STORY BY P.J. PEREA
PHOTOS BY ADELE HODDE

Mussels of Illinois: A. plain pocketbook; B. giant floater; C. pimpleback; D. yellow sandshell; E. butterfly (state-threatened); F. deertoe.     Higgins' eye mussels like this female (top) and male (bottom) are being used to reestablish new populations in the Mississippi River Basin.

It must be really difficult to be a Higgins' eye pearly-mussel. After surviving the unregulated harvest of freshwater mussels for the mother-of-pearl button and pin industry during the late 1800s and early 1900s, and living through the habitat destruction and toxic runoff of the industrial and agricultural era of the 1900s, you'd think things would be looking better for them today. Federal, state and local programs ensure cleaner water, restore habitats and control erosion, and many species of fish and wildlife have recovered in our river systems. Yet the Higgins' eye pearlymussel, which has suffered greatly at the hands of people, may be in danger of experiencing a slow, choking death while entangled in the byssal threads of a distant cousin, the zebra mussel. Granted, it's people who are ultimately responsible for introducing this biological pollutant into North America, but this destructive invader from Asia may wield a deadly blow to an already beleaguered group of bivalves. Zebra mussels are small, fingernail-sized mussels native to the Caspian Sea region of Asia. Their young, known as veligers, apparently hitchhiked a ride in the ballast water of transoceanic vessels entering the Great Lakes. They were discovered

16  OutdoorIllinois

Hope Oodd (left) and Ann Holtrop of the Natural History Survey place their mussels into a mesh collection bag.

in Lake St. Clair near Detroit in 1988 and have spread throughout the Great Lakes, and the Illinois and Mississippi rivers.

They continue to spread along the Mississippi River as boats and barges carry the adults further and further upstream, and current shoots their offspring downstream.

Scientists monitoring the zebra mussel infestation in Pool 9 of the Mississippi River at Prairie du Chien, Wisconsin, were alarmed to find that, in only two years (1999 and 2000), the population of Higgins' eye pearlymussel collapsed to undetectable levels. The zebra mussels appeared to have wiped them out completely.

Due to the frighteningly quick local extinction at Prairie du Chien and the rapid decline of other mussel species in the lower pools of the Mississippi River, the U.S. Fish and Wildlife Service moved forward with the Higgins' eye pearlymussel recovery plan to save the species from almost certain extinction.

During the summer of 2001, state and federal biologists came to Cordova, a small town located along the banks of the Mississippi River in northwest Illinois, to assess the situation of the Higgins' eye pearlymussel, teach mussel identification, bivalve collection and zebra mussel removal techniques to biologists and also to recover live Higgins' eye specimens for relocation. Cordova was chosen because it had one of the greatest concentrations of Higgins' eye pearlymussels left in North America. As a remaining stronghold, it held hope for repopulating the rapidly dwindling species.

Kevin Cummings of the Illinois Natural History Survey, Bob Schanzle of the Illinois Department of Natural Resources and Kurt Welke of the Wisconsin Department of Natural Resources led workshops, teaching biologists how to identify the numerous mussels that inhabit the local waters near Cordova and explaining their complex life history.

"The Higgins' eye uses an elaborate mechanism for reproduction. The female mussel actually uses a minnow-shaped lure to attract the attention of a hungry fish. Once the fish grabs the lure, the mussel injects tiny mussel larvae known as glochidia into the mouths of fish. These glochidia attach to the gills of the fish and steal a free ride. The inoculated fish are not harmed by the glochidia. Eventually, the glochidia transform into juvenile mussels and fall to the river bottom where they develop into adult mussels. It's a fascinating method of dispersal," Cummings explained.

He mentioned the introduction of the zebra mussels in the Mississippi river system as a factor in the decline of the Higgins' eye pearlymussel, as well as many other species.

David Heath of the Wisconsin DNR talked about the effects the zebra mussel has on the endangered Higgins' eye pearlymussel.

"The zebra mussels put an enormous amount of stress on the Higgins' eye. They colonize the outer surface of the shell. This makes it difficult to feed and siphon fresh water. The water quality becomes poorer as the zebra mussels generate ammonia waste products, which create low dissolved oxygen conditions. Carrying the extra weight of sometimes dozens of zebra mussels saps energy reserves of the Higgins' eye, and the mass of zebra mussels interferes with the process of reproduction," Heath said.

Kevin Cummings discusses the complex life history of various freshwater mussels with one of the collection teams.

March 2002 17

Bob Schanzle points out the identifying characteristics of the numerous mussel species found at Cordova.

Once familiarized with identifying the Higgins' eye and other rare species of mussels, the teams of biologists scoured the bottom of the Mississippi River. Besides gathering the endangered Higgins' eye, the teams also removed the persistent zebra mussels from the shells of live native mussels using KEVLARTM gloves to protect their hands from the razor-sharp shells.

Some groups waded up to their chests into the balmy, bath-temperature water, probed the muck and pulled the mussels from the bottom. Others donned snorkeling and scuba gear and swam out to deeper water. One small group hopped into a boat and dragged the bottom with a device called a brail bar. The bar had small rounded hooks, known as crow's-feet, that hung from a string or chain. The device would drag along the bottom until one of the crow's-feet encountered a mussel with its shell open. The alarmed mussel would then close its shell and grab the end of the hook, resulting in the mussel being extracted from the bottom.

