder, strong chlorine and other drugs are highly toxic to pike and should be used with caution) to prevent the occurrence of diseases;

Third, feed pollution-free medicated bait regularly, every 15 to 20 days. Crush and dilute garlic, then mix it with feed to make medicated bait. The amount added is 3% to 10% of the feed. Use it for 3 to 5 consecutive days. This can effectively prevent the occurrence of diseases.