Prevention and Treatment of Acute Poisoning in River Crab Culture

Acute poisoning in river crabs has two types of symptoms:

1) Toxic agents, because of their high invasion intensity, within a relatively short time pass through the gills and triangular membranes of the river crab, causing the rear edge of the crab's carapace to swell and split, producing a false “molting”, or the triangular membranes to show abnormal red or black muddy conditions, or the crab's abdominal flap to open and droop, with the limbs becoming stiff and death occurring.

2) Toxic agents, within a relatively short time, are brought in through the eating of aquatic plants and artificial feed, and via the blood circulation of the stomach and intestines, cause endocrine disorders in the river crab, so that the chelipeds and walking legs separate from the cephalothorax and death occurs.

The factors causing poisoning and death in river crabs include those inside the pond, such as toxic gases at the pond bottom like hydrogen sulfide and ammonia, and biological toxins in the water. There are also exogenous ones, such as excessively high-concentration medication and feed contaminated by toxic substances.

Prevention and treatment methods:

① Before stocking crab seed, after the culture pond is drained, use 100 kg of quicklime per mu to clear the pond. From June to September, use 10 kg of quicklime per mu each month, dissolve it in water, and splash it over the whole pond.

② At the end of the year, remove excess silt from the pond bottom (retain 5 cm).

③ Plant pondweed and alligator weed in the pond to purify the water quality.

④ Once symptoms appear, immediately replace with fresh water.