Researchers to search Iowa River for Higgins eye pearly mussels

Already found in Wapsipinicon River near Central City

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August 18, 2014 | 12:01 am

JOHNSON COUNTY — Researchers confirmed last year that the federally endangered Higgins eye pearly mussel is reproducing naturally in the Wapsipinicon River below Central City.

Starting August 18, during Iowa’s annual “mussel blitz” research project, they hope to make a similar discovery in the Iowa River.

“We found adults in the Iowa in 2011 and this year we are hoping to find their offspring,” said Department of Natural Resources fisheries research biologist Scott Gritters, the state’s mussel recovery coordinator.

Using a technique known as pollywogging, which consists of crawling along a stream bed and probing the bottom with gloved hands, dozens of biologists and volunteers will search the Iowa River for mussels from Coralville to Hills.

“Finding young Higgins eyes in the river would prove they are reproducing — a milestone in our efforts to establish sustainable colonies in the state’s interior rivers,” Gritters said.

At a minimum the researchers will add to the growing body of knowledge about the state’s freshwater mussels and the river DNR fisheries biologist Paul Sleeper calls “the premier mussel area in Iowa,” based on species diversity and population density.

“That stretch of the Iowa River has every kind of mussel habitat, from the muddiest mud to beautiful sand, gravel and rock beds,” Sleeper said.

That it is dam-free from Iowa City to the Mississippi River, permitting the passage of many fish species that play vital roles in the life cycles of fresh water mussels, contributes to its mussel friendliness, Gritters said.

For the past dozen years, the DNR and the U.S. Fish and Wildlife Service have been engaged in an elaborate stocking program to establish in Iowa’s interior rivers colonies of Higgins eyes, which are rapidly being driven to extinction by zebra mussels in the Mississippi River.

Beginning in 2003, the biologists stocked stretches of the Cedar, Wapsipinicon and Iowa rivers with walleyes and bass whose gills had been inoculated with the mussels’ larvae.

The researchers hoped some of those tiny glochidia, which look like grains of salt on the fishes’ gills, would drop in suitable habitat and grow to be adults.

They found their first juvenile Higgins eyes in 2005 and have since found dozens of adults, all in the Wapsipinicon, until the 2011 find in the Iowa.

They have yet to find a Higgins eye in the Cedar River, though that does not mean some aren’t there, Gritters said.

Though the river is vast and juvenile mussels are small, the researchers will deploy techniques that give them a sporting chance to find them if they are there.

At 60 different sites, researchers will carefully sift the contents of 10 quarter-meter quadrants, he said.

The search crews include personnel from the DNR, county conservation departments, the U.S. Fish and Wildlife Service and volunteers.

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