“Gui Jie” in Beijing, meaning Ghost Street, is dedicated to crayfish and is filled with towering bright red crayfish statues. While it might just seem like a show for tourists, the Chinese are responsible for 90 percent of the world’s crayfish consumption and crayfish is on menus throughout the country. Between 2006 and 2016, crayfish production more than tripled to 850,000 tons. Surprisingly, crayfish is not native to China but the Chinese began raising them when aquaculture began expanding in the 1980s. 

Nile tilapia, largemouth black bass, channel catfish, and red swamp crayfish are all alien species and their production through Chinese aquaculture exceeds even the growth of native species. An alien species is either accidentally or deliberately relocated into an area outside of its natural range. If they escape from aquacultural operations, they can become invasive in a new environment with no predators. Alien species can also bring in pathogens and transmit diseases and other uninvited “hitch-hikers” to wild populations.

North American Crayfish Invade China

Crayfish are one of the most famous invasive species in the world. Native to the south-central United States, the red swamp crayfish were introduced into China in 1929. In a suitable habitat they quickly become the dominant species and put pressure on the native plants and animals. 

Crayfish consume nearly all of the available food and burrow into and degrade riverbanks, levees, and dams. They have invaded the Three Gorges Dam Reservoir, which is already facing geological hazards from earthquakes and landslides, and are compounding the risk and severity of bank collapse. Crayfish have spread throughout China threatening local fish, crustaceans, and aquatic plants like rice and lotus. They have been called an invasive ecosystem engineer because of the way that they can change the environment to improve their own performance.

Rice terraces, used for 1300 years in southwest Yunnan Province, are now being damaged by the burrowing crayfish. Despite the damage they are causing, farmers continue to stock ponds with crayfish because of their high market price. In 2016 crayfish sold for 60 yuan per kilogram, compared to the same weight of rice at 32 yuan. Even though crayfish damage the rice and cause the rice paddy to leak, they are often grown together as the extra value of the crayfish outweighs the losses. At a value of 60,000 yuan, a rice crop on 4 hectares grows to 250,000 yuan with the addition of crayfish.

Asian Carp Escape in the U.S.

Asia is aquaculture’s epicenter with 90 percent of the production and 80 percent of the value. By comparison, the United States has a modest aquaculture industry, ranking 17th in the world.

But still, the damage done by alien fish species in the United States is extensive. 138 non-native fish species have been introduced in the United States, creating annual economic losses of $5.7 billion. The most famous U.S. invasive species is Asian carp. The fish are ravenous eaters of aquatic plants and were brought into the United States to control excess weed and algae growth in ponds. Pond flooding led to accidental release into the Mississippi River system and now Asian carp are a notorious pest. These fish are thriving and make up 97 percent of the Mississippi River’s biomass today. In a bid to reduce the population, the United States Geological Survey recently announced it will rename the fish to something more appetizing for consumers.

Asian carp are famous for leaping out of the water when startled and are a danger to boaters. To block the Asian carp from threatening the $7 billion Great Lakes commercial fishing industry, the U.S. Army Corps of Engineers installed and continues to operate an underwater electric fence in the Chicago Sanitary and Ship Canal. Now the Corp of Engineers, along with Illinois and Michigan, will fund a nearly $800 million project to further fortify the electric fence. 

China’s Policies Lag the U.S.

Regulating the introduction of invasive species through aquaculture is a challenge as most of the commercially popular species, like Nile tilapia, Atlantic salmon, and Pacific oysters, are not native. Within the United States, the Lacey Act authorizes the U.S. Fish and Wildlife Service to regulate and ban the import and transportation of animals and plants. The Service publishes a list of injurious species and grants permits for zoos, and for scientific and medical purposes. At the state level, governments limit the import, possession, transport, and sale of non-native species through a permit system. Some states already prohibit some species that cause a great risk to human and environmental health. For example, Florida prohibits the import of piranhas. Florida also prohibits 86 species of tilapia, an otherwise popular farmed fish.

Other states require permits for aquaculture facilities to make sure that non-native species cannot escape. For example, Minnesota prohibits pond aquaculture in the floodplain. Mississippi and Utah must first approve proposed aquaculture facility designs and require screens on all inflow and outflow points to prevent the escape of animals and their eggs. Sometimes predators can carry a non-native animal away and allow it to escape. Florida, for example, requires bird nets to reduce this risk.

By contrast, concern about invasive species is new to China with little to no regulation. In 2003, China’s Ministry of Agriculture established an Office for the Management of Invasive Alien Species. They began collecting and cataloging information on the major invasive species. However, China is lagging in the adoption of plans, laws, and regulations to prevent damage from non-native species. 

Stricter controls of invasive species are seriously needed and the Convention of Biological Diversity (CBD) set the 2011-20 targets to identify species and pathways and begin controlling and eradicating priority species. Some progress has been made, but overall is still inadequate to address the threat.

China was scheduled to host the 2020 Convention, until the Coronavirus outbreak postponed the 15th U.N. event in Kunming. As host, China assumed the Convention presidency and has the opportunity to show leadership. Becoming a signatory of the CBD in 1992, China is required to pass new laws. While China is making progress in protecting terrestrial environments, non-native aquatic species remain a huge biodiversity threat. Planning and standards for aquaculture facilities in China are needed to prevent escapes during floods and storms increasing in a changing climate. The estimated damage from China’s 544 invasive species is more than 200 billion RMB ($30 billion) each year. As a result of aquaculture, 179 non-native aquatic species have been introduced. The small crayfish, though tasty, is the poster child for the impact of unregulated import of non-native species for aquaculture.