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Anodonta oregonensis Lea, 1838
Oregon Floater
Family: Unionidae
Species account authors: Ethan Jay Nedeau, Allan K. Smith, Jen Stone, and Sarina Jepsen.
Extracted from Freshwater Mussels of the Pacific Northwest, 2nd Edition (2009)
© Xerces Society for Invertebrate Conservation.
Introduction to the Molluscs of BC

Photograph

© Lea Gelling     (Photo ID #8677)

Map

E-Fauna BC Static Map

Distribution of Anodonta oregonensis in British Columbia in British Columbia

Species Information

Size: Adult size from 4.75 to 7.25 inches.

Shape: Elliptical; L:H ratio close to, or exceeding, 2.0. Dorsal posterior margin may be compressed and formed into slight wing, but this trait is variable. Valves laterally inflated, thin, and fragile.

Beaks: Low; rarely project above the hinge line.

Periostracum: Yellowish, yellowish-brown, brown, or black. Some specimens may have a tinge of green. Periostracum is usually shiny, and growth lines are usually evident.

Hinge Teeth: None.

Nacre: White or bluish-white, sometimes pinkish toward the central portion of the nacre and iridescent toward the posterior end.

For a discussion on Anodonta taxomony, please refer to the original publication, The Freshwater Mussels of the Pacific Northwest.

Biology


Like other Anodonta, this is thought to be a fast-growing species that reaches sexual maturity in four to five years and lives only ten to 15 years. Host fish are unknown. Like other Anodonta, this species is likely long-term brooder that breeds in the summer and spawns in the fall or spring. Coho salmon have been identified as hosts for the Oregon floater.

Habitat


A. oregonensisand A. kennerlyi inhabit low gradient rivers, lakes, and reservoirs. They often share habitat with A. californiensis where their ranges overlap.

Distribution

Global Distribution

The geographic range of this clade is in question because of the taxonomic uncertainty that has plagued these “species.” A. oregonensis were confused with A. beringiana in the northern part of their range and confused with A. californiensis in the southern part of their range. Currently, A. oregonensis and A. kennerlyi are thought to belong to a lineage that is distinct from the other western Anodonta. A. oregonensisis thought to range as far north as southern British Columbia. A. kennerlyi has been considered a more northern species found in watersheds of Oregon, Washington, Alaska, British Columbia, Alberta, and northern Saskatchewan. It is found in the Peace River in British Columbia, which is part of the Arctic watershed, and also on coastal islands in British Columbia.
Distribution in British Columbia

In BC, this species is known throughout BC north to 56°N latitude (Gelling 2008).

Conservation

Conservation Concerns

This clade is likely affected by the same factors that affect other western Anodonta, including water diversion, dams, loss of host fish species, pollution, and invasive species. Thorough surveys are needed to determine the current distribution of this clade, although the authors are not aware of any evidence that suggests this clade is in decline.

Comments


The Unionidae are distributed throughout the world, but are most diverse in eastern and central North America, and in China and Southeast Asia.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)		COSEWIC
UnlistedUnlistedUnlistedUnlisted



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