Efforts to rein in the region’s escalating blue catfish population through an expanded fishery and other measures could face numerous obstacles, the greatest of which is a lack of basic information about the voracious predators, a new report says.

Nonnative blue and flathead catfish were introduced into Virginia tributaries in the late 1970s but have since exploded in numbers and spread to Maryland.

They are a top predator, and their rapid expansion has raised concerns that they could outcompete native species and also consume large numbers of shad, river herring, blue crabs and other species of concern to fishery managers.

In response, the Bay Program’s Sustainable Fisheries Goal Implementation Team created an Invasive Catfish Task Force, made up of biologists from state and federal agencies, which last spring suggested a variety of actions to control the invasive fish, which is native to the Mississippi basin.

Those recommendations included promoting a large commercial fishery, using electroshocking to harvest fish and targeting high-priority areas such as shad spawning grounds for extra control efforts.

Since then, efforts have proceeded to promote the commercial catch of blue catfish — including marketing the fish to consumers — and to experiment with techniques such as using electroshocking to harvest the invasive predator.

Now, a report from the Bay Program Scientific and Technical Advisory Committee commended the task force actions as a good first step, but said it was unclear whether those efforts would succeed in controlling blue catfish, primarily because of a lack of information.

For instance, it’s unclear exactly how large the blue catfish population is, or what amount of reduction is needed to reduce the fish’s threat to other species — and whether such a reduction is feasible. In some cases, the report cautioned, control efforts could actually exacerbate problems.

“You can go out and fish a species, but there can be a lot of unintended consequences, or it just might not work,” said Donna Bilkovic, a researcher with the Virginia Institute of Marine Science, and co-chair of the STAC review panel, which included six biologists with fisheries or invasive species experience.

The scientific review panel said a clear goal was needed for any fishery. Is it to maintain a sustainable fishery, or reduce blue catfish to the lowest feasible levels? Each of those goals would require different types of management, and if states do not agree on a single goal, problems could be exacerbated, the report cautioned.

“If this becomes a highly profitable fishery, then there is going to be a desire by many groups to maintain it at a certain level,” Bilkovic said. “But if it is maintained at that level, is the ecosystem still compromised? That is unknown.”

The ability of a fishery to control the blue catfish population could also be limited because of opposition to harvesting the largest, trophy-size fish in the population. Those fish are popular with recreational anglers, but also produce the greatest numbers of eggs, the report said. “It seems probable that the largest fish could effectively negate any gains made in the reduction of only smaller fish,” the report said.

If the commercial fishery proves to be lucrative, it said, it could also create a “perverse incentive” to move blue catfish into areas where they are not presently found. And the report cautioned that large fishing pressure on blue catfish could also have unintended consequences for non-target fish, who might also be caught as bycatch.

Another concern is that new sources of mortality introduced to a fish population often cause fish to grow, and reach maturity faster, said Tom Ihde, an ecological modeler with the National Oceanic and Atmospheric Administration, and also co-chair of the STAC review panel. “If that were to happen, we are in effect making the population produce more catfish,” he said.

Bruce Vogt, ecosystem science and synthesis manager for the NOAA Chesapeake Bay Office, and coordinator for the catfish task force report, agreed that recommendations in the task force report — now nearly a year old — need to be updated.

The STAC review “raised some good points, and we are going to revise our report accordingly,” he said.

Although commercial fishing interest has increased sharply over the last year, jurisdictions that manage the species — Maryland, Virginia, the Potomac River Fisheries Commission and the District of Columbia — do not have a common goal.

“If your goal is to remove all the blue catfish from the Bay with a fishery, that is a lot different than if you are going to manage the population through a fishery,” Vogt said. “I think there might be different perspectives on what the goal of the fishery is.”

Research is under way to address some concerns raised in the report, such as trying to estimate the size of the population, learn exactly what the fish eat, and discover their level of threat to other species. But, Vogt said, it would still likely be several years before scientists could identify a “safe” blue catfish level that would control impacts on other species.

Bilkovic and Ihde said nothing found in their review should halt the implementation of the task force’s recommended actions because those actions can provide important information. For instance, ongoing commercial fishing efforts could answer questions about whether gear used to catch blue catfish also catches large numbers of non-target fish.

The STAC review panel also endorsed the task force recommendation for increased monitoring of the size and distribution of the catfish population, but cautioned that managers needed to be cognizant that to be effective, such efforts will require maintained effort and expenditures.

It also endorsed the idea of a cross-jurisdictional review of blue catfish regulations, but warned that reaching agreements on changes would be difficult and would require input from all stakeholder groups. The scientific review panel said a key obstacle to effective management — which has been recognized by the task force — is a lack of agreement on what to do with trophy-size blue catfish.

Those fish, which can exceed 100 pounds, support economically important fisheries, but the largest catfish are also those with the greatest reproductive potential. “For management to succeed,” Bilkovic said, “you need to have all the stakeholders on board and kind of moving in the same direction.”

Toward that end, the review panel said a broader management plan should be developed for blue catfish, that not only contained the task force recommendations, but also research needs. Such a report should include input from stakeholders to help achieve consensus, and clearly identify actions that would be taken by each jurisdiction.

“Because there is so much that has to be done, we were concerned that it be done in the most efficient manner,” Ihde said “You can’t do that without a coordinated plan, especially in the Bay where you have so many jurisdictions with different ideas about how things should be managed.”