The Great Lakes and St. Lawrence River make up the world’s largest freshwater ecosystem. These waters are home to thousands of different species of plants, animals, and fish. Some of these, like the lake sturgeon and lake trout, are a special part of this great eco-system.

But, this home has been invaded by over 185 non-native aquatic plants and animals. Though seemingly harmless, many are permanently altering the health of the ecosystem and causing tremendous economic damage. These are invasive species, and represent one of the biggest threats to the integrity of the Great Lakes and St. Lawrence River ecosystem.

Most invaders arrived as a result of human activity. In some cases, introductions were intentional, such as a new fish species, like the Chinook salmon. It was introduced to enhance the sport fishery and control populations of alewife, a fish native to the Atlantic Ocean that invaded the upper four lakes when the Welland Canal was constructed in the 1800’s. Some exotic plants and animals were imported for use in aquariums, water gardens or aquaculture, like the European frogbit. Eventually they escape into the wild.

Most often in the past 50 years, though, invasive species have hitched a ride on the hulls or in the ballast tanks of ocean ships. When the ballast tanks are emptied, these invaders are discharged into the Great Lakes. Once here, invasive species spread to connecting water bodies and steadily make their way inland. This spread can be accelerated by unaware recreational boaters and anglers who do not realize the presence of this unintentional cargo on their boats and gear.

Invasive species are a problem because they do not have any predators or enemies to maintain a natural balance. With nothing to keep them in check, their numbers explode, pushing aside native species whose populations decline to dangerous levels. For example, the sea lamprey, a large eel-like parasite, feeds on native fish populations, killing them with ruthless efficiency. The lake trout, once king of the Great Lakes, was nearly annihilated by the lamprey. Another invader, the notorious zebra and quagga mussels, brought to the lakes in ocean ships, continue to cost the region hundreds of millions of dollars annually.

Canada and the U.S. both have federal regulations in place requiring that ocean ships to flush out their ballast tanks with salt water in the open ocean to remove or kill some of the invading species; however, these regulations are far from perfect. Neither country has any binding rules to require ballast water be treated to a standard that will protect our environment. The Great Lakes are a treasure to both countries and so collaborative work is needed to enact strong federal laws on both sides of the border.

Aquatic Invasive species have permanently and drastically altered the ecosystem of the Great Lakes and St. Lawrence River. But preventing new invasions and controlling the invasive species already here is necessary to preserve the integrity of the ecosystem and people’s quality of life. Dedicated actions today will help restore and protect it this diverse and precious treasure.