How can hairy crabs go to Europe?

God's dining table is a treasure, but a foreign land has become dross. Recently, the BBC reported that the hairy crab with the scientific name "Eriocheir sinensis" has become a household name "invader" in Britain.

In fact, hairy crabs have been listed as the most destructive invasive species in 100 by IUCN. Hairy crabs, which appeared on the dining table of China people more than two thousand years ago, have not only become the public enemy of European biologists, but also British researchers suggest that monitoring and catching mechanisms for hairy crabs be introduced nationwide in order to get rid of them quickly.

The BBC report originated from an article by Bentley, a researcher at Newcastle University.

Bentley published an article in the journal Biological Invasion, saying: Just as the invasion of gray squirrels pushed the British red squirrel to the brink of extinction, the "Eriocheir sinensis" will also pose a threat to British marine life, preying on native species protected in British waters, such as white crayfish and salmon eggs. They will also dig holes up to half a meter deep in the riverbank to make the soil on the riverbank loose and unstable.

Bentley also warned that hairy crabs that have taken root in the Baltic Sea may further explore Scotland. He believes that hairy crabs have the ability to crawl upstream 1200 km, and once they climb to the salmon spawning ground, it will bring a fatal blow to the salmon industry in Scotland. He suggested that the authorities should introduce a national mechanism for monitoring and fishing hairy crabs as soon as possible.

Hairy crabs "sneak into" Europe

"I don't know if Lushan lives up to its eyes and doesn't live up to its stomach by eating crabs."

Hairy crabs have always been unique to China, living in places where salt and fresh water meet, such as estuaries and lakes. How did this little hairy crab cross the ocean to "invade" Europe? Experts say that hairy crabs can go to Europe, which is purely "smuggling".

According to Professor Cheng Yongxu of Shanghai Fisheries University, during the five-port trade period of Qing Dynasty, 100 years ago, merchant ships from Europe docked at the ports along the Huangpu River in the Yangtze River estuary, and Dutch merchant ships transported China's tea and porcelain to Europe. In order to increase the stability of merchant ships, the storage tanks are full of ballast water, which is usually pumped directly from Huangpu River. Hairy crab eggs and crab seedlings arrived in Europe with ballast water, which was discharged by merchant ships after they arrived at Dutch ports. Because the water systems in Holland and other places are very close to the Yangtze River system in China in temperature and salinity, hairy crabs thrive in Europe and form a population.

In fact, hairy crabs have been listed as the most destructive invasive species in 100 by IUCN.

At present, biologists are generally worried that the appearance of hairy crabs will destroy the biodiversity of the Rhine and Thames. Because hairy crabs are fierce by nature, most of the fish and shrimps in the same river with them are its delicious meals. Moreover, hairy crabs like to cut off the aquatic plants in the river with sharp crab claws. The reduction of aquatic plants will reduce the self-purification ability of rivers, and once a large number of broken aquatic plants rot, it will aggravate river pollution. In the 1980s, a large number of aquatic plants died in the marshland in the northeast of the Netherlands, because of the destruction of river crabs.

At the same time, hairy crabs also brought economic benefits to European fishermen. In 200 1 year, Professor Cheng Yongxu went to the Netherlands to investigate the local hairy crab population. On 1937, he saw a paper on hairy crabs written by a doctor of biology from a local oceanographic institute, which described that the nets used by European fishermen to catch eels or lobsters were full of thousands of hairy crabs, and eels and lobsters had no place at all.

European eating habits promote the "expansion" of hairy crab family

Although the "immigration" of hairy crabs has become the public enemy of Europe, in Professor Cheng Yongxu's view, the threat of hairy crabs to European native creatures is not necessarily accurate.

He believes that the life cycle of hairy crabs is two years, and there is only one breeding period from June 1 1 to April next year. If you stay in the sea, you will return to shallow water at other times. This period of time is very short, and it is winter. The mother crab's main job is to protect the crab seedlings, and she seldom moves, only catching some shellfish around her to eat, so it generally does not affect salmon eggs. In addition, as far as the damage to the river bank is concerned, crabs generally make holes during the wintering period, and the wintering crabs are generally small crabs, with weak hole-making ability and shallow depth.

An important reason for the continuous expansion of the hairy crab family in Europe is the eating habits of Europeans. Unlike China and crabs, Europeans don't like crabs. There is no need to eat crabs. Naturally, no one catches crabs, and hairy crabs breed more and more, leading to "biological invasion" in Europe.

Professor Cheng Yongxu said, "On the one hand, it is caused by eating habits, on the other hand, it is due to ignorance of crabs. Westerners have a misunderstanding that crabs are the hosts of paragonimiasis. After eating crabs, paragonimiasis will enter the human body and get lung disease. In fact, the host of paragonimiasis is Eriocheir sinensis, mainly Eriocheir sinensis living in the Yangtze River. For a long time, the English names of Chinese crab and hairy crab are the same, which makes hairy crabs suffer a lot. "

There is still no hope for the "returnees" hairy crabs to return home.

Surprisingly, compared with the impure germplasm of local hairy crabs, "immigrant" hairy crabs have to. According to the molecular genetics research conducted by professors of Shanghai Fisheries University, the quality of hairy crabs from other places is more pure.

According to reports, due to the vigorous development of river crab breeding in China, the crab seedlings in the Yangtze River were once fished out. People introduced crab seedling culture from Liaohe River system and Oujiang River system, which made the original pure hairy crabs cross with "Liao Crab" and "Ou Crab", which seriously damaged the germplasm of hairy crabs. There are no other freshwater crabs in Europe, and hairy crab "immigrants" have only mated in their own populations, and the varieties are very pure. So when Professor Cheng Yongxu went to the Netherlands, he brought the hairy crabs from the Netherlands back to his hometown to cultivate crab seedlings. From June to February last year, 5438, with the enthusiastic help of overseas Chinese, Shanghai experts shipped back 540 kilograms of Rhine crabs from the Netherlands, accounting for more than 3,000 crabs. In March this year, the first batch of crab seedlings survived more than 80 kilograms, and these crab seedlings were robbed by aquaculture bases all over Jiangsu.

Then, can we let the "returnees" hairy crabs return to their hometown, and Allah can also eat cheaply?

Professor Cheng Yongxu said that this issue is still very sensitive. Because some biologists believe that the hairy crabs brought back from Europe are also exotic species in a strict sense, it is difficult to assert what consequences this exotic species will bring in a short time.