The Invasive Species That Could Destroy Our Rivers

Humans have a knack for meddling with the environment, and typically in a way that we don't even realize until far too late in the game. Such is the case with invasive species, organisms that are placed into non-native environments through human negligence. These environmental invaders attract a lot of attention, but few have garnered as much notoriety as the northern snakehead.

Snakeheads are freshwater fish of the genus Channa, and they get their name from the fact that their long, narrow heads are eerily reminiscent of snakes. There are dozens of snakehead species, but one in particular — the northern snakehead (Channa argus) — is perfectly suited to thrive in the temperate waters found through most of the United States. Unfortunately, they are native to northeast Asia, and their presence in American waters is a major concern.

The snakehead invasion was discovered in 2002, when an angler reeled one out of a pond in Maryland. The discovery instantly made headlines. At over two feet in length and with its frighteningly reptilian look, the fish soon inspired a series of made-for-TV horror films with titles like "Snakehead Terror," "Snakehead Swamp," and "Frankenfish." These exaggerated depictions were so extreme that they ignited a panic around children being dragged into rivers by snakeheads, which was a complete fabrication. Now, two decades later, the snakehead problem persists, and if they are to be dealt with, people need to set aside the monstrous fish of fiction, and learn about the real thing.

Snakeheads have some unique traits that make them a particularly challenging invasive species. They are rare amongst fish in that they can breathe air from the surface, allowing them to survive in low-oxygen waters unsuitable for most other fish. They can even survive as long as four days on land. They can also go into torpor, an inactive state that conserves energy and allows them to endure extremely cold winters, even when the surface water freezes. Interestingly enough, some species of hibernating snakes are also capable of torpor, adding yet another serpentine layer to this invasive fish.

The most concerning threat posed by snakeheads is their highly aggressive nature. They are ambush predators that lurk in shallow waters and strike out viciously at any prey that passes. They feast on practically anything, from fish to bugs to reptiles and amphibians. Predation is one way that invasive species can cause extinctions, and with the snakehead's indiscriminate taste, many species could be at risk. They will even attack species similar to themselves, most notably the bowfin. Bowfins are ambush predators of similar size and shape as snakeheads, so much so that the two are sometimes mistaken for each other. The most important difference is that bowfins are native to North America, and not only that; they are the last remaining members of an ancient family often described as living fossils. A threat to the bowfin could mean the end of its line forever.

Dealing with invasive species is extremely difficult because it's hard to know how far they have spread. It's not even clear when, where, and how the northern snakehead was released into the American wild. The U.S. banned the import and transport of snakeheads after the 2002 discovery, but before that, they were sold at pet stores and fish markets coast to coast. Snakeheads probably entered wild waters via negligent pet owners, or perhaps even anglers looking to stock ponds with an easy food supply.

Most invasive snakeheads have been found in the mid-Atlantic region, and their proliferation in the Potomac River has raised particular concerns. On top of that, individual snakeheads have been caught in several other states, and the full reach of the invasion is unknown. The fish's unusual traits present another challenge here, as unlike most fish, northern snakeheads spawn multiple times per season, and females can carry up to 50,000 eggs. Both the mother and father guard the eggs and young as they develop, and they become especially aggressive during this time.

Many anglers have responded to the snakehead invasion by seeking out these fish for a catch, some even targeting them with bows and arrows. They aren't killed for nothing, as the flaky meat of northern snakeheads makes a lovely meal. But the lesson here is clear: species diversity is essential to an ecosystem, but introducing outsiders can actually reduce that diversity, and when they thrive, the locals suffer.