The Northern Snakehead Trout is one of the most famous invasive species of Northern America. A fish that can survive on land would gain press coverage any day, and this one happens to be spreading through our nation’s river system at an incredible rate, eating all native fish in its way. However, all the media and government concern has done nothing to stop the snakehead’s expansion.
Part of the problem is that the snakehead’s movements are nearly impossible to predict. The fish can survive in a wide range of temperatures and environments, and its land-travelling abilities allow it to jump across rivers in ways no other fish can. As such, humans generally do not become aware of the snakehead’s presence in an ecosystem until it is firmly entrenched there. At that point, there is no means of removing the invader short of poisoning the entire lake.
Fortunately, there may be a way to detect the next environment that the snakehead invades. It has been provided not by ecologists or environmental agencies but by genetic researchers, who have discovered that water contains trace amounts of DNA from the creatures that live in it. These traces have been dubbed environmental DNA or eDNA, and can be analyzed to determine the species of fish present. If there are any snakeheads in the water, their eDNA will be detected and preventive measures can begin before their population increases.
Of course, this is not quite as easy as it sounds. “Fish share a lot of the same DNA, so you have to know what part is different,” says Ming Leung of Duke University. “On the other hand, one species can have many different genotypes [genetic variations among individuals].” Leung is currently gathering snakehead DNA and comparing it to other similar fish to find the unique genes. Once those genes are known, the information can be stored on a microchip and used by scientists to check gathered eDNA.
This genetic screening has already been used to gather information on Asian carp, another invasive fish that threatens to spread to the Great Lakes. Government agencies have managed to keep large numbers of carp out, thanks in part to speedy eDNA warnings in nearby areas. Leung hopes that it will be just as useful against snakeheads.