Invasive Species

Whether you live in Green Bay, Chicago, Buffalo, Toronto, or anywhere in between, the Great Lakes are under “attack.” From sea lamprey to zebra mussels to hydrilla, non-native invasive species are slowly taking over our local ecosystem. These plants, animals and even microscopic organisms are threatening to upset the native ecosystem that sustains life in the region.

Sadly, the majority of invasive species arrived in the Great Lakes as a consequence of human activity, both intentional and unintentional. Today, the greatest source of invasive species in the lakes is ballast water from ocean-going ships. International cargo ships carrying millions of tons of goods to and from Great Lakes ports every year rely on ballast water to help stabilize them on the seas. When these ships pick up new cargo, they dump tens of thousands of gallons of ballast water — often taken from distant seas — into the Great Lakes. Even the tiniest microscopic organisms found in this ballast water can take hold and cause a significant disturbance in the lakes.

Sometimes called “biological pollution,” invasive species can cause irreversible harm to native plant and animal species in the Great Lakes and related basin lands. By altering habitats, outcompeting natives for shelter and food, and reproducing unchecked without any natural predators, invasive species could cause the regional extinction of many economically and ecologically valuable species that have survived here for millennia.

The stakes are high, and local, state and national governments are spending billions of dollars each year in an attempt to contain the problem and protect the native ecosystem that supports our way of life. One study estimates that invasive species cost the federal, state and Canadian governments in the Great Lakes region more than $5 billion per year.

The high cost of controlling these invaders is borne primarily by taxpayers. More than 160 invasive fishes, plants, viruses and other organisms have settled in the Great Lakes basin and new species arrive at a rate of one every eight months.


Top Five Great Lakes Invaders

Sea Lampreys
Sea lampreys, a primitive jawless fish native to the Atlantic Ocean, began invading the Great Lakes in the 1920s. For part of its life cycle, the sea lamprey feeds on the blood and tissue of larger fishes, consuming up to 40 pounds of fish. Sea lampreys contributed to the population collapses of several large Great Lakes fishes, including lake trout, turbot and lake whitefish. Before sea lampreys invaded Lake Superior, the lake trout harvest averaged 4.5 million pounds. By 1960, it was less than 500,000 pounds.

Zebra and Quagga Mussels
While zebra mussels were a large concern over the past decade, their threat is being overshadowed by the more recently introduced quagga mussels. Quagga mussels can live in deeper, colder water than their zebra mussel cousins, enabling the quagga to capitalize on a previously uninhabited niche. Both of these mussels filter-feed up to a liter of water a day, removing large amounts of phytoplankton and decreasing the food supply for other species. A single female can produce more than a million eggs in a spawning season, creating an abundance of mussels to clog water intake structures, requiring costly upkeep and repairs.

Round Goby
The round goby is a bottom-dwelling fish less than 7 inches long, introduced in 1990 through contaminated ballast waters of transoceanic ships. A voracious feeder that can forage in total darkness, the goby’s effective sensory system detects water movement better than native fishes’, giving it a food-foraging advantage. Anglers have reported areas where round gobies appear to be the only fish present.

Spiny Water Flea
The spiny water flea is a not an insect but a crustacean with a sharp barbed tail spine that makes up 70 percent of its inch-long body and is used for protection. With few predators, populations of the spiny water flea are booming, causing populations of its food, plankton, to decline. This means a shortage of food for other species that also eat plankton, like small fishes and zooplankton. A rapid reproducer, female spiny water fleas can produce up to 10 offspring every two weeks in the summer months. In lakes dominated by the spiny water flea, anglers often find cottony clumps of the species entangled on their fishing lines that are so massive that their lines must be cut.

Asian Carp
A potential Great Lakes invader, Asian carp include four species: black carp, grass carp, bighead carp and silver carp. These large fishes (weighing up to 110 pounds) were imported into the United States for use in aquaculture in southern states. Flooding allowed bighead and silver carp to escape fish farms and enter the Mississippi River, where they quickly swam upstream into the Illinois River. If Asian carp enter the Great Lakes, via the Chicago Sanitary and Ship Canal, they are expected to become a dominant species due to a lack of predators, high reproductive rates and their ability to crowd out other fishes. Asian carp consume huge amounts of the same food eaten by native fishes, aggressively outcompeting them and eventually displacing them altogether. Silver carp periodically leap out of the water when startled, injuring boaters, skiers and anyone else in their path. Asian carp spotted just 50 miles from Lake Michigan are being prevented from entering the Great Lakes by an electric barrier in the waters of the Chicago Sanitary and Ship Canal. The barrier is only a temporary solution that requires ongoing support.

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