Hot and spicy crayfish is a favorite for many Chinese. [Photos provided to China Daily]

All of this was the result of a single migrant worker to Yunnan who made the unfortunate decision to raise them on his rice field for a bit of extra cash.

Overall, China seems ill-equipped to deal with invasive species such as the crayfish. Indeed, Liu Wanxue at the Center for Management of Invasive Alien Species says China did not begin in-depth research into invasive species until 2000.

"In the last century, we didn't have invasion biology," he says. "What we did was just pest control in general. It wasn't until 2002 that ... invasive species research got off the ground in China."

While academic achievements in monitoring and risk evaluation have made great strides, the practical prevention and control methods remain relatively archaic, including the use of pesticides and the introduction of predators.

China's biodiversity is suffering an invasion of an estimated 544 nonindigenous species. According to Liu, of the 100 most threatening invasive species in the world, 51 can be found in China. He also says invasive species cause estimated losses of more than 200 billion yuan a year.

Considering crayfish, it is no surprise the authorities have concentrated efforts on the economic effects of the crustacean rather than the ecological impacts. In some east coast areas, fish farms use a lot of chemical pesticides to eliminate crayfish, causing no end of havoc to the ecosystem.

What is worse, some of these poisoned crayfish make their way to the market. The lack of clear and effective laws and regulations in this field is cause for concern. But the good news, according to Liu, is that the Ministry of Agriculture is planning to propose more specific measures for the management of alien invasive species, which will hopefully be passed this year.

But this is just the first step toward long-term, effective solutions. For now, the responsibility falls to the Ministry of Agriculture as well as the State Forestry Administration and the Ministry of Environmental Protection.

As always, there is work to be done on the education side of things, too. Attitudes toward freshwater crayfish and other invasive species are increasingly polarized; the mere mention of them strikes fear in people, while conspiracy theories and rumors continue to flourish. There are even those who think the problem can be solved by simply eating a way out of this mess.

The problem of invasive species is a serious one, a problem that garners more sensational headlines than practical solutions: In 2012, a man in the Guangxi Zhuang autonomous region got a chunk taken out of his hand by a piranha; the silverleaf whitefly caused a total crop failure in Shaanxi province in 2010; the Canadian goldenrod plant eliminated more than 30 species in Shanghai alone; and the water hyacinth has killed untold numbers of fish and has even grown so thick as to obstruct navigation.

There is no easy solution to invasive species, but the authorities must concentrate their efforts on protecting ecosystems, stopping the influx of invasive species, and dealing with the already damaging species safely and with care.

Courtesy of The World of Chinese, www.theworldofchinese.com

The World of Chinese