The ebonyshell is a thick-shelled freshwater mussel of large rivers, and a twenty-mile reach of Pickwick Lake on the Tennessee River, river miles 236 to 256, from about the Natchez Trace Parkway's bridge up to Florence, is where researchers have recorded it dying in numbers. A 2011 study in the Journal of Shellfish Research described die-offs there in successive years over about a decade. They fell mainly on the ebonyshell, less heavily on the butterfly, the pimpleback and the mapleleaf, and they coincided with low inflows to the basin and warm water. The lake itself dates from 1938, when the Tennessee Valley Authority closed Pickwick Landing Dam and put the last of the shoals below Florence under water.
Most of the dying and freshly dead ebonyshells were females, which the authors suggested may reflect the stress of ongoing reproduction. Sick mussels sampled in 2006 and 2008 carried far more bacteria than healthy ones, more than a hundredfold in 2008, and the dominant bacteria were different in the two years.
The species depends on a narrow set of fish. Its larvae must attach to a host fish before they can drop off as juveniles, and a 2018 study in Aquaculture Reports confirmed the skipjack herring as a host while finding none of twelve other fish species tested suitable. The authors pointed to dams and other changes that disrupt herring migrations as likely key factors limiting where such mussels live. On the upper Mississippi, the dam at Keokuk, Iowa, finished in 1913, blocked the herring, and the mussel could no longer complete its life cycle above it. They were cut for pearl buttons, and later the shell was shipped to Japan as seed for cultured pearls.
Getting there
34.8400, -87.9335
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