The Asian carp epidemic with The Invasive Species Centre

Fishbrain catches up with our friends at the Invasive Species Centre to talk about the Asian carp problem and what Canada is doing to prevent further spread.

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The Asian carp epidemic with The Invasive Species Centre

How did each carp species end up in American waters?

Asian carp were brought to the United States in the 1960s and 1970s for use as biological control. Bighead Carp and Silver Carp were used to control algae and Black Carp were used to control snails in aquaculture facilities in Arkansas. Flooding events allowed them to escape and make their way into the Mississippi River Basin. The spread of Grass Carp in the U.S. is largely the result of stocking for aquatic vegetation control. Grass Carp can either be fertile (called, “diploid”) or sterile (called, “triploid”). Some states allow fertile Grass Carp to be stocked, some only allow triploid Grass Carp to be stocked, and some states do not allow them at all. 

State regulations for Grass Carp. (Mississippi Interstate Cooperative Resource Association 2015)

Are there Asian carps in Canada yet?

There are currently no established populations of Asian carps in Canada. There have been a few rare individual captures of Asian carps in the Canadian waters of the Great Lakes. In terms of Bighead Carp, only three single specimens have been collected, all in western Lake Erie, between 2000 and 2003, and these are believed to have been intentionally released. In terms of Grass Carp, there have been 29 captures since 2012 in the waters or tributaries of lakes Huron, Ontario, and Erie. Of those tested, nine were determined to be fertile. It is likely that these fish were escapees from areas where populations were being used for aquatic plant control, or live releases. No Silver Carp or Black Carp have been found in the Great Lakes to date.

Is Canada solely worried about Grass Carp right now?

Canada is worried about all four species but Grass Carp are the most immediate risk because there is thought to be natural reproduction of Grass Carp occurring in two U.S. tributaries of Lake Erie – the Sandusky and the Maumee rivers.

Grass Carp. Photo by Ryan Hagerty, USFWS

 How recently were Grass Carp discovered in Erie tribs on the American side?

Grass Carp have been stocked for aquatic vegetation control in Ohio since 1988, however they must be sterile and unable to reproduce. The issue is that there is evidence of naturally reproducing populations of Grass Carp in two U.S. tributaries of Lake Erie. Some of the fish being transported and sold as sterile may be fertile and may escape the waters where they are stocked. The United States Geological Survey (USGS) USGS confirmed that larval fish caught in the summer of 2018 in the Maumee River were Grass Carp. Evidence of reproducing populations was found in the Sandusky River in 2016 and it doesn’t take many fish to reproduce and establish a population.

 How fast are we seeing Grass Carp wipe out native vegetation?

Grass Carp can eat up to 40% of their body weight a day in aquatic vegetation and risk assessments suggest that just 10 Grass Carp per hectare would reduce wetland vegetation by 50%. Since they’re not established in Canada, this presents a really big threat to wetlands that are already under stress.

 How big do Grass Carp get?

Grass Carp can weigh over 80 pounds and reach lengths of over 5 feet.

 Do the other species of Asian carp eat vegetation too?

No. Bighead Carp primarily eat zooplankton, Silver Carp primarily eat phytoplankton, Black Carp primarily eat mollusks (snails, mussels) and Grass Carp primarily eat aquatic vegetation.

 What are some methods being used to control their spread?

A lot of work is being done in the U.S. to control their spread. There are electric barriers at the Chicago Sanitary and Ship Canal within the Chicago Area Waterway System. These barriers were designed to prevent fish passage between the Mississippi River and the Great Lakes. In addition to this, the state of Illinois removes millions of pounds of Asian carp annually, which helps to keep the leading edge of the invasion back. Asian carp invaded the Mississippi River Basin and the 28 states that makeup this river are impacted in one way or another and they are also working on removal and management efforts.

Electrofishing at Barkley Dam

The Electrofishing demonstration at Barkley Dam resulted in dozens of Asian carp jumping out of water. Photo by USFWS.

How is Canada monitoring and preventing the fish from crossing into Canadian waters?

Canada is currently in the prevention phase of the invasion curve. At the Invasive Species Centre, we focus on education and outreach specifically targeting anglers and teaching them about the threats these fishes pose, how to identify them and how to report them. We do this through working with organizations like FishBrain, through social media, working with influencers, putting ads in angling magazines, and hosting information sessions and webinars, and more! Prevention is a collaborative effort and we have a lot of great partner organizations that also work on education and outreach.

From more of an on-the-ground perspective, our partners at Fisheries and Oceans Canada take the lead on conductingearly detection surveillance work– every year from May to November, they sample at up to 37 sites in the Great Lakes, using up to 9 different traditional gear types to detect and capture Asian carp. This surveillance is done in higher risk areas, based on modelling of tributaries that have suitable spawning conditions for Asian carp.  

A crew from Fisheries and Oceans Canada's Asian Carp Program conducting early detection surveillance for Asian carp in the Grand River, Ontario, with an electrofishing boat

Photo by Fisheries and Oceans Canada

Realistically is there any going back, or are they stuck here in the states now? 

Unfortunately, once an invasive species becomes established it’s nearly impossible to eradicate it completely. Prevention is key and much more cost effective. Once you need to start controlling and managing an invasive species, the cost goes up.

 How many states are carp in? 

 Asian carp are established throughout the Mississippi River Basin, the Illinois River, and the Missouri River. You can learn more about where they’re found throughout the U.S on the USGS Nonindigenous Aquatic Species database. Please note that the points on the map are grouped by specimen so for example, a small yellow dot only indicates 1 specimen observed.

 Grass Carp Map

Bighead Carp Map

Silver Carp Map

Black Carp Map

Which bodies of water in Canada are of most worry of Asian carp crossing into?

 Risk assessments have found that Asian carp would have no problem surviving in Canada’s climate. The Great Lakes are of major concern due to Asian carp current proximity but that doesn’t mean that other waterbodies in Canada aren’t at risk too.  For example, Asian carp are a threat to Manitoba waters because of their proximity through Minnesota and North Dakota, and Quebec has had occurrences of Grass Carp.

 Which species do Grass Carp disrupt the most?

Grass Carp would have negative impacts on many native fishes and birds. Many species depend on vegetation for nursery and spawning grounds, for habitat, and some fish will even use heavily vegetated areas to hide out while hunting for prey.  

According to a study by Gertzen et al. 2017, some of the species that would experience negative impacts as a result of Grass Carp establishment are:

  • Grass Pickerel

  • Northern Pike

  • Muskellunge

  • Largemouth Bass

  • Walleye

  • Yellow Perch

  • Bigmouth Buffalo

  • Pumpkinseed

  • Smallmouth Bass

  • White Crappie

  • White Sucker

  • Spotted Gar

  • Longnose Gar

  • Bowfin

 What can anglers in Ontario do to help? ( I added this question)

Anglers are more eyes on the water. Learning how to properly identify and report suspected sightings can aid in response and help prevent establishment.

We encourage all anglers to download thisfact sheet which goes through how to correctly identify Grass Carp and what to do if you’re certain you’ve caught one.

Visit to learn more! You can also find and follow the Invasive Species Centre's page on Fishbrain!

Now let's go fishing and please leave the invasive carp at home.

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