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March 28, 2014

Reintroduced Northern Riffleshell Thrives in Ohio’s Darby Creek

The life cycle of the northern riffleshell mussel is surprising both in its violence and its pacifism. The female riffleshell captures a small fish and releases its larvae onto the host. As the host fish swims, the mussel’s progeny go on the ride of their lives, being dispersed far and wide.

“The riffleshell lives about 20 years, feeding on protozoa and bacteria,” says Dr. G. Thomas Watters, curator of the Division of Molluscs at Ohio State University’s Department of Evolution, Ecology, and Organismal Biology. (That’s a mouthful, isn’t it?) “They filter the water and are a major part of the water’s biomass and a major part of the food chain.” Watters adds, “They ride around on the fish as a means of being dispersed, but they’re pretty benign as parasites go.” He says the riffleshell actually does little or no harm to its host as he refers to an otherwise gruesome photo of the process.

Photos via Ohio State.

Once upon a time, the riffleshell was abundant in the upper Ohio River and western basin of Lake Erie, according to OSU’s EEOB Department. Unfortunately, the species slowly dwindled over the course of the past 30 years.

Dr. Watters regards the riffleshell as a bioindicator, like many mussel species. A bioindicator species is one of the first to display signs and symptoms as a result of pollution or other environmental stresses. When these organisms disappear, it typically indicates something it the ecosystem is amiss.

Dr. Watters cites multiple causes for the decline. “It’s sort of the straw that breaks the camel’s back,” Watters says. “Water quality, habitat destruction, lots of pollution, and of course dredging the river is not good.” He says freshwater mussels in general across North America have been disappearing, and once gone, they may never come back.

That was not going to be the fate of the beloved riffleshell. In 2008, Dr. Watters and his team first took part in Ohio’s largest endangered species relocation in the state’s history.

Views of the Allegheny River by Heather Lovelace; 1 & 2.

“The Allegheny River in Pennsylvania has thousands of individual riffleshells, so it was determined to be a good source for the relocation,” says John Navarro, program administrator of Ohio’s Department of Natural Resources Division of Wildlife. Once the team determined the populations in Darby Creek and the Allegheny River were similar enough, they initiated the project. With the help of the Pennsylvania Boat Commission, they reintroduced 50 individual mussels into Darby Creek as a trial. The trial went smoothly, so 1800 more mussels were reintroduced into Battelle Darby Creek Metro Park in 2008. Another reintroduction took place, and to date, 3800 mussels have been relocated to Darby Creek.

The program has been a huge success. Dr. Watters says about 50 percent of the mussels were accounted for after the relocation. “Those are really good numbers, indication the reintroduction is going well.” The relocation team also includes the Columbus Zoo and Aquarium’s Freshwater Mussel Conservation and Research Center, where Dr. Watters is the science director. Other partners are U.S. Fish and Wildlife Service, Ohio’s Department of Natural Resources Division of Wildlife, and Columbus Metroparks.

Photo via US Fish & Wildlife Service.

Navarro says he also has high hopes for the reintroduction of the clubshell mussel, which is also endangered. “That’s one they’re still looking at the genetics of the population, to make sure [the species] in the Allegheny River is similar to the one in Darby Creek. Hopefully they’ll be able to figure that out. Then we’ll be able to move ahead.” Navarro says citizens can help fund these types of projects through “the sale of wildlife license plates, tax-checkoffs, and wildlife legacy stamps.”

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Posted by Mark Contorno.

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