It's been four years since the northern snakehead (Channa argus) hit the big time in the Potomac River, and while the fish have continued to spread successfully, scientists have not as of yet found any adverse affects caused by the invasion. Could it be that the species will find a niche in the ecosystem with nary a negative impact? It's more likely that it will just be many years before the full effects on the Potomac are known. Either way, there's no realistic chance of eradicating the fish, so they're here to stay. National Geographic News has the full story.