I water quality management 1. Fertilizing shrimp ponds should not only improve the water quality by applying base fertilizer before putting crayfish fry, but also apply some fertilizer according to the change of water quality to ensure the supply of zooplankton in the water. Top dressing is mainly decomposed organic fertilizer, with little chemical fertilizer, especially ammonium bicarbonate. When topdressing, it is necessary to apply less frequently, and the amount of fertilizer should not be too much at a time to control the water quality. Generally, it is applied once a month 1 time, and the amount of fertilizer applied per mu is about 100 kg each time. The amount of topdressing should be adjusted according to the season, weather, temperature and water color. Generally, due to the low water temperature and slow decomposition of organic matter in spring and autumn, the amount of fertilization can be appropriately increased; In hot seasons such as summer, the amount of fertilization should be reduced. Apply more on sunny days and less on rainy days; The sultry weather before a thunderstorm is not applicable. Fertilization depends on the color of water. Generally, the water in the pool is grass green, brown and not turbid. When the transparency is below 30 cm, no fertilizer is applied, and when it is above 30 cm, timely fertilization is applied. If the water is dark brown or yellow-green bloom and accumulates on the water surface, it should be replaced before fertilization. 2. Adjust the water quality In the process of crayfish culture, when the temperature is low in early spring, the water level can be lowered, and the water depth can be kept at 30-60 cm, so that the water temperature can rise rapidly. Later, with the gradual increase of temperature, the water level can gradually increase. In hot summer, the water depth is kept at1.5-2m. When the temperature is high in summer, if the water level is too low, it will accelerate the gonad development of crayfish, cause the precocity of shrimp and make the commercial shrimp smaller. Generally, during crayfish culture, fresh water is added every 10- 15 days when the temperature is low, and water is added every 7-1 0 days in summer to keep the dissolved oxygen in the water above 5 mg/L. Aerators should be installed where conditions permit. In shrimp ponds, air compression aerators and spray aerators should be selected. Their advantage is that they are not afraid to disturb the water and avoid the injury of prawns. Under the same power, impeller aerator and waterwheel aerator have larger gyration range than spray aerator, which is easy to damage shrimp. When using this aerator, the water depth must be kept above1.5m. If a large number of crayfish are found crawling out of the water when the weather is clear during the day, which proves that there is lack of oxygen, fresh water should be replenished in time. Usually, we should always observe the changes of water quality, so that the water quality will be in a state of fat, lively, tender and refreshing for a long time. Fertilizer: refers to a large number of phytoplankton with suitable water color concentration, which is beneficial to the digestion of shrimp. Generally, the transparency is 25-35cm, and the water color is dark brown or grass green. Activity: refers to the color and transparency of water changing with the intensity of sunlight. This is mainly because the dominant phytoplankton population in the pond appears alternately and is full of vitality. Fishermen often say "early clearing and late green", "early red and late green" and "half pond red and half pond green" all refer to this change. If there is a fog-like spray mixed with yellow and green in the pool, it means that there are too many undigested algae in the water, which is a manifestation of the deterioration of water quality. Change the water in time. In addition, the activity of pond water changes not only at different times every day, but also periodically every 10- 15 days, which means that the beneficial algae population is in a virtuous circle of continuous utilization and continuous growth. Tenderness: refers to water and fat but not old. There are two main signs of water aging, one is that the water is yellow or tan, and the other is that the water is white. The appearance of these signs is due to the deterioration of water quality caused by the aging and death of a large number of indigestible cyanobacteria or algae cells in water. Cool: refers to fresh water, the water color is not too strong, and the transparency is 25-35cm. Second, feeding crayfish in natural water can grow well because of its low density and aquatic plants, benthos and other bait can meet its growth requirements. However, in the artificial high-density intensive culture environment such as ponds, due to the lack of natural food, we have to artificially feed bait to meet the needs of crayfish growth and development. 1. Food type Crayfish is omnivorous. Except larvae and shrimps, they only eat zooplankton such as cladocera and copepods, and other individuals also eat plant and animal foods. Such as aquatic plants (Alternanthera philoxeroides, duckweed, POTAMOGETON malayi, POTAMOGETON crispus, Haematococcus verticillata, Ceratophyllum, Eichhornia crassipes, etc.). ), terrestrial green grass (fresh and tender wheat seedlings, rice seedlings, Sudan grass, ryegrass, alfalfa, green vegetables, etc. ), fruits (bran, sweet potato, barley, corn, rice, peel, etc. ) In the production of crayfish culture, it is necessary to feed animal and plant bait reasonably to meet the needs of crayfish growth. At the same time, it can also save feed and reduce costs. Adding 0. 1%-0. 15% ecdysone to the feed can shorten the ecdysone cycle of crayfish, ensure the synchronization of ecdysone in the population and improve the yield of crayfish. 2. When feeding crayfish, you can set up a feeding table on the shore of the pond. Generally, reed mats or plastic woven bags can be fixed under the water surface, and bait can be put in for shrimp to eat. You can also put the bait on aquatic plants or on the shore water without setting a bait platform, so that the shrimp can climb to the shore to eat. It is necessary to develop the habit of feeding crayfish at fixed points to facilitate feeding crayfish. 