Snakeheads, nutria among unwelcome critters

Throughout Maryland’s waterways, there is a growing problem with non-native invasive species. As global trade and transportation have become major facets in our everyday lives, the susceptibility of coastal areas such as Maryland to fall victim to harm from invasive species has increased significantly.

The Maryland Department of Natural Resources defines an invasive species as showing tremendous capacity for reproduction and distribution throughout its new home and having a negative impact on environmental, economic, or public welfare priorities.

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 in this category in part due to invasive species.

In Maryland, we have a number of invasive species that include both plants and animals. Many have traveled here from surrounding states or have been introduced accidentally – or on purpose. Some are hitchhikers in the ballast of ocean-going vessels such as the zebra mussel.

Others were intentionally introduced, such as the European starling for its beautiful feathers or the European carp for its sought after sport fish characteristics.

One fish species that was brought to the United States for its food quality but managed to escape into our waterways is the northern snakehead fish. The northern snakehead is a native fish of the Yangtze River basin in China. It can grow to lengths 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 amphibians. Because of its varied diet and aggressive feeding behavior, it can out-compete other native fish such as bass for food and habitat.

Anglers are asked to take any snakeheads caught, regardless of size.

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 and 1980s.

They have spread into major tidal tributaries in the Chesapeake Bay 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, but 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 and can consume massive amounts of native fish and shellfish.

Of of the two species, the blue catfish is considered to be of more concern. Anglers are asked to remove any of these catfish if caught.

A mammal of concern for its invasive potential is the nutria.

These large rodents look similar to beavers except they have long, thin tails, which has little resemblance to a flat beaver tail. Nutria have thick brown fur, webbed feet and large front teeth, weigh up to 20 pounds and may reach 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 watersheds, especially in 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 waters.

On the Eastern Shore of Maryland, nutria 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 loose sediment being lost from the marsh, resulting in channels and fragmented marsh segments. Through the Chesapeake Bay Nutria Eradication Project, all known nutria populations have been removed from over a quarter million acres on the Delmarva Peninsula.

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 former Education Coordinator for Maryland Coastal Bays Program and current graduate student at Clemson University.

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NOTEWORTHY INVASIVE SPECIES IN THE CHESAPEAKE

Blue catfish

Flathead catfish

Nutria

Snakehead fish

Zebra mussel