Freshwater Mussels in Peril


blog post photo
Above: Tagged mussels

Most freshwater mussel species burrow in the bottoms of rivers and streams. They draw water inside their shells, breathing and filtering food with gills. When mussels move, they don’t move far – one hundred feet for a mussel is impressive – but they do have a muscular limb that assists in burrowing and travel.

It might surprise you, but North America’s freshwater mussels are in peril. Threatened by a combination of habitat destruction and water pollution, their demise is a direct reflection of human influence. And with nearly 300 species living in the United States, case studies on freshwater mussels may help identify human errors and save a species.

“Freshwater mussels are a part of our natural heritage and their loss indicates that we have been doing something wrong – we have not been good stewards of the environment if we allow species to slip away,” says Dr. G. Thomas Watters of The Ohio State University Museum of Biological Diversity. “Who’s to say which species are important and which are not? Mussels form a huge amount of the biomass in a creek or river and have been shown to stabilize the riverbeds they populate. They are food to other organisms. They filter the water 24/7. They are our sentinels of water quality, the canary in the coal mine. If I go someplace and find abundant mussels, to me it suggests that this is a place where I can take my family and fish, boat, swim, etc… If I go someplace and there are no mussels – that is a red flag that something may have happened here that needs to be investigated.”

The Columbus Zoo and Ohio State University are conducting collaborative studies on a freshwater mussel, the endangered Northern Riffleshell (NRS). This species was once abundant in the upper Ohio River system, but now only a few reproducing populations remains.

“If you look at freshwater mussels as a group, they are one of the most imperiled group of animals in North America – more so than mammals and bird combined,” says Doug Warmolts, the Director of Animal Care at the Columbus Zoo. Adds Watters, “The US Fish & Wildlife Service has declared this based on the fact that of the 300 or so species in North America, several dozens are extinct and, as a whole, about 20% of all remaining species are federally endangered – meaning they are on the verge of extinction…. No other group of North American animals has such a large percentage of their total diversity on the brink. Most people are completely unaware of this however because FW mussels have an image problem. They are not part of the “charismatic mega fauna” – they’re not cute or cuddly or majestic, people don’t pay money to go see them on boats. Most people are oblivious to them.”

But with federal and state approval, these researchers are rearing out, releasing, tagging and tracking endangered freshwater mussels. “The ultimate goal is to re-establish a reproducing population of NRS in Ohio,” explains Watters. “We have been working on this for about 3 years and have made two augmentations for a total of approximately 3,300 individuals.”

“We glue microchips to the shell of the mussels using an underwater hypoxy and we released them in the Darby Creek,” Warmolts shares. These microchips are the Passive Integrated Transponder – PIT – tag variety.

blog post photo
blog post photo
blog post photo

The researchers return to the site every year with an electronic scaner. Each mussel has a unique identification number, allowing the team to determine where they are and how they are doing.

To date, the collaborative teams have recaptured approximately half of the 1,700 mussels in their monitoring system. “We have found fewer than 10 dead individuals,” reports Watters. “Most mussels don’t move much by themselves but possibly many our NRS were carried downstream by flood events. This essentially removes them from our study area… the other 50% could very well be downstream.”

blog post photo
blog post photo
blog post photo
blog post photo

The general public can help save freshwater mussels and riverine life by “using common sense approaches to how they treat the landscape, be it pesticides, fertilizers, bank stabilization, etc,” says Watters. “And support the groups and people who are on the ground trying to save these animals – agencies like USFWS and ODNR, or conservation groups such as TNC or zoos.”

Photo Credits: Grahm Jones

Learn more about freshwater plants and habitats at National Geographic.