Exotic Species: Invading the Great Lakes Basin

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What does a ship exchanging ballast water in the Great Lakes have in common with a flood at an Arkansas fish farm or the importation of wood crates? Each has resulted in the introduction of an invasive species into the Great Lakes Basin. Invasive species include non-native fish, insects, mammals and mollusks that out-compete native species for habitat and food. Successful invaders, sometimes called exotic species, are usually very prolific and have few natural predators. Since the 1800s, over 160 invasive species have invaded the Great Lakes Basin; in other words, on average one new species takes hold every 11 months. Since invasive species cause hundreds of millions of dollars of damage to the Ontario economy and are irrevocably altering our ecosystems, the International Joint Commission (IJC) now considers invasive species as the number one threat to the health and biodiversity of the Great Lakes.

Raw wood crates used for shipping goods to the United States from Asia are thought to be the source of the emerald ash borer. First identified in 2002 in Michigan, when hundreds of thousands of ash trees began dying, this insect is now threatening to spread across southwestern Ontario, putting at risk the more than one billion ash trees in the province. Ocean-going ships travel the Great Lakes, bringing with them potential invaders in their ballast water or in their holds. Ballast water dumped into the Great Lakes has been identified as the source of many invaders, including zebra mussels, fishhook water fleas, and round gobies. Ships with ballast account for only 10 per cent of the ocean-going ships in the Great Lakes, but are responsible for at least one-third of the invasive species. Although the remaining ocean-going ships have very little ballast water, studies have nevertheless found up to 600,000 invertebrate eggs per tonne of sediment in their holds. These “no ballast on board” ships have the potential to become a significant source of invasive species.

The Asian carp, which was imported to the United States from China to control algae and snails on fish farms, escaped into the Mississippi River when Arkansas fish farms flooded in the early 1990s. The Asian carp can weigh 45 kilograms and be over one metre in length. Called a “large aquatic vacuum cleaner” by the IJC, it eats almost half of its weight a day in fish, mussels, zooplankton and vegetation. Extremely prolific, the female Asian carp carries up to one million eggs. Recently the Asian carp has been found in the Chicago Sanitary & Ship Canal, only a few kilometers from Lake Michigan. An electric fish barrier was installed in the Canal in 2002 to prevent the Asian carp and other invasive species from entering Lake Michigan. The IJC is concerned that the Great Lakes could become a “carp pond.”

Although invasive species are a significant threat to the economic and ecological health of the Great Lakes Basin, response by government has been slow and piecemeal.




This is an article from the 2002/03 Annual Report to the Legislature from the Environmental Commissioner of Ontario.

Citing This Article
Environmental Commissioner of Ontario. 2003. "The Canada-Ontario Agreement on the Great Lakes, 2002." Thinking Beyond the Near and Now, ECO Annual Report, 2002-03. Toronto, ON : Environmental Commissioner of Ontario. 76.

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