2015 Iowa Mussel Blitz

This annual research project continued this season to inventory and map the distribution of Iowa’s mussels on the Wapsipinicon River and for the first time since the first survey in 2005, the Mississippi River.

Ten species of freshwater mussels were collected in the Wapsipinicon and 23 species in the Mississippi by nearly 70 biologists, students and volunteers during the three day event. “We had excellent participation from volunteers and county naturalists in this year’s survey,” said Scott Gritters, Iowa DNR Fisheries Biologist.

Live mussels were inventoried, measured for growth; and then returned to the water. Most of the mussels were found using a technique known as pollywogging, which consists of crawling along a stream bed, probing the bottom with gloved hands.

“There’s a lot of purposes for these studies,” said Gritters. “One of the biggest things is we don’t want to harm them, and we also want to learn about the areas they live and thrive.”

“On the Mississippi River we are looking at habitat restoration projects that not only benefit fish but also provide the flows and substrates needed for mussels,“ added Gritters.

The Iowa Department of Natural Resources, U.S. Fish and Wildlife Service, and the U.S. Army Corps of Engineers began researching the disappearance of native fresh-water mussels ten years ago in Iowa, including the federally endangered Higgins eye pearly mussel. Once ranging across most of the upper Midwest, this species has been eliminated from most of the river systems it once thrived in.

"Historically, there were maybe 54 species in Iowa. Now, it's about 42. Of those, nine are endangered. Another six are threatened," explains Gritters. Several more species are very hard to find any more in Iowa

Over the past several years, stretches of the Cedar, Wapsipinicon and Iowa rivers have been stocked with walleyes and bass whose gills had been inoculated with the mussels’ larvae.

“It’s a way to reintroduce mussels into our rivers by stocking fish, which is something we commonly do anyway,” applauds Gritters. “We stock a lot of fish for our anglers and this way we can ‘double dip’, so to speak.“

This year’s Mussel Blitz proved that the Higgins eye mussels stocked previously are still successfully reproducing in the Wapsipinicon.  

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

Mussels are a good indicator of the health of a river. The better the water quality, the more mussels there are in that water. Mussels compact the algae they filter then kick out the crushed pellet to waiting fish; much like the feeding done in fish hatcheries. Many of the major walleye spawning areas are in mussel beds on the Mississippi River.
 
“Fish and mussels have ‘co-evolved.’ They somewhat depend on each other,” said Gritters. “The more mussel species; the better the mussel density; the better our fish populations; the better our water quality.”