CATDOLL : CATDOLL: Things to note when raising crabs in water

1. Precautions for raising crabs in water

1. Pay attention to water quality management: ① Frequently add new water, add water once a week, change water once every half a month, add water more than 20 cm every day in high temperature season, and change water once every three to five days. ② Adjust the pH value, use quicklime, once every 10 to 15 days, the amount is 10 kg per meter of water depth per 667 square meters. ③ Control the water level and adjust the water temperature. The water level is 0.8 to 1 meter in spring, 1.2 to 1.5 meters in summer, and stable at about 1 meter in winter.

2. Feeding palatable and high-quality feed: River crabs are omnivorous aquatic animals and there are many types of bait. In the early stage of crab stocking, nutrition must be strengthened to ensure the first successful molting, which is conducive to improving the survival rate. The feed varieties used mainly include small fish, clam meat, snail meat and river crab complete granular feed; in the middle period, which is a high temperature season, no animal bait is used to avoid diseases caused by poor digestion and absorption of river crabs. Water plants and pumpkins are used as the main feed, and wheat, corn, soybean meal and other plant concentrates are appropriately matched to maintain the normal metabolism of river crabs; in the later stage, animal bait and river crab granular feed should be used as the main feed, and green feed should be appropriately matched to strengthen nutrition to ensure that the river crabs can meet the nutritional needs of the last molting, so as to increase the individual size and yield of river crabs.

3. Control disease prevention and control: Common diseases of river crabs include shell rot, black gill disease, limb rot, tremor disease, edema, Saprolegniasis, and polyzoan disease, more than 30 types. Therefore, strengthening disease prevention and control is the fundamental guarantee for healthy crab farming.

2. Only the right temperature is suitable for survival. What is the appropriate temperature for crab farming?

The dissolved oxygen in the water should be greater than 4 mg/L, the pH should be between 6.8 and 8.5, and the transparency should be between 25 cm and 30 cm. The optimum water temperature for river crab growth is 15℃-30℃, and the optimum water temperature for river crab growth is 25℃~28℃. The breeding waters should fully consider the harmonious ecological habits and create an ecological environment conducive to the growth and development of river crabs.

Water plants are where river crabs live and hide from enemies while molting. They can also purify water, carry out photosynthesis, and increase dissolved oxygen in the water. They are also good bait for river crabs. Deep water areas should plant submerged plants such as Vallisneria angustifolia, Hydrilla verticillata, Potamogeton malachiana, and Chlorella vulgaris, while shallow water areas should plant Echinochloa crus-galli and Alternanthera philoxeroides. It is necessary to optimize the structure of aquatic plants and control the coverage area so that submerged plants, emergent plants, and floating plants account for more than 1/3 of the total water surface.

The stocking time is generally controlled from the end of February to March, with a stocking specification of 80 to 160 per kilogram and a stocking density of 450 to 500 per 667 square meters. When stocking crabs, soak them in 0.008‰ potassium permanganate for 10 to 15 minutes before putting them in. River crabs are omnivorous aquatic animals with a wide variety of baits. In the early stage of stocking crabs, it is necessary to strengthen nutrition to ensure the smooth first molting, which is conducive to improving the survival rate. The main feed varieties used are small fish, clam meat, snail meat, and river crab full-price granular feed; the middle period is a high temperature season, and animal bait is not used to avoid diseases caused by river crab digestion and absorption. Aquatic plants and pumpkins are mainly used, and wheat, corn, soybean meal and other plant concentrates are appropriately matched to maintain the normal metabolic space in the body of river crabs; in the later feeding period, animal bait and river crab granular feed are mainly used, and appropriate green feed is used to strengthen nutrition to ensure that river crabs increase their nutritional needs for the last molting, thereby increasing the individual specifications and yields of river crabs.

