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 likely to become in danger of extinction in the foreseeable future. are also expected to intensify these threats. Under the Endangered Species Act, threatened species are
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.
The Ouachita fanshell currently occurs in the Lower Red-Ouachita basin in Arkansas and historically occurred in Louisiana. Approximately 228 river miles in Arkansas, all of which are occupied by the species, fall within the boundaries of the critical habitat designation. About 53% of the proposed critical habitat for the Ouachita fanshell overlaps with critical habitat already designated for the rabbitsfoot.
We excluded about 165 river miles from the original critical habitat proposal based on information received during the public comment period that these areas are already covered by other conservation agreements.
The final 4(d) rule promotes conservation of the two fanshell species by encouraging management of the landscape in ways that meet both land management considerations and the conservation needs of the two mussels.
The Service has finalized an economic analysis of the critical habitat designation for both species, as required under the Endangered Species Act.
Both species are typically found in medium and large rivers with good water quality, moderate to swift current, and gravel-sand streambeds. Like all mussels, these two species are omnivores that primarily filter feed on a wide variety of microscopic particles in the water. As with most freshwater mussels, fanshell mussels have a unique life cycle that relies on fish hosts for successful reproduction.