Without Solid Science, Government Plans to Expand Cormorant-Killing Efforts

The Fish and Wildlife Service is considering a nationwide program to kill the fish-eating birds, which scientists say have been unfairly persecuted.

Among North American birds, the Double-crested Cormorant serves as a sort of Rorschach test. To some, the long-necked diving birds are an overabundant scourge. They eat about a pound of fish a day, which some commercial fish producers and recreational anglers see as a threat to their livelihood or pastime. And their acidic guano can damage everything from vegetation at nesting sites to rooftops where they roost, invoking the ire of coastal property owners and potentially harming both manmade structures and habitat for other birds. 

But many conservationists and bird lovers see the situation differently. To them, cormorants have long been unfairly maligned for doing exactly what they’ve evolved to do—eating fish. From this perspective, the birds are a native species that has been around since long before people introduced fish farms, sport fishing, and lake houses into their environment, and a conservation success story after their rebound from the devastating impacts of the insecticide DDT. Moreover, while cormorants can be an issue for aquaculture operations, there is no clear evidence linking them to declines in wild fish populations.

Federal policies have aimed to mollify the first group. Although the species is protected under the Migratory Bird Treaty Act (MBTA), culling programs have allowed freshwater aquaculture operators and wildlife agencies in parts of the country to kill cormorants by the hundreds of thousands to reduce their impacts, real or perceived, on farmed and wild fish. Federal courts, however, have agreed with the conservation camp that the government hasn’t done its due diligence to justify the killing or seriously considered non-lethal alternatives. 

Nevertheless, the U.S. Fish and Wildlife Service (FWS) is now considering what would be its most sweeping program yet to control cormorants—one that could expand the killing across all of the 48 contiguous states. Earlier this month, the agency announced a proposal that may involve expanding lethal control at fish farms and giving states authority to kill the birds when, where, and why they choose. While the agency is just beginning to accept public comment and hasn’t yet fully defined the program’s scope, experts describe the proposed expansion as troubling and unsupported by science. 

I am genuinely concerned that the changes in cormorant management that the FWS is now seeking put the Double-crested Cormorant at risk of unsustainable persecution the likes of which we haven’t seen in this country for over a century,” said Daniel Roby, a retired biologist who studied the birds with the U.S. Geological Survey and Oregon State University, in an email.

Linda Wires, a former FWS conservation biologist who has written a book about cormorant management, expresses similar concerns. “I think this latest proposal of the Fish and Wildlife Service is absurd,” she says. “There’s not much of a sense of wise ecosystem management going on with these kinds of plans.”

A History of Persecution 

To understand why the proposed program is so contentious, it helps to know what came before. In the 1990s, the nation's cormorant numbers were at an all-time high of about 360,000 breeding pairs, having rebounded as a result of their protection under the MBTA and the ban of toxic DDT, both in 1972. The aquaculture industry, meanwhile, had just experienced a decade of explosive growth. The easy pickings attracted cormorants, and fish farmers sought help from the government to address what they said were increasingly costly losses from the fish-eating birds. 

Hoping to ease these conflicts, the FWS in 1998 issued an aquaculture “depredation order,” which allowed fish farmers in 13 eastern and central states to kill cormorants without a permit. Aquaculture producers could now shoot an unlimited number of cormorants that were preying on, or about to prey on, their fish. Wildlife Services, part of the U.S. Department of Agriculture, could also kill the birds at roost sites near fish farms. On average, about 20,000 birds per year were killed under that order.

Recreational and commercial fishers, however, also claimed that cormorants were depleting populations of the wild fish they sought. So, in 2003, the FWS issued a separate “public resource” depredation order in 24 eastern and central states. That measure allowed state, tribal, and federal wildlife agencies to kill cormorants to protect wild fish populations and fish at government hatcheries, and to prevent nesting or roosting birds from degrading habitat. It authorized killing of the birds via “egg oiling (100% corn oil), egg and nest destruction, cervical dislocation, firearms, and CO2 asphyxiation.” That order led to an average of 22,000 cormorant deaths annually.

Some scientists and conservation groups thought the depredation orders went too far. The nonprofit Public Employees for Environmental Responsibility sued the FWS in 2014, arguing that the agency had renewed both orders without seriously considering non-lethal options, studying the impact on cormorant populations, or demonstrating that the orders were having their intended effect. At that point, about a half-million cormorants had been killed under the orders. A federal judge sided with the group in 2016, revoking the orders and directing the agency to conduct a new review of its cormorant program’s environmental impacts. 

