U.S. Geological Survey scientists from the Eastern Ecological Science Center (EESC) —Leetown Research Laboratory are sampling blue catfish in five locations of the Patuxent River to measure levels of per- and polyfluoroalkyl substances, or PFAS, in the blood of the invasive species. The EESC team led by Heather Walsh, Ph.D., works in partnership the Maryland Department of Natural Resources, who use electro-fishing to collect the blue catfish. The objective of the sampling is to determine if there are potential human health concerns for consumption or concerns for use of blue catfish as animal food or fertilizer.

The spread of blue catfish is a growing concern for scientists and fisheries managers. The invasive species is quickly becoming abundant in Maryland’s rivers and outcompeting native fish for food and habitat. Blue catfish are preying on blue crab, Atlantic menhaden, American eel, and other economically and ecologically important species.  

Recent efforts to reduce blue catfish populations include promoting them as a commercial fishery while highlighting the flaky and delicious nature of the fish’s white meat to consumers and restaurant owners. Additionally, Maryland state officials have proposed adding blue catfish to the menus of state institutions such as hospitals, public schools, universities, and prisons. Other proposed efforts to reduce blue catfish abundance include composting them as fertilizer for crops or as food for zoo animals.  

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PFAS are an emerging and ubiquitous contaminant associated with human and wildlife health effects such as an increased risk of cancer, immunosuppression, fatty liver disease, and reproductive, thyroid, behavioral, and developmental effects. Wild-caught, freshwater fish have been identified as a source of PFAS exposure to humans. 

To date, the Maryland Department of the Environment has tested blue catfish muscle for PFAS in a limited number of waterbodies in Maryland and levels of PFAS in catfish blood is unknown. Understanding levels of PFAS in the blood and other tissues will be important to determine if blue catfish are safe to use for the proposed alternative uses that may use whole fish.

Dr. Walsh’s team sampled 10 blue catfish per location to collect blood samples to be analyzed in EESC’s dedicated PFAS Lab in Kearneysville, WV. The team is also leveraging this effort to collect samples (visible abnormalities, plasma, gills, liver, kidney etc.) for potential associated fish health effects. Results are expected approximately six months after sampling.