Chicago has long been characterized as the last line of defense in the war to prevent bighead and silver carp from reaching the Great Lakes. But as efforts ramp up, another little-discussed species of Asian carp is already spawning in the region and could become the first to be established.
Illinois and the U.S. Army Corps of Engineers have moved closer to constructing a channel at the Brandon Road Lock and Dam near Joliet that features a suite of deterrents, including a sound barrier and bubble curtain, intended to impede ravenous bighead and silver carp from wending up the Illinois River and into Lake Michigan.
Illinois state representatives are set to host a roundtable next month in Chicago with staff representing other Great Lakes states to discuss project costs, now estimated at nearly $831 million. Though construction is not expected to be complete until 2028, pending funding from Congress, the Illinois Department of Natural Resources has reported that the leading edge of the silver and bighead population has been contained to a section of the Illinois River 47 miles downstream of Lake Michigan for over a decade.
But grass carp, a third variety of Asian carp, has already been found in the lower four Great Lakes, and recent evidence suggests it is spawning in Lake Erie.
The gluttonous herbivore, imported to control unwanted vegetation and algae in private ponds and golf course water hazards, has been found in Lake Erie since the 1980s. For years, commercial fishermen and fishery managers assumed the grass carp were sterilized, as many states require by law. However, of the 53 grass carp captured in Michigan and Ohio’s waters between April 2014 and June 2016, 85% were determined to be fertile. Newly hatched grass carp and fertilized eggs have been recovered, all but confirming the species is reproducing.
“Any more than zero grass carp (found in the Great Lakes) is enough to get people’s attention,” said Marc Gaden, director of communications and legislative liaison for the Great Lakes Fishery Commission. “What we don’t know is whether we’re seeing more signs of reproduction because we’re looking, or if it’s because we’re on the leading edge of an invasion.”
‘Cows of the fish world’
At a recent meeting among U.S. and Canadian environmental agencies, the U.S. Fish and Wildlife Service said 20 grass carp were captured earlier this month in the Sandusky River near Toledo, half of which were fertile. Meanwhile, in the Chicago River system, a routine search for bighead and silver carp this month yielded two grass carp in Lake Calumet, an embayment a mere 6 miles away from Lake Michigan on the city’s Far South Side.
Experts believe the fallout from a sustainable grass carp population could be dire for dwindling Great Lakes wetlands. Today, less than 50% of the historical coastal wetlands in the Great Lakes basin still exist. The remaining 500,000 acres are threatened by pollution, development and invasive species.
Unlike silver and bighead carp that scientists say would compete directly with Great Lakes fish for food, grass carp eat vegetation that provides vital habitat for the region’s waterfowl and protection for some species of juvenile fish, frogs and snails.
“I have seen places where you get a flood and grass carp will mow down a line of vegetation, or you actually can see where they nibbled on the trees that have been flooded,” said Kevin Irons, the manager for the aquatic nuisance species program at the Illinois DNR. “They are the cows of the fish world.”
Grass carp grazing not only would deliver a blow to fishermen, bird-watchers and duck hunters, it also would harm beaches and coastal areas. Shoreline erosion could increase without the roots of wetland plants holding them in place. Grass carp feces may also deteriorate water quality and nourish toxic, nuisance algae known to befoul beaches and kill birds.
Without further efforts to remove grass carp, the socioeconomic costs to commercial and recreational fishing in the Great Lakes in the United States alone would be around $15.3 billion over a 40-year period, according to a binational risk assessment of grass carp led by Fisheries and Oceans Canada.
Some Great Lakes states — Illinois, Indiana, Ohio, Pennsylvania and New York — still allow grass carp to be imported, so long as fertilized eggs are sterilized through drastic changes in temperature or pressure. Others — Minnesota, Wisconsin, Michigan — prohibit grass carp from being imported altogether, as does Ontario, Canada.
“This seems like a terrible idea,” said Molly Flanagan, vice president of policy at the Chicago-based nonprofit Alliance for the Great Lakes. “It seems like all states should ban possession of grass carp. We know they pose a threat to the Great Lakes. We know you can’t tell by looking at the fish whether it’s sterile or fertile. So why would we allow anyone to possess this fish? It doesn’t make any sense.”
