Factors affecting the benefit of crayfish culture

Germplasm reason

Because crayfish have the habit of natural reproduction, the vast majority of farmers adopt the culture mode of releasing seeds in one year and cultivating them for many years, which inevitably leads to the problem of inbreeding among lobsters, and finally leads to the germplasm degradation of lobsters. Individuals are getting smaller and smaller, and in the process of breeding, they all adopt the method of catching large and retaining small ones, and wait until around September every year when the parent shrimp is selected. Large lobsters have long been sold out, so only those smaller lobsters are reserved for next year's parent shrimp. Such parent shrimp itself is poor, and it is even more difficult to guarantee the quality of the next generation.

It is suggested that farmers should thoroughly clear the pond every three years, clear all the lobsters in the pond, replace the new parent shrimp next year, or introduce a certain number of large size lobster from other local farmers as parent shrimp around September every year. Note: when introducing parent shrimp, you only need to introduce one sex parent shrimp in the same place. If both male and female parent shrimp are introduced in the same place, there may also be the problem of inbreeding. The choice of parent shrimp requires complete appendages, strong physique, no disease, no injury, strong movement ability, and the weight is about 30g / 50g.

Causes of water quality

In recent years, due to the influence of climatic factors, there is drought and little rain in spring in our province, so the water level of most farmers' ponds is shallow in spring, but with the rise of air temperature and the increase of bait consumption, the decomposition of residual bait, feces and organic matter in the pond will have a negative impact on the water quality, and there is no fresh external water for timely injection to regulate the water quality. The quality of water quality will directly affect the feeding, shelling and growth of crayfish, which restrict the growth of crayfish.

It is suggested that photosynthetic bacteria and quicklime should be used alternately every half a month to sprinkle the whole pond to improve the water quality, adjust the PH value of the water, and reduce the content of ammonia nitrogen in the pond. in addition, calcium dihydrogen phosphate is regularly applied to increase the content of ionic calcium in pond water to promote crayfish shelling and growth. the dosage of calcium dihydrogen phosphate is generally 2 kg / mu. Rice. When there is exogenous water, fresh water is injected every 7 to 10 days, and the amount of water each time is about 15% or 20% of the original pond water.

Feed reason

Lack of feed, poor quality and incomplete nutrition will certainly affect the shelling growth of crayfish when they can not meet the normal growth needs of crayfish, resulting in small size, but if high-protein concentrate feed is fed for a long time, it will lead to the accumulation of nutrients and the formation of precocious puberty and stop growth of crayfish, and the final specification will be too small.

Crayfish are omnivorous animals, and both animal and plant baits can be eaten, so we should consider not only some high-protein concentrate fodder, but also some cereal plant feed and live snail feed, but also plant water peanuts, verticillium verticillata and other aquatic plants in the pond, because on the one hand, aquatic plants can be used to supplement plant feed for crayfish. On the other hand, aquatic plants can also be used to purify the water quality of ponds. And the survival rate of shrimp in the pond with good aquatic plants is also high, and the quality is good, but the area of aquatic plants can not exceed 60% of the total area of the pond, and snails must be reared in the ponds before and after the Qingming Festival, usually about 500 kilograms per mu. In the future, it can be determined whether to replenish some snails according to the specific conditions of the pond.

Density reason

Because of the natural breeding habit of crayfish, it is very difficult to control the appropriate culture density all the time in the pond culture process, but the crayfish is ferocious and the phenomenon of killing each other when the density is too high is very serious. in this way, the crayfish will be shelled late because they can not find a safe shelling place, resulting in the reduction of shelling times in the culture process and the final specification is too small.

In the process of crayfish culture, we should take the way of catching the big and keeping the small, in order to reduce the culture density of the pond, and do not expect to wait until the market price of the crayfish is high, because no matter how high the market price is, if the specification of the crayfish is too small, it is impossible to sell the crayfish at a high price, on the contrary, even if the market price is not high, as long as the crayfish has large specifications and good quality, it will sell at a good price. Crayfish have the habit of clinging to aquatic plants, so planting aquatic plants such as water peanuts and verticillium verticillata in the pond can not only provide a hiding place for crayfish, but also increase the living space of crayfish and reduce the chance of killing each other.

Cause of disease

Disease is also a major reason that restricts the size of crayfish, especially ciliosis. When the ciliate parasites on the shrimp, it will absorb nutrients from the shrimp and make the crayfish thin, and the crayfish will not be able to shell and grow normally because of lack of nutrition. In addition, when the ciliate parasites on the Gill of the crayfish, it will affect the respiratory function of the Gill of the crayfish, resulting in the crayfish can not breathe normally and be in a state of long-term hypoxia. Eventually, the crayfish will not be able to eat, shell and grow normally because of long-term hypoxia, resulting in a small size. In addition, a large number of crayfish die because the parasitism of ciliates can even cause other diseases of crayfish, and no consumers are willing to buy such crayfish after entering the market.

1. About a week before the "barley yellow" in spring, a week or so before the arrival of the "plum rain season" (Jianghuai region generally enters the plum rain season in late June every year), and about a week before "White Dew" in autumn, respectively, use pesticides, that is, first use insecticides, and then use disinfection drugs every other day.

2. In the summer high temperature season, photosynthetic bacteria and quicklime are alternately sprinkled throughout the pond every half a month or so to regulate the water quality. Fresh water is injected every 7 to 10 days to keep the water fresh, and the amount of water each time is about 15% or 20% of the original pond water.