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The United States Fish and Wildlife Service (“Service”) issued a final rule addressing an Endangered Species Act (“ESA”) listing for the Ouachita and western fanshell mussels whose habitat includes the State of Arkansas.

The final rule also designates critical habitat for both species.

The Service listing determines that both the western and Ouachita fanshell meet the definition of threatened species under the ESA.

The final rule designates both species as threatened pursuant to Section 4(d) of the ESA.

The western fanshell is described as a medium-sized freshwater mussel found in the Lower Mississippi-St. Francis, Neosho-Verdigris, and Upper White River basins, within Arkansas, Kansas, Missouri, and Oklahoma. They have a thick, compressed to moderately inflated, round to triangular shell that is up to three inches in length. The posterior ridge is prominent and raised with a shallow sulcus from umbo to middle of the ventral margin.

Western fanshell are stated to be omnivores that primarily filter feed on a wide variety of microscopic particulate matter suspended in the water column. Their life cycle relies on host fish for successful reproduction.

The Ouachita fanshell is stated to currently occur in the Lower Red-Ouachita basin in Arkansas and occurred historically in Louisiana. It is an undescribed species that is stated to be now recognized by species and taxonomic experts as distinct from western fanshell.

The species is stated to be typically found in large creeks and rivers with good water quality. Such waterbodies are stated to be moderate to swift current and gravel-sand substrates. The Ouachita fanshell is also an omnivore that primarily filter feeds on a side variety of microscopic particulate matter suspended in the water column. Like the western fanshell, they have a unique life cycle that relies on fish hosts for successful reproduction.

The Service, pursuant to the final rule, has designated critical habitat for both species.

Approximately 261.4 river miles are designated as critical habitat in Arkansas and Missouri for the western fanshell. Further, approximately 227.7 river miles in Arkansas are designated as critical habitat for the Ouachita fanshell.

The final rule also provides measures the Service has determined that are necessary and advisable to provide for the conservation of both species.

A copy of the final rule can be downloaded here.