“You have some very conflicting regulatory approaches,” said Greg Conover, a Mississippi River basin coordinator for the U.S. Fish and Wildlife Service. “But businesses have gotten very good at developing (sterile) grass carp. In most cases the largest producers are in Arkansas, and they regularly produce (sterile) grass carp in the 98%-plus range.”
Grass carp in Lake Calumet
While government agencies don’t consider grass carp to be established in the Great Lakes, in part because of their low abundance, risk assessments by Canada say that if no action is taken, it’s “very likely” the presence of spawning will translate into a sustainable population in Lake Erie, beyond which there are no barriers to deter its spread upstream. A newly formed “strike team” has been tasked with trying to eradicate grass carp in the western basin of Lake Erie, a watershed roughly the size of Maryland.
A summary of the risk assessment by Fisheries and Oceans Canada describes the Chicago-area waterways as “the most likely entry point” for grass carp as sampling efforts there resulted in collection of more than 70 grass carp above the electric barrier between 2010 and 2014. At least two grass carp have been collected from the southern portion of Lake Michigan: one near Navy Pier in 1990 and one near the Port of Indiana in Burns Harbor in 2014.
In the Chicago area, golf courses upstream from the Army Corps of Engineers electric barriers near Romeoville stock sterilized grass carp, according to Irons, who acknowledged there is no response plan for grass carp — fertile or sterile — found in Chicago-area waterways.
On June 7, a 32-pound grass carp was found in Lake Calumet. The U.S. Geological Survey database on non-native species says the fish “probably” was sterile, but the “test was not clear.” A sterile 35-pound grass carp was captured a week later near the same location.
Only days earlier, a response team formed by the states of Michigan and Ohio, the U.S. Fish and Wildlife Service and the University of Toledo conducted a sweep of the Sandusky River by employing nets and using electric current to stun and attract fish, collecting 20 grass carp, half of which were fertile. However, while these techniques can be effective in rivers and bays, the open waters could be more challenging, especially with limited resources.
Michigan State University’s Department of Fisheries and Wildlife has attempted to help Michigan and Ohio fishery managers track the movement and abundance of grass carp. Researchers tagged and released grass carp — fertile and sterile — in Michigan and Ohio waters to better understand their migration. To date, scientists can’t be sure if grass carp in Lake Huron may have made their way there from lakes Erie or Michigan.
If grass carp are swimming considerable distances, the extent of potential spawning areas could be greater than once thought.
“There has been a lot of movement of fish in the western basin, going to the eastern basin and then returning,” said Scott Koproski of the U.S. Fish and Wildlife Service. “There’s been a few examples of individuals that have moved up the St. Clair River system through the Port Huron area and subsequently back down.”
So far, experts say migration has been limited, and Lake Erie remains the only known location where grass carp are spawning. But research suggests they may have staying power.
Young grass carp can tolerate near-freezing water temperatures and withstand oppressive heat (up to 100 degrees), flourishing in the warm aquaculture ponds of Vietnam in addition to the species’ native Amur River at the China-Siberia border. Here, only parts of northern Lake Superior may be too cold. There’s enough food in the Great Lakes watershed to sustain them over winter. Fisheries and Oceans Canada says there are 57 rivers in the Great Lakes basin that could provide suitable spawning habitat. And the fish, which has proved capable of growing to nearly 100 pounds, would have few predators capable of devouring it.
To environmentalists, the early grass carp invasion is a reminder of what happened with the eel-like sea lamprey, the parasitic fish responsible for crashing the native lake trout population. While their population has been reduced 90%, the sea lamprey control program costs about $16 million each year.
For Flanagan, of the Alliance for the Great Lakes, there is no better allegory on why prevention efforts, such as Brandon Road, can be cheaper than removal efforts.
“That’s why preventing invasive species from getting into the Great Lakes is so important,” she said. “And I think that’s why you see so much tension on bighead and silver carp, because they are not in the Great Lakes yet. We know they would have devastating impacts on the economy and environment. So spending the money and time to implement the protection at Brandon Road makes a lot more sense than the amount of money we would have to spend forever if bighead and silver carp got into the Great Lakes.”