Article

Mussels at Homestead

Lurking in the mud of Cub Creek are creatures with names like Lilliput, Heelsplitter, Fatmucket and Plain Pocketbook. Whether you call them freshwater mussels or something else like unionid mollusks, pearly mussels, naiads, or clams, the bivalves of Cub Creek are amazing!

Freshwater mussels live a very sedentary lifestyle moving only a few meters in their lifetime. They filter water to obtain their food, eating microorganism like algae and bacteria. As they feed, they are pulling nutrients out of the water column down to the bed of the creek repackaging it so the nutrients available to other aquatic organisms. Their shells serve as rocks to help stabilize the creek bed. Their burrowing mixes the sediment.

Freshwater mussels are food for many species such as raccoons, muskrats, fishes, turtles, and some birds. Mussels that don’t serve as food for other creatures are long-lived species. For example, the Mapleleaf mussel has an average lifespan of over 20 years, sometimes they live over 60 years.

The freshwater mussels’ sedentary lifestyle does not allow them to swim away from danger like all-terrain vehicles driven in the creeks and rivers. Their lack of long-distance mobility also makes them very susceptible to changes in the watershed including siltation and impoundments. Their feeding habit of constantly filtering water make mussels very susceptible to pollutants such as pesticides.

Because of their long life, feeding habits, and sedentary lifestyles, mussels serve as a great bioindicator of watershed health. They are the “canary in the coal mine” and sadly many of them have stopped singing in their waterways. In fact, 72% of the 300 species of mussels that live in North America are listed as either threatened, endangered, or as species of concern.

To reproduce, the males send sperm into the water column and then it is filtered out of the water by the female to fertilize her eggs. To move the species upstream, the mussels rely on fish. Some species, like the plain pocketbook, use a lure to attract fish. When the fish goes for the lure, glochidia (tiny parasitic mussels) are released from the female’s specialized chamber in the gills, called the marsupia, so they can attach to the fish’s gills. The fish hopefully swims upstream so the baby mussels can fall off after hanging on for a week or so.

Ellet Hoke found evidence of twenty-five different species of native freshwater mussels living in the Big Blue watershed of which Cub Creek is located (Hoke, 2005). In Cub Creek, nine species have been identified during the 2020 and 2021 surveys. (See the table below.) The most abundant mussel is the Mapleleaf mussel. It represented 85% of the over 800 live mussels found during 2020 and 2021.

Common Name	Scientific Name	Years found
Mapleleaf	Quadrula quadrula	2020, 2021
Pimpleback	Quadrula pustulosa	2020, 2021
Pink papershell	Potamilus ohiensis	2020, 2021
Fragile papershell	Leptodea fragilis	2020, 2021
Giant floater	Pyganodon grandis	2020 shell only 2021 live
White heel splitter	Lasmigona complanata	2020 shell only
Fingernail clams	Family Sphaeriidae	2020, 2021
Yellow sandshell	Lampsilis teres	2021 shell only
Lilliput	Toxolasma parvum	2021 shell only
Fatmucket	Lampsilis siliquoidea	Reintroduced in 2020 found in 2021
Plain pocketbook	Lampsilis cardium	Reintroduced in 2020 found in 2021

The State of Nebraska recognizes, “The loss of freshwater mussel populations is our fault and restoration in Nebraska must occur if we are to ensure their presence for future generations.” (Ohlman, et al., 2019)

The goal of mussel conservation in Nebraska is, to restore native mussel species back to their native range from where they were extirpated or severely reduced. (Ohlman, et al., 2019)

To ensure the presence of mussels, the Nebraska Game and Parks Fisheries Division has been actively raising mussels since 2015, focusing on the Fatmucket and the Plain Pocketbook.

Conversations between Nebraska Game and Parks and Homestead National Historical Park began in the fall of 2017 regarding the possibility of reintroducing Fatmucket and Plain Pocketbook mussels back into Cub Creek.

Park managers had to answer some questions before doing so. They needed to know what species were present, if the habitat was suitable and if host fish were present. Plans to complete the survey did not work out in 2018 or 2019. In 2020, Natural Resource Manager Jesse Bolli and four Youth Conservation Corp Members spent four-days crawling up the creek searching for mussels. During the four-day survey which covered 0.87 miles (1.402 km), 311 live mussels were encountered 302 (97%) were mapleleaf mussels (Quadrula quadrula), 7 (2%) were pimpleback mussels (Quadrula pustulosa), a single live pink papershell (Potamilus ohiensis) and a single live fragile papershell (Leptodea fragilis).

The survey showed that yes, Cub Creek is a suitable habitat for the Fatmucket and Plain Pocketbook: other mussels with similar needs were present. Data from the Heartland Networks fish monitoring showed that yes, the correct host species were indeed present in Cub Creek. The survey also proved that Plain Pocketbook and Fatmucket were not present. On July 22, 2020 - 500 Fatmucket and 500 Plain Pocketbook mussels were delivered from the North Platte Fish Hatchery and stocked into Cub Creek.

After the stocking, the questions became: How are they doing? Are they growing? Should we stock more? To answer those questions, it was decided that another survey needed to be completed in 2021. So, during late June, Bolli, an intern hired for the project and seven Youth Conservation Corp members started the second survey of Cub Creek within the park looking for mussels. During the eight days of sampling the team crawled on their hands and knees 0.87 miles sifting through the sediment of Cub Creek with their fingers. In 2021, 508 live mussels were encountered 20 of which were Fatmucket and 18 which were Plain Pocketbook. When they were stocked in 2020, 100 of each species had Passive Integrated Transponder (PIT) tags glued to their shells. One-hundred of the 200 tagged mussels were recovered. Ten were Plain Pocketbook and 19 live Fatmucket mussels.

While we had hoped for a higher survival rate than the 14.5-29% survival rate that we found managers felt it provided them with the information they needed to warrant additional stocking.

Through partnership with Nebraska Game and Parks it is hoped that increasing the diversity and numbers of mussels in Cub Creek will help them continue their role invigorating the freshwater ecosystem and improving the water quality for everyone from Gage County to the Gulf of Mexico.

Do your part by, when needed, wisely using pesticides and fertilizers, and limiting disturbance to the stream beds.

References

Hoke, E. (2005). The Unionid Mussels (Mollusca: Bivalvia: Unionidae) of the Big Blue River Basin of Northeastern Kansas and Southeastern Nebraska. Transactions of the Nebraska Academy of Sciences, 33-57. Retrieved from https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1042&context=tnas

Ohlman, L., Sweet, B., Bartels, T., Stoner, K., Schainost, S., Rosenthal, D., & Panella, M. (2019). Draft: Nebraska Freshwater Mussel Restoration Plan. Lincoln: Nebraska Game and Parks.