The invasive Northern snakehead fish can grow up to one metre long and weigh up to 7kg. Native to China, Russia and North and South Korea, where it is eaten as a delicacy, the fish was inadvertently introduced to the United States, where efforts are underway to control its expansion.

C. argus is a voracious eater of everything from zooplankton and insects to crustaceans and fish, and can easily dominate and annihilate ecosystems that are not its own. It has the ability to survive in water with very low oxygen levels, giving the species a competitive advantage over other fish that require more oxygen. Most notably, the Northern snakehead can breathe oxygen from the air, and can survive two to three days out of water. Young Northern snakeheads even have the ability to move over land from one water source to another by way of wiggling their bodies.

The first recorded sighting of a Northern snakehead in the US was in 2002 in a pond in Crofton, Maryland. It eventually emerged that the fish was purchased from an Asian live food market and released into the pond. Officials immediately went to great lengths to eradicate the species from the pond, which was heavily dosed with the chemical rotenone, a piscicide. Six adult Northern snakehead and over 1000 juveniles were found and destroyed. The story became a national event, with an influx of media in the area and unprecedented television coverage. Perhaps it was the name ‘snakehead’ or the news media exaggerating the fact that the fish could ‘walk’ that led snakehead fascination to spawn its own horror films: Snakehead Terror (2004), Frankenfish (2004) and Swarm of the Snakehead (2006).

Since 2002, C. argus have turned up elsewhere along the east coast, and even in Florida, Illinois, Arkansas and California. Strict laws are in place to try and stop the spread of the species, yet the specimen pictured here was collected in Burnham Harbor in Chicago.