3. Feeding method The frequency and quantity of artificial feeding bait should be determined according to the season, the size of shrimp, feeding habits, etc. Generally, for crayfish with the size of 1-3 cm, because of its small size, it is not necessary to choose the time when feeding, and it can be fed 2-3 times a day, and spilled along the edge when feeding. At the same time, because fat water can provide more bait for it, the amount of artificial feeding bait does not need to be large. If young shrimps are put into stocking mode, 200-500 grams of minced fish, minced snail meat, soybean milk, etc. In the early stage, put it in per mu, or feed the special shrimp feed100-200g. After feeding for about 60 days in spring and autumn and 40-50 days in summer, crayfish become larger and can be fed as prawns. Young shrimps over 250/kg can be fed with bait twice and three times a day in the high temperature growing season; When the water temperature is lower than 13℃, stop the water inflow. Generally, aquatic plants of100-150kg are put into each mu every15 days, and at the same time, the animal and plant bait that crayfish like to eat is fed, and the protein content of the bait is kept at about 25%. The daily feeding amount should be controlled at 2%-6% of the total shrimp in the pond, and it should be increased or decreased according to the season, weather, water quality, physiological status of shrimp and feeding situation of crayfish. When the temperature is high, it grows rapidly, eats vigorously and eats a lot; When the temperature is low, the growth is slow, the food intake is weakened and the food intake is small. From June to September, the water temperature is suitable, which is the peak growth period of crayfish. Generally, crayfish are fed 2-3 times a day at 9- 10 in the morning and in the evening or at night, and the daily feeding amount is 5%-8% of the weight of shrimp. In other seasons, feed 1 time every evening, or supplement 1 time the next morning according to the feeding situation, and the daily feeding amount is 1%-3% of the body weight. Bait feeding should pay attention to the good weather, hot, stuffy, rainy or the water quality is too strong; A large number of shrimps throw less when molting, and more after molting. When feeding bait, animal and plant bait should be reasonably matched according to the specific situation. Generally, animal bait accounts for 35%-40%, and plant bait accounts for 60%-65%. In plant bait, grass and fruit each account for half. When feeding, the feeding focus of plant bait can also be determined according to the growth of grass and grain. If the grass grows vigorously in summer and the yield is high, you can invest more appropriately; When the grass species decrease in spring and autumn, you can throw more fruit bait. Third, the daily management of shrimp ponds focuses on patrolling the ponds. The focus of patrolling the pond is to observe shrimp activities, changes in water quality and weather. If crayfish rest during the day, exercise at night and eat normally, it means that shrimp is healthy and the pond environment is good. If shrimp comes out during the day, check for illness. If the shrimps are disease-free, their food intake suddenly decreases, and a large number of shrimps emerge from the water during the day, indicating that the water body lacks oxygen and needs to be changed or oxygenated in time. When watching the water, we should not only master the change of water color and adjust the water quality in time, but also repair the damaged embankment and salvage the unfinished bait in time. When patrolling the pond, we should also do a good job of guarding against theft and enemies (frogs, rats and snakes). In addition, check the growth of crayfish. Adult shrimps are cultured in ponds. After 7 months, the growth status is checked every 15 days/time, and the body length, weight and body surface color are checked. Samples can be randomly selected during inspection. In order to avoid damaging shrimp during inspection, do not drain the water for inspection unless it is seriously ill. Cages and boxes can be used for trapping. Don't weigh multiple shrimps together to avoid injury. 4. Fishing Because crayfish grow fast, it can reach the commodity specifications in 3-4 months. When the crayfish turns red, its carapace becomes hard and its weight exceeds 20-30g, it can be caught and put on the market. Crawfish can be caught for a long time all year round, and can be caught in various ways from March to June+065438+1October. From February 65438 to February of the following year, because of the cold weather, crayfish entered the cave for the winter, and they could be caught by digging holes manually. However, crayfish in winter can't meet the commodity specifications, or they will be used as parent shrimps in the coming year, which is seriously wasted after fishing, so they are generally not caught. 1, cast a net to fish at night, put the net flat in the bottom of the pool, then spread the bait that crayfish like to eat in the middle of the net, lure crayfish into the net, and pull up the four corners of the net to fish out the shrimp. 2. Fishing with a net is to catch shrimp with a fishing net just like pulling a fish. 3. Cage net catching There are special fishing net production enterprises to produce cages for catching crayfish. Each cage is 10-30m long, about 30cm wide and 30cm high. Every 40-50cm, it is supported by a 30cm× 30cm box bracket made of iron wire or bamboo pieces, and a grid is formed between the two brackets. There are barbs on both sides of each grid, and a shielding net is woven above the cage. The two ends of the ground cage are respectively round, and the ground cage net is preferably net-shaped. Every morning or afternoon, put a cage on the edge of the shrimp pond and put fish, chicken intestines and other strong-smelling things as bait. When crayfish came out for food at night, they smelled the fishy smell and thought it was very interesting. Because there was a net on the cage, they couldn't climb it, so they looked around for the entrance and got into the cage. The shrimp that entered the cage slipped into the depths of the cage and became the shrimp in the cage. This fishing method is suitable for catching wild crayfish and crayfish with deep water. 4. Pull the net by hand to catch fish and shrimp and tie it into a square, leaving a funnel with a barbed cone below. Along the edge of the shrimp pond or the place covered with aquatic plants, the shrimp are constantly driven by poles. When the shrimp enters the square net, it is caught by lifting the net. This fishing method is suitable for places with dense crayfish. 5. The dried pond catches the water discharged from the pond, crayfish will appear at the bottom of the pond, and shrimps can be caught by hand. In addition, there are fishing methods such as net and running water.