It’s well documented that the invasive blue catfish is a nuisance within the Chesapeake Bay ecosystem. Native to the Mississippi, Missouri and Ohio river drainages, blue catfish were introduced to the Bay watershed in the 1970’s and these menaces have patrolled the Bay and its tributaries ever since. As a large, ravenous fish with few predators and exponentially growing populations, blue catfish devour many native species like shad, menhaden and the Chesapeake Bay’s beloved blue crab.
As if we needed another reason to dislike the blue cat, research also shows that the fish’s size and gluttonous eating habits cause it to consume higher amounts of toxic chemicals called polychlorinated biphenyls or PCBs when in contaminated waters.
This means that if you’re fishing for blue catfish in the Bay—whether that’s for environmental reasons or because it’s all you’re catching—you should be mindful of the size of the fish, how you’re preparing the meat and how often you are eating it.
How PCBs accumulate in blue catfish
PCBs are synthetic chemicals that were created to manufacture products like transformers, caulk and fluorescent light ballasts. These chemicals are hydrophobic so when they run off into water bodies, they do not dissolve easily. Instead, they attach to sediments, sink to the Bay floor and remain there indefinitely; that is, until a process called biomagnification occurs where these chemicals are consumed by benthic communities (organisms that live at the bottom of the Bay) and travel up the food chain.
While PCBs were banned in 1979, the contaminants still had 50 years to weave themselves into the Bay ecosystem—and they continue to be used in enclosed electrical equipment under carefully controlled conditions. As of 2020, 78% of the Chesapeake Bay’s tidal segments were partially or fully impaired by PCBs.
In both animals and humans, PCBs affect immune, reproductive and endocrine system health. Without a complete purge of production and with decades of PCBs still present in our ecosystems, these chemicals continue to infiltrate food chains and pose risk to people who eat fish.
The blue catfish is a prime example of wildlife that can be easily contaminated by PCBs. As the invasive fish moves throughout the Bay, eating, growing and outliving many other species, it continues to accumulate PCBs in its fat tissue. People who catch and eat blue catfish on the Chesapeake Bay are therefore at risk. But that risk can be reduced by taking proper precautions.
When is it safe to eat blue catfish?
With a widespread presence of PCBs throughout the Chesapeake Bay, it's important to understand the guidelines around what you should and shouldn’t eat.
In Maryland, the Maryland Department of the Environmental (MDE) provides a blue catfish advisory that takes into account where the fish was caught, its size and who is eating it. In the Middle River, the general population is recommended to eat no more than four meals a month from a blue catfish measuring 15-24 inches, with a serving of eight ounces. In the same river, women are advised to have only three meals a month, and children (up to age six) are advised to have only two meals a month with a serving of three ounces. In tributaries such as the Choptank River, there are no limits for blue catfish measuring 15-24 inches for adults, but children are recommended to only have five meals a month.
These recommendations assume that people are removing the fat of the blue catfish before they eat them, which is where a substantial portion of contaminants are stored. It’s also recommended that if you eat the maximum monthly amount of blue catfish in a specific river, that you don’t eat any other additional fish from that river.
“As more work is done, we expect to include advisories for additional locations and size ranges,” says Amy Laliberte, an environmental health specialist with the Maryland Department of the Environment.
Similar advisories exist for Virginia and the District of Columbia. In the Anacostia, regardless of blue catfish size and whether the fat has been removed, it is recommended to avoid any consumption for men, women and children. In the Potomac, blue catfish greater than 30 inches should be avoided by all groups unless the fat is removed. If removed, the general population and women are permitted two meals per month and children are permitted one.
Besides following local advisories, there are many things you can do when cooking blue catfish that can help reduce your risk of consuming PCBs.
One is being able to identify fatty portions of the fish and learn the proper way to remove them. Catfish have fat on their back, sides and belly. These areas should be carefully cut and trimmed to remove contaminated fat. When preparing catfish, broil, grill or bake the fish on a rack and avoid breading and batter so that any excess fat can drip off.
What is being done to remove PCBs?
There are a number of practices in place across the watershed to reduce the level of PCBs in the water. In some instances, state agencies will remove contaminated sediment and treat it for PCBs before placing it back in waterways. There are also efforts to remove PCBs from fields near industrial sites where there is known to be higher levels. Wastewater treatment plants are also used to remove PCBs from wastewater before discharging it into the Bay.
The Clean Water Act requires each water body that is contaminated by PCBs to have a pollution management strategy known as a Total Maximum Daily Load (TMDL). The towns and municipalities that have a TMDL for PCBs have a goal to keep the contaminants out of their water. While this provides hope for a future of a PCB-free Bay and safe-to-eat blue catfish, there are many contaminated waterways that have no TMDL in place.
“When there is a TMDL in place, we want to be smart, efficient and effective in helping them be the best they can be,” explains Greg Allen, environmental scientist with the Environmental Protection Agency’s Chesapeake Bay Program Office and chair of the Toxic Contaminants Workgroup. “Where there are none [TMDLs] planned, we’re asking why not? How do we get capacity where we can address those?”
The Chesapeake Bay Program’s Toxic Contaminants Workgroup is dedicated to reducing chemical contaminants in the Chesapeake Bay watershed. One of the workgroup’s focuses is preventing PCBs and other chemicals from entering our waterways in the first place, and coordinating with different jurisdictions and industries to phase out technology that still contains PCBs.
PCB accumulation in blue catfish is a complex and multifaceted issue but luckily, a wide variety of partners are advocating and working towards a healthy, PCB-free Bay. Until then, we must remain educated and aware of toxic chemicals that we may not see, but are all around us.