Searching Iowa Waterways for Native Mussels

Aug 6, 2015 | 08:15

(This video was originally broadcast on Iowa Outdoors, Episode 504, August 6, 2015.)

Iowans with a keen eye for angling take pride in knowing each one of the different types of fish species that inhabit our waters every year. But how many Iowans know each and every one of the 54 different types of mussels in our state? Well, at least Iowa used to have 54 different mussel species, before losing nearly a dozen over the past couple decades. Iowa's species loss is echoed throughout North America, and it's part of the reason why you'll see researchers wading and groping along the Iowa River for everything from Fat Muckets to Elktoes.

Every August since 2005, a group of people gathers over the course of a couple of weeks to survey Iowa's mussel populations in eastern Iowa rivers. It's called the annual Mussel Blitz. They're doing important research about a struggling population of simple-looking, yet complex creatures in Iowa waterways, where they once thrived, but now can be hard to find.

Scott Gritters, Fisheries Biologist, Iowa DNR: It has been a fun effort trying to teach people, trying to have the world's experts here and then having people that just don't know much about it at all but want to learn. It's one of the opportunities where somebody can just walk off the street and get in with, they sign a waiver and they can come in our boat and they can be sitting right next to the world's expert on this type of restoration. And it has just been a neat effort.

Over the years, the Blitz has targeted several rivers, including the Cedar, Maquoketa, Wapsipinicon and different pools along the Mississippi. This particular Blitz is covering several miles of the Iowa River near Iowa City.

Dan Kelner, U.S. Army Corps of Engineers, St. Paul District: And this site on the Iowa River is one of ten areas where we've tried to re-establish species through propagation and reintroduction and relocation of existing populations to areas within the species' historic range. And the main reason was to remove the species from the threat of Zebra mussels. 
Gritters: If you're familiar with the Zebra mussel, the exotic mussel got introduced into the Mississippi and really threatened our mussel populations on the Mississippi. So we felt we really needed, now is the time to really start reintroducing mussels back into where they historically were. So we didn't have all our eggs in one basket though, we didn't have all our mussels remaining in the Mississippi. 

Researchers and volunteers search for mussels by using a technique called pollywogging. 

Ashley Knudson, Volunteer, Iowa City: Essentially we're just kind of on our hands and knees deep in the water and then just rubbing our hands back and forth. We've got knee pads on in case it's kind of rocky and then gloves and we're just picking up any mussels and a lot of them, false alarm, rocks. And then people have got bags and we'll collect them as we go along and then throw them back if they're alive. 

With the help of scuba gear, they also use a quadrat to do density studies, documenting what they find in a quarter meter square area. Over the course of this Blitz, they'll take as many as 600 quadrat samples. 

Kelner: Here is Fawnsfoot. They don't get much bigger than this. So one of the reasons we use this bag is so we can collect little guys like this, otherwise we would never be able to see it or feel it, so we need to do a whole substrate sample. Hey we did get a live Fawnsfoot in that first one… So this is the first live mussel we've found in a quadrat today, quadrat sample. That's a Fawnsfoot, Truncilla donaciformis. This is one of the more rare mussel species in the upper Midwest, Mississippi, Iowa River. So this is pretty good news. So we'll measure it, we'll age it. This individual looks like it's two years old. You can age them just like you would a tree, by counting the anuli lines that they lay down annually. So the number of annuli they have is close to its age. 

At one time, Iowa had 54 species of freshwater mussels. Only about 40 species exist today, and about a third of those are endangered or threatened. 

Gritter: This is the kind we're looking for. This is a Higgins' Eye. This is the ones that we've actually stocked.

One of the main goals is to help re-establish the Higgins' Eye pearly mussel to areas where it historically lived, such as the Iowa River. On this mussel Blitz, crews found seven Higgins' Eye pearly mussels.

Gritters: Mussels are awesome indicators of water quality. They have to sample our water 24/7. These things have to live out there the whole time. The health of the rivers that we swim in, drink in, boat in, we could use mussels, if we can get good water quality, if we have mussels those will be good places to be.

Kelner: We were just walking the quadrat back to the shore and I stepped on this one actually. So it's all sand and mud like this, so I just felt it with my foot and just reached down and grabbed it and it was this guy. 

Mussels and fish are linked. Mussels use fish as carriers to reproduce. Iowa DNR and Fish and Wildlife officials have put tiny young mussels, about the size of a grain of salt, onto fish gills at the hatchery. Then, when they stock those fish in the rivers, hopefully some of those mussels will find a permanent home. Mussels aren't just hitchhikers, they benefit fish too. 

Gritters: Some fish, like drum, catfish, eat mussels. But also the mussels are feeding the fish. Would we have fish out here without mussels? Yes, we would. But we wouldn't have as many. We wouldn't have maybe some of the kinds that our anglers enjoy catching. 

Kelner: And we have found individuals that we have placed into the river, we have found them living twelve, thirteen, fourteen years after. So we know once we put them there, those individuals can live. But now we have also found evidence of recruitment of individuals back into those populations. So, the individuals we put out are reproducing so new individuals are coming into that area. And that's really the ultimate goal of this is to establish self-sustaining populations on their own where they won't need our assistance anymore.

Kelner: These obviously are dead. The animal inside died, but we find a record of what was here by collecting empty shells, either along the bank or in the water.

The mussel Blitz brings together a number of government agencies and biologists from states along the upper Mississippi. They also recruit the help of volunteers. You can find out more information about the annual August Mussel Blitz through the Iowa DNR.

Gritter: Here you can actually do that, you can come and be a part of it. And, frankly, volunteers make an effort. Last year our first Higgins' Eye that we found was found by a pure volunteer, that person just showed up off the street. So it was awesome. 

Mussel research and restoration is an important part of protecting Iowa's waterways, helping to create a healthy ecosystem in an Iowa outdoors that is plentiful with species of native freshwater mussels.

Gritter: If we're willing to give up things like mussels, which a lot of people seem to be willing to do that, we start cutting out parts of our ecosystem and pretty soon the ecosystem is just a simple, non-interesting place. It's a lot easier keeping the species that we have here now than to have to do this whole reintroduction later. 

Gilchrist Foundation