A small group of volunteers gathered under the Hazen Bridge for a mussel survey last Saturday.

For nearly three hours, they combed the Sangamon River.

The Upper Sangamon River Conservancy (USRC) is a group that runs the mussel survey every year.

The goal is to measure the amount of mussels, which can be used to determine the health of the Sangamon River.

"Mussels are filter feeders so they can be used as indicators of stream health because they are so directly exposed to it," USRC President Bruce Colravy said. "Some think they are the most imperiled animal group because of that."

The USRC was founded in 2009 and has been running the mussel surveys since 2011.

Colravy usually leads a group of seven to 10 people every year at the Hazen Bridge site.

"We started to do the bridge a few years ago, but I think last year we weren't able to do it," Colravy said.

"If the water level doesn't get low enough, then we can't get in. But this year, it's at an ideal level, so it'll be good."

The group discovered 10 different varieties of mussels.

Pimpleback is the most prevalent variety, and the group discovered 113 of them.

"We've gotten a total of 18 live species in our surveys," Colravy said. "Fourteen species at any one site is the most we've ever had."

Historically, there are 80 species of mussels in Illinois, so the small numbers show how the mussels have deteriorated over the years.

Brooks Hauser is a senior at the University of Illinois and is the president of the UI's Wildlife Society.

"The first time I did this was my freshman year of college at the U of I. I didn't actually get more involved until the beginning of last summer," Hauser said.

"It's great. These are my favorite things to do."

The USRC hopes to get more people involved with the Sangamon River.

With more hands-on contact, they also hope that people will want to take better care of the Sangamon.

"People can be a citizen scientist and the information can be used to judge the potential failures of conservation efforts or the health of the stream," Colravy said.

"People have no clue that these even are here," Hauser said. "The biggest benefit is getting more people to care about it."

The USRC will have another mussel survey on Sept. 9 at the Sangamon River Forest Preserve.

"Our purpose is to preserve, maintain, monitor and promote public use and awareness of the Sangamon River," Colravy added.