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The wedgemussel has been on the United States endangered species list since 1990, and is thought to be extinct in Canada.
"We were astounded to see this mussel in the Tenmile basin," stated David Strayer, a freshwater ecologist at the Institute of Ecosystem Studies in Millbrook.
"It's been seen only once anywhere in the Housatonic basin, and that was before 1843. Everyone thought it was long gone from the area," he stated.
According to the U.S. Fish and Wildlife Service, little is known about the creature's life history and reproductive cycle. The mussel usually lives in creek and river areas with a slow to moderate current in sand, gravel or muddy bottoms.
"There was one old record of a mussel like this being found there in 1843, but that's it," said Strayer.
"When it was marked as endangered in the 1990s there was a rush of survey work in the Housatonic to find them, but none were discovered," he said.
Strayer was originally doing research on another type of fresh water mussel that was having trouble reproducing when he came across the wedgemussel.
"The mussels we were looking for are about 50 to 100 years old. My assistant showed me the mussel and I said, 'if we were in the Neversink River I'd say that's a wedgemussel,'" he said.
"There are two large populations of them there and in Connecticut. I really didn't think it was a wedgemussel, and even offered odds of 10 to 1 against it. Having three people searching exclusively for that species over a period of a day and finding four would be considered a success," he said.
After doing research on the sample, it was discovered that the find was in fact the rare species.
The U.S. Fish and Wildlife Service said water pollution and the construction of impoundments are the main reasons for the decrease in population.
Toxic metals from acid rain and pesticides used to treat land that seep into the water are some of the pollutants that have affected the mussel. The construction of dams has caused problems because it builds up silt in the water, which is dangerous to the creature.
Thayer said that even though the Housatonic has seen a lot of changes through the years, none of them have had an extremely negative impact on it.
"It's hard to know just how many there are in the river. This shows that the mussel was able to survive the changing landscape," he said.
"The river isn't perfect, but it hasn't gone through any really terrible times and is in reasonably good shape," Thayer said.
The researchers are continuing their project on the other freshwater mussel in the Housatonic, but are keeping a very sharp eye out for another wedgemussel.
"It's quite a rare animal, and right now the sample is being sent to the American Museum of Natural History," said Thayer.
"There they will do further confirmation and perform a DNA test of the sample," he said.
