This article begins a series of 10 posts dedicated to discussing introduced fish species in US waters. Some species are headliners, while others have been around so long that we think of them as part of our wild fauna. Check back for more installments, and Get to Know an Introduced Species!
Northern Snakeheads (Channa argus) are one of the 30+ snakehead members of the family Channidae, which are native to parts of Africa and Asia. They are predators in their native systems, but have natural predators and other ecological interactions which keep their populations (and the population of other species in their ecosystem) on balance. In many parts of their native range, they are harvested for food.
|Northern snakehead. (Source)|
Most of us have heard about northern snakehead fish, which was first discovered (established) in Maryland in 2002. The pond in which the snakeheads were first caught was drained, uncovering more than 1,000 individuals—all which could likely be traced back to the introduction of two (yes, just two) snakeheads by one person. Subsequent occurrences of snakehead along the east coast are thought to be separate introductions—good news if you were worried about their terrestrial migration abilities, but bad news in that the source of the problem has not yet been resolved. Northern snakeheads can be aquarium fish, but owing to their culinary popularity and availability live, it’s likely that some introductions came after a visit to a fish market.
|Although not (yet?) wide-spread, northern snakehead have been found on both coasts, and unfortunately, each red area likely represents several, repeated introductions.|
Like so many invasive species, northern snakehead lack a natural predator. Combine this high rate of survival with aggressive and carnivorous feeding behavior, and you get individuals that grow to very large sizes. Although not a concern for attacks on humans, large snakeheads will necessarily alter the balance of other fish, many of which are desirable sport fish, or threatened and endangered species. Snakeheads are known to survive out of water for extended periods, and even to move across short distances of land. Regardless of the specifics, this proves them to be a hardy species—not an easy type of species to eradicate. Perhaps the worst of the snakehead facts is that occurrences represent several, different introductions. We can try to eradicate what is there, and learn more about their biology, but if the source of introduction goes unabated, we may only be delaying the inevitable.
|Without natural predators and plenty of food, introduced northern snakehead can grow to very large sizes. (Source)|
Cable nature shows would lead you to believe these fish can traverse great distances on land and breathe air as for as long as they would like. And while it may be true that they have some adaptations for oxygen acquisition, their land-movement is likely hyped. Genetic tests have even found that fish from different locations are likely separate introductions, not migrations. And while it’s still too early to tell, the overall invasion might not be as bad as originally forecast. Finally, of the 30+ species of snakehead, the northern snakehead is likely the only one able to survive in US waters—so there is little concern of additional snakehead species introductions.