Invasive Species

Whether introduced accidentally or on purpose, invasive species can cause harm to native plants and animals by encroaching on their food or habitat.

The invasive northern snakehead was first discovered in the Chesapeake Bay watershed in a Crofton, Maryland, pond in 2002. Use the map above to learn about additional snakehead sightings from 2014 to the present.

Invasive Species

There are more than 200 known or possible invasive species in the Chesapeake Bay watershed, competing with native plants and animals for food and habitat.


The number of invasive species that may live in the Chesapeake Bay watershed

Almost all of our major rivers are home to invasive fish. Scientists at Virginia Commonwealth University estimate between 94 and 111 million blue catfish live in the region's fresh and brackish waters, and the U.S. Fish and Wildlife Service has confirmed the presence of northern snakeheads in more than 120 river miles of the Potomac. Blue catfish and northern snakeheads are voracious predators, and scientists are particularly concerned about the former's impact on menhaden, blue crabs and other species that play an important role in our ecosystem and economy.

On land, the once pervasive nutria has been all but eradicated from marshes on the Delmarva Peninsula: while the semi-aquatic rodent has destroyed more than 7,000 acres of marshland at Blackwater National Wildlife Refuge since its introduction in 1943, their numbers have fallen from an estimated 50,000 in 1998 to a few hundred individuals. But the region's forests are facing threats from the southern pine beetle, whose burrowing behavior can kill a tree in less than four months. Rising temperatures and milder winters have allowed the insect to expand its range and damage forests in Maryland, Virginia, West Virginia, Delaware, Pennsylvania and New York.