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Invasive Species

The introduction of invasive and non-native species can cause irreversible changes in the food web. Several invasive species of concern are listed below. For information on other invasive and non-native species, and to see a list of species prohibited from transport, visit To report the illegal transport or unauthorized introduction of invasive species, contact the Natural Resources Police—800-628-9944.


It is against Maryland, Virginia, and federal laws to possess, import, or transport live northern snakehead. If you catch a snakehead and want to keep it, you must immediately kill the fish. Anglers are encouraged to catch and keep snakeheads year round. There is no minimum size or creel limit for snakeheads. The Department of Natural Resources asks anglers to report snakeheads caught outside of the Potomac River and its tributaries or upstream of Great Falls. Send catch information to or call 410-260-8300 to help the department track the range of the species. If you catch a snakehead with a blue or red tag, please report the tag number and the location, date and time of day when the fish was caught to the U.S. Fish and Wildlife Service at 800-448-8322.

Blue and Flathead Catfish

Chesapeake Bay blue catfish and flathead catfish are invasive species that have spread rapidly throughout the Chesapeake Bay and its tributaries. These catfish have few natural predators, eat a wide variety of native fish and shellfish, and may cause ecological harm. It is illegal to release live invasive catfish into a waterbody different than where it was caught. This illegal act is punishable by a fine of up to $2,500. Anglers are encouraged to catch and keep blue and flathead catfish year round. There is no minimum size or creel limit for these catfish.

Zebra Mussels

Zebra mussels are an aggressive invasive species and reproduce at a very prolific rate, out-competing native species for needed resources. These mussels quickly overtake and cover all available areas to such an extent that they can clog water intake structures, boats, moorings, ropes, fishing lines, traps, and even dams and power plants. Zebra mussels are established from the Susquehanna River and Flats to the upper Bay. Additionally, The Department of Natural Resources recently confirmed the presence of zebra mussels in tributaries of the upper Western Shore near Middle River in Baltimore County. More information on zebra mussels is available at, including a fact sheet and reporting form. The department asks citizens, to report any suspected sightings to

Harvest an invasive fish and help Reduce the spread of invasive species

Questions on what gear is legal to harvest invasive species? Check out the gear tables in the Sport Fishing Regulations section on Freshwater Fishing Regulations and Saltwater Fishing Regulations.

There are two licenses available that let you sell invasive species caught in tidal waters. The Commercial Northern Snakehead License allows you to use either archery equipment or hook and line to harvest and sell Northern snakeheads.

The Invasive Catfish Finfish Trotline License allows you to use a finfish trotline to harvest and sell blue and flathead catfish. If you would like more information about these licenses, contact our Licensing and Registration Service at 410-260-3220.


  • Catfish, Blue — 84.0 lbs., Ed Jones, 8/13/2012, Near Fort Washington, Potomac River
  • Catfish, Flathead — 57.0 lbs., Joshua Dixon, 12/27/2020, Lapidum Boat Ramp, Susquehanna River
  • Northern Snakehead — 19.9 lbs., Andrew D. Fox, 5/24/2018, Indian Head, Mattawoman Creek

To view more state records visit or go to State Records.