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NCBO-funded Research on Invasive Catfish

Initially introduced for sportfishing in several Virginia tributaries, blue and flathead catfish are considered invasive in the Chesapeake Bay. Since their introduction (blue in the 1970s and 1980s; flathead in the 1960s), their range and population have increased dramatically.

While prized as a recreational fishery, these fish are top predators in several river systems, and may be contributing to changes in the overall Chesapeake Bay ecosystem. In order to learn more about how these fish may be affecting the Bay, the NOAA Chesapeake Bay Office has funded several studies to take a closer look at the biology and feeding habits of these fish.

A project conducted by Virginia Commonwealth University researched what kinds—and how much—prey blue and flathead catfish consume, and how that may change throughout the year. The VCU researchers found that these catfish may contribute to substantial losses of key Bay fishery species including white perch, menhaden, and blue crabs. The researchers also developed recommendations on how the effects of invasive catfish might be mitigated, including the experimental use of electrofishing to increase commercial harvest.

Researchers at the Virginia Institute of Marine Science (VIMS) focused on whether contaminant burdens in blue catfish could pose a human health risk if people eat these fish. Like other larger fish that live for a relatively long time, blue catfish may “bioaccumulate” mercury and other contaminants to such levels that cause human health concerns. The VIMS researchers explored how much of these contaminants blue catfish bioaccumulated in the Potomac, Rappahannock, and James Rivers. The research found that contaminant levels in fish under 32 inches are under current consumption advisory levels.

Another team at VIMS quantified the growth of individual blue catfish by tracking the length of fish at different ages and how much fish of a given length weighed. Fish collected and measured in the Potomac, Rappahannock, York, and James Rivers had slightly different growth characteristics—but overall, they grew to be impressively long and heavy fish. The fish that were measured sometimes reached 13 inches by their fifth year and nearly 40 inches by their 17th or 18th year. Better understanding these rapid growth rates will help fishery managers asses and identify potential impacts blue and flathead catfish could have on the ecosystem as these fish quickly approach large sizes and apex predator status.

Two additional research projects are still under way:

  • VIMS research is estimating the population numbers of blue catfish in the James River, as well as their survival rates. They are doing this by tagging blue catfish and working with a waterman to track them when they are recaptured.
  • Researchers at the Smithsonian Environmental Research Center are investigating how blue catfish fit into the Chesapeake Bay’s food web, including cataloging undigested fish prey items from blue catfish stomachs. Work by SERC scientists to date has been conducted in the Patuxent, Nanticoke, Sassafras Rivers and Northeast/Swan Creek/Susquehanna Flats.

Results from this research are being used by the Chesapeake Bay Program’s Sustainable Fisheries Goal Implementation Team, which brings together resource managers and other experts from around the watershed to discuss topics related to fishery management in the context of the most up-to-date science. The Fisheries Goal Team has also convened an Invasive Catfish Task Force that has developed recommendations for dealing with these species. This is a living document that may be adapted as more is learned about these fish. The Fisheries Goal Team is working to implement these recommendations, which include:

  • Jurisdictions work together to design and implement removals of invasive catfish in places of significant ecological value.
  • Develop a large-scale commercial fishery for these species, coordinated across jurisdictions.
  • Consider options to incentivize increased harvest of invasive catfish by small-boat operations; explore the use of electrofishing for commercial harvest purposes.
  • Establish monitoring programs dedicated to identifying and tracking invasive catfish distributions and population status.
  • Consider the potential spread of invasive catfish when removing barriers to fish migration.
  • Conduct a review of current fishing policies and regulations across jurisdictions.
  • Make information on invasive catfish more accessible, consistent, and clearer to anglers and the general public.