Sihaiwang: it's time to eat crayfish again. Can't you hold back those who like to eat small? Do you know which country crayfish comes from? The crayfish, whether fried, steamed with garlic or stir fried with spicy sauce, is very delicious and delicious. It's a delicious food that can never be missed.
Crayfish is actually a foreign crayfish from that country
Which country is crawfish from
Indeed, China is the country with the largest area and production of crayfish cultivation in the world, and also the largest consumer of crayfish in the world. However, the crayfish is not from home, it is a genuine 'foreign product'. There may be many misunderstandings. Crayfish, whose scientific name is crayfish, is actually originated in North America. It is a kind of saprophytic animal in Louisiana in the south of the United States. In the early 20th century, crayfish entered China along with the biological invasion ways such as the foreign cargo ship's ballast water.
How did crawfish come to China
China is a crawfish imported from Japan in the 1930s-1940s, first brought into Nanjing, China. Detailed historical data can be seen in "China biological invasion research", Science Press Wan Fanghao, Guo Jianying, etc.). Japan was introduced from the United States earlier.
1. In 1927, the Japanese introduced a small amount of crayfish from Hawaii, the United States, only for the purpose of feeding bullfrogs, then the shrimp quickly 'captured' Japan.
2. Around 1929, crawfish flowed into Nanjing of China through Japan. This is also the source of the rumor that crayfish was introduced into China by the Japanese in order to eliminate the corpses during the Second World War, which is nonsense. Otherwise, it's too time-consuming and laborious to kill the body with crayfish.
3. Japan is the springboard for crawfish to enter East Asia. By the 1960s, crayfish had been found in Japan, including Hokkaido, except for some islands. Even the Japanese relative of crayfish, Japanese black crayfish, was almost killed by it.
4. In the early 1990s, crayfish quickly set foot on the tables of big stalls in Hubei, Anhui and Jiangsu. And the crayfish sellers are looking forward to the international market.
5. Crawfish has become an important resource of freshwater shrimp in China, which is widely distributed in the middle and lower reaches of the Yangtze River. Then, in order to adapt to the harsh living environment, crayfish has undergone a unique evolution in China, mutating into spicy crayfish, fennel crayfish, steamed crayfish and other new varieties.
Why does crawfish grow little
1. Inbreeding
At present, the germplasm of almost all aquaculture species is degenerating, and crawfish is inevitable. In order to improve the economic benefits, the breeding mode of everyone is becoming more and more chaotic. In addition, most of the breeding households adopt the one-year breeding mode, which has been developed for many years. This will inevitably lead to the problem of inbreeding between lobsters, and eventually lead to the degradation of lobster germplasm, the smaller the individuals are, and the general breeding households do not pay attention to the problem of species conservation. When the number of high-quality parent shrimp is getting less and less, the germplasm will be withdrawn Transformation is inevitable.
2. Water quality factors
In recent years, due to the influence of climate factors, the water level of most farmers' ponds in spring is not stable because of either lack of water or too much rain. With the rise of temperature and the increase of feeding quantity, the decomposition of residual bait, feces and organic matters in the pond will bring adverse effects on the water quality, which will directly affect the feeding, shelling and growth of crawfish, and these will affect the size of crawfish.
3. Feed factors
The lack of feed, poor quality and incomplete nutrition will certainly affect the shelling growth of crawfish and lead to a smaller physique. However, if the high protein concentrate feed is fed for a long time, it will lead to the accumulation of nutrition and the formation of precocious puberty and stop growing, and the final specification will be smaller. Therefore, the feed selection and proportion control of crayfish are very important.
4. Breeding density
Due to the natural breeding habits of crayfish, it is very difficult to control the appropriate breeding density in the pond breeding process. However, crayfish is fierce, and when the density is too high, the phenomenon of killing each other is very serious. In this way, crayfish will fall back late because it can't find a safe shelling place, resulting in the reduction of shelling times in the breeding process and the final specification Smaller. In addition, when raising crayfish, it is necessary to pay attention to the difference between the stocking specifications. Otherwise, the crayfish must be raised in large, medium and small pools. In the process of cultivation, we should also pay attention to the specifications of crayfish. If the specifications are different, there will be a phenomenon that prawns eat crayfish, so that the survival rate will be greatly reduced, which will affect the increase of cultivation yield.
5. Disease factors
Disease is also one of the main reasons for the size of crayfish, especially ciliate disease. When the ciliates parasitize on the shrimp body, they will absorb nutrition from the shrimp body and make the body of the crawfish thin, and the crawfish will not be able to grow normally because of lack of nutrition; and when the ciliates parasitize on the crawfish gill, they will affect the breathing function of the crawfish gill, resulting in the crawfish unable to breathe normally and in a state of long-term hypoxia, and finally the crawfish will be deprived of oxygen for a long time Can not eat, shelling and growth normally, resulting in smaller specifications.