Following a review of the best available scientific and commercial information, the U.S. Fish and Wildlife Service is protecting the western fanshell (Cyprogenia aberti) and a newly identified species known as the “Ouachita” fanshell (Cyprogenia cf. aberti) as threatened under the Endangered Species Act. These two freshwater mussel species are found in rivers and streams throughout Arkansas, Kansas, Missouri and Oklahoma.

Habitat loss, degraded water quality, changes to river and stream flows, and construction of dams and other barriers are the primary threats to these species. Effects of continued urbanization and climate change are also expected to intensify these threats. Under the Endangered Species Act, threatened species are likely to become in danger of extinction in the foreseeable future.

The Service also designated critical habitat and finalized a 4(d) rule for the western and Ouachita fanshells. Critical habitat is an area that contains essential habitat features for the survival and recovery of a listed species. A critical habitat designation imposes no requirements on state or private actions where no federal funding, permits or approvals are required. A 4(d) rule promotes conservation of listed species by encouraging management of the landscape to benefit both land management and conservation needs.

The western fanshell is currently found in the Lower Mississippi-St. Francis, Neosho-Verdigris, and Upper White River basins, in Arkansas, Kansas, Missouri and Oklahoma and is considered locally extirpated in the Lower Arkansas basin. Approximately 261 river miles in Arkansas and Missouri, all of which are occupied by the species, fall within the boundaries of the critical habitat designation. About 54% of the proposed critical habitat for western fanshell overlaps with critical habitat already designated for two other imperiled mussels, the Neosho mucket and rabbitsfoot, and one endangered fish, the yellowcheek darter.

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