Technical points of grass carp culture in cage

In recent years, due to the improvement of grass carp market, grass carp culture, especially intensive culture such as cages, is more common. How to achieve high yield and high efficiency in culture is an urgent need for many farmers. In this paper, the main technical points of grass carp cage culture are discussed in combination with practice.

Culture conditions should be suitable.

Cage culture of grass carp should choose places with leeward to the sun, open water, stable water level, fresh water quality, no pollution of water source and convenient transportation, requiring rich dissolved oxygen in water, pH 7.0-8.5, water depth 4 m ~ 5 m, water transparency above 50 cm, dissolved oxygen about 5 mg / L, and the aquaculture area has complete water conservancy facilities, can discharge and irrigate, and is not easy to be affected by flood.

The cage setting should be reasonable.

The cage shall be made of polyethylene material and have a double-layer structure. the interior is a jointless cage (closed), the outside is a nodular cage (open), the upper cover is a single layer, the inner mesh is 3 cm ~ 3.5 cm, the outer mesh is 4 cm, and the cage specification can be 5 m × 5 m × 2.5 m. The frame of each cage is made of four 8-meter-long bamboo bamboos to support the entire cage. Shen Zi uses long stones and knots at the four corners below the cage, so that the cage can be fully formed in the water. The cage is fixed with a thick polyethylene rope with a diameter of 4 cm. The cable crosses the water surface and is tied to a fixed pile on the bank after straightening. The two cables are 8 meters apart. After the cage is fixed by the cable, the top of the cage is 20cm ~ 30cm above the water surface. The cage should be installed 10 days after the fish species into the box, so that the net coat with algae, so that the net smooth, fish species into the box to avoid net clothes scratch the fish, because the fish species generally do not adapt, easy to collision, easy to scratch. The cage can be set up in a single box or by group. The distance between individual boxes is more than 25 meters. According to the group setting, every 5 ~ 10 boxes as a group, in series, single-row or double-row, the distance between the boxes in the group is 4 meters, and the distance between the groups is about 100 meters. 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 waters.

Fish stocking should be scientific

Fish stocking should grasp four aspects: first, the fish species should be excellent, and the fish species require strong physique, neat specifications, complete scale fins, no disease and no injury. The fish in the box should be healthy, avoid trauma, and prevent the net from scraping away the fish's mucus, because the fish's mucus can bond and remove attached microorganisms and debris, which is the first barrier for the fish to resist disease. Therefore, the selection of fish should be smooth, sticky and greasy, but not rough ones. Fish fishing should follow the direction of swimming, do not catch head-on, so as not to cause harm. Second, the specification should be large. When releasing fish, it is appropriate to put large fish species of more than 20 centimeters, which has strong disease resistance, high survival rate, short culture cycle and can be put on the market by the end of the year. Third, the density is appropriate. In general, the size of grass carp is 300 g / m ~ 500 g / m ~ 2, and the amount of grass carp is about 20 / m ~ 25 / m ~ 2. The size of silver carp and bighead carp is 100 g / m ~ 2. Fourth, pay attention to methods. Before entering the box, the fish should be bathed and disinfected to kill the body surface parasites and reduce the transmission rate of pathogens. Generally, they can be washed with 3% or 5% salt water or 20ppm potassium permanganate for 15 minutes. The stocking time is generally in late autumn or early winter, and it is better when the water temperature is about 15 ℃. Grass carp can still feed after entering the box, and there is a recovery period. It can start feeding early after spring, increase the growth time of fish, and lay the foundation for high yield and high efficiency.

Feed should be carefully fed.

When raising grass carp in cage, it is generally not suitable to feed grass carp in large quantities, because the lack of grass nutrition is difficult to promote its growth, and full-price pellet feed should be fed to improve the utilization rate of feed and reduce the pollution of residual bait to water quality. Grass carp can be fed 2 ~ 3 days after entering the box, and should be domesticated before feeding. According to the "slow-fast-slow" rhythm and "less-more-less" feeding amount, the grass carp can be domesticated for 1 hour ~ 1.5 hours a day, and after 10 days of continuous domestication, normal feeding can be carried out when most of the fish can float and grab food. The daily feeding amount is 3% ~ 5% of the total body weight of fish, 3 ~ 4 times a day, each time about 0.5 hours ~ 1 hour, to the degree that most fish species have enough to eat. The amount of each feeding should be reasonably adjusted according to changes in water temperature, weather, fish intake and activities. In the method of feeding, we should pay attention to the principle of "four determinations". Bait to take a small cast, one after eating and then sprinkle the second, when the fish food is not fierce, can be a small amount of slow casting, so that weak fish can also eat feed, to 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.