Freshwater mussels: western floater (Anodonta kennerlyi)

(Bivalvia: Unionoida: Unionidae)

Profile prepared by Lisa Schonberg, the Xerces Society for Invertebrate Conservation

The western floater inhabits muddy or sandy habitats in rivers and lakes. It prefers middle to high elevation watersheds. Its reproductive biology and host fish are unknown. The western floater is a northern species that can be found in watersheds of Oregon, Washington, Alaska, British Columbia and Alberta. It is also found on coastal islands of British Columbia and in the Peace River, which is inside the Arctic watershed.

The genus Anodonta, commonly known as “floaters,” includes six of the eight currently recognized freshwater mussel species native to the western United States. The Anodonta are fast-growing generalists, and are more tolerant of lower dissolved oxygen levels than other native mussel species. They prefer the softer substrates, such as sand and silt, that are characteristic of permanently flooded wetlands, lakes, and reservoirs. The shells of Anodonta species are thinner and usually lighter colored than those of other Northwest genera. They also have a light colored interior, are generally rounded, and lack a prominent ridge on their shell. Much of the information on this page was adapted from the guide: Freshwater Mussels of the Pacific Northwest.

conservation status

Anodonta kennerlyi currently receives no state or federal protection. Anodonta species have disappeared from many historic sites and are subject to many of the same threats that have decimated populations of freshwater mussels in the eastern United States. More research is needed on the taxonomic status and distribution of all western Anodonta species in order to understand their conservation status. The Xerces Society, in collaboration with members of the Pacific Northwest Native Freshwater Mussel Workgroup, is currently investigating the conservation status of this species.

description and taxonomic status

The western floater can be up to 4.75 inches long.  It is elliptical or elongate, with a rounded anterios and bluntly pointed posterior.   Its valves are thin and fragile.  Its beak is low and flat, with aout 15 concentric irregular ridges.  The nacre is white or bluish-white, with some pink towards the center and some iridescence sometimes at the posterior end.

The taxonomic status of Anodonta kennerlyi (Lea 1860) is currently under review. Chong et al. (2008) found that A. kennerlyi and A. oregonensis belong to a single clade, which is highly divergent from the clade that A. californiensis and A. nuttalliana belong to. The genetic