After entering the crab seedling stage, they can leave the seawater environment and live in freshwater. River crabs usually live in freshwater bodies such as rivers and lakes. They especially like to live in lakes and weeds with lush aquatic plants, fresh water sources, and abundant natural bait. River crabs are suitable for growing in slightly alkaline freshwater, with a pH value of 7.5-8.5 and dissolved oxygen requirements of more than 5 mg/L. Juvenile crabs can survive and die in water temperatures of 15-20℃, and the suitable temperature is 19-25℃. When the water temperature drops to 4℃ or exceeds 36℃, young crabs are prone to death. The survival temperature of adult crabs is 5-30℃, and the most suitable water temperature for growth is about 22-28℃. River crabs generally hibernate in caves in winter and can withstand low temperatures of -8℃, but they are prone to death if the ambient water temperature suddenly changes above 3℃. River crabs cannot move normally when the water temperature exceeds 38℃ in summer, and they are prone to death when the water temperature exceeds 40℃.

The best temperature should be maintained at around 20-25 degrees, which allows crabs to grow comfortably.

It is best to control the temperature at around 18-20 degrees, so that its metabolism rate is slow and it is easy to survive.

The appropriate temperature for crab farming is 18-20 degrees, which is conducive to the survival of crabs.

River crabs hide during the day and come out at night. They like clean water with high oxygen content, are afraid of strong light, and love quietness. They start to feed when the water temperature is above 10℃, and shed their shells and grow at around 15℃. The growth period is 20-28℃, so the pond structure should be suitable for their habits.

⑴ Area and water depth: Generally, 2 to 5 mu is appropriate, and the water depth is usually maintained at about 1 meter.

⑵Pond marriage. The slope of the pond is 1:2.5, and crab holes are set up on the slope of the pond, accounting for about 20% to 25% of the area; a "dark island" should be built in the pond for crabs to dig holes, eat and molt.

⑶ Water quality. The water quality should not be too rich, and the transparency should be maintained at 30 to 50 cm. Too rich water is prone to lack of oxygen, and in severe cases it can cause death of fish. The water source is preferably river water.

⑷ Dark islands. Dark islands are places where river crabs dig holes, eat and molt, and are generally 10 cm below the water surface. Do not feed on dark islands where they molt to prevent river crabs from killing "soft-shell crabs" while foraging.

3. How to preserve crabs and how to keep them for a few days

To preserve crabs, you usually need a bucket and put them in it, but don't stack them up. It's best to spread them out flat. Put an appropriate amount of water in the bucket, but it's best not to cover the crabs. It's enough to reach half of the body. If conditions permit, you can use an oxygen pump to oxygenate the water, so that it can live longer. In addition, pay attention to the temperature, which is usually better to control between 15-25℃. 1. How to preserve crabs If it is a live crab, it is best to raise it in a bucket. If you raise it at home, it can live for about three days. Put the crab in a bucket, add water appropriately but don't cover it, so that it can't crawl out, and it won't affect its breathing. If you want to preserve it for longer, you need to put it in the refrigerator and freeze it. It's best to freeze the live crab directly. Freezing it after it dies will affect the taste.

2. How to keep crabs for a few days 1. Water level: If you want to keep crabs, you first need a certain amount of water. This animal lives in water and can easily die from dehydration. It should be noted that you cannot use too deep water to keep it. It is best not to submerge it in water so that it can breathe from the air and live longer.

2. Oxygen: Crabs have a relatively high demand for oxygen. It is relatively easy to raise them at a low water level. However, if the water level is relatively high, the crabs will be completely immersed in the water. It is necessary to constantly oxygenate the water to ensure that there is sufficient oxygen in the water, so as to avoid the crabs dying from lack of oxygen.

3. Temperature: Crabs cannot tolerate high or low temperatures, so if you want to keep them alive, you must take good insulation measures. Usually the temperature should be controlled between 15-25℃. If it is lower than 15℃, it will affect its feeding and may even freeze it to death. If it is too high, it is not conducive to its survival.