Mussel Blitz

An annual research project to inventory and map the distribution of Iowa’s mussels, often called clams.

More than 50 biologists, students and volunteers collect species of freshwater mussels in the during the three day event held each August since 2005.

“We have excellent participation from our conservation partners, volunteers and county naturalists with each year’s survey,” said Scott Gritters, fisheries biologist with the Iowa Department of Natural Resources (DNR). “These studies help us learn more about mussels and the areas where they live and thrive,”

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

The Iowa DNR, the U.S. Fish and Wildlife Service and the U.S. Army Corps of Engineers started researching the disappearance of native fresh-water mussels in Iowa 12 years ago, 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 of native mussels in Iowa,” Gritters said. “Now, it’s about 42. Of those, nine are endangered. Another six are threatened and several more species are very hard to find any more in Iowa.”

For more information, contact Scott Gritters,  Fisheries Biologist with the Iowa Department of Natural Resources (DNR). Bellevue Fisheries:  
24143 Hwy. 52, Bellevue, IA 52031, Phone:  563-872-4976

Please forward corrections or additions to