Blue catfish, the invasive fish with a big appetite that is overwhelming many Chesapeake Bay tributaries, is probably here to stay.
But a new management plan says that with coordinated action — including ramped-up efforts to get people to develop an appetite for them — states can help limit their ecological harm.
The state-federal Bay Program recently released an Invasive Catfish Management Strategy, which represents the first Baywide effort to coordinate actions for dealing with the fish.
Blue catfish are a native of the Mississippi River basin but were introduced in Virginia’s Bay tributaries in the 1970s and 1980s to help build a recreational fishery.
For nearly two decades, they persisted without much notice. But in the mid-1990s, their numbers surged as the species proved surprisingly adaptable to the region’s nutrient-rich tidal rivers.
In recent years, they have spread to the Potomac River and Maryland’s Western Shore tributaries, as well as some on the Eastern Shore.
Because of their huge numbers, long lifespan, large sizes and voracious appetites, scientists have worried that blue catfish have the ability to upend river ecosystems, harming populations of native fish like American shad and potentially even blue crabs.
There’s been little consensus about what to do about them, though. Some have advocated trying to eradicate them, but they are enormously popular with anglers. In the James River, surveys have shown as much as 40% of the recreational fishing effort is aimed at blue catfish.
The new strategy, approved by fisheries agencies in each state around the Bay, tries to balance those competing aims.
It says plans should ultimately be developed for each major Bay tributary, because management goals and the level of threat is not the same everywhere. Studies have found that the population density, growth rate and diet of blue catfish can be dramatically different from place to place.
For instance, in the James River their diet switches from primarily vegetation and invertebrates to mostly fish when they reach 20 inches. In the Mattaponi and Pamunkey rivers, that doesn’t occur until the fish are almost 36 inches.
The tributary approach tacitly acknowledges that the invader will never be eradicated from the Bay. In some places, like the James River, management would likely focus on promoting a robust recreational fishery.
But in other tributaries, where their populations are small, biologists may pursue more aggressive actions to control their numbers and protect other species.
“Maybe eradication would still be possible in some of the tributaries where they aren’t quite established,” said Mandy Bromilow, a fisheries specialist with the National Oceanic and Atmospheric Administration Chesapeake Bay Office, who coordinated the effort to develop the plan. “But someplace like the James where we’re seeing insane densities of the catfish, maybe that’s not quite possible.”
One common thread throughout the strategy is to launch education efforts that warn people about the threats caused by invasive species. Those efforts would also encourage people, including anglers, to eat blue catfish, rather than tossing them back into a river.
The strategy promotes eating more blue catfish, before they can eat too many native species, as part of the solution.
“We want to bring awareness to the tastiness of this fish,” Bromilow said. “People have this misconception about catfish being this dirty bottom feeder — like ‘who would want to eat that?’ But that’s not really the case.”
Similarly, the strategy calls for trying to build commercial markets for the fish.
Large numbers are already being harvested. About 2.8 million pounds of blue catfish were netted in the Potomac River in 2018, and commercial catches in the James have been averaging about 1 million pounds in recent years, according to the strategy.
But more would need to be caught to make a significant dent in the population, which would require building a bigger consumer market.
Efforts to expand the blue catfish market have been constrained in part by a provision in the 2014 Farm Bill that requires the U.S. Department of Agriculture to inspect catfish before they can be processed and sold. That’s created a processing bottleneck, as harvests often take place at times when inspectors are not available.
The strategy calls for trying to exempt the Bay from the processing requirement, and for developing an economic impact analysis to support their case.
Still, even if harvests are increased, biologists don’t know how many catfish would need to be removed to reduce potential ecological impact. The strategy cites improved tributary-based population estimates, along with improved ecosystem modeling, as a key research need to support management decisions.
Another research priority is trying to piece together a more complete picture of their actual ecosystem impact. There is evidence they are outcompeting native white catfish for habitat. But it is unknown whether they are eating enough other fish to cause problems, which may vary from place to place.
“Blue catfish are feeding on species that we would consider to be of conservation concern — things like river herrings, blue crabs, American eels,” Bromilow said. “It’s just a question of whether they are really eating so much that it’s going to significantly affect their populations. That’s something where we need more data.”
One thing the plan envisions is developing a scorecard or indicator for each river that estimates the status of blue catfish or the risk of invasion if blue catfish have not arrived. If at-risk tributaries are identified, monitoring efforts could be ramped up so that if the invaders are detected, removal might be possible before they become established.