We think we know a thing or two about fish, mostly that all fish live underwater and breathe dissolved oxygen through their gills, correct? The standard answer is "yes, usually." But there are fish that can breathe air through their gills.
There are about 11 different genera of amphibious fish on this crazy planet — perhaps you've heard of lungfish and mudskippers — and it seems as if many of them evolved separately from the others, which suggests being able to breath out of the water gives some fish a real advantage over the competition.
This seems to be the case for the northern snakehead fish (Channa argus), which, when you look at its stats, appears to be a sort of indestructible movie supervillain. Native to China, Russia and Korea, the northern snakehead is one of 29 species of long, tubular brown and black spotted fish resembling eels, with flattened, snakelike heads. But their serpentine appearance isn't what makes them frightening.
"Snakeheads are aggressive predators that can survive in poor water quality conditions and even survive out of water for several days if they can stay moist," says Scott Robinson, a fisheries manager with Georgia's Wildlife Resources Division, in an email interview. "They have the ability to take oxygen from air or water with their gills. Since they can survive in poor conditions they are more likely to spread and persist than some other species of fish."
Basically, they eat everything, can survive aquatic conditions that would have nearly any other fish belly up on the surface, and to top it all off, they're able to wriggle out of a pond they don't like in the interest of slithering overland to greener pastures (though the babies seem to be better at this than the adults). Not only that, they're long-lived, have a wide temperature tolerance, can adapt to nearly any aquatic habitat, and reproduce twice a year — in some situations doubling their population in as little as 15 months.
The Snakehead Is a Fearsome Invader
In their home range, northern snakeheads are probably pretty fearsome, but the problem is, outside their native lands, they're unstoppable.
Nobody's entirely sure how northern snakeheads have made their way into the wild in the United States, but it was probably a combination of the pet trade, fish markets and aquaculture — they used to be farmed in the state of Arkansas before they were federally outlawed in 2002. At this point, they've been found in 16 U.S. states — most recently Georgia.
"In October, 2019, an angler in Georgia reported catching one from a private pond," says Robinson. "Sampling revealed several adults and young fish from at least two different spawns in the pond and also downstream of the pond in a wetland area and a small tributary to the Yellow River. We suspect that one or more pairs of adults were illegally stocked or disposed of in the pond."
Robinson thinks it's likely they will spread farther in that watershed. But at the end of the day, what's so wrong with a snakehead showing up in your local waterway?
Just like with any invasive species, snakeheads provide competition with native fish and animals that rely on aquatic systems for food. Snakeheads are voracious predators, and not only do they eat what could otherwise be eaten by a native species, they eat the native fish, as well as frogs, lizards and other small animals that hang out in the water. According to Robinson, they also may carry diseases that could infect other fish species.
What to Do if You Find a Snakehead
"We want people to understand that they should not dispose of aquarium fish in lakes, streams, or ponds or stock non-native fish anywhere," says Robinson. "In Georgia, if someone catches or finds a snakehead, we ask that they kill the fish – do not return it to the water – and report it to their local Georgia DNR fisheries office. In the case of other states, they should report snakeheads to their state fish and wildlife management agency or Department of Natural Resources."
You can find a list of state fish and wildlife agencies on the website of the Association of Fish & Wildlife Agencies.