Endangered Resources Program Species Information
Ebony Shell (Fusconaia ebena)

Overview

Species Overview

Ebony shell (Fusconaia ebena), a mussel listed as Endangered. It is found in the western and southern part of Wisconsin in large rivers and is usually on a gravel, sand, or mud bottom in water at least six feet deep where the current is swift. Only very old relic individuals have been found since 1920. Although five fish have been reported as hosts, it is believed that the skipjack herring was the primary host.

Status and NHI Documented Occurrences in Wisconsin

The table below provides information about the protected status (State and Federal Status) and the rank (S and G Ranks) for Ebony Shell (Fusconaia ebena). See the Working List Key for more information about the abbreviations used. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. For invertebrates, dots depict locations from the "Invertebrate Atlas," a database with occurrences of rare and common aquatic and select terrestrial invertebrate species found in Wisconsin and adjacent areas. While the invertebrate atlas is a quality assured database, not all records have been verified. The map is provided as a general reference of where this species has been found to date and is not meant as a range map.

Summary Information State Status: END Federal Status in Wisconsin: none State Rank: S1 Global Rank: G4G5 Tracked by NHI: Y Species of Greatest Conservation Need: Y

Detailed Information

Identification: Shell is subelliptical, thick, and inflated. Epidermis is dark brown or black and without rays. In young shells the epidermis is yellowish followed by bright green and brown. Beaks are elevated and turned forward. Posterior end rounded, dorsal margin evenly curved, and the surface has many concentric ridges. Length to 4 inches (10.2 cm) or more.

Habitat: Inhabits large rivers and is usually on a gravel, sand, or mud bottom in water at least six feet deep where the current is swift.

State Distribution: Occurs in the Mississippi River, the lower Wisconsin and the St.Croix.

Phenology: Host fish is skipjack herring (Alosa chrysochloris). Breeding season is June to September. Black crappie (Pomoxis nigromaculatus), white crappie (P. annularis), and largemouth bass (Micropteris salmoides) have been used by the mussels in June as well.

Management Guidance: The primary host fish for this species, the skipjack herring, has nearly been eliminated in the upper Mississippi due to locks and dams restricting migration from the Gulf of Mexico. Prior to the building of the locks and dams, the ebony shell was the most abundant species in the Mississippi River. It is rarely, if ever, encountered today. It was used extensively for the pearl button industry because of its high quality, thick "mother-of-pearl" shell. Habitat destruction and river pollution have resulted in mussel declines. Protection of habitat and improvements in water quality along with restriction of dredging, impoundments, sand and gravel mining, and navigational improvements would benefit this species. The development of fish runways to facilitate the movement of host species through or around dams could help to protect the ebony shell.

Information compiled from publication PUB-ER-085-99 (now out-of-print).

Photos

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Photo ©  Illinois Natural History Survey.

Related Links

Links to Additional Ebony Shell Information

• MN Department of Natural Resources [Exit DNR]
• Illinois Natural History Survey [Exit DNR]

Other Links Related to Mussels and Clams

• Illinois Natural History Survey [Exit DNR]
• The Field Museum [Exit DNR]
• Conchologists of America [Exit DNR]
• EPA Biological Indicators of Watershed Health [Exit DNR]
• Milwaukee Public Museum [Exit DNR]