China has a vast territory. Because of the difference in geographical environment, the seasons for crayfish rearing on different regions are different. Now the management work that should be done for crayfish rearing in spring is described as follows:
I. Preparation before stocking
In addition to disinfecting, clearing, removing wild and fertilizing ponds in accordance with the criteria for clear ponds, the following tasks should also be focused on:
1. Take measures to increase the horizontal area of ​​the water body. The greater the number of places per unit area of ​​pond that can be used to make holes or habitat for crayfish, the greater the amount of stocking and the higher the yield. To this end, the following measures can be taken: First, build more than a few ponds in the pond. The location of the cormorants should be staggered and the width should be 30 cm. The second is to construct artificial caves with bamboo tubes, tiles, and plastics.
2. Transplant water plants. Aquatic grass is a place where crayfish hides, inhabits, hides, and grows. At the same time, aquatic plants can also purify water and improve the water environment. In the case of insufficient artificial feeding, aquatic plants can also be used as feed for crayfish. There are many types of plants that can be cultivated in the lobster ponds, including Vallisneria, Pogosia, Hydrilla verticillata, Chlorella, Eichhornia crassipes, water hyacinth and water peanuts. Aquatic planting area should not exceed 2/3 of the total pond area.
3. Release the snails. From the end of February to the middle of March, the best time to put snails is 200 to 300 kg/mu, which is then added gradually as needed. The release of snails can not only supplement animal feed for crayfish, but also purify the bottoms.
Second, seed stocking time
Crayfish are ideal for stocking in late March and early April, so crayfish have started activities to facilitate catching of seed.
Third, the stocking mode
1. Crayfish main mode. The pond is mainly crayfish, with a small amount of other fish. There are three kinds of crayfish fry stocking patterns: 1 stocking shrimp. Per mu of water, about 3 cm of body length of about 2 to 3 million shrimp seedlings, according to the survival rate of 50% to 55% of the calculation, it is expected that the mu shrimp yield up to 400 to 500 kg. In addition, 150 lbs. of white pheasant and 50 pods of 50 g. Calculated according to the survival rate of 85%, per mu produce flowers, adult white peony 75 to 100 kg. 2 broodstock stocking. Store broodstock directly and let it breed naturally. A 50-55 kg of broodstock is placed per acre of water, and the specifications are 30-40 tails/kg. It can be cultivated to 23,000-33,000 tails and it is estimated that 500-700 kg of shrimp will be produced per acre. In addition, each mu of water with flower, white pheasant 250 tail (specification of 50 grams / tail, which accounted for 20% of scapes), according to the survival rate of 85%, per mu yield of 80 to 110 kg of fish. 3 Stocking shrimp that have not reached the market specification. The main stocking shrimps that have not reached the market specifications will be stocked every year starting around April, with stocks of 100 to 200 tails per kilogram and 10,000 shrimps per kilogram.
2. Mixed mode of fish and shrimp. 1 Stocking shrimp. The shrimp seedlings are distributed between 15,000 and 20,000 per acre of water, and it is estimated that 250 to 300 kg of shrimp can be harvested. In addition, 350 to 400 kilograms of adult fish can be harvested per mu, including 250 white storks, 50 calyxes, 80 scorpions and 150 squid. 2 stocking broodstock. Each mu of water will be placed 30 to 40 kg of broodstock, and it is estimated that 250 to 300 kg of shrimp can be harvested. In addition, 500 to 600 kilograms of adult fish can be harvested from 500 to 600 tails of white pelicans, flower pods, head bream or squid per acre of water.
Fourth, shrimp disinfection
Disinfection of shrimp species is an important part of preventing and treating shrimp diseases. Even if the returned shrimp or broodstock is healthy, some pathogens are inevitable. Without disinfection, shrimp or broodstock will bring the pathogens into the culture ponds. Once the conditions are right, pathogens will multiply and cause disease. Shrimp body disinfection commonly used bath method, the choice of drugs are as follows: First, copper sulfate, a concentration of 8 mg / l, dipping 15 to 20 minutes; second salt (excluding iodine), the concentration of 3% to 4%, Dip for 3 to 5 minutes; third, bleach, with a concentration of 10 mg/L, and dip for 10 to 15 minutes. The specific drug used for disinfection should be selected based on local drug sources and prevalent diseases. The length of the disinfection time of shrimp body immersion is based on the principle of killing pathogens, but over time will often cause lobsters to lose oxygen and float or die. Therefore, during the actual disinfection operation, observe the lobster dynamics at any time. If lobster is found to be unwell, immediately put it into the culture pond.
Fifth, feeding management
When shrimps and shrimps are stocked, their temperature and water temperature are lower, the crayfish are smaller, their predation ability is weaker, and their grass volume is less. At this time, concentrate feed is mainly used, and a small number of feedings are taken. method. The type of feed should be small fish, shrimp or bean cake, wheat, corn, etc., and can also be used as feed for young shrimp. The daily feeding amount is full, eaten, and no residual bait is left.
6. Water Level Control and Prevention
The water temperature in spring is low, and the water depth should be kept at 30-60 cm, so that the water temperature will rise as soon as possible. In the later period, due to the temperature rising, the high water level should be increased to more than 1 meter, and the water temperature should be kept above 20°C by adjusting the water depth. There is also more rainfall in spring, and the water level must be adjusted according to the amount of rainfall. The water level is too high for shrimp to escape. In particular, it is necessary to drain water in a timely manner after heavy rain, keep the water level relatively stable, and prevent the flood pond from causing crayfish to escape. In order to do a good job of flood prevention, we must also prepare enough flood control equipment and strengthen the field ridge and escape prevention facilities in advance.
Seventh, the catch of shrimp
The broodstock that is stocked in the spring (the larvae have left the mother) can be arrested one after another in late spring. Listed shrimps that are not stocked before and after April, can be listed in the market in late May, with specifications up to 30 grams/tail. The juveniles that were bred in the fall of the first year of stocking from March to April are generally listed on the market from May to June. The fishing tools are mainly ground cage nets, hand nets, etc.
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