The Park

Invasive species

Invasive species are species that move into a new ecosystem and make a new home. That might not sound so bad. After all, if you and your family were to move to a new city, no one would complain about that. But with no natural predators, invasive species can quickly spread through a new ecosystem. Once they make a new home, these species, like the zebra mussel in the Great Lakes, can cause problems for the species that already live there. Invasive species can take away habitat, food resources and spawning sites from native species, driving native species to retreat or even extinction.

How do invasive species get here?

Back when people didn't know as much about our environment, some species were released on purpose to improve the local fishing or to remind a homesick settler of the old country. The coho and chinook salmon, the rainbow trout and the brown trout were introduced to improve sports fishing. Some fish have escaped from fish farms and hatcheries. Some species are dumped into the nearest lake along with the other contents of an aquarium or a bait bucket.

In the Great Lakes, at least one-third of invasive species entered through ballast water in ocean-going ships. Once they have unloaded, large cargo ships refill their ballast tanks with local harbour water, which includes local aquatic life, to help maintain stability, especially on rough seas. When this ballast is discharged at the final destination, all of the organisms are released into the local waters. A single cargo vessel in the Great Lakes can carry up to 20,000 tonnes of ballast water and contain several hundred different aquatic species.

Follow this link to learn more about invasive species.