Key techniques of cage culture of grass carp with high yield in intensive culture

In recent years, the grass carp market is getting better, and grass carp culture, especially intensive farming methods such as cages, is more common. How to achieve high yield and high efficiency in intensive culture is an urgent need for many fish farmers. Combined with practice, this paper talks about the technology of grass carp cage culture.

Cage culture of grass carp

Suitable culture conditions:

Cage culture of grass carp should be selected in the leeward to the sun, the water surface is open, the water level is stable, the water quality is fresh, the water source is pollution-free, the transportation is convenient, the water body is rich in dissolved oxygen, the pH value is 7.0m 8.5, the water depth is 4-5m, the water transparency is above 50cm, the dissolved oxygen is about 5mg / L, and the water conservancy facilities are complete, can discharge and irrigate, not easy to be impacted by flood.

The cage setting is reasonable:

The cage is made of polyethylene material and has a double-layer structure. the inside is a closed jointless cage, the outside is an open nodular cage, the upper cover is a single layer, the inner mesh is 3-3.5cm, the outer mesh is 4cm, and the specification of the cage can be 5m × 5m × 2.5m. The cage frame is made of 4 bamboo bamboos with a length of 8 m. The sunken son uses long stones and knots at the four net corners under the cage, so that the cage can be fully expanded and formed in the water. The cage is fixed with a cable, and the cable is a thick polyethylene rope with a diameter of 4cm. The cable crosses the water surface and is straightened and tied to the fixed pile on the shore. The distance between the two cables is 8m. After the cage is fixed by the cable, the top of the cage is 20-30cm above the water surface. The cage should be put into the water 10 days after the fish is put into the box, so that the net coat is attached to algae, so that the net is smooth. After the fish enter the box, avoid the net coat to scratch the fish, because the fish do not adapt to it after entering the box, it is easy to collide and scratch. The cage can be set up in a single box or by group. The spacing of single box is more than 25m. When set up according to the group, 10 boxes per 5ml were made into a group, in series, single row or double row, the distance between the boxes in the group was 4m, and the distance between the groups was about 100m. The cage should be arranged perpendicular to the direction of the current. In order to prevent sundries from damaging the cage, fences should be set up outside the aquaculture water area.

Fish stocking should be scientific:

First, the fish species should be excellent, requiring strong physique, neat specifications, complete scale fins, disease-free and injury-free. The fish in the box should be healthy, avoid trauma, and prevent the net from scraping away the fish mucus. When choosing fish, it should be smooth, sticky and greasy, but not rough. When fishing for fish, you should swim in the direction of the fish and do not catch them head on, so as not to cause harm. Second, the specification should be large. When releasing fish, it is appropriate to put large size fish above 20cm, which has strong disease resistance, high survival rate, short culture cycle and can be listed at the end of the year. Third, the density is appropriate. Grass carp are stocked in cages with a size of 300ml / 500g / tail and a stocking capacity of about 20ml / m2. Some silver carp and bighead carp with a specification of 200ml / 300g / tail and bream bream species of 100g / tail can be reared in the cage. Fourth, pay attention to methods. Before entering the box, fish should be bathed and disinfected to kill surface parasites and reduce the chance of pathogen transmission. Generally, they should be soaked in 3%-5% salt water or 20ppm potassium permanganate solution for 15 minutes. It is generally released in late autumn or early winter when the water temperature is about 15 ℃. Grass carp can still eat after entering the box, and there is a recovery period. It can start eating early after spring, increase the growth time of fish, and lay the foundation for high yield and high efficiency.

Feed should be fed carefully:

Grass carp should not be fed in large quantities in cage culture, but should be fed with full-price pellet feed in order to improve the feed utilization rate and reduce the water pollution caused by the residual bait. Grass carp can be fed 3 days after it is put into the box. Domestication should be carried out before feeding. According to the "slow-fast-slow" rhythm and the "less-more-less" feeding rate, domestication should be carried out for 1.5 hours a day for 10 consecutive days. When most grass carps can float and grab food, normal feeding can be carried out. The daily feeding amount is 3%-5% of the total body weight of the fish, and the daily feed is 3%-5% of the total body weight. The daily feed is 3%-5% of the total body weight of the fish, and the daily feeding amount is 3%-5% of the total body weight of the fish. The amount of each feeding should be reasonably adjusted according to the water temperature, weather, fish intake and activities. In terms of feeding methods, we should pay attention to the principle of "four determinations". Take a small handful of bait, eat one, and then sprinkle the second. When the fish is not fierce, you can cast a small amount slowly, so that the weak fish can also eat the feed and ensure its balanced growth. Grass carp grow fastest when the water temperature is 25 ℃ ~ 34 ℃, so the feeding amount should be increased, and the feeding should be reduced or stopped in the bad weather such as overcast rain, muggy heat, thunderstorm and so on. The green fodder can be fed once every night, sterilized with 1% bleach and put into the cage, and the feeding amount shall prevail if there is no leftover grass the next day.

Daily management should be strengthened:

Daily management of grass carp in cage culture is very important. Mainly do a good job in the following aspects: (1) adhere to box inspection. We should inspect the boxes every day, check the growth of fish regularly, adjust the feeding reasonably, carefully observe and analyze the fish situation, deal with the problems in time, and make a good log of cage culture to record the daily water temperature, feeding, dead fish and diseases. (2) be diligent in brushing boxes. Wash the cage every 10 to 15 days or so to remove the residual bait dirt and attached algae, so that the water body can be fully exchanged. (3) check the box regularly. Often check the cage, find damage and repair in time, so as to avoid escaping fish or fierce fish into the box. In the flood season, it is also necessary to check the strength of the rope, whether the cable is firm, whether the net clothing is deformed, and so on. (4) change boxes frequently. With the fluctuation of the water level of the reservoir, the cage must be adjusted to a suitable position of water depth and water quality.

Attention should be paid to the prevention and control of fish diseases:

First of all, we must adhere to healthy farming, according to the rules of operation, disease prevention. Secondly, it is necessary to do a good job of prevention and artificial immunity. Generally, before entering the box, inactivated vaccines are injected into the tissue plasma of grass carp "three major bacterial diseases" and tissue plasma of grass carp hemorrhagic disease. Fish species ranging from 0.2ml to 0.5ml can be injected, mainly at the base of the dorsal fin and the base of the ventral fin. At the same time, the fish should be disinfected with salt water before entering the box, and should be disinfected regularly to prevent disease. Bait should be given every 10 days or so for 3 ~ 5 days to prevent parasites in the fish. Every 10 ~ 15 days, each cage should be sprinkled with 150 ~ 200 grams of quicklime in the whole box while hot to purify the water quality. Use insecticides and fungicides to sprinkle the whole box every month. In the high temperature season, the bag can be hung around the cage, and the medicine can choose the mixture of bromochlorohydantoin, copper sulfate and ferrous sulfate. In addition, it should be noted that the green feed must be sterilized before feeding. Adhere to the feeding of high-quality feed, do not feed deteriorated or expired feed. Grass carp farmed in cages are generally prone to water mildew disease, red skin disease, Gill rot disease, enteritis, hemorrhagic disease, etc., when the disease occurs, it is appropriate to ask professional and technical personnel to make a correct diagnosis, prescribe the right medicine to the case, do not treat the disease or treat indiscriminately, and cause losses artificially.