Asian carp: are they set to explode in the Great Lakes?

by John Peck | July 12, 2013

asian carp - three fish on a blue table

Aquatic invaders have been living in Ontario lakes and rivers for decades. Studies say over 185 non-native aquatic species are present in the Great Lakes basin, and more are being discovered every year in Ontario.

But, without a doubt, the aquatic invader most feared by scientists, industry, government, commercial fisheries and anglers alike is the Asian carp.

The term Asian carp covers four species: silver, bighead, grass, and black. Silver and bighead spread fastest and are considered the most disruptive. They have few natural predators and if they make it into our waters, could rapidly become the dominant species.

Asian carp aren’t established here yet, but they’re in position — just south of the Great Lakes — and are more than capable of expanding their range, which would forever change the ecosystems of our lakes and rivers.

The economic stakes for Ontario are huge. The Great Lakes hold 21% of the world’s above-ground freshwater. Annual revenue from commercial and sport fisheries, and tourism and recreational industries — estimated at more than $9 billion — are at risk.

Fortunately, many people on both sides of the border are working hard to keep them out of the Great Lakes and Ontario.

Governments in action
In 2011 the province of Ontario and the government of Canada partnered in mock exercises to test how well the province could respond to a sudden introduction of Asian carp.

“Our government takes the issue of invasive species very seriously and recognizes that species such as Asian carp pose a real threat to our environment, our health and the economy of Ontario,” says Ontario Natural Resources Minister David Orazietti.

In May of 2012, Federal Minister of Fisheries and Oceans Canada (DFO), Keith Ashfield, allocated $17.5 million over five years for Asian carp prevention, early warning, rapid response, management, and control. “We will continue to do what is necessary to keep them (Asian carp) from taking over this valuable watershed,” said Ashfield.

To that end, DFO staff are conducting a research pilot using implanted acoustic tags and underwater receivers to learn how large fish like Asian carp move through canal systems, and are building a new lab in Burlington to manage their early-warning surveillance and research programs.

“Sometimes when you’re dealing with aquatic invasive species it can be like looking for a needle in a haystack,” says Becky Cudmore, Acting Manager of DFO’s Asian Carp Program, of the surveillance effort. “We’re hoping not to find any. But if they are there, we hope to find them early so we can do something about it.”

Aquatic invaders not new to Ontario
Many invasive species, such as Eurasian water-milfoil and more recently, zebra and quagga mussels, have already entered our waterways. Common carp and sea lampreys have been with us since the 1800s.

Sea lampreys likely entered Lake Ontario in the 1830s, and spread to Lake Erie via the improved Welland Canal in the 1920s. They prey on large fish by attaching themselves with their suction-cup mouths and feeding on the fish’s blood. Prey fish often die from the attack.

The invasive lampreys spread to the upper Great Lakes, devastating stocks of lake trout, whitefish, chub and lake herring in the 1930s and ‘40s. Reduced numbers of top predator fish allowed alewife populations to soar, and that affected other native fish stocks.

Governments on both sides of the border have poured millions of dollars into lamprey control for many years, with varying rates of success and no silver bullet to wipe them out. Whenever efforts are reduced, populations quickly bounce back.

Last summer, while diving a shallow wreck off Christian Island in Georgian Bay, I came across hundreds of round gobies, a recent invader that I’d heard of, but not observed locally. Despite their small size, they’ve already reduced populations of local sport fish by eating their eggs and young, and competing for food.

Public enemy number one
Chances are, Asian carp are the invasive species most on Bob Lambe’s mind these days. Lambe directs the Invasive Species Centre in Sault Ste. Marie, established in 2011 by the Canadian and Ontario governments to mount a coordinated defence against all kinds of invasive species.

“Silver and bighead carp are very successful competitors because of how they feed and what they eat,” says Lambe. “Their mouth and gill systems allow them to ingest large amounts of water at all depths and filter food out of it. They eat phytoplankton, zooplankton and bottom debris, which is a very diverse diet.”

