Invasive Blue and Flathead Catfish Threat to Bay Ecosystems

The Sustainable Fisheries Goal Implementation Team of the Chesapeake Bay Program (CBP Fisheries Team) recently agreed on the need to manage blue and flathead catfish. These invasive species have been shown in other regions to pose a significant threat to important native species. In the Chesapeake Bay region, blue and flathead catfish may harm species such as American shad and blueback herring in rivers from Virginia to Pennsylvania. The CBP Fisheries Team will work to develop bay-wide management actions for blue and flathead catfish based on existing and new science.

Although valuable as a recreational fishery, blue and flathead catfish are problematic for several reasons. Both have the ability to grow to a large size – the world record blue catfish, caught in Virginia waters, is 143 pounds. They eat a varied diet including crustaceans, worms, other fish, and even each other. The number of invasive catfish is also a concern. Results from electrofishing sampling indicate that blue catfish represent up to 75 percent of the total fish biomass in portions of the tidal James and Rappahannock rivers, where they may be competing with native fishes and other ecologically and economically important living resources for available food. These characteristics make blue and flathead catfish “apex predators”—at the very top of the food chain—and may negatively affect native fish and their habitats. Finally, their long life span amplifies their possible long-term impacts on a given river’s ecosystem.

Although they are usually found in freshwater, these catfish can tolerate saltwater. Both species have been present in Virginia rivers since the 1960s and 1970s. In recent years they have been found in the Potomac River, Susquehanna River, and other upper Chesapeake Bay areas in Maryland. The spread of these fish may in part be due to people moving fish from one tributary to another, even though this is illegal in Maryland and Virginia.

All of these factors led the diverse CBP Fisheries Team, which includes experts from the Virginia Department of Game and Inland Fisheries, Virginia Marine Resources Commission, Potomac River Fisheries Commission, D.C. Department of the Environment, Maryland Department of Natural Resources, Atlantic States Marine Fisheries Commission, and the National Oceanic and Atmospheric Administration, to decide these catfish need to be managed.

The recently signed "Invasive Catfish Policy Adoption Statement" outlines the need to control and lessen the effects of these invasive, non-native fish on Bay tributaries and includes different perspectives such as those of recreational and commercial fishermen who have come to enjoy the sport of catching blue catfish. Actions to be considered include examining methods to reduce the high numbers of these fish and ways to limit their expansion into new rivers and evaluating the possible negative ecological impacts.

An invasive species is defined as a “non-native species that does or is likely to cause economic or environmental harm or harm to human health.” Additionally, it is one that “may prey upon, displace or otherwise harm native species, or alter ecosystem.”