Twin Cities Field Office
4101 American Boulevard East
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The U.S. Fish and Wildlife Service listed the sheepnose and spectaclecase mussels as endangered species.
The spectaclecase is a freshwater mussel that occurred historically in at least 44 streams in the Mississippi, Ohio, and Missouri Rivers and in dozens of tributaries to these rivers. It has declined significantly relative to its historical distribution and is now now known to occur in only 20 streams in 11 states. The species evidently is absent from hundreds of river miles and from numerous reaches of habitat in which it occurred historically. Of the extant populations, six are represented by only a single specimen each and are likely not viable. Although many populations have been extirpated for decades, most surviving populations face significant threats.