Every fall, the crabs have entered the season of maturation and harvest, and they have also entered the stage of death. If farmers do not pay attention to strengthening management and regulating the water quality of crab ponds, they may cause heavy losses due to batch deaths of crabs. The crabs should prevent the following three kinds of deaths in the fall:
First, prevent natural death. As the saying goes, “Since the West Wind, Crab Feet Itchesâ€, from September to November every year, there are a group of crabs that have been growing for two years and have been husked from “Yellow Crab†to “Green Crabâ€. The gonads mature and enter the final period of their lives. All crabs with “foot itch†have been unable to adapt to the environment of low osmotic pressure due to maturation of gonads and increased osmotic pressure in the body. Such crabs must escape to find a new environment, and eventually they will naturally die. These crabs should be arrested and sold in time to avoid losing their economic value due to natural death.
Second, prevent indigestion from death. “The temperature difference between day and night is large, and the pressure and water temperature change will increase. The appetite of the crab will change, and it will easily cause indigestion and death. This is what is usually called “bloat death.†Prevention and control measures: improve water quality, and regularly use lime Water disinfection; regularly add antibiotics and auxin in foods; do not feed or feed vegetal foods, increase animal feeds, especially high-protein diets such as barnyardgrass and snails, etc. Feeding should be done regularly and quantitatively. Reduce the amount of feeding accordingly.
Third, prevent "cold" death. There is a large temperature change during the day and night, and there is a large difference in water temperature. The crabs are not adaptable and are prone to “cold†and cause breathing difficulties and death. Preventive measures: pay attention to regulating the water level to prevent drastic changes in water temperature; the temperature difference when injecting new water cannot be greater than 3°C; the water surface should be longer than some water hyacinths, water peanuts and other cover plants, but the coverage area can not be greater than 1/2 of the water surface; Deepen the water level.
Pay attention to regulating the quality of crab pond water
Crab ponds, water quality is of great importance, it will not only affect the growth rate of crabs, survival rate, but also affect the individual size of crabs, fullness, color of carapace, and thus affect economic efficiency. Autumn is the peak season for crabs. The water quality of crab ponds is prone to deterioration. In particular, attention should be paid to regulating water quality.
If you want to adjust the water quality, you must first know the quality of water quality, generally yellow-brown, light brown, pale oil green, good water quality; dark green, blue-green water, water quality tends to become richer and older, there is a danger of deterioration; If it is red-brown, dark brown and black, the water will start to deteriorate. If the water is turbid, bubbles will appear and the water will be bitter and emaciated, with dark brown, rust-colored, copper-green floating membranes, etc., indicating that the water quality is very poor.
In the usual management, we must pay attention to the adjustment of water quality. The main methods are:
First, add new water. First adjust the water level. In summer, the water depth should be kept between 1 and 1.5 meters. In the fall, it should be kept between 1.3 and 1.5 meters. Secondly, change the water regularly. At the beginning of summer, change the water every 10 to 15 days. Change the water by 1/3 each time. Change the water every week from June to September. Change the water every time by 1/3 to 1/2. When changing the water, pay attention to the fresh water quality.
Second, planting plants. Aquatic grasses are both attachments to river crabs, as well as shelters for their habitats and clam shells; they also have the effect of absorbing fertilizers in water and blocking sunlight. Planted water plants mainly include water peanuts and bitter herbs. Planting area can account for 30% of the pool area.
Third, open aerator. An aerator can be installed to regulate the water quality. With oxygen aerators, we must adhere to the principle of "opening up and opening up." That is: the sunny noon boot, cloudy days when the boot the next morning, rainy days or more water and fat crabs, midnight boot; evening does not boot, overcast and rainy days during the boot.
Fourth, timely fertilization. The timely application of some chemical fertilizers (urea, superphosphate) can better regulate water quality. Be careful not to apply organic fertilizer.
Fifth, other ways. (1) Splash lime once every 10 to 15 days. This will not only regulate the water quality, but also increase the calcium of the pool water, which will facilitate the crab shell. (2) Too much cyanobacteria in the water, and the water quality is not good. Quanxi is splashed with copper sulfate to kill cyanobacteria. (3) Gypsum powder of 20-30 grams per cubic metre of water shall be splashed on the whole pool for 3 consecutive days at intervals of 3 to 4 days to kill the blue mud mud in the pool and adjust the water quality. (D) The application of photosynthetic bacteria to form a dominant population, through its decomposition of organic waste, reduce water, ammonia, nitrogen, hydrogen sulfide and other harmful substances, and well regulate water quality.
If the water quality is too strong or bad, first-aid measures should be taken. First change the water 1/4 to 1/3. After two consecutive passes, mix the river mud with lime to make a slurry. After discoloring the water, stir the bottom of the pool and apply some. Fertilizers regulate water quality.
Strengthening crab management
First, strengthen anti-escape facilities. In the autumn, strong winds and heavy rains will stimulate the crabs to escape. Therefore, before the rainy season, it is necessary to increase the height of the ponds, check the facilities for escape prevention, and prepare flood prevention materials. In addition, crabgrass can not have high stalk crops.
Second, scientific feeding. In the autumn should be appropriate to increase plant foods (such as bean cakes, wheat, pumpkin, etc.), in order to facilitate the accumulation of crabs. In the fall, when the crabs are in the fattening season, high protein diets such as snails, clams, animal waste, and miscellaneous fishes should be properly added. Feed twice a day, and daily feeds account for 5% to 8% of crab body weight.
Third, strengthen disease prevention and control. Autumn is the high season of crab disease and it is easy to cause large-scale diseases. Therefore, regular use of internal medicine (such as oxytetracycline, Radix, dehulling, etc.) and external use (carapace net, etc.) combined approach to prevent crab disease. It is best to splash lime once every 15 days: from time to time, you should sprinkling the entire pool with bleach, crab paste, etc. Monthly use of terramycin, sulfa drugs and other mixed baits to feed 3 to 4 times, after the beginning of autumn should focus on doing a good job of crab "shivers" prevention and control work, available chlorine dioxide, dichlorohydantoin drug Quanchiposa, And combined with a new oral medication (such as the virus busters, glocking spirit, etc.) taken orally for 1 week for prevention and treatment.
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