Every few hours, the teams would come together and sort their finds. Dozens of specimens with interesting names, such as washboard, pistol-grip, wartyback, monkeyface, three-ridge, spike, pocketbook, Wabash pigtoe, butterfly, deertoe, pink heel-splitter, yellow sandshell and Higgins' eye, crowded the tables. The collection proved to be an immense learning experience for the biologists, many of whom were unfamiliar with the wealth of mussel diversity found in the Mississippi River.

The Higgins' eye mussels were separated, and the rest were returned to their homes. The Higgins' eye mussels were cleaned of any zebra mussels and etched with a unique letter and number combination using a small rotary grinding tool.

Bonnie Bowen of Iowa State University clipped a small piece of flesh from the mantle, the organ responsible for creating the brilliant nacre or mother of pearl found on the inside of mussel shells. Bowen explained that she was studying the genetic structure of the Higgins' eye mussels to see if there were distinct populations.

After two days of sampling, 271 Higgins' eye pearlymussels were processed and tagged.

A multi-agency team of biologists gathers to sort its mussel finds. Despite the hundreds of mussels collected by the group, only a few were Higgins' eye mussels.

Mussel Bound: looking for mussel resources? INHS Freshwater Mollusk Collection Page—Site includes online version of Field Guide to Freshwater Mussels of the Midwest, Illinois collection database and useful links about freshwater mussels www.inhs.uiuc.edu/cbd/collections/mollusk.html. The Freshwater Mollusk Conservation Society—FMCS is an organization devoted to the advocacy for, public education about, and conservation science of freshwater mollusks, North America's most imperiled fauna. Freshwater Mollusk Conservation Society, c/o Heidi Dunn, 1417 Hoff Industrial Park, O'Fallen, MO 63366, phone (636) 281-1982. Online at ellipse.inhs.uiuc.edu/FMCS/. The USGS Zebra Mussel Information Page—Online at nas.er.usgs.gov/zebra.mussel/docs/sp_account.html. The National Sea Grant Non-Indigenous Species Site—Online at www.sgnis.org/. References Field Guide to Freshwater Mussels of the Midwest. Illinois Natural History Survey Manual 5 by K.S. Cummings and C.A. Mayer. Available through Publication Office, Illinois Natural History Survey, 607 East Peabody Drive, Champaign, Illinois 61820 (217) 333-6880 or online at www. inhs.uiuc.edu/chf/pub/.

18  OutdoorIllinois

Kim Bogarshultz of the Iowa DNR practices her mussel identification skills.

Many scenarios were discussed by the recovery team about the fate of the Higgins' eye mussels found at Cordova. One involved moving some of the mussels to the "clam palace" at the Genoa National Fish Hatchery in Wisconsin, where fishery scientists were attempting to culture Higgins' eye mussels and stock the new juveniles in safer areas via inoculated fish.

Another idea was to move the mussels to an upper pool of the Mississippi, where the zebra mussels had not established a foothold. In the end, it was decided that the Higgins' eye mussels would be sent to Minnesota and placed in Pool 2 of the Mississippi River.

New strategies in 2002 for Illinois Due to the successful inoculation and release of young Higgins' eye mussels in Iowa and other locations, Illinois will be using some of the Cordova Higgins' eye mussels in an attempt to re-establish the species in Pool 24 of the Mississippi River and in several locations on the Rock River. Pregnant female Higgins' eye mussels from Pool 2 will be taken to Genoa National Fish Hatchery and used to inoculate fish that will be sent to Illinois.

Recently, Mike Davis of the Minnesota Department of Natural Resources provided an update on the status of the Higgins' eye mussels from Cordova.

"As of the fall of 2001, they were doing very well. We'll continue to monitor their progress. They are in an area that is relatively free of zebra mussels. A few (zebra mussels) are still brought in by barges, but they have never established themselves in Pool 2," Davis said.

Roger Gordon of the Genoa National Fish Hatchery and Kurt Welke of WDNR reported that a dozen gravid females from the Cordova population living in Pool 2 were used to inoculate more than 1,700 largemouth bass, small-mouth bass, walleye and sauger in the fall of 2001. The fish were released in the Cedar River in Iowa in an attempt to reestablish populations in the area.

Zebra mussel chowder anyone? Native mussels on the Mississippi River were given a brief respite last fall as low water levels and high water temperature proved to be fatal to millions of zebra mussels. Tremendous die-offs were reported throughout the Mississippi River as dead zebra mussel shells washed up in piles along shorelines. The byssal threads that allow them to tenaciously cling to any hard substrate proved to be their undoing, as they were unable to move. While native mussels protruded a slimy foot and slid to cooler waters, the zebra mussel beds baked in the hot sun and simmered in the hot, shallow water. "We hope that this die-off will allow some of our native mussel populations to recover," commented Dan Sallee of DNR's Division of Fisheries.

Hopefully, their new homes are suitable for the Higgins' eye mussels, and they'll be able to multiply enough to provide a stable population. The Cordova population in Pool 2 will be used to seed new generations of mussels in the Mississippi River drainage. If by some miracle the zebra mussels are eradicated or become less of a threat, many generations down the road, the Higgins' eye mussel may some-day find its way back home to Cordova, its young attached to the gills of an unsuspecting walleye. Otherwise, the zebra mussel may provide a slow, quiet death for the species and silence the clamor over the Higgins' eye pearlymussel.

Les Morrow of the Illinois EPA lowers the brail bar into a deep pool hoping to find mussels.

March 2002   19