sealPurdue News

September 5, 1997

Sea Grant experts study zebra mussel spread, enlist boaters' aid

WEST LAFAYETTE, Ind. -- A single zebra mussel isn't much bigger than the end of your thumb, but as groups of the bivalves cling to nearly every solid object they touch, they're killing off native mussels and clogging municipal, agricultural and industrial water pipes.

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Specialists from the Illinois-Indiana Sea Grant Program, based at Purdue University, are studying their spread and looking for ways to stop the pest.

"Researchers think zebra mussels eventually will colonize most of the lakes and streams in the United States," says Pat Charlebois, Illinois-Indiana Sea Grant nonindigenous species specialist. They've already invaded all of the Great Lakes.

"Great Lakes industries and municipal water firms spent an estimated $120 million in clean-up costs in one five-year period following the initial zebra mussel invasion," Charlebois says.

A free videoconference titled "Zebra Mussels: Lessons Learned in the Great Lakes Region" will be shown from 2-4 p.m. Wednesday (9/10) at Purdue in Room 211 of the Agricultural Administration Building. The nationally broadcast program is sponsored by the Illinois-Indiana Sea Grant Program in cooperation with the Great Lakes Sea Grant Network and the Purdue University Cooperative Extension Service. To register to attend at Purdue, call 1-800-319-2432. A list of downlink sites nationwide is on the World Wide Web at

Zebra mussels look like small, yellow and brown clams. Their D-shaped shells usually show alternating dark and light bands of color. Most are less than an inch long and grow in clusters.

In the past, researchers thought the mussels only attached themselves to solid objects like rocks, boat hulls and other mussels. However, recent studies show that zebra mussels can cluster on soft surfaces. That means it's just a matter of time before they infest lakes bordered primarily by mud and sand, according to Sea Grant researcher David Garton.

When zebra mussels start growing on native mussels, they form such large masses that they kill them either by smothering or by permanently propping the natives open. Kept open, mussels are vulnerable to predators and pollutants.

"Investigators have found that heavy loads of zebra mussels have killed essentially all native unionid mussels in western Lake Erie," says Jeffrey L. Ram, a physiology professor who studies zebra mussel reproduction at Wayne State University in Michigan.

Indiana-Illinois Sea Grant researchers also are checking to see if zebra mussels play a role in the decline of yellow perch and lake trout.

"If zebra mussels are indeed impeding lake trout egg development and hatching, they may be just one more nail in the coffin for lake trout rehabilitation in Lake Michigan," says Sea Grant researcher Mike Chotkowski.

Zebra mussels grow up fast. Mussels can develop from egg to adult in less than three months. In their free-swimming, larval stage, young mussels can live in standing water in bait buckets and in engine cooling systems, Charlebois says.

"The tiny mussels form clusters that can clog a boat's water lines. They can damage boat engines if cooling systems are clogged," Charlebois says. "And as boats move about, zebra mussels are often unknowingly transported from one body of water to another."

Although no one is sure, boats probably brought the first zebra mussels to the Great Lakes. Researchers think they came over in the ballast water of a ship from Europe in the late 1980s, Charlebois says. By the autumn of 1989, zebra mussels had colonized the surfaces of nearly every firm object in Lake Erie.

As of this week, people in 19 Indiana counties have reported zebra mussel sightings to the Nonindigenous Aquatic Species section of the U.S. Geological Survey. Most mussels were seen along the banks of Lake Michigan and the Ohio River, but some have been found in the St. Joseph River and in more than a dozen inland lakes in the state.

To slow the spread of zebra mussels, Charlebois recommends that boaters do the following:

Source: Pat Charlebois, phone (847) 872-0140; e-mail,
Writer: Rebecca J. Goetz, phone (765) 494-0461; e-mail,
Purdue News Service: (765) 494-2096; e-mail,


Zebra mussels cluster on a native fresh-water mussel from the Great Lakes. Zebra mussels kill native mussels by smothering them or by permanently propping them open. (Underwater Archaeological Society of Chicago photo by Chet Childs)
Color photo, electronic transmission, and Web and ftp download available. Photo ID: Charlebois/Mussels
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