Prevention and Treatment of the Hairy/Fuzzy Condition in Farmed River Crabs

During the growth of farmed river crabs, hair-like growths sometimes appear on the carapace and abdominal appendages, making the crab's surface very dirty, and causing slow movement, poor appetite, malnutrition, difficulty breathing, claws that do not pinch, and even death before molting. The cause of this condition is mainly disease in the river crab, so prevention and treatment must be carried out early; the earlier the prevention and treatment, the better the effect, and losses can be avoided. Which diseases of river crabs cause the hairy condition, and how should they be prevented and treated?

First, saprolegniasis. The hyphae of Saprolegnia are grayish-white and cotton-like, and can produce hair-like growths on the crab's body. The causes of the disease are related to pond water being too fertile and not fresh, too little water being added, and mechanical damage to the crab's body. Prevention and treatment method: for a crab pond with an average water depth of 1 m, use 333 g of dichlorohydantoin per mu, mix with water, and splash it over the whole pond.

Second, sessile ciliate disease. Epistylis, Carchesium, and other ciliates parasitize or attach to the back shell, walking legs, and gills of river crabs, forming a downy appearance. The cause is pond water being too fertile or the pond water not being changed for a long time. Prevention and treatment method: for a crab pond with an average water depth of 1 m, use 500 g of Xianchongjing or Shachongjing or other insecticides per mu, mix with water, and splash it over the whole pond.

Third, filamentous algae disease. Filamentous algae attach to the surface of the river crab's body, causing relatively long green filamentous down to grow on the surface, with the down curved and irregular. The causes are related to water being too fertile, pH less than 7.5, and moss growing in the pond. Prevention and treatment method: for a crab pond with an average water depth of 1 m, use 15 kg to 20 kg of quicklime water per mu and splash it over the whole pond to raise the pH; and use 500 g of chelated copper mixed with water and splash it over the whole pond, or use 200 g of Shaqingtai mixed with soil and broadcast it over the whole pond, then partially change the water after 8 hours.