The northern snakehead (Channa argus) has a most unusual ability: It can breathe outside of the water, as well as within. Juveniles can also wriggle their long, narrow bodies onto land, enabling them to travel from one pond or stream to another if needed.
This aggressive fish is native to China, southern Siberia, and North Korea, where it is fished and occasionally raised for food. But it’s also been introduced around the world, including most recently, the United States, where the invasive species has caused environmental problems.
The fast-growing creatures are carnivorous, eating zooplankton when they are young, but quickly progressing to insects, small amphibians, and other fish.
These fish, whose elongated bodies earned them their name, can grow up to three feet long in introduced areas, and even larger in their native range. They have sharp, dagger-like teeth, and canine teeth on their lower jaw. Their long dorsal fin, which runs much of the length of their body, and a powerful anal fin make them speedy swimmers. The scales are golden tan to pale brown, and they have distinctive splotches along their flank.
The juveniles are adept at moving short distances on land, however when they get older and their bodies become more rounded, it becomes more difficult. During times of drought, snakeheads generally burrow into the mud; however during rainstorms, they can more easily migrate.
Channa argus has a special chamber adjacent to its gills called a suprabranchial organ. This allows the animal to absorb oxygen directly from air by gulping it in through its mouth. This adaptation enables snakeheads to thrive in low-oxygen, stagnant bodies of water in a variety of settings, from swamps to muddy rivers to canals to ponds. It can survive outside of water for up to four days.
However, snakeheads can also use their gills to respire underwater, which they often do in the winter months. In summer, and in warmer conditions—which necessitates more oxygen—the fish solely breathes air though its suprabranchial organ.
The northern snakehead is not alone in this ability: Walking catfishes, lungfishes, and betta fish can all breathe air directly as well.
Reproduction and rearing young
These fish reach sexual maturity between one and three years, depending on growing conditions, and breed from April to August. They can spawn up to five times, each time laying more than a thousand orange-yellow eggs, which are buoyant. Sometimes they can lay many more, however, approaching 50,000 eggs per year. Snakeheads often make floating nests made of bits of vegetation to protect their eggs.
Parents defend their young for several weeks, and have even been known to attack people who get too close, like a Delaware boy whose hand was bit when he reached into a pond to investigate the shimmering color of a juvenile snakehead.
The northern snakehead has been introduced into Central Asia, including Kazakhstan, eastern Europe, Japan, and the United States. Because they are voracious predators that quickly grow and reproduce, they have the potential to outcompete native species, making them a significant ecological threat. (Read more: Fishermen battle invasive ‘frankenfish’ snakeheads.)
The largest U.S. invasive population lives in the Potomac River drainage of the Chesapeake Bay watershed. In 2002, a snakehead was first found in a pond in Maryland. Although that population was eradicated with the use of rotenone, a fish poison, more snakeheads were found in the Potomac in 2004, and they’ve been well established there ever since.
Snakeheads have also been found in open water in in Arkansas, Florida, Virginia, Delaware, and New York, according to the U.S. Geological Survey. In early October 2019, a fisherman caught a snakehead in Gwinnett County, Georgia, the first sighting of the fish in the state. Federal and many state laws dictates that snakeheads be killed if they are caught. Environmentalists are concerned the fish could spread to the Great Lakes, where they could wreak havoc to those sensitive ecosystems.
However, there are several efforts to eradicate them and limit their spread, including programs to fish and eat the creatures. The state of Maryland, for example, has an annual snakehead fishing derby that teaches people how to fillet the meat and gives a small award to the person who catches the biggest one. When snakeheads are found, serious measures are often taken, such as killing everything in that particular body of water, when that’s deemed possible or appropriate.
Their import is also banned in the United States, they are illegal to own in many states, and shipping or moving them across state lines is illegal under the Lacey Act.