Elktoe

Distribution

The Elktoe historically inhabited streams throughout much of the New and upper Tennessee River basins in southwest Virginia. Current populations occur only within the Clinch and New River watersheds. However, the New River population has been dramatically reduced, and its status is currently unknown.

Identifying Characteristics

• Shell is elongated and inflated, thin in younger individuals but thickens with age
• The anterior end is round, and the posterior end is bluntly pointed or square
• The ventral margin is straight
• The outer covering of the shell (periostracum) ranges from yellowish-brown to green in color, with numerous dark green to black rays and spots
• The inner portion of the shell (nacre) is bluish-white and iridescent, some individuals may have shades of pink

Habitat

The Elktoe inhabits fast-flowing, shallow riffles in medium to large streams and rivers, with a stable substrate composition of gravel and sand.

Life History

Freshwater mussels have a very unique life cycle. Parasitic larvae, called glochidia, develop in the gills of the female mussel. Once mature, the glochidia are expelled from the gills of the mussel and must attach to the gills of a suitable host fish, where they complete their transformation into a juvenile mussel. They then detach from the fish and begin their free-living existence on the river bottom.

Some freshwater mussels are host-specialists, meaning that metamorphosis can only occur on a limited number of closely related fish species, while others are host-generalists, with the ability to complete their life cycle using many different species. Female mussels employ a variety of strategies that “trick” their host fish into becoming “infested” with their glochidia. Some have elaborate mantle displays that protrude out of the shell that a fish attacks, while others release their glochidia in packets called “conglutinates” that resemble prey items that fish will ingest.

The Elktoe relies on species of Suckers (Family: Catostomidae) and exhibits a preference towards Northern Hogsucker (Hypentelium nigricans). Female Elktoe likely use a more passive approach to infest their host fish by broadcasting their glochidia into the water column, which then attach to the fins and gills of fish as they swim by.

Conservation

The Elktoe has declined throughout much of its range in Virginia. DWR’s Aquatic Wildlife Conservation Center (AWCC) is currently propagating this species for population augmentation throughout the Clinch River.

Special Considerations

Freshwater mussels are extremely imperiled organisms. DWR regulates the take and possession of freshwater mussels occurring within the state. It is unlawful to take mussels from any inland waters in the Commonwealth except as provided for in §§ 29.1-418 and 29.1-568 of the Code of Virginia.