How to prevent river crab from escaping in lake culture

River crab culture in large water lakes can not set up anti-escape facilities, and the escape of river crabs has caused great economic losses. There are certain reasons for the exodus of river crabs. If we can grasp it correctly and take appropriate measures at the same time, the loss can be greatly reduced.

Catch in time to prevent physical maturity from escaping

River crabs have the habit of living in fresh water, growing up, and breeding in estuaries or shallow seas. Every autumn, when the west wind blows, sexually mature crabs leave their daily fresh water to mate in brackish water and spawn in the sea. Even if the big water surface does not have the conditions to enter the sea, because of the need for "physiological maturity" of river crabs, they will go ashore blindly and escape. Therefore, fishing should be done in a timely manner.

Provide sufficient bait to prevent insufficient bait from escaping

River crab eating is very miscellaneous, but most like to eat animal bait, but also eat aquatic plants and other plant bait. If too many seedlings are put into the water body and the supply of natural bait falls short of demand, river crabs will escape because of foraging, so the bait resources in the water area must be analyzed to achieve a reasonable stocking density.

Provide a good environment to prevent bad environment from escaping.

Generally speaking, river crabs have a strong ability to adapt to the water environment, but they will flee beyond the limits of tolerance. First, water pollution, low dissolved oxygen, high concentration of harmful substances, river crabs are forced to move out; second, there are no aquatic plants or too few aquatic plants. The fishing proverb says, "the size of a crab depends on the water plants." The importance of aquatic plants to river crabs is as follows:

1. Directly used as bait.

2. Provide bait indirectly: where aquatic plants are rich, there are many small fish and shrimp and benthos, which are easy to be preyed on by crabs.

3. It can provide a good living environment for crabs, such as concealment, rich dissolved oxygen and cooling when it is hot.

4. Escape prevention measures

When ① is released, first put it in a cage or net enclosure for a few days to adapt to the new water environment, and then open the box and remove the net to allow the crab to move freely in the lake.

If ② has no or little water plants, it is necessary to artificially transplant bitter grass, water peanuts, etc., and you can also use straw, branches and leaves to do some artificial "crab nests" for crabs to hide.

Set up a light source to prevent light-induced flight

River crabs have a strong phototaxis and can even climb to the lights regardless of the danger of being caught. Therefore, the phenomenon that the river crabs in the big water surface fled to the surrounding villages and towns, factories and mines, and farmhouses is universal. About 1 meter above the central surface of the water area, several strong lights can be set up to counteract the temptation of external lights. If the light is strong, it can not only prevent escape, but also lure back the crabs that climb ashore.