Detailed Explanation of Disease Prevention and Control Methods for Crayfish Farming

Because crayfish farming has only just started, and because disease occurs less under extensive farming conditions, the time devoted to researching crayfish diseases has also been relatively short. At present, many questions are still not fully understood, and viral diseases in particular still cannot be effectively treated. In dealing with shrimp diseases, one should base one's approach on the principle of “prevention first, combining prevention with control”. Below are several prevention and control methods for common crayfish diseases.

1. Gill rot disease

The pathogen of gill rot disease is bacteria. The symptoms are blackened gill filaments and local moldy decay in diseased shrimp.

Prevention and control methods: Frequently remove leftover bait and debris from the shrimp pond, add fresh water, keep dissolved oxygen in the water body above 4 mg/L, and avoid water quality contamination. Dissolve 2 g/cubic meter of bleaching powder in water and splash it over the whole pond, which can achieve a relatively good therapeutic effect.

2. Black gill disease

Black gill disease is mainly caused by severe water quality pollution, with the shrimp gill filaments being infected by mold. The symptoms are that the gills change from red to brown or light brown, and eventually become completely black; the gills shrink, and diseased shrimp often lie motionless by the shore, finally dying from breathing difficulty.

Prevention and control methods: Keep the water body clean and dissolved oxygen sufficient, and regularly use quicklime to regulate water quality. Soak and wash diseased shrimp in 3%-5% salt water 2-3 times, for 3-5 minutes each time, or dissolve 10 g/cubic meter of methylene blue in water and splash it over the whole pond.

3. Tail rot disease

Tail rot disease is caused by injury to crayfish, cannibalism among them, or infection by chitin-decomposing bacteria. In the early stage of infection, blisters appear on the tails of diseased shrimp, and the edges ulcerate, become necrotic, or become incomplete. As the condition worsens, the ulceration spreads from the edges toward the middle. In severe infections, the entire tail of the diseased shrimp ulcerates and falls off.

Prevention and control methods: When transporting and releasing shrimp fry and shrimp seed, do not stack them under pressure or damage the shrimp bodies. During rearing, feed must be supplied in sufficient and even amounts to prevent shrimp from competing for food or killing each other due to insufficient feed. If this disease occurs, soak 15-20 g/cubic meter of tea seed cake and splash the liquid over the whole pond; or dissolve 5-6 kg/mu of quicklime in water and splash it over the whole pond.

4. Zoothamnium disease

The pathogen of Zoothamnium disease is Zoothamnium. The symptom is that shrimp have difficulty molting smoothly, and diseased shrimp often die during the molting process. It can occur in both larvae and adult shrimp, and is more harmful to young shrimp.

Prevention and control methods: Thoroughly clear the pond to kill pathogens in the pond. If this disease occurs, large water exchanges can be made frequently to reduce the number of Zoothamnium in the pond water.

5. Ciliate disease

Common pathogens of ciliate disease include Epistylis and Vorticella. Ciliates attach to the body surface, appendages, and gills of adult shrimp and shrimp fry. When attached in large numbers, they hinder the shrimp's breathing, activity, feeding, and molting, affecting growth. Especially when attached in large numbers on the gills, they affect gas exchange in the gill filaments and can cause oxygen deficiency in the shrimp, leading to suffocation and death.

Prevention and control methods: Maintain a reasonable stocking density, pay attention to the environmental hygiene of the shrimp pond, frequently exchange fresh water, and keep the water quality fresh. Soak and wash diseased shrimp in 3%-5% salt water, with 3-5 days as one treatment course, or soak and wash them in 25-30 mg/L formalin solution for 4-6 hours, for 2-3 consecutive times.