Invasive Mussels

The United States is experiencing a devastating attack from some very small invasive species--called zebra and quagga mussels.

Zebra mussels on a stick

Zebra mussels and quagga mussels are virtually identical both physically and behaviorally. Originally from Eastern Europe, these tiny trespassers were picked up in the ballast water of ocean-going ships and brought to the Great Lakes in the 1980s. By 1990 zebra mussels and quagga mussels had infested all of the Great Lakes.

Now, both quagga mussels and zebra mussels have spread to 29 states by hitching rides on boats moving between the Great Lakes and Mississippi River Basins. Artificial channels like the Chicago Area Waterways System facilitate their spread. These man-made channels act like super-highways and are also a pathway for Asian carp, which are currently spreading towards the Great Lakes.


In her five-year lifetime, a single quagga or zebra mussel will produce about five million eggs, 100,000 of which reach adulthood. The offspring of a single mussel will in turn produce a total of half a billion adult offspring. It’s easy to see why there are an estimated 10 trillion quagga and zebra mussels in the Great Lakes today!


Zebra and quagga mussels feed on small organisms called plankton that drift in the water. The 10 trillion quagga and zebra mussels blanketing the bottom of the Great Lakes filter water as they eat plankton and have succeeded in doubling water clarity during the past decade. Clear water may look nice to us, but the lack of plankton floating in the water means less food for native fish.


It is imperative to prevent zebra and quagga mussels from spreading further, and to keep new invasive species out of the Great Lakes. NWF supports stronger ballast water regulation as well as improved methods of ensuring recreational boats are cleaned of invasive species before moving between bodies of water.

Zebra and quagga mussels harm native fish populations, ruin beaches and attach to boats, water intake pipes, and other structures causing the Great Lakes economy billions of dollars a year in damage.

They devastate native species by stripping the food web of plankton, which has a cascading effect throughout the ecosystem. Lack of food has caused populations of alewives, salmon, whitefish and native mussel species to plummet.

Zebra and quagga mussels promote water clarity by filter feeding. Clearer water allows sunlight to penetrate to the lake bottom, creating ideal conditions for algae to grow. In this way, zebra and quagga mussels have promoted the growth and spread of deadly algae blooms. Algae foul beaches and cause botulism outbreaks that have killed countless fish and more than 70,000 aquatic birds in the last ten years.


Once zebra and quagga mussels become established in a water body they are impossible to fully eradicate. Scientists have not found solutions that kills zebra and quagga mussels without also harming other wildlife.

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