At some stage in their life almost all our native fish feed on plankton, so all fish — up to and including predators like yellow perch and walleye — could be affected. Experience south of the border has shown it’s almost impossible to keep Asian carp from spreading once they’ve invaded.

Asian carp are very well suited to the colder waters of our lakes and rivers, which are similar in many ways to the habitat of their native China. Many Ontario rivers provide suitable spawning conditions, and there’s lots of wetland to provide the right nursery habitat. According to a recent study by Fisheries and Oceans Canada, only ten females (and the minimum required males) would be needed to establish a sustainable population.

Most weigh from 4 to 9 pounds, but they can grow to over 90 pounds and well over 3 feet in length. They’re voracious feeders — eating up to 20% of their weight in plankton each day — and prolific spawners. They have already proven that they could out-compete our native species, as they represent over 90% of total bio-mass (all living things) in some waterways they’ve invaded.

And they jump! When disturbed by vibrations from passing boats, Silver carp are known for their bizarre habit of launching well clear of the surface, sometimes as high as 10 feet. Youtube hosts some spectacular and disturbing videos of this behaviour, which poses a serious safety risk to people travelling in boats. Some have suffered broken bones and been knocked out of boats after high-speed collisions with these flying fish.

Entry into the U.S.
Silver carp were introduced to North America in the 1970s to control plankton blooms in Arkansas fish farms. It didn’t take long before they found their way into natural waterways, and by the 1990s were well established in the Mississippi River basins. Now they’re in the Missouri and Ohio River systems too, and have been found in commercial shipping channels just below Chicago.

So far no established populations have been detected in the Great Lakes. The latest sightings are two lone bighead carp caught by U.S. commercial fishing boats in Lake Erie in 2010; another was caught off Point Pelee in 2000. No one knows how they got there, and none have been found since, despite repeated searches.

Some states well south of the border are trying to reduce populations by encouraging commercial catches, but these aren’t making much of a dent in total numbers. Because of their filter-feeding habits, Asian carp are next to impossible to take with angling gear.

On the other hand, enterprising bow hunters in the U.S have created a new sport: shooting jumping silvers from the sterns of speeding boats.

Three possible points of entry
There are three most-likely routes of entry into Ontario:

  • via the Chicago Sanitary and Ship Canal into Lake Michigan;
  • through the importation of live fish destined for fish markets; and
  • via bait buckets that are emptied into a lake or river.

The Chicago waterway, which connects directly to Lake Michigan from the carp-inhabited Illinois River system, is thought to be the highest risk. Asian carp have been found in the channel not far below Chicago.

To hold them back, the U.S. Army Corp of engineers built and maintains an electric barrier in the shipping channel. The barrier consists of electrodes on the bottom of the channel that emit a pulsing DC current uncomfortable to fish. When they encounter it they turn and swim away. It seems to be doing the trick so far, but the engineers are looking to make improvements.

High levels of carbon dioxide also seem to be effective in repelling fish, so scientists like Cory Suski — a Canadian now working at the University of Illinois — are looking at adding it as a second line of defence. “In the lab, we’ve had good results,” he says. “Our next step is to move it into the field to see if it holds up there.” Suski hopes to have a field experiment in place by this fall, with possible implementation in 2014.

But barriers of this type are costly to maintain and prone to failure. Historically, the Illinois River was not connected to the Great Lakes. Many are now calling for the restoration of that natural divide. Costs would be high but, on the other hand, 1.4 million anglers fish in Ontario every year, spending more than $2.3 billion dollars annually, and the commercial fishery in the Great Lakes is valued at $200 million a year.

Controlling invasive species is also expensive. Zebra-mussel control projects cost Ontario $75- $95 million a year, now and into the foreseeable future.

