Diseases That Farmed Crayfish Are Prone to in May and Their Prevention and Control Methods

In recent years, crayfish farming has become increasingly popular, but in the actual farming process there are often some diseases that interfere with crayfish yields. Late April to early May each year is the peak period for disease and death in crayfish, with a wide range of outbreaks in shrimp ponds and high mortality, and individual ponds even becoming “empty ponds” in about a week, bringing serious losses to farmers. What diseases are farmed crayfish prone to in May? How to prevent and control them?

1. What diseases are farmed crayfish prone to in May?

“When wheat ripens yellow, fish die”: April to June each year is the peak period for disease outbreaks in aquaculture. During this period there are many kinds of diseases, they strike quickly, and mortality is high, causing great losses to aquaculture. Crayfish farming is the same: during this period the disease rate is very high and deaths are numerous, and it has long been known as the “May curse”.

1. If the pH value in the pond exceeds the standard, it can easily cause crayfish not to molt, to grow slowly, to suffer from metabolic disorders, to feed poorly, to climb onto the banks and come ashore, and so on.

2. If ammonia nitrogen, nitrite and similar substances in the water exceed the standard, diseases such as crayfish gill rot and tail rot may occur.

3. If the crayfish pond bottom deteriorates or there are problems with the feed, it can easily lead to crayfish enteritis.

4. If the aquatic plant coverage rate is too large (a coverage rate of generally 30%-55% is best), oxygen deficiency occurs at the bottom, leading to large numbers of dead crayfish or crayfish that cannot be caught.

5. If water deterioration is relatively serious, phenomena such as crayfish gasping at the surface, abnormally coming ashore, and caught crayfish lacking vigor will appear.

6. If there is relatively little natural food in the crayfish pond, soft-shelled crayfish and a low survival rate are likely to occur.

7. If the crayfish pond was converted from rice fields and detoxification treatment was not done well in the early stage, diseases break out during the high-temperature weather in May.

8. If the aquatic plant coverage rate in the pond is too low, the water quality remains unclear for a long time, and the water level is insufficient, small hard-shelled crayfish are very likely to appear.

9. Blue-green algae and similar organisms break out, producing large amounts of toxins in crayfish farming ponds and causing crayfish deaths.

There are also hepatopancreatic disease, white spot disease, shell ulcers, cases where only large crayfish die and not small ones or only small crayfish die and not large ones, crayfish bodies turning white or black, and many other situations. All of these can be called by the general term "May curse".

2. Preventive measures

1. Supplement calcium regularly to promote crayfish molting, shorten the molting and hardening time, and reduce cannibalism.

2. Regularly improve the bottom, detoxify, and adjust the water to decompose leftover feed and feces at the bottom and inhibit the breeding of bacteria and insect eggs.

3. Carry out disinfection work in advance at the end of April and the beginning of May.

4. Control the feeding amount well, do not feed feed with too high a protein content, and regularly mix in oral medications (vitamins, lactic acid bacteria, and liver- and gallbladder-protecting types) to improve the crayfish's immunity and disease resistance.

5. When harvesting crayfish, try not to harvest continuously every day; harvest for three or four days, then stop for two days, and sun-dry the ground cages to reduce the degree of damage to crayfish seedlings as much as possible.

6. Maintain the aquatic plants well and cut the grass tips in time.

7. If conditions permit, change the water regularly and appropriately deepen the water level.

In short, farming crayfish is also a matter of first cultivating the water. Water quality is the key. When the living environment of crayfish is good, the disease rate will naturally be somewhat lower and the success rate of treatment will be somewhat higher.