The Park

Beware! Invasives Lurk Beneath!

Invasive species are invaders from other ecosystems. These invaders can be plants or animals, or even bacteria that have been moved from their home ecosystem into another ecosystem. Invasive species are often bullies that are bigger, tougher and faster than the native species. These greedy invasives usually eat more food leaving less for the others and even steal the best places to make their homes! Some invasives even eat native species! Invasive species compete with native species. This means that invasive species use up the food or space of native species.

How Did Invasive Species Arrive in Canada?

Humans…

Large sea-going ships such as freighters pump water into their bilge tanks to make them heavier and more stable. When water is pumped into the tanks in one port, invertebrates, plankton or even fish are pumped in too! These species survive in the tanks until the ships have crossed the ocean and then arrive in another port where the water from the bilge tanks is pumped out. The stowaway species are then released into their new ecosystem. It only takes a couple of individuals from one ship to cause problems.

Boats as small as canoes or rowboats can also transport species from one ecosystem to another. Mussels and larvae can stick to the bottoms of boats. When the boat is pulled out of the water and moved somewhere else, unless the boat has been washed and left to properly dry, these tiny animals will be moved too. Once the boat reaches the new water body, the animals will drop off the boat into their new environment.

Boats with propellers also move species from one place to another. Plants can get tangled in propellers and if they are not removed before the boat is put into another water body, the plants and their seeds will be moved too.

Another way invasive species can be transferred from one place to another is by dumping live fishing bait overboard. Baitfish are not often the same species as those found in the lake or river you are fishing in. These small baitfish compete with native small fish for food and space.

Unwanted aquarium pets are another source of invasive species. When people dump their aquariums into local waterways, the turtles, fish, snails, and even plants may continue to live and reproduce. These invasives compete with native species and may even eat them!

Aquaculture is another way that invasives can be introduced into new areas. Aquaculture is a type of underwater farming. Fish or mussels are raised in large pens or nets where they are grown for food. Aquaculture fish or mussels are different from native fish and mussels because they may be different species and they are fed lots of food to make them bigger and stronger than native species. Aquaculture fish and mussels may also carry diseases because they live in crowded conditions. If these fish escape from their pens, they may bully the native species by competing with them for food and space or infecting them with diseases.

What can you do to help prevent invasives from moving into your neighbourhood?

1. Never release pet or aquarium species into the wild
2. Don't move species from one place to another
3. Wash your boat or any other water equipment before moving it to another water body
4. Don't dump baitfish overboard
5. Call your local Ministry of Natural Resources or Conservation Authority if you catch or see invasive species

What kinds of invasive species live in Canada?

Marine Plankton
Plankton are tiny microscopic organisms that drift in the top layers of the water's surface in oceans, lakes, rivers and ponds. The word plankton comes from the Greek word planktos meaning wanderer. Plankton is made up of two groups: tiny microscopic plants called phytoplankton and tiny microscopic animals called zooplankton. These tiny organisms are very important in aquatic ecosystems because plankton are eaten by insects, fish and even whales!

Canadian waters have many different kinds of plankton, and the species that live here are unique to North American waters. This plankton is different from the plankton found in European or Asian waters. When plankton species are moved from one side of the world to another in the ballast water of ships, they may bring diseases or change the food web.

Green Crab, Carcinus maenas
The European green crab is a small shore crab. Adult crabs measure 7 cm across and have dark green shells with yellow markings. Their bellies are red or yellow. These crabs are native to northern Europe.

Green crabs were first found along the east coast of North America during the early 1800's. During the 1900's these crabs invaded the east coast of Canada and the coasts of Australia, Japan and South Africa. More recently, during 1998 and 1999 green crabs were found along Canada's west coast, at Vancouver Island.

The invasion of the green crab has not been healthy for coastal ecosystems because these crabs are greedy. They eat a lot of native juvenile crabs and shellfish and compete with native fish and shorebirds for food.

Humans have helped to spread green crabs around the world in ship ballast water. But green crabs have also been spread by anglers dumping bait buckets overboard and by pet owners who no longer want their green crabs as pets.

Aquarium fish
Many different kinds of pet or aquarium species have been dumped into lakes, rivers and oceans. Aquarium species are often tropical or come from different areas of the country. These species are often bullies and may even eat native species!

Common Carp, Cyprinus carpio
Common carp are large fish measuring 35-50 cm long, which makes them the biggest members of the minnow family. Common carp are native to the fresh waters of Europe and Asia. These fish were first brought to Canada and the United States in the 1800's because they were thought to be a good fish to eat. Unfortunately, this fish spread rapidly and moved into other areas. Common carp are invasive because they damage shorelines by uprooting plants and muddying the water. This ruins the habitat for other fish and insects.

Round goby, Neogobius melanostomus
Round gobies are small European fish measuring 7-15 cm long. They live on the bottom of freshwater lakes and are able to hunt for their food in total darkness! Round gobies were transported to Canada from Europe in the ballast water of ocean ships and were first found in the Great Lakes in 1990. Since their arrival in Canada, anglers have spread this species around even further by accidentally transporting them in baitbuckets and in the holding tanks for fish in fishing boats. Round gobies are sneaky fish because they eat the eggs and the young of native Great Lakes fish and they also chase native fish like sculpins and darters away from their nests and spawning sites.

Ruffe, Gymnocephalus cernuus
The ruffe is a small, spiny, European member of the perch family that does not grow much bigger than 12 cm. They were transported to the Great Lakes in the ballast water of an ocean ship during the 1980's. Since their arrival in Canada, anglers have spread this species around even further by accidentally transporting them in bait buckets and in the holding tanks for fish in fishing boats. The ruffe competes with native fish like yellow perch and minnows for food and space because it lays mores eggs, grows faster and eats more food. Their spines also protect them from being eaten by larger fish.

Zebra mussels, Dreissena polymorpha
Zebra mussels are stripy fingernail-sized mussels from Asia. They were transported to the Great Lakes in the ballast water of an ocean ship in 1988. Since their arrival in Canada, zebra mussels have spread quickly from the Great Lakes into other waterways in Ontario and Quebec. Zebra mussels are able to spread to new locations quickly because their tiny larvae are free floating allowing them to be carried by the waves. Humans have also played a role in the spread of this nuisance species. Zebra mussels stick to the bottom of boats or any other type of underwater equipment. When boats are moved from one body of water to another, the zebra mussels move too. Fishing activites also spread zebra mussels around because anglers accidentally transport them in bait buckets and in the holding tanks for fish in fishing boats.

Female zebra mussels lay more than 1 million eggs a year! The mussels crowd together on hard surfaces including metal pipes, boat hulls, rocks, crayfish, native clams and even themselves. Zebra mussels are deadly to native clams because they smother them preventing them from moving and taking in water or food.

Links

The Great Lakes Information Network
http://www.great-lakes.net/envt/flora-fauna/invasive/invasive.html