Aquatic Invasive Species in Atlantic Canada

What are They?

Aquatic invasive species are non-native plant or animal species that are introduced to a new freshwater or marine water area and have the potential to impact Canada’s ecosystems and economy. They can affect everyone!

What you Should Know!

  • When a new species arrives, it may spread rapidly.
  • New species compete with native species for food and habitats or may even eat native species.
  • They can change the habitat or introduce new diseases.
European Green Crab
European green crab

How do They get Here?

  • As “hitchhikers” on boats, fishing gear, or in the ballast water released from ships.
  • People releasing live fishing bait or unwanted aquarium pets and plants.

Once here, they may spread by human activities or as larvae or fragments drifting in water currents.


Marine Species of Concern in Atlantic Canada

There are a number of marine invasive species that scientists are watching for in Atlantic Canada (Nova Scotia, Prince Edward Island, New Brunswick and Newfoundland). For example, the European green crab has been in the Bay of Fundy since the 1950s and is well established and outcompeting native species for habitat. Others are just entering our waters and their impact is not yet well understood.

Mussel sock infested with vase tunicate
Mussel sock infested
with vase tunicate

Some invasive species harm our fishing and aquaculture industries. For example, in the last ten years, tunicates (small marine animals that have a tunic-like skin and are commonly called “sea squirts”) have spread rapidly and are affecting crops and profits of mussel farmers in Prince Edward Island and Nova Scotia. Sea squirts like to live on the underwater mussel lines or socks. This can cause the socks to become heavy and difficult for the farmer to lift. In addition, mussels often slip off of the lines and part of the harvest is lost. While the mussels remain healthy and marketable, it takes a lot of time and effort to remove the sea squirts so it costs farmers more money to produce mussels.

European green crabs in trap
European green crabs in trap

How do we Monitor for Them?

Clean collector plate
Clean collector plate

Fisheries and Oceans Canada Scientists work with others to monitor for marine invasive species. There are a number of ways to watch for their invasion in our waters.

Scientists do regular sampling of plankton, the small microscopic plant and animal organisms that drift in the ocean, using small mesh nets. By looking at the types of plankton, scientists can determine if new species are entering our waters.

Fouled collector plate
Fouled collector plate

Scientists also place “collector plates” where new invasive species may be found (such as on wharves, buoys and floating docks for tunicates). The plates are put in the water in the spring and are removed and looked at in the fall to see what species are there. This information is used to track, if and how quickly, the invasive species are moving along the coast.

Rapid assessments are also done in areas where an invasive species may be likely to arrive. For example, the pancake batter tunicate is moving up the eastern coast of the United States and has been found in Eastport, Maine. Researchers have done several detailed surveys of bays in Canada using divers, underwater video cameras and bottom samplings to see if the pancake batter tunicate has arrived. Pancake batter was located in 2013 by a diver off of Parrsboro, Nova Scotia in the Minas Basin and Fisheries and Oceans Canada is currently in the process of assessing its spread.

Scientists have sampled ballast waters from ocean-going ships to watch for new invasive species. This information has been used by Transport Canada and the International Maritime Organization to develop regulations regarding where and when to empty ballast waters, reducing the chance of new species introduction.

Did you Know?

Once an aquatic invasive species becomes established, it is next to impossible to get rid of it. Prevention is the key!

What can you do to Help?

Recognize and learn to identify aquatic invasive species to help prevent their spread and establishment. Never remove aquatic plants or animals from their original area and then release them into another waterway.

Remove aquatic plants and animals from boat hulls and motors and dispose of them away from water in proper garbage and compost containers. Then CLEAN and DRY your boat and all of your gear.

Report all sightings of Aquatic Invasive Species to Fisheries and Oceans Canada scientists at:

1-888-435-4040 or