Throughout Maryland’s waterways, there is a growing problem with non-native invasive species. As global trade and transportation has become a major facet in our everyday lives, the susceptibility of coastal areas, such as Maryland, to fall victim to harm from invasive species has increased significantly.
Executive Order 13112, which created the National Invasive Species Council, defines invasive species as “… an alien, or non-native, species whose introduction does, or is likely to cause economic or environmental harm or harm to human health.” Invasive species can range from microscopic plankton to mammals, reptiles and even fish, but regardless of size, they all can pose a serious threat to local ecosystems.
Invasive species are problematic because they can aggressively establish themselves very quickly after introduction, and often end up in direct competition with native species. Because of this, invasive species can quickly and dramatically alter natural habitats and displace native flora and fauna species. In the U.S. alone, 45 percent of species that are listed as rare, threatened or endangered are designated into this category in part due to invasive species.
Here in Maryland, we have a number of invasive species, including both plants and animals. Many have either traveled here from surrounding states or have been accidentally introduced, such as aquatic animals in ballast water or insect larvae in plant shipments.
The northern snakehead, Channa argus, is a native fish of the Yangtze River basin in China. It can grow to longer than 33 inches and tolerate a wide range of temperatures. While the snakehead prefers freshwater streams and rivers with some aquatic vegetation, they can also tolerate low salinity levels and even survive out of the water. Snakeheads have a simple labyrinth organ, which allows the fish to breathe in atmospheric air as opposed to dissolved oxygen in water. This lets the fish survive out of water for short periods or in water with low dissolved oxygen, which has aided it in spreading through the mid-Atlantic states.
The northern snakehead is a voracious predator of fishes, freshwater crustaceans and even amphibians. Because of its varied diet and aggressive feeding behavior, it could outcompete other native fish such as bass for food and habitat. Anglers are asked to take any snakeheads caught, regardless of size.
Some other non-native fish of concern in Maryland include the Blue and Flathead catfish. These are native to the Mississippi, Missouri and Ohio River basins and were introduced in Virginia between the 1960s-1980s. They have spread into major tidal tributaries in Maryland and can live 20 years or more. These catfish can grow to more than 100 pounds, feeding on fish and shellfish.
These invasive catfish prefer freshwater, buth thrive in brackish waters as well, which means they are a real threat to the Chesapeake and Coastal bays and their tributaries. Because of their large size, adults have few natural predators in our bays and can consume massive amounts of native fish and shellfish. Out of the two species, the Blue catfish is considered to be of more concern.
Nutria are large rodents that look similar to beavers except with long, thin tails. Nutria have thick brown fur, webbed feet and large front teeth, weighing up to 20 pounds and reaching 24 inches long. Nutria were introduced on purpose for their fur by settlers, but have had an extremely negative effect on marshes throughout the Chesapeake and Coastal bays watershed, especially Blackwater National Wildlife Refuge.
Nutria eat a wide variety of wetland plants, including Cordgrass, bulrush, cattails and other wetland species, and prefer the roots, rhizomes and tubers if available. Nutria will eat entire plants and will exploit wetlands in fresh, brackish and salt water.
On the Eastern Shore of Maryland, nutria currently pose the greatest threat to salt marshes throughout the Chesapeake and Coastal bays, including those in Dorchester, Wicomico, Somerset and Worcester counties. As nutria feed on wetland and marsh plants, they create patches of bare ground. This often leads to this loose sediment being lost from the marsh, resulting in channels and fragmented marsh segments.
It is of vital importance that we do our best to stop the introduction and spread of non-native invasive species, or there could be negative repercussions for local ecosystems and economies.
Harrison Jackson is the Coastal Stewards Coordinator for the Maryland Coastal Bays Program.