Plenty to Carp About

Trying to hold the line against a big, hungry fish that would thrive in our ever-warmer waters

By Alex Roslin
May/June 2010

A highly invasive fish that could devastate the Great Lakes ecosystem has penetrated into Lake Michigan for the first time, and fish biologists say climate change will likely exacerbate its onslaught.
“It’s a potential knockout blow for the Great Lakes,” says Scott Parker, a Parks Canada biologist who monitors invasive species at the Fathom Five National Marine Park in Georgian Bay. “They’ll dominate (native species) and have a huge impact.”
The notorious Asian carp, a voracious plankton-eater sometimes called the aquatic vacuum cleaner, grows to 45 kilograms and consumes up to 40 per cent of its weight daily. It has already decimated the ecosystems of the Mississippi and Illinois rivers and their once-diverse fisheries. Carp, which are virtually worthless commercially, now make up 90 per cent of the fish caught in those rivers.
While a live Asian carp has yet to be found in Lake Michigan, a test used to detect the species’ DNA in water indicates a live fish was very likely present in the immediate area, says Jennifer Nalbone, an invasive species specialist at Great Lakes United, a joint Canada-U.S. environmental group. This despite the fact that American authorities put up an underwater electric barrier in April 2009 in the Chicago Sanitary and Ship Canal, the only link between the carp-infested Mississippi River and the Great Lakes, to prevent the species from reaching the Great Lakes.
Carp DNA was first detected beyond the barrier in August. In subsequent months, more of it was found further down the canal and in two rivers that drain into Lake Michigan. This past January, the DNA was detected in Chicago’s Calumet Harbor in the lake itself. [See the carp's progress on this map.]
The discoveries have set off panic among Canadian and U.S. fish scientists, environmentalists and the $7-billion Great Lakes fishery. In mid-February, the White House hosted a summit on ways to stop the carp invasion. And Michigan and Ontario authorities have gone to court to get the state of Illinois to block the canal. Illinois opposes the idea, saying it would hurt the state’s economy.
“The DNA evidence has certainly raised the sense of urgency,” says Nalbone, who faults authorities for not moving quickly enough and calls for a “very aggressive monitoring and eradication plan.”
Asian carp—a term that encompasses several invasive species of the fish such as bighead and silver carp—were imported to control nuisance algae in the southern states, but escaped into the Mississippi River during floods.
Apart from displacing native fish, silver carp are infamous for jumping out of the water when startled by watercraft [see video], something Becky Cudmore, a biologist and invasive species expert with the Fisheries and Oceans Canada, experienced first-hand when she and other carp scientists headed out on the Illinois River. Carp started flying out of water all around, some soaring as high as three metres and many landing in the boat.
One five-kilogram specimen smashed into Cudmore’s calf. “It left a good mark and numbed my leg for four hours,” she says. “It was very sobering. We really wouldn’t want them in Canada.”
Asian carp are a temperate-water fish, well suited to existing climactic conditions in the Great Lakes, even without global warming. But climate change will likely make the lakes even more susceptible to a carp invasion, says Bryan Neff, a biologist at the University of Western Ontario.
“Climate change can destabilize the natural ecosystem in the lakes and make it more susceptible to invaders,” he says. “The ability of a native ecosystem to repel invaders would diminish.”
With climate change, for example, Great Lakes water levels will likely fall, which could in turn “cause native species to become more sensitive and susceptible to invasive species,” Neff says.
Cudmore agrees. “Climate change will certainly help—not hinder—invasive species like the Asian carp.”
Alex Roslin is an award-winning journalist in Lac Brome, Qc., and writes a blog on investigative reporting at

Invasive species of wildlife and plants, which already cost $120 billion annually in the United States alone, are far more able to adapt to climate change than native species, a new study in the journal PLoS One says.
Two Harvard scientists studied plant-flowering data going back 150 years in Massachusetts, including information collected by conservationist Henry David Thoreau around the famed Walden Pond.
As the average temperature increased 2.4 degrees Celsius over this period, invasive plant species were able to advance their flowering time to be 11 days earlier than native species.
As a result, invasive species have significantly increased their population significantly more than native plants like lilies and orchids, with nearly two-thirds of the species Thoreau documented seeing sharp declines or disappeared.
“These results demonstrate for the first time that climate change likely plays a direct role in promoting non-native species success,” co-author and Harvard biologist Charles Davis told