The FWS completed that court-ordered environmental assessment in 2017, and determined it could issue individual permits to kill up to 51,571 cormorants a year at fish farms across a 37-state area without a significant impact on the bird’s population. In December, 2019, citing requests from permit holders, the agency announced it was increasing that total annual kill to 74,396 cormorants, which its models said still would not have a significant impact. Notably, the FWS decided those permits could not be used for protecting wild fish, citing a lack of evidence that killing cormorants would help. “The science to-date has limited examples demonstrating causality between the presence of cormorants as a sole or primary limiting factor for declines in free-swimming fish on a landscape level,” its assessment said

And yet, despite the 2017 report not finding a strong connection between cormorants and wild fish populations, the FWS has now proposed its most far-reaching program yet for killing the birds. The agency says it will not only consider creating a new aquaculture depredation order, but may also give the lower 48 states—not just those covered by the earlier orders—authority to kill cormorants for a range of reasons, including to protect wild fish. 

The FWS announced four webinars about the proposal on February 11 and 12, and will accept public comment through March 9. This initial stage of public input, called scoping, will be followed by further public comment periods as the agency puts forward a more formal plan.

The Catfish Farmers of America welcome the FWS proposal, says spokesman Chad Causey. Before pulling a trigger, aquaculture producers try everything else they can—scarecrows, pyrotechnics, inflatable arm-waving tube men—to keep cormorants away from their ponds, Causey says. “Honestly, it’s not an easy thing to take these birds by legal means,” he says. “Really you have to hunt these birds. And these folks don't want to hunt cormorants. They just want to farm fish.”

Nevertheless, the birds eventually get accustomed to non-lethal harassment, and sometimes killing them is the only option to protect farmed fish, he says. Citing a 20-year-old study, the FWS says cormorants cost the aquaculture industry $25 million a year. “It’s important to have good policies in place that protect both the species and farmers’ livelihoods,” Causey says. 

A Lack of Clear Evidence 

While shooting cormorants at fish farms certainly has its critics, it’s perhaps less controversial than doing so to protect free-swimming fish. Scientists assert that there is scant evidence for claims that cormorants have a significant impact on wild fish populations.

“I am confident that virtually all of the case studies of cormorant impacts on fish stocks of commercial or recreational importance fail to demonstrate the role of cormorant predation in limiting those fish stocks,” Roby says. “Killing cormorants was cathartic and satisfying, given that many of the other factors causing declines in fisheries were out of managers’ control,” he adds, citing dams, pollution, and aquatic invasive species among those factors. 

When asked if new studies or data have emerged to influence the FWS's decision to consider wild fish in the proposed new rule—thus contradicting the agency’s 2017 conclusion that cormorants aren’t a major factor in wild fish populations—a FWS spokesperson directed Audubon magazine to a document summarizing four invite-only, information-gathering meetings held in 2018 with state wildlife agencies, tribes, and other partners. However, meeting notes in that document seem to further call into question the scientific basis for the new proposal. “The data we have doesn’t show that Double-crested Cormorants are having a large impact on fish populations,” one participant from North Carolina said, per the meeting notes. “Have conducted diet studies on large public reservoirs, but can’t link diet to impacts on overall fish populations,” another from Texas commented. “We have long-term fish population data sets, but it’s been hard to link to double-crested cormorant factors vs other factors,” a Sioux tribal representative reported. “Have done diet studies for several years via fisheries,” a Vermont participant reported. “Trying to figure out how best to use all the data we have, but have been stymied at showing a cause-effect in regards to cormorants.”

One participant asked: “Is this more of an education issue to get anglers to realize that double-crested cormorants don’t impact as much as they think the birds are?” 

Even more worrisome to conservationists is that certain states where fish are big business have found lethal control a particularly alluring management option. For example, a 2015 map of areas that Oregon’s wildlife agency determined could not tolerate formation of new [cormorant] colonies or increases in active colonies” included almost all of the state, including its entire coast. That makes the prospect of delegating cormorant-killing authority to states “terrifying,” says Bob Sallinger, conservation director for Portland Audubon. “There is tremendous pressure and tremendous antagonism toward this species,” he says. “The minute the federal government relinquishes its control over killing of cormorants, you will see wholesale slaughter of cormorants in Oregon.” 

The recent FWS press release included members of Congress from states where lethal cormorant control has been aggressive. Rep. Jack Bergman (R-MI) called the proposed management program “a desperately needed next step for Michigan’s First District, where over-population is threatening the health of our free swimming and recreational fisheries.” And Rep. Bruce Westerman (R-AR) echoed the sentiment: “Science has consistently proven that managing cormorants is necessary to protect not just aquaculture but fishing as well.” Audubon asked the offices of both congressmen about the sources of the science underpinning their statements, but neither responded. 

The tone of the press release suggests that, despite just beginning to take public comment, the FWS has already made up its mind, says Stan Senner, vice president of bird conservation for the National Audubon Society.

“It’s sort of like, what’s the point of the scoping exercise if you already know what you’re going to do?” he says. “One of the tragedies of the day is that we have these birds that have managed to persist in the face of everything humans have done. They’ve managed to come back and thrive. So what do we do? We penalize them.”

Senner says he’s not opposed to government agencies making judicious use of lethal control of birds when necessary. “But what we’re seeing here with cormorants is a very weak scientific foundation to justify their actions,” he says. “We’re seeing the birds scapegoated because that’s the easy and convenient thing to do.