Mussel sampling is a fun way to experience your river
I was fortunate to join a mussel sampling expedition on the Cedar River in Iowa a couple weeks ago. The Iowa DNR is updating their statewide inventory of mussels, so they are sampling many new areas as well as repeating visits to sites that were known to host mussel populations years ago. Biologists at the DNR encourage the participation of interested volunteers, which offers a great opportunity to learn about the sampling techniques, the biology of mussels and how to identify a variety of species. It’s also just a great excuse to get wet and look closely at a stream, something no American Rivers staffer can resist.
Mussels are usually considered to be intolerant of poor water quality. A large diversity of mussels can suggest the presence of good fish populations because mussels require fish for the transformation from their infant stage (glochidia) to the self-sustaining stage. Mussels also provide a unique service of water filtration as they pump water in and out in search of food. In some eastern states, restoration of mussels is now desirable for the improvements gained in water quality and some researchers have estimated that the healty mussel beds of the free-flowing sections of the Delaware River can filter the river’s normal flow more than six times before it reaches the Delaware Estuary!
But back to the Cedar River. Our crew broke up into 3 separate groups, consisting of 4-7 people each, to sample a section of the upper Cedar River in Floyd County, Iowa. The Cedar River actually begins in southern Minnesota and flows south through central Iowa before merging with the Iowa River and finally dumping in to the Mississippi River near the small town of Toolesboro, IA. We were in a lovely section of the river that flows across the Iowan Surface, which is geologic terminology for a landscape with long, rolling terrain that contains glacial features.
Our group searched in the section pictured here. A few folks snorkeled in the shallow water, others just used masks to stick their head partially in, others waded in boots or old shoes and reached in when they spotted a mussel. We spread out across the river channel and walked upstream in search of mollusks. Whenever we spotted a living mussel, we pulled it out from the river bottom and placed it in a mesh bag that stayed underwater. We also collected a lot of empty shell so we could record the recent presence of species that we may not have found in our living collection. The type of surveying we conducted is known casually as “timed effort” surveying because the number of searchers is multiplied by the time spent searching to generate a value that represents the effort invested in finding mussels.
Having learned most of my mussel knowledge in the mid-Atlantic, I was treated to an entirely new suite of mussels in the Cedar. I was struck by how heavy, large and sturdy many of these species were in comparison to the mussels I usually found in Pennsylvania. Midwestern mussels also have much more interesting common names. Some of the ones we saw include the monkeyface, plain pocketbook, strange floater and elktoe.
American Rivers listed the Cedar River as one of the Most Endangered Rivers of 2010 in recognition of the need for improved flood and water quality management to safeguard communities and the rivers they depend upon. Since that time, we have been participating in the Cedar River Watershed Coalition to help develop locally-supported plans for managing floods that maximize the services a healthy river can provide to communities.