Recently, the "List of Invasive Alien Species in Yunnan Province" was released, and the protocrayfish (crayfish) was listed in the Class II serious invasive class. As soon as the news came out, many media launched a vote to vote "Which invasive alien species do you most want to eat as an endangered species?" "What flavor of crayfish do you like to eat?" As a summer must-have delicacy, crayfish has been named "the most tragic invasive species in history" by many netizens. ”
However, behind the ridicule, the disaster brought about by the crayfish invasion should not be ignored.
The crayfish we are familiar with, also known as protocellfish, is native to the Gulf of Mexico in North America. In the early 20th century, crayfish were introduced to Japan as bullfrog feed. At the same time, with the rise of international trade, crayfish were also carried around the world by the ballast water of freighters.
Due to its ferocious habits, strong reproductive ability and high adaptability to different environments, it soon became the dominant species in the local area of "dove-occupying magpie's nest" in various invasion sites, and has been listed by the International Union for Conservation of Nature (IUCN) as one of the 100 most destructive invasive species in the world.
Invading crayfish are on the market in Germany
Wen Cheng, a member of the Turtle Expert Group of the IUCN Committee on the Survival of Species, said that crayfish invasion can be understood as adding a predator to the ecosystem. It can threaten native shrimp, such as the native northeast black shrimp in China, which is squeezed to the brink of extinction by crayfish in the southern part of the distribution area. Crayfish are also capable of preying on small and medium-sized fish such as the crayfish, as well as the larvae of amphibians, such as tadpoles.
At the same time, the damage of crayfish to aquatic plants is also very serious. Qin Haiming, an associate professor at Qufu Normal University, said that crayfish are opportunistic predators and omnivorous animals, while plant foods are more easily accessible. Although the crayfish belongs to the long-tailed class in the crustacean, its lifestyle is closer to that of the short-tailed class (crab), and when it is active in wetlands and underwater, it will use its claws to clip the aquatic plants it encounters from the roots or the lower part of the stem, and eat the tenderer parts, which is very serious to the damage to the plants. While destroying aquatic plants, it also destroys the original ecological environment, further affects the reproduction and life of native fish and shrimp, and causes more serious indirect damage.
At the same time, the crayfish's burrowing ability is very strong, and some holes even reach the thickness of adult arms, so it is very easy to cause the collapse of the field. In 2013, due to the flooding of crayfish, the Hani Terraces were hollowed out by more than 30,000 acres, even threatening the local heritage application process.
The situation in Europe is more tragic than in China, because the protocrayfish from the Americas carries a lobster plague fungus, and the European crawfish are very resistant to this plague fungus, and many native freshwater shrimp die quickly.
Volunteers of the Wild Fun Nature Academy catch invasive species crayfish at Lake Biwa in Nanjing Zhang Bing on the left Photo by Zhou Mengshuang, a reporter of this newspaper
This can be said to be a fantasy. In human history, there has not been a single invasive species that has been solved by eating. Nanjing is a big consumer of crayfish, in April this year, when the author visited the Lake Biwa area in Nanjing at night, he found dozens of crayfish densely packed in the ditch of just over ten meters, as if it had become the top local predator.
For invasive species, the larger the culture, the more invasive individuals will escape and spread. The time-consuming and laborious fishing of crayfish in natural water bodies not only has high labor costs, but also the catch is far from meeting market demand, so the more cultured, the more escape, the more serious the invasion of the vicious circle.
Wen Cheng, a member of the Turtle Expert Group of the IUCN Committee on the Survival of Species, said that as long as the ecosystem is healthy, invasive species can be curbed to a large extent. Crayfish infestations tend to occur where native species have declined for various reasons.
White-boned chicken that preys on crayfish
Crayfish are not without natural predators, such as blackfish that can prey on larvae of crayfish. Chinese river crabs and serrated Chinese crabs can prey on adult crayfish. Birds of prey on crayfish adults, including black waterfowl, small cockroaches, and white-breasted bitter birds.
In a water body with good biodiversity maintenance in Lili, Suzhou, the author found that crayfish coexisted with native black-shelled shrimp, slender-footed rice shrimp, beautiful white shrimp, and Chinese small-arm shrimp, and became part of the ecosystem, thanks to the prosperity of local native species.
Finally, a reminder, don't release crayfish!
(Author: Zhou Mengshuang Source: Guangming Daily)