The Invasives Attack

Learn about the spooky invasive species that threaten the Great Lakes

October 23, 2019

Are you afraid of what’s lurking in the Great Lakes? This Halloween, we’re getting spooky with some invasive species that have invaded the lakes – and more species threatening to cause havoc if we don’t stop them.

Sea Lamprey

This species, native to the Atlantic Ocean, spread throughout the Great Lakes through the creation of man-made canals. The lamprey is especially spooky looking, with a disc-shaped, suction-cup mouth ringed with sharp, horny teeth.    It latches onto native fish, then uses its rough tongue to rasp away the fish’s flesh so it can feed on its host’s blood and body fluids. One sea lamprey kills about 40 pounds of fish every year.

Zebra and Quagga Mussels

Unlike the vampire-like sea lamprey, zebra and quagga mussels cause damage in another way. Economically. They’re native to the Black and Caspian Seas, but came to North American in the untreated ballast water of ocean-going ships. They were first discovered in 1986 but quickly spread to the Great Lakes and across the U.S. There are an estimated 450 trillion quagga mussels in Lake Michigan alone. Even though they’re only several inches in size, they can filter up to one liter of water daily. They like to eat native species like diporeia, wreaking havoc on the food chain. They spit out organisms like mycrosystin, which causes harmful algal blooms. Additionally, they clog water pipes and screens, costing industry and water treatment plants millions of dollars annually.

Spiny Water Flea

This European native was brought to North America in the untreated ballast water of ocean-going ships. The spiny water flea is a plankton species with a long spiny tail that covers about 70 percent of its entire body. It is difficult for juvenile native fish to eat them because of this tail, allowing the spiny water flea to outcompete native zooplankton species and threaten the food supply.

Not Established but Potential Invaders of the Great Lakes

Invasive Asian Carp

The bighead and silver carp are native to China and were brought to the U.S. to control weeds on fish farms in the 1970s. They escaped the farms during floods and have been spreading throughout the U.S. They are not yet established in the Great Lakes, but they loom closer each year. Adult bighead carp average 40 pounds but can weigh up to 100. Adult silver carp weigh between 20 and 60 pounds. They eat between 20 to 120 percent of their body weight in plankton every day. This depletes the food source for native species. Additionally, silver carp can leap 8 to 10 feet out of the water and have injured boaters.

Killer Shrimp

This species of shrimp is native to the Black and Caspian seas and could invade through untreated ballast water of ocean-going ships. They get their spooky name for their penchant of killing and injuring prey, but not always eating it.

Northern Snakehead

This species of fish was originally native to Russia, China, and Korea. They have been found in the U.S., including in the Mississippi River Basin, and a few have even been found in the Great Lakes, though they are not believed to be established here yet. They use their sharp teeth to kill and eat other fish, amphibians, and small mammals. The snakehead is able to move across land and live out of water for up to a week—earning it the nickname “Frankenfish.”