Invasive species are those plants and animals that have been introduced, whether accidentally or on purpose, into their current habitat. Invasive species can cause harm when they establish themselves at the expense of native plants and animals, encroaching on their food or habitat. Once an invasive species is established, it can be difficult or impossible to eradicate. Instead, habitat managers must focus on reducing its numbers or containing its range. Controlling invasive species takes time, money, cooperation and commitment, which is why it is crucial to prevent them from being introduced in the first place. There are more than 200 known or possible invasive species in the Chesapeake Bay watershed. Phragmites, mute swans, nutria and blue and flathead catfish are just four examples of invasive species that can be found in the region.
Phragmites (Phragmites australis)
Phragmites (Phragmites australis) is a perennial plant with feathery plumes at the top of tall, stiff stalks. Native to Europe and Asia, it grows in wetlands and along roadsides and shorelines throughout the Chesapeake Bay watershed. Phragmites were introduced to the United States in the 19th century when ships from Eurasia inadvertently carried phragmites seeds in their ballasts. While there is a type of phragmites that is native to the United States, it is very rare. Unlike many native wetland plants, phragmites is not a valuable food source for waterfowl.
Image courtesy Glen Darrud/Flickr
Mute Swan (Cygnus olor)
Mute Swan (Cygnus olor) is a large, white bird that lives on shallow waters throughout the Chesapeake Bay region. It is an invasive species and found year-round throughout the watershed. Mute swans eat bay grasses and puts out whole plants, including their roots and rhizomes. Originally native to Europe and Asia, it was introduced in the Bay region in 1962 when five mute swans escaped from an estate in Talbot County, Maryland. Mute swans can be confused with native tundra swans. You can distinguish a mute swan by its orange bill and gracefully curved neck. Also, mute swans live in the Bay region year-round, while tundra swans only visit in winter.
Image courtesy wabatson/Flickr
Nutria (Myocastor coypus)
Nutria (Myocastor coypus) are large, brown, semi-aquatic rodents that live in marshes and wetlands on the Delmarva Peninsula and other parts of the Chesapeake Bay watershed. They are native to South America (including Argentina, Bolivia, Chile, Paraguay, Uruguay and southern Brazil), and feed on the roots, rhizomes, tubers and young shoots of marsh plants by using their large front teeth and powerful feet to dig into the marsh. This causes significant erosion and damage to marshes. Nutria were eradicated from Blackwater National Wildlife Refuge on Maryland’s Eastern Shore in 2004 after contributing to alarming losses of marshes at the refuge.
Blue catfish (Ictalurus furcatus) and Flathead catfish (Pylodictis olivaris)
Blue catfish (Ictalurus furcatus) and flathead catfish (Pylodictis olivaris) can be found in almost every major tributary in the watershed. Native to the Mississippi, Missouri and Ohio River basins, blue catfish were introduced to the James, Rappahannock and York rivers in the 1970s and 1980s as a recreational catch. Flathead catfish were introduced to the James in the 1960s for the same reason. Both blue and flathead catfish have a long lifespan and an expansive diet, which can include crustaceans, worms and other fish. Their growing numbers and rapid expansion throughout the region have raised concern about their potential impact on menhaden, blue crabs and other native species that play an important role in our ecosystem and economy. In 2012, the Chesapeake Bay Program’s Sustainable Fisheries Goal Implementation Team adopted an Invasive Catfish Policy statement, which outlines the need to control the effects of these nonnative fish. The Goal Team’s Invasive Catfish Task Force hopes to manage their spread while keeping in mind their recreational value.