Problems

This invasive aquatic plant is native to Europe, Asia and North Africa. It grows underwater, producing flowers on spikes held above the water's surface. It can form dense mats one to ten metres deep in the water. Eurasian watermilfoil has been present in Quebec since at least 1927. It was first introduced in ballast water, then by aquarists. Ballast water is used to maintain ship stability. When a ship is not fully loaded, water is added to the ballast tanks to compensate for the load. Pleasure craft can also spread this plant if they are not properly cleaned. Eurasian watermilfoil starts growing early in the season and grows very quickly, allowing it to outcompete native plants.

Zebra and quagga mussels are native to the Caspian and Black Sea region, and were carried here in ballast water. Scientists did not differentiate between the two species until 1991. These mussels were first detected in Lake Erie in 1989. Since then, they have aggressively colonized all sorts of habitats, attaching themselves to wharfs, boats, breakwaters and beaches. Their colonies can block the water intakes of power stations and water treatment plants. Unlike native mussels, they are resistant to the toxins produced by cyanobacteria. Zebra mussel colonies can even attach themselves to the shells of native mussels, preventing them from moving or feeding.

The Asian clam is a small bivalve that can reach a size of 3 to 5 cm. It was first detected in North America in 1924, when shells were found in Nanaimo, on Vancouver Island, B.C. In 1981, living specimens were seen in Lake Erie. In 2009, the species was first detected in Quebec. A population has become established in the thermal plume downstream of the Gentilly-2 nuclear power station. This is the northernmost known occurrence of the species in Eastern North America.

The spiny water flea Bythotrephes longimanus is a planktonic crustacean under 15 mm long. This species of zooplankton is native to fresh water in Northern Europe and Asia, and was introduced to the Great Lakes region in the 1980s. Spiny water fleas were probably carried in the ballast water of Eurasian cargo ships. The species was first observed in Quebec in August 2015, in the Upper Richelieu region.

Spiny water fleas can spread to new water bodies by forming clumps that cling to pleasure craft, canoes, kayaks and fishing gear. Their eggs can survive in harsh conditions—even in the digestive system of fish that have eaten gravid females. These eggs can also be found in engine water or stuck to fishing gear.

The scud Echinogammarus ischnus is a freshwater amphipod approximately 1 cm long. It is native to the Aral, Azov, Caspian and Black Seas, and was introduced in ballast water discharged from cargo ships. It was first observed in 1994 in the Detroit River, which links Lake St. Clair to Lake Erie. Within three years, it had spread throughout the Great Lakes. This highly aggressive invasive species attacks the females of a similar native crustacean. In certain regions, it is gradually replacing the native species. This scud disrupts benthic communities by preying on macroinvertebrate fauna, depriving young fish of their food. It is also tolerant of high levels of calcium in the water.

The bloody red shrimp is a crustacean that can reach around 8 mm long. It lives in fresh water, but can tolerate salt water. Native to the Caspian region, it was first reported in Lake Ontario and Lake Michigan in 2006. This species was introduced in the ballast water of ocean-going ships. In 2008, specimens were found in the St. Lawrence near Châteauguay. These shrimp feed on zooplankton, and may threaten fish populations by decreasing the amount of food available.

The European green crab is a highly invasive species, native to Europe and North Africa, that can destabilize marine ecosystems. Larval crabs were probably introduced in ballast water. This species has very resistant larvae and a long larval stage. Adults are also capable of surviving for long periods in ballast water. The green crab was first reported in Canadian waters south-west of New Brunswick in 1951. In the early 1980s, it was observed along the eastern coast of Nova Scotia. In 1984, it was seen for the first time in the Gulf of St. Lawrence. Green crabs are very tough, and can survive for long periods in fresh water or even outside the water. They are aggressive and territorial towards native species. The green crab feeds on mollusks, crustaceans and even small fish, and can pose a threat to oyster and mussel farms.

The Chinese mitten crab is the only freshwater crab found in North America. However, it reproduces in salt water. It was first reported in Canada in 1965, and in the St. Lawrence in 2004. Its larvae were probably introduced in ballast water. This species can tolerate a wide range of temperatures and salinities, and can survive in polluted environments. The Chinese mitten crab feeds on the eggs of salmon, trout and sturgeon, and represents a significant threat to the survival of these species. Its burrowing habits also accelerate shoreline erosion and damage fish habitat.

The round goby is native to Asia and the Azov, Aral, Caspian and Black Seas. This invasive species arrived in ballast water. It was first reported in the St. Clair River in 1990, and has since invaded the Great Lakes. It has been present in the St. Lawrence since 1997. In 2009, a specimen was seen near Rivière-Ouelle, indicating that the species can tolerate brackish water. This highly aggressive fish feeds on fish eggs and fry, as well as insect larvae and zebra mussels. When gobies feed on zebra mussels, they ingest contaminants and reintroduce them into the food chain.