Fish
Northern Snakehead
Channa argus · also called snakehead, frankenfish, amur snakehead
The northern snakehead is a long, mottled, air-breathing predatory fish that can survive in filthy water, wriggle across land to a new pond, and guard its young like a pit bull. In its native Asia it is a valued food fish; in the United States it is one of the most publicised invasive species, nicknamed the “frankenfish.”
Overview
Northern snakeheads are native to the fresh waters of eastern China, Korea, and the Amur basin of the Russian Far East, in slow rivers, oxbows, canals, ponds, ditches, and reservoirs with plenty of vegetation. Unlike most snakeheads, which are tropical, this species is cold-tolerant and overwinters buried in mud under ice. It was found breeding in a Maryland pond in 2002, and it has since colonised the Potomac River system and several other eastern US drainages.
The invasive toolkit
Several traits make the northern snakehead a formidable coloniser:
- Air breathing. A lung-like chamber lets it live in oxygen-starved water and survive out of water for days if damp.
- Overland movement. It can wriggle short distances across wet ground, so drained ponds and low barriers do not contain it.
- A broad, aggressive appetite. Adults are the top predator in small waters, eating fish, frogs, crayfish, and more.
- Prolific, protected breeding. A pair can spawn several times a year, building a floating nest and defending schools of thousands of fry for weeks.
- Cold hardiness. It thrives in temperate climates that stop most tropical invaders.
In its native range
Where it belongs, the northern snakehead is a normal and useful part of the fish community and an important aquaculture and market fish, prized for its firm flesh and, in traditional medicine, for supposed healing properties — demand that fuelled its live transport and, ultimately, its escape abroad.
Management in the US
US agencies treat the northern snakehead as a serious threat and have tried eradication (poisoning enclosed ponds), containment, and public campaigns urging anglers to kill and report any they catch and never to move a live one. It is a federally injurious species, illegal to import or transport across state lines. Complete removal from an open river system like the Potomac is considered unlikely; the goal now is to limit further spread.
Status
As a species the northern snakehead is Least Concern — abundant and secure in Asia. Its significance elsewhere is entirely as an invasive predator, and it stands as a cautionary example of how the live-food and aquarium trades can move an ecologically disruptive animal across the world.
Northern Snakehead: common questions
Can a snakehead really breathe air and walk on land?
It can breathe air, and it can move on land, though "walk" oversells it. The northern snakehead has a chamber above its gills lined with blood vessels that works like a primitive lung, so it can — and, as an adult, must — gulp air at the surface. This lets it live in stagnant, low-oxygen water that would kill other predatory fish. On land it cannot use fins as legs; instead it flexes its body and pushes with its tail to wriggle across wet grass or mud for short distances, typically to escape a drying pond, and it can stay alive out of water for several days if it stays moist.
Why is the northern snakehead such a feared invasive species?
It combines several dangerous traits. It is a voracious apex predator that eats native fish, amphibians, and crayfish and can dominate a small pond or slow stream. It breeds prolifically, spawning several times a year, and both parents fiercely guard large schools of young. It tolerates poor water, cold winters (it survives under ice), and brief spells on land, so barriers that stop other fish do not stop it. Since it was discovered breeding in a Maryland pond in 2002, it has spread through the Potomac basin and to other states despite eradication attempts.
What should you do if you catch a snakehead in the US?
In states where it is established, wildlife agencies generally ask anglers not to release it — to kill it (removing the head, separating the gill arches, or gutting it), keep it, and report the catch. It is illegal to transport a live snakehead across state lines or possess one live in many states. It is also, incidentally, good to eat, with firm white flesh, and "eat the invaders" is part of the management message.
Are snakeheads dangerous to people or pets?
Not really. There is no record of a snakehead injuring a swimmer, and stories of them attacking people are folklore. A guarding parent will charge and can give a nip with small sharp teeth if a hand comes near the nest, and a large fish thrashing on a line or in a boat can scratch someone, but the northern snakehead is not a threat to humans or, realistically, to dogs. The real damage it does is ecological.