Shipments of live fish from the U.S., where Asian carp are raised legally, are another possible entry point. Live Asian carp have been found for sale (illegally) in Toronto food stores. To guard against this, the buying and selling of live fish for several invasive species, including Asian carp, was banned in Ontario in 2005.

Still, they keep coming. Six shipments of live Asian carp have been seized at the Windsor and Sarnia border crossings in the last two years. Two cases are before the courts, say MNR enforcement officials, and fines in the other four cases were high, ranging from $20,000 to $60,000.
There’s another problem with the importation of these fish, which are brought in by the truckload. Asian carp can survive out of water for extended periods, especially when iced. Even after many hours or even days out of water, they can potentially be revived. For this reason, officials are looking at tightening the laws to restrict the import of Asian carp to eviscerated (internal organs removed) fish only.

The third likely point of entry is via bait buckets, where young Asian carp could be mixed in with bait minnows. This threat is seen as highest in the U.S., but it could be a factor here in Ontario too. It’s never a good idea to empty a bait bucket in or near water, and it’s illegal in Ontario.

Monitoring our waterways
Officials on both sides of the border are keeping a close eye on our waters so any outbreaks of Asian carp can be tackled as soon as possible.
Many surveys are carried out by commercial fishing operations, and authorities are encouraging anglers to report any sightings.

Scientists are refining eDNA, (environmental DNA) tests to monitor for Asian carp invaders. In these tests, random water samples are analysed for minute traces of Asian carp DNA, but work has to be done to make the technique more effective.

Alarm bells sounded
Alarm bells sounded last year when Great Lake water samples taken by U.S. authorities turned up positive for Asian carp DNA. Extensive searches have since failed to find any actual fish, and scientists are now wondering whether the DNA could have been transported via birds or as slime on commercial nets or boats. Those who suspect Asian carp are already present doubt there are sufficient numbers to sustain a population.

Another problem with eDNA testing is that it takes months to obtain results, so work is underway to improve lab processes and eliminate false positives.

Ontario Ministry of Natural Resources (MNR) Asian carp expert John Cooper reports the ministry completed eDNA analysis of water samples last year from 124 sites along St. Clair River, Lake St. Clair, Detroit River and Lake Erie shorelines. Fortunately, none were positive.
Ontario is continuing its surveillance program this year using both eDNA sampling and electro-fishing.

Scientists in Minnesota are working on a new Asian carp monitoring technique, dubbed the Judas fish. Sterilized Asian carp would be fitted with electronic radio tags and released into lakes. Because fish tend to seek out others of their kind, their movements could lead scientists to groups of invasive fish, which would then be destroyed.

Researchers are looking for ways to sterilize the Judas carp before they are released. There’s little existing research because — up until now — there’s never been a need.

How you can help
Authorities are also asking the public to lend a hand. To keep costs down, governments everywhere are increasingly relying on the cooperation of organizations like the OFAH, cottage associations and stream keepers. They need eyes and ears in the field to help them monitor all invasive species.

Anyone who sees an Asian carp in the wild, whether dead or alive, is encouraged to report it as soon as possible. Silver and bighead carp are easily identified by their low-set eyes, downward slanting mouth, dark blotches on the back and bloody blotches on the skin.

If you see one, call the Invading Species Hotline at 1-800-563-7711. For more information or to make an online report, visit

If you think you’ve seen a live Asian carp for sale or being transported, call the MNR Tips line at 1-877-TIPS-MNR. You can also anonymously call Crime Stoppers at 1-800-222-8477.

Soon there will even be a smartphone app to help members of the public monitor invasive species in Ontario. The Invasive Species Centre is working with the OFAH, MNR and the University of Georgia to create the app, with field tests starting later this year and an expected launch in 2014.

First published in the June 2013 of Ontario OUT OF DOORS magazine. 

Sign up for our mailing list

indicates required
Email format


  1. Raymond Hietapakka wrote: Blah blah blah the Chicago Sanitary Canal back to its original watercourse, and f*** all the blah blah blah....