Endangered Resources Program Species Information
Elephant Ear (Elliptio crassidens)

Overview

Species Overview

Elephant ear (Elliptio crassidens), a mussel listed as Endangered in Wisconsin, is found in large rivers in the western part of the state. Only very old relic individuals have been found since 1920. The only known host is the skipjack herring, which only very rarely occurs in the upper Mississippi River and its tributaries.

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 Elephant Ear (Elliptio crassidens). 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: G5 Tracked by NHI: Y Species of Greatest Conservation Need: Y

Detailed Information

Identification: The black to brown shell is moderately compressed and elongated. Anterior end is rounded and the posterior end is obliquely truncated and sharp. The ventral margin is almost straight and the beak is slightly elevated. The nacre color ranges from salmon to purple. Length to 6 inches (15.2 cm).

Habitat: The black to brown shell is moderately compressed and elongated. Anterior end is rounded and the posterior end is obliquely truncated and sharp. The ventral margin is almost straight and the beak is slightly elevated. The nacre color ranges from salmon to purple. Length to 6 inches (15.2 cm).

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

Phenology: The only known host fish is the skipjack herring (Alosa chrysochloris). Breeding season is from April through July.

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. 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 locks and dams would help to protect the elephant ear. Without a suitable host fish, extirpation is inevitable in Wisconsin and other upper Mississippi states.

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 Elephant Ear Information

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