Aquatic Invasive Species

An aquatic invader is a non-native species, whose introduction will likely cause (or has already caused) damage to the host ecosystem, existing species therein, the economy or human well-being. Invasive species thrive in the absence of their native predators and have the potential to drastically alter habitat, rendering it inhospitable for native species.

Aquatic invasive species (AIS) have already been responsible for significant devastation of some native fish species and fisheries in Canada. Annually, the problem is responsible for billions of dollars in lost revenue and control measures. Canada, with its huge freshwater resource and extensive coastline, is especially vulnerable to this threat. The Environmental Science knowledge base and scientific resources play an invaluable advisory role to the government in its goal to address the problem. As an example, we have provided scientific advice on alternate ballast water exchange zones. (Ballast water contained on international ships is a major pathway by which invasive species can enter Canadian waters.) The work done by Environmental Science has facilitated Transport Canada's proposed revisions of the Canada Shipping Act Ballast Water Regulations.

You can read about Canada's plan to address aquatic invasive species at:

• Proposal for a National Action Plan to Address the Threat of Aquatic Invasive Species - Draft for consultation

Examples of aquatic invasive species found in Canadian waters:

Sea lamprey were a significant factor in the collapse of the lake trout and whitefish fisheries in the 1940’s & 1950’s. The Sea  Lamprey Control Program, implemented in 1955, resulted in a 90% reduction in sea lamprey populations.

Sea lamprey is a primitive eel-like fish that feed on the body fluids of other fish by clinging by their mouth and goring though the scales and skin with their tongue. They prey on all species of large fish in the Great Lakes.

Zebra mussels are small freshwater molluscs introduced to North America in the mid-1980s via ballast water from  transoceanic vessels. They have since spread rapidly to all of the Great Lakes and inland waterways in the United States and Canada causing millions of dollars in damage annually to human infrastructure.

Their feeding causes an increase in water clarity in the Great Lakes which, in turn, results in increased light penetration and an overgrowth of vegetation and toxic algal blooms.
They colonize on a variety of surfaces, such as docks, boat hulls, fishing nets, pipes, etc. The photos show zebra mussels growing on a golf ball and a boat.

Green crabs eat a variety of native East Coast clams, mussels and oysters, and threatens West Coast shellfish. The small shore crab is an efficient predator and colonizer.
It has invaded numerous coastal communities outside of its native range, including South Africa, Australia, and the Pacific & Atlantic coasts of N. America.

Clubbed tunicate interfere with the settlement of oyster and mussel larvae and compete for space and food with young native oysters and mussels.

Here, the photo shows tunicates growing on mussel lines.
 

Japanese oyster drills will bore holes into young oysters and feed on them. They do not inherently migrate, however still managed to cause significant damage to the oyster industry until they were brought under control in the 1990’s.
(Photo credited to the Washington Department of Fish and Wildlife.)

Round Gobys have spread rapidly within the Great Lakes since their discovery in 1990. They are very competitive and populate quite easily. In addition to habitat domination, they will also eat the eggs and the young of indigenous fish. It is presumed that they arrived via the ballast water of transoceanic vessels.




 

Rusty Crayfish are more aggressive than the native freshwater crayfish. They can consume the eggs and young of surrounding fish. They are also quite devastating to native aquatic plant life, on which they feed. Rusty crayfish will displace and/or hybridize with native crayfish.

Spiny and Fishhook Waterfleas are small crustaceans. The spiny water fleas were first discovered in the early 1980's in the great lakes and the fishhook variety, later, in the late 1990's. They damage fishing gear and compete with native fish for food . They collect on fishing lines and cables, clogging rods and damaging reels.



 

Asian carp will compete for food with indigenous species and prey on their larvae. They can also cause significant habitat damage and ecological disruption. Moreover, Asian Silver carp tend to jump out of the water and endanger recreational boaters and water skiers. Asian carp have become a serious problem in US waterways, and have the potential to invade Canadian freshwaters. With the support of DFO, proactive efforts are underway to reduce the likelihood of Asian carp species becoming established in Canada. Fishers are urged to keep a watch for Asian carp in Canadian waters!

You can read more about the risks of Asian Carp in the CSAS document:

• Risk Assessment for Asian Carp in Canada

Last updated : 2005-12-06

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