Published on Fri, 08/03/2018 by Nature Conservancy of Canada

Nature Conservancy of Canada asks Canadians to help stop the spread of invasive species through summer recreational activities

The Nature Conservancy of Canada (NCC) hopes people are enjoying the outdoors and connecting with nature this summer, but at the same time is encouraging them to help control the spread of invasive species. 

Many invasive species have few natural predators to control them. Once they get into ecosystems, they’re often able to spread and out-compete our native plants and animals for space, water, food and other resources.

The not-for-profit, private land conservation group is highlighting 10 invasive species that can be spread as a result of people going about their summer outdoor recreation. Activities such as camping, hiking, biking, fishing, boating, horseback riding and driving ATVs can unintentionally spread invasive species into our rivers, streams and forests. 

NCC senior conservation biologist Dan Kraus says the list contains some species that people may be familiar with and others that may be surprise them. They range from emerald ash borer beetle spread by moving firewood, spotted knapweed plant, which is spread through hiking and camping, to the Eurasian milfoil, which is spread by boating.

“Many invasive species have few natural predators to control them. Once they get into ecosystems, they’re often able to spread and out-compete our native plants and animals for space, water, food and other resources,” said Kraus. “People may unknowingly be contributing to the spread of invasive species when they are enjoying the outdoors through their recreational activities. That’s why it’s important to share information and these steps so that people can minimize the spread of these invasive species to new areas in Canada.”

Here is a list of the top 10 invasive species spread through summer recreational activities:

Ten invasive species spread through outdoor recreational activity in Canada

Spotted knapweed

Spotted knapweed: This aggressive invasive plant invades prairies, meadows and open woods. It can take over these habitats and reduce the number and diversity of native plants and animals. Each plant produces thousands of seeds that can be spread when they adhere to ATVs, horses, bikes, hiking boots and camping equipment.

Where it’s found: Yukon, British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick and Nova Scotia.

Garlic mustard: This biennial plant is rapidly spreading across Canada, into forests and woodlands. It can form dense stands that exclude native plants, and can impact forest regeneration. Garlic mustard can be spread when the small seeds adhere to boots and clothing.

Where it’s found: British Columbia, Alberta, Ontario, Nova Scotia, New Brunswick, Prince Edward Island,  Newfoundland and Labrador

Eurasian milfoil: Known as the “zombie plant,” this aquatic weed grows quickly in the spring, forming a thick mass of tangled stems under water. These stems get caught in boat propellers and rudders and reduce native aquatic plants and impact fish habitat. It is primarily spread when boats are moved by trailer between lakes.

Where it’s found: British Columbia, Manitoba, Ontario, Quebec, New Brunswick, Prince Edward Island

Round Goby

Round goby: This small, bottom-dwelling invasive fish was found in the Great Lakes in 1990 and is spreading. It reduces native fish populations by eating the eggs and young of species such as lake trout and smallmouth bass. Round goby can be spread when it’s used as bait, or when released upstream from dams and waterfalls.

Where it’s found: Great Lakes basin

Zebra and quagga mussels: These small freshwater mussels have been spreading across North America. They can completely cover the bottom of lakes, impacting fishes, native mussels and water quality. They are spread when they attach to boat hulls, trailers and motors that are moved between lakes.

Where it’s found: Ontario, Manitoba, Quebec

Emerald ash borer: This non-native invasive beetle has decimated tens of millions of ash trees and continues to spread rapidly. It can quickly kill large areas of ash trees, impacting forests, areas along streams and rivers and urban forests. It has spread to some areas through people moving firewood that has been cut from infected ash trees.

Where it’s found: Manitoba, Ontario, Quebec, New Brunswick

Spiny waterflea: This small freshwater crustacean feeds on zooplankton in lakes. Spiny waterflea can alter the food chain and impact native fish populations. Large numbers of spiny waterfleas form a jelly-like mass that clogs fishing gear and other equipment. It is spread by water from infected boats or when bait buckets are moved between lakes.

Where it’s found: Ontario, Manitoba

European and Asian earthworms: Many people are surprised to hear that most of the earthworms they encounter are non-native and invasive, including the “night crawler” often found in gardens and used for bait. Invasive earthworms damage forests, as they change the soil chemistry and structure. Earthworms can be introduced to forests by anglers dumping their leftover bait on land or in the water, and vehicles can transport earthworms or cocoons in their tire treads. 

Where it’s found: throughout much of southern Canada

Whirling fish disease: This infectious invasive parasite affects salmon and trout. First found in Canada in 2016 in Alberta, this disease invades the fish’s cartilage and impairs its nervous system, which causes it to swim in a whirling pattern. It can be spread by moving infected fishes, bait or boats between lakes and rivers.

Where it’s found: Alberta

Domestic cats: Domestic cats can have a significant impact on populations of migratory birds, reptiles and small mammals, and are considered one of the world’s 100 most invasive species.

Cats that are brought to cottages and camps can kill birds and other wildlife of conservation concern and should be kept indoors, or on a leash outside.

Where it’s found: All provinces

For more information, including species profiles and tips on how you can help, visit NCC's Invasive Species Gallery.



The Nature Conservancy of Canada is the nation's leading not-for-profit, private land conservation organization, working to protect our most important natural areas and the species they sustain. Since 1962, NCC and its partners have helped to protect 2.8 million acres (more than 1.1 million hectares), coast to coast. To learn more, visit

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round_goby_photo_by_eric_engbretson_-_u.s._fish_and_wildlife_service.jpgRound Goby (Photo by Eric Engbretson - U.S. Fish and Wildlife Service)288.06 KB
spotted_knapweed_photo_by_alan_vernon-wikimedia_commons.jpgSpotted knapweed (Photo by Alan Vernon-Wikimedia Commons)430.59 KB