Last updated: February 26, 2022
Article
Partnership Is Helping Us Restore Mussel Diversity in Cub Creek
Freshwater mussels help keep our rivers and streams clean and healthy, but they’re vanishing. Our park is working to reverse their decline.
By Jesse Bolli
Image credit: NPS
“Can you eat them?” is a question I often get when I mention to visitors that freshwater mussels live in Cub Creek. This 35-mile perennial warmwater stream flows through Homestead National Historical Park, near Beatrice, Nebraska. Homestead sits about four miles upstream of where Cub Creek meets the Big Blue River. The creek drains over 90,000 acres of land. On average, Cub Creek is a little more than 16 feet wide and about one foot deep. It has steep, unvegetated banks, flanked by riparian woodlands with hackberry, bur oak, and elm.
A Vital Underdog in Need of Help
Even though freshwater mussels are overlooked by most visitors to creeks and rivers, they are a vital part of the aquatic ecosystem. They provide valuable services to water users and aquatic organisms. They filter water, repackaging nutrients and making them more available to other aquatic life. Mussels help hold the stream bed in place by acting like rocks, creating places where caddisflies and other small aquatic animals can build their homes. Their long, sedentary lives and their size make them important indicators of ecosystem health.
Estimates are that about 10 percent of freshwater mussel species in the United States are extinct as a result of human activity, and 60 percent are imperiled or vulnerable. We don’t fully know the impacts of decreased mussel diversity, but removing any nexus of a food web can have ripple effects throughout the ecosystem. Restoring freshwater mussel diversity will help the aquatic ecosystem be more resilient to change. Evidence exists for 25 different species of native freshwater mussels in the Big Blue watershed in Nebraska. The maximum range of 16 of those species has decreased by 70 percent or more. We are hoping to reverse that trend.
An Important Partnership and Some Unanswered Questions
In 2017, the Nebraska Game and Parks Commission approached Homestead about stocking native mussels within the park’s boundaries. Because Homestead is a federally protected area, it is a particularly attractive place to reintroduce extirpated species. Although park management was very interested in partnering to help these imperiled animals, our resource specialists recognized right away that we needed more information.
We consulted National Park Service Midwest Regional Aquatic Ecologist Brenda Moraska-LaFrancois. Based on her counsel, we realized that we needed an inventory of the mussels in the stream before the park could make a final decision. We made plans for LaFrancois to visit the park and lead the survey in both 2018 and 2019, but those plans were foiled by high water. In 2020, with a pandemic locking down travel, we had to come up with a new plan. We arranged for Youth Conservation Corp members to help us complete the survey of Cub Creek.
The 2020 survey took four days. The team surveyed all of the stream within the park’s boundaries, about one mile (1.4 km). We observed 311 live mussels comprising four species: mapleleaf (Quadrula quadrula), pimpleback (Quadrula pustulosa), fragile papershell (Leptodea fragilis), and pink papershell (Potamilus ohiensis). We also found shells from three additional species: giant floater (Pyganodon grandis), white heel splitter (Lasmigona complanata), and fingernail clams (Sphaeriidae family). This was a far cry from the 25 mussel species that could have inhabited Cub Creek, making a good case for the reintroductions.
Image credit: NPS
The survey data answered two main questions for the park: Was the habitat suitable for mussel introduction (yes; other similar species with similar needs were present)? Were the species we proposed to introduce already there (no)? Based on our observations, National Park Service regional staff concurred with our bid to reintroduce the missing mussels. The park approved Nebraska Game and Park’s plan to stock Cub Creek with 500 fatmucket (Lampsilis siliquoidea) and 500 plain pocketbook (Lampsilis cardium) mussels.
The stocking team fitted 100 of each species with passive integrated transponder (PIT) tags. The tags were about the diameter of a pencil lead and about 0.4 inches (1 cm) long. We attached them to the mussels using dental cement. These tags have a unique number that staff can read with portable handheld devices. This allowed us to find, identify, and determine the growth of individual mussels. The team divided the mussels evenly between two different stocking sites. Each of the stocking sites was about 328 feet (100 m) long.
Image credit: NPS
Further Actions Required More Data Collection
In 2021, Homestead and Nebraska Game and Parks discussed additional stocking. Before moving forward, the park felt it prudent to determine the success of the 2020 stocking. That year, Jorge Vargas-Barriga, a Mosaics in Science intern, joined the team of staff and YCC members to help us determine the survival and growth rate of the mussels we had stocked.
During that more intensive eight-day survey, we found 508 live mussels. We found 66 of the fatmucket mussels we stocked in 2020, 21 live, 19 of which were tagged. We also found 84 plain pocketbook mussels, 18 live, 10 of which were tagged. We found many of the shells on the banks of the creek, likely placed there when we stocked during high water, or deposited by predators.
We recovered 100 of the 200 mussels that we had fitted with PIT tags, 29 of which were live and had grown an average of about three quarters of an inch (19.9 mm). Knowing that 14.5 percent of the tagged mussels were thriving, we determined that additional stocking would be a good idea. We stocked the same sites in July 2021. Our hope is that by stocking the mussels in the same area, the population will be big enough to reproduce naturally.
"Farming practices, chemicals, water flow changes, low head dams, changing fish populations and many more things have had a negative impact. Reintroductions give mussels a chance to regain part of their native range.”
The Right Time for Reintroductions
Nebraska Game and Parks Fisheries Biologist Bryan Sweet feels that this is the right time to be focusing on reintroductions. “The landscape of Nebraska and the U.S. in general has changed greatly in the last few hundred years, and with that change has come a change in the native fauna and flora,” he said. “Mussels are one group of native species that were greatly affected in a negative way during this time. Farming practices, chemicals, water flow changes, low head dams, changing fish populations and many more things have had a negative impact, whether it is direct or indirect in nature. Many of these negative factors affecting mussels, though not all the above, have been mitigated to some degree. Reintroductions give mussels a chance to regain part of their native range.”
Image credit: NPS / Jesse Bolli
Success on Many Levels
Homestead views this project as a great success on many levels: reintroducing extirpated species, expanding our partnership with Nebraska Game and Parks, and introducing the public to the importance of mussels in an aquatic ecosystem. By partnering with the state agency, we hope for an even more abundant and diverse mussel population in the future. But maybe the greatest success is getting staff, interns, and conservation corps members into the creek, giving us all a more intimate connection to our resource.
As to the question, “Can you eat them?,” muskrats and raccoons do, but I am not planning on it.
About the author
Resource Management Specialist Jesse Bolli has served Homestead National Historical Park since 2002. Getting visitors and volunteers to experience the park through hands-on science has been a major theme for him over almost 20 years. Jesse has the most fun when students assist him with monitoring deer or the water quality in the creek. Image credit: NPS / Amy Genke