Monster blues like this 75-pounder might be only half grown! The record is over 140 pounds. (Capt. Brian Barton)
Blue catfish are a much-sought native North American species found in millions of acres of natural habitat across the heartland of the nation. But even a native can become an invasive when it winds up in the wrong place.
Maryland and Virginia are voicing alarms over the incredible multiplication of blue cats in the upper reaches and the tributary rivers of Chesapeake Bay, the 41 million acre coastal sea that is one of the nation’s leading suppliers of seafood as well as hatchery for most of the striped bass that spread all along the Atlantic Coast.
The spread of blue catfish is a growing concern for scientists and fisheries managers. The invasive species is quickly becoming abundant in coastal rivers and outcompeting native fish for food and habitat. Scientists say the blue cats are preying on blue crab, menhaden, American eel, and other economically and ecologically important species.
There isn’t extensive monitoring data on how many blue catfish are in the waters here now, but Branson Williams, the invasive fishes program manager at the Maryland Department of Natural Resources, said looking at harvest data can be a good indication of how much the population has expanded.
In the Potomac River and Maryland waters, commercial landings of blue catfish skyrocketed from 609,525 pounds in 2013 to 4.2 million pounds in 2023, an increase of more than 500%.
In the Potomac River and Maryland waters, commercial landings of blue catfish skyrocketed from 609,525 pounds in 2013 to 4.2 million pounds in 2023, an increase of more than 500%. (Maryland DNR)
Commercial landings of blue catfish from Maryland waters and the Potomac, starting in 2012, the first year when blue catfish were differentiated in the overall harvest numbers.
Looking at Virginia rivers, where blue catfish became established a few decades earlier, also gives a sense of the scale of the issue.
In portions of the James and Rappahannock rivers, surveys have found blue catfish making up 75% of the total fish biomass—or 3 out of every 4 pounds of fish. Williams noted that survey work in Maryland’s upper Patuxent River has found more than 500 fish per hectare. A hectare is about 2.5 acres. So, say 200 blue catfish per acre—catfish soup.
With the severity of the problem, blue cats have quickly shot up as a priority among Maryland’s big three invasives, which include northern snakehead and flathead catfish, and are a focus for increasing management efforts and targeted fishing in order to contain the fish.
How did they get here? Oddly enough, state fishery managers put them there in an effort to improve fisheries. From 1974 to 1985, the Virginia Department of Game and Inland Fisheries (now the Department of Wildlife Resources) released more than 300,000 juvenile blue catfish into waters of the commonwealth, first into the James and Rappahannock rivers, followed by additional stockings in the York River 11 years later.
Here's what a 100-pound catfish from the Tennessee River looks like. Even bigger ones may be swimming in Chesapeake tributaries in a few years. (Capt. Mike Mitchell)
Though biologists at the time believed the salty Chesapeake Bay would serve as a barrier for the freshwater fish. They would populate the stocked rivers, but couldn’t get to any of the others that ran into the bay due to the salt barrier.
The catfish proved otherwise. The catfish quickly began spreading from river to river northward around the bay. By the late 1980s, they had arrived in the Potomac. By the 2000s, they became abundant in that river and reached the Nanticoke and Patuxent rivers. DNR scientists believe the wet years of 2018 and 2019 enabled them to spread throughout the upper Bay.
Now, they’re in every major river in Maryland—and often at high densities. One large factor in their favor is their physical size. Blue cats are the largest North American catfish and among the largest freshwater fish. They can grow to be 5 feet long and top 100 pounds. An angler in 2011 caught the world record blue catfish at143 pounds—reeled in on a lake in their introduced range in Virginia. The current Maryland record is an 84-pounder caught on the Potomac River in 2012. Fifteen pounders are just average sized—and a catfish that big can gulp down a whole lot of crabs, shrimp and young sportfish.
They grow fast because they eat just about anything, and they are fast moving predators rather than strictly bottom feeders like some in the catfish family. A 2018 study on the stomach contents found that James River blues consumed 80 different species, from fish and mollusks to birds and turtles. DNR monitoring on the Patuxent River has found blue catfish to eat about 40 species—as well as rocks, chicken bones, a doll arm, an entire 16-ounce Coke bottle and electronic parts—they are sort of the tiger sharks of fresh water.
It’s clearly way too late to shut the gate on blue catfish in Chesapeake Bay tributaries. Hopefully, enough anglers and commercial fishermen will take advantage of the new resource to keep them somewhat in balance with the other species there, as they are in their natural habitat.
But the result of the improvident stocking in the 70’s and 80’s remains a cautionary tale for all fishery managers, most of whom now won’t even think of stocking non-native fish into healthy fishery habitats.
— Frank Sargeant
Frankmako1@gmail.com
