Invasive Blue Catfish Are Devouring Maryland’s Chesapeake Bay

CALIFORNIA, Md. — The Chesapeake Bay is renowned for its beautiful scenery and biological diversity of plants and animals. However, there’s a creature prowling the waters of Maryland’s aquatic systems threatening this biodiversity. Like many invasives, it’s not immediately apparent that it’s harmful or that it doesn’t belong, and most would assume it is just another harmless creature.

But they would assuredly be wrong.

Swimming on the sandy bottom of the Patuxent is a fish that swallows anything that it can fit in its mouth, lurking in search of its next victim. That creature is the blue catfish.

They may seem like harmless whiskered bottom-feeders, but have quickly become one of the most invasive threats to Maryland’s waterways and have grown into a dominant predator across the region. It feeds indiscriminately on native species such as blue crab, white perch, American eels, and essentially anything else it can fit into its mouth.

To put into perspective why this creature is such a threat, The BayNet reached out to the Department of Natural Resources. Branson Williams, a freshwater biologist with the Department of Natural Resources, is the invasive fishes program manager, and he spoke to The BayNet and explained the history of how it got into local waters, why people should be concerned and what efforts are being done to curb the dangers it poses.

History Of The Blue Catfish

As Williams explained, in the 1970s, blue catfish were taken from the mighty Midwestern river systems and their associated tributaries, such as the Missouri and Ohio, and stocked in Virginia waters, specifically its rivers, as the fish is primarily a freshwater species.

The intent was for recreational purposes; the blue catfish grows to large proportions, and so naturally there is a trophy aspect to them. In addition to being a prized game fish, they also make great table fare, with fried catfish being a staple in many households. At the time, it was thought that the fish would not leave the rivers they were stockpiled in, as the fish were believed to be intolerant to the salinity of the Chesapeake’s brackish waters.

Unfortunately, this was not the case — quite the opposite.

The fish proved hardier than expected, tolerant of brackish water, and with the aid of a few overly wet years, took the opportunity to expand. A little over a decade later, in 1987, the first blue catfish was detected in the Potomac, and by the year 2000, they had expanded into the Patuxent and made themselves welcome in Southern Maryland’s river systems.

“It was rare to catch a blue cat in the upper bay about a decade ago,” Williams said, “but now, people are catching 60- to 70-pound blue catfish regularly.”

When asked how many catfish were estimated to be in the area today, Williams said the numbers were equivocal at best, but based on estimations derived from commercial harvesting, in 2024, 4.7 million blue catfish were harvested; 3.5 million alone came from the Potomac River.

Why The Blue Catfish Is A Threat And Why We Should care

The big question hovering, however, is why. What about this fish is so dangerous? After all, it’s just a fish. So what if it eats a few natives here and there? No harm in that, right?

Well, as it turns out, it’s a pretty big deal culturally and economically.

Take the blue crab, for example — a staple food here not only for humans, but for a wide variety of fish, birds and other local animals. And though not endangered at the moment, its population has seen steep declines in recent years. This is in part due to climate change, underwater grasses disappearing, pollution and predation from invasives, aptly the blue catfish.

Using data as proof that blue catfish are a stressor on the beloved crustacean, a 2025 peer-reviewed study published in Marine and Coastal Fisheries found that blue catfish prey on blue crabs year-round in estuarine Chesapeake Bay habitats, with juvenile crabs most vulnerable. It’s estimated that hundreds of thousands of juvenile blue crabs are consumed annually by blue catfish in a single bay tributary.

In other words, blue catfish consume thousands of pounds of blue crab year-round, nonstop, and mostly prey on blue crabs that have yet to reproduce, causing even further irreparable damage.

In summary, the concern is the speed at which blue catfish are spreading throughout Maryland waterways and the rate at which they are consuming native animals and fish that people rely on for sustenance and economically. This affects many Maryland residents of all walks of life.

If this continues uninterrupted, it would also have a tumbling effect on the Chesapeake Bay ecosystem as a whole.

Other species that rely on the blue crab could also become endangered and disappear, further disrupting the ecosystem and causing economic harm, displacing other species of fish that fishermen and harvesters rely on and that residents of Maryland enjoy and eat.

The Chesapeake Bay is an important symbol of state and cultural identity and also an economically important resource that many enjoy. But if things such as blue catfish are allowed to continue disrupting the natural environment, it may not be around for long.

Imagine a Chesapeake Bay devoid of life — a myth of yesterday, told to future generations tomorrow.

If blue catfish continue to expand and grow throughout river systems and entrench themselves further, then one day the Chesapeake that people know and love may become a barren waterway.

What Can Be Done?

While eradication is unlikely, fisheries managers say public participation plays a key role in controlling blue catfish populations.

“People can help by purchasing blue catfish,” Williams said. “That supports processors and harvesters.”

Williams also encouraged recreational fishing, noting that the species’ culinary appeal has helped create demand.

“We’re fortunate that blue catfish taste good,” he said. “They’re a mild, white-fleshed fish, and there’s definitely a market for them. Supporting that market helps reduce biomass.”

Residents are also encouraged to report sightings through the Maryland Invasive Species Tracker, a web-based tool managed by the Department of Natural Resources.

“The most important thing is realizing it’s happening right in your backyard,” Williams said. “Once an invasive species becomes established, it’s very difficult to get rid of. The blue catfish is a cautionary tale.”

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