Alien Aquatic Species

Biological invasions are now one of the leading environmental threats to aquatic habitats worldwide. When aquatic invasive species are introduced and survive, their populations usually increase very rapidly and often outcompete, prey upon, or smother native species. (Sounds like a wrestling match!)  Invasive species are known to be one of the leading threats to biodiversity. The loss in biodiversity occurs when invasive species:

  • outcompete native populations for food and space
  • alter established food webs
  • interbreed with native species, changing the gene pool
  • introduce diseases and parasites

Alien invasives are being transported to new regions of the world everyday. One major mode of species transportation is through shipping. Non-native species travel to our region by ships in ballast water or attached to hulls.

According to the Nova Scotia Department of Fisheries and Aquaculture, on any one day, an estimated 3,000 species are transported in the ballast water of ocean-going vessels around the world. Anything from fish, to snails and clams, crabs, and aquatic plants can be transported in ballast water to almost any port in the world. Click on the map below to read more about global transportation of invasive species (UNEP-GRID).

In addition to shipping, alien aquatic invaders can arrive and spread through:

  • hitching a ride on any type of boat (canoe, kayak, motor boat), trailer, and all boating equipment (gear bags, coolers, ropes)
  • hitching a ride on fishing gear including bait buckets, tackle and hip waders
  • aquarium and backyard pond trade
  • release of live bait
  • aquaculture
  • man-made canals

Nova Scotian shorelines have recently been invaded by several notorious marine invaders such as the European green crab, Dead Man's Fingers (Codium), the lacy crust bryozoan and numerous sea squirt species (tunicates). In addition, there are a number of other marine alien species that have already invaded nearby US coastal waters, such as the Chinese mitten crab in Hudson River, New York. 

Freshwater habitats in Nova Scotia have also been recently affected by invasive alien species. Right here in Cape Breton, the non-native spinycheek crayfish was accidentally introduced and has successfully colonized Freshwater Lake near Ingonish in the Cape Breton Highlands. It is the only crayfish species in Nova Scotia, we do not have any native crayfish species here.

It's not surprising that scientists and resource managers in Nova Scotia are concerned: some of these alien invaders are on the Top 100 List of Global Invasive Species.

How do alien aquatic invaders affect Cape Bretoners? 

Aquatic invasive species affect everyone that uses our waters, including recreational fishermen, boaters, and shoreline property owners. These invaders can:

  • reduce populations of native fish, clams and mussels that inhabit our waters
  • degrade the natural beauty of our lakes and waterways
  • reduce the numbers of popular sportfish
  • foul fishing gear
  • clog boat engines which may lead to expensive repairs
  • foul boat hulls and any equipment that gets left in the water such as ropes, anchors, floating docks
  • choke lakes and waterways and restrict use by swimmers and boaters
  • reduce waterfront property value
  • spread diseases, pathogens and parasites

 Additional websites related to aquatic alien invaders

To find out more about the aquatic alien invaders that are either already in Cape Breton or threaten our local marine and freshwater ecosystems, please choose from the menu on the top right.