Aquatic Invasive Species
Table of contents
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.
The Canadian Action Plan to Address the Threat of Aquatic Invasive Species (PDF 101,69 KB), which was approved by the Canadian Council of Fisheries and Aquaculture Ministers (CCFAM), outlines a national approach for managing AIS.
The Aquatic Invasive Species Identification Booklet contains information on major species that have invaded marine environments in eastern Canada, how to identify them and what you can do to prevent their spread and establishment.
Examples of aquatic invasive species found in Canadian waters:
Asian carp collectively refers to four species of carps: Bighead, Silver, Grass and Black. During the early 1970s, aquaculture managers in the southern United States imported these species for biological control of algae, plants and snails in their ponds.
Reaching lengths of a metre or more and weighing over 35 kg (with Grass carp weighing up to 45 kg), Asian carps, and in particular the Silver and Bighead carps, have steadily been outcompeting native fishes in the Mississippi River and in some of the lakes and tributaries that feed the river. They are voracious eaters, able to consume 5 to 20 per cent of their body weight each day, leaving far less of the microscopic plant and animal life (phytoplankton and zooplankton) to support native fishes. Grass Carp primarily consume aquatic plants, and their foraging can disturb lake and river bottoms, and destroy valuable wetlands. Their foraging increases water murkiness, making it more difficult for other fish to find food. The destruction and loss of aquatic vegetation also leaves native juvenile fishes without adequate cover from predators and reduces possible spawning habitats. A physical danger comes from Silver Carp, which are responsible for generating much of the public’s attention on Asian Carp. When startled by noise, such as a passing boat motor, it will leap from the water, sometimes as high as three metres above the surface.
Three species of Asian carps: Bighead Carp, Silver Carp, Grass Carp. Black carp is not shown.
Photo credit: ACRCC http://asiancarp.us/
Sea lampreys entered the Great Lakes from the Atlantic Ocean through man-made shipping canals and were first observed in Lake Ontario in the 1830s. Niagara Falls acted as a natural barrier preventing sea Lamprey movement to Lakes Erie, Huron, Michigan, and Superior. However, when the Welland Canal (constructed to bypass the falls) was deepened in 1919, sea lampreys gained access to the rest of the Great Lakes. By 1938, they had invaded all of the Great Lakes. Sea lamprey attach to fish with their suction mouth and teeth, and use their tongue to rasp through a fish’s scales and skin so they can feed on its blood and body fluids.
A Sea lamprey attached to Lake Trout/ The Sea lamprey mouth forms a sucking disk filled with sharp, horn-shaped teeth that surround a rasping tongue.
Photo credit : Great lakes Fishery Commission
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.
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:
Clubbed 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
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.
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