From parasites to crabs and living slime affectionately dubbed "rock snot," invasive species can wreak havoc when introduced into a new habitat. The U.S. administration is taking steps to fight one of the worst offenders, the Asian carp, pledging $50 million US in 2012 to keep them out of the Great Lakes.

We take a look at 10 non-native plants and animals that are disrupting ecosystems in Canada.

Asian carp

Silver carp, native to Asia, can grow to be up to 1.3 metres long and weigh up to 50 kilograms while bighead carp are a little smaller. Both are types of Asian carp, several species of which have been multiplying rapidly through the Mississippi, Iowa and Illinois river systems since the 1990s when flooding allowed them to spread throughout the Mississippi watershed. Since then, bighead carp have been caught a mere 10 kilometres downstream from Lake Michigan, beyond barriers built to keep them out, and a type of Asian carp DNA has been found in Calumet Harbour on Lake Michigan. Under the U.S. administration's new plan, water samples will now be taken to see whether the carp have established a foothold in the Great Lakes. Officials told the Associated Press new plans to prevent a carp invasion include increased trapping and netting in rivers that could provide access to the lakes, field tests of chemicals that could be used to lure carp in order to capture them and an acoustic water gun used to scare the fish away from waterways that flow into Lake Michigan.

European green crab

The European green crab preys on mussels, clams and other crabs, threatening shellfish stocks on the Atlantic coast. It's a naturally aggressive and territorial crab species, found near Prince Edward Island, Quebec's Magdalen Islands, Nova Scotia's Cape Breton Island and the waters off southern Newfoundland, where it was first discovered in 2007. According to Fisheries and Oceans Canada, unless controlled, the crab's impact will surely be felt in Newfoundland's ecosystem.

Purple loosestrife

Purple loosestrife, a European invader introduced to Canada in the 1800s, degrades wetlands. It can decimate and choke out native plants that make up the habitats where fish, birds and animals feed, seek shelter and rear their young. A single plant can produce over 300,000 seeds. The plant grows in ditches, irrigation canals, marshes and even standing water. In some locations, purple loosestrife has also begun invading dry habitats like pastures and cropland.

Zebra mussel

Industries with operations on the Great Lakes spend millions of dollars a year dealing with zebra mussels, which multiply so quickly that they clog intake pipes and sink navigational buoys. They also filter out large amounts of phytoplankton, affecting the local food chain. They can also end up strewn over beaches, leaving behind sharp shells and foul odours when they die and decay. The mussels are native to the Black Sea and Caspian Sea regions of Asia.

Sea lamprey

The sea lamprey is a primitive, parasitic fish that has made its way from the Atlantic Ocean into our waterways by stowing away on cargo ships. These eel-like creatures with suction-cup, bloodsucking mouths can kill more than 18 kg of the fish they prey on during their 12- to 20-month adult life stage. Their circular mouths puncture through the skin of fish, ensuring that prey die from blood loss or the after-effects of the wounds. Sea lampreys entered the Great Lakes through a man-made canal system and by 1938 were present in all five Great Lakes.

Emerald ash borer

The transport of firewood is banned in certain parts of Quebec and Ontario to curb the spread of this beetle. The emerald ash borer originated in eastern Asia and was first found in Canada in 2002 in Windsor, Ont. Its larvae burrow through the inner bark of ash trees while the young beetles feed on leaves, damaging and eventually killing the tree. The pest is very difficult to detect early, as infested trees often aren't found until a year or more after the infestation occurs.

Didymo

Also known as "rock snot," this single-celled algae forms slimy mats and clumps in rivers that make the water look polluted. Although didymo is native to North America, it has now spread to many parts of the continent where it hadn't been seen before, such as Vancouver Island. Didymo blooms may affect the growth of other algae and change the types of invertebrates in the ecosystem. The didymo isn't toxic but is still undesirable because of its ability to mask as a pollutant.

Gypsy moth

Larvae of the gypsy moth are known to eat the leaves of about 300 plants, causing widespread damage. The European species was first introduced in the 19th century and is considered a major pest. The moths are well established in Ontario and Quebec and have been threatening parts of southern New Brunswick and Nova Scotia for many years. Birds and small mammals are gypsy moth predators and useful as natural enemies of the bug. The gypsy moth will also eat blueberries, hazelnuts and several other important crops.

Asian long-horned beetle

This beetle from China attacks hardwood trees such as maples. It first appeared in North America in 1996 in New York state. In Canada, it was first found in 2003 in an industrial park between Toronto and the city of Vaughan. Officials are trying to eradicate it, and affected areas are placed under strict quarantine. The pest is believed to have been brought to North America in packaging materials used in shipping. Canada's temperate climate is well suited to the insect, whose larvae spend winters burrowed deep within trees to protect themselves from harsh winter conditions.

Round goby

This aggressive fish is known for stealing bait from fishermen. It was introduced to Ontario's St. Clair River from eastern Europe in the late 1980s and has multiplied so quickly that there are now more than 100 per square metre on the lake or river bottom in some areas.