There are more than 500 species of crabs in China, but only a few are suitable for freshwater aquaculture. Take the Chinese river crab that is now promoted to breed, because it grows faster, the individual is also large, the nutritional value is high, and the breeding benefits are good. So it is loved by many people, especially for farmers, but do you know the identification method of crab fry?
1. Body color appearance identification
The Chinese river crab species is bluish gray in color, the abdomen is silvery-white, the body shape is irregular oval, the four frontal teeth are sharper, and the fourth tooth on the anterior margin is obvious.
2. Identification of good or bad physique
Good quality crab fry have strong support and mobility. Crab seedlings are stacked together when the clumps are in a granular structure, if they are put into the nursery, the seedlings are fluffy, and the individuals maintain a certain gap; where the crab seedlings are picked up and then released by hand, the crab seedlings can quickly crawl open, or make their abdomen turn over and reset quickly after the day, or bury the crab seedlings with water droplets, they can quickly get rid of the stickiness of the water and escape from the water, all of which are high-quality crab seedlings with strong support, mobility and anti-stickiness
3. Identification of maturity level
When purchasing crab species, young crabs that have not reached sexual maturity should be selected; the survival rate of early maturing crabs that have reached sexual maturity is extremely low and easy to die, so they cannot be purchased. The belly of the female crab of the precocious crab is full, and the four sides of the navel have many hairs on the four sides of the navel, which are dark in color; the bristles on the feet of the male crab are thick, long and dense, and the external genitalia are pointed long. The juvenile crabs are thin and blue-gray in color, the female crab has a pagoda-shaped umbilicus, and the posterior genitalia are grayish white instead of purple; the male crabs have sparse bristles and short external genitalia.
4. Identification of specifications and uniformity
Good crab species are uniform, tender and consistent, and the specifications meet quality standards. Crab seedlings with insufficient daily age or poor quality are small. Before the formal purchase of seedlings, a certain number of crab seeds should be randomly extracted from the nursery pond, first placed on the ordinary balance or torque balance with a sense of 0.1-0.01 grams, weighed, and then counted, calculated the number of crab seedlings per gram or the average weight of each crab seedling, and finally judged whether the specifications of the crab seedlings met the quality indicators.
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