During the hot season, rapid changes in water quality and high crab intake are the fastest growing periods for crabs and the most difficult periods to manage. In order to ensure the safety of crabs through the high temperature season, the management of this period should pay attention to the following aspects: First, water quality management Aquaculture crab water quality management includes water color, transparency, oxygen content, pH, salt content, water depth and other aspects. 1. Aqua colors Algae grow fast in hot seasons, and the color of the water varies depending on the amount of algae in the water. Deep water color shows that there are many algae, nutrient salts and organic matter in the water, which is unfavorable to the life of crabs. Excessive algae can overwhelm crabs and cause the crabs to die without shelling. Crabs do not like fertilizer, if you find that there are many water and fertilizers and algae, you should pay attention to constantly changing the water or stocking some algae fish. 2. The higher the transparency of transparency, the thinner the water quality. Crabs like to lean water, requiring a transparency of 35 cm ~ 45 cm, if higher can better. 3. Oxygen content Crab requires an oxygen content of 5 mg/L to 7 mg/L. Hypoxia generally does not occur in natural pools, but in artificially intensive cement pools, when there are no large aquatic plants in the pool, hypoxia is prone to occur. In particular, after a sudden shower in hot afternoons, a little carelessness can lead to a large number of deaths due to lack of oxygen. If a large number of crabs are found crawling on the shore during the day and it is proved that there is a serious lack of oxygen in the water, it is necessary to immediately take such oxygenation measures as flushing. 4. pH The suitable pH for crab growth is 7.8-9.0. Every afternoon, when there is a bubble in the water or a pool of organic matter on the bottom of the pool, it indicates that the water quality is changing. In the case of water, it can be adjusted by flushing; when there is no water source, the water quality is adjusted by lime, and the water quality is adjusted by baking soda. Before the adjustment, it is necessary to test first, calculate the required amount, and then spill the whole pool. 5. Salinity crabs like to grow in fresh water. In coastal ponds, salt water will infiltrate into the water, affecting the growth of crabs. The salt content of pool water should be controlled between 1 ‰ and 5 ‰, and water should be changed when it is too high. When changing the water, the water from the bottom of the pool is the highest because of the lower salt content. 6. The pool water depth The water temperature in the pool can be adjusted by the depth of water. The optimum water temperature for crab growth is between 20°C and 28°C, and the water level in the pool is low in summer, the water temperature will rise, and the temperature can be controlled with a deeper water level. Second, the daily feeding time of the bait is arranged at 8 to 9 o'clock in the morning, 4 to 6 o'clock in the afternoon, and 9 to 11 o'clock in the evening. The feeding site is from the edge of the beach that is 50 to 80 centimeters from the edge of the pool. Third, shading crabs are afraid of light, so the high temperature season above the pool needs to build a reed shed, or in the pond to raise the water lotus, planting melons and other large aquatic plants, in order to prevent direct sunlight in the pool. Fourth, to prevent diseases in the hot season, in addition to algae will affect crab growth, the crab is very susceptible to bacterial disease. For the prevention and treatment of bacterial diseases, some antibiotics such as antibiotics can be added to artificial diets. Generally, they are fed once every 7 days to 10 days. At the same time, calcium should be properly added to the bait to facilitate long shelling and shelling of crabs. In high-density cement ponds, crabs often climb on walls and are prone to mechanical damage. Plastic sheets can be laid on the walls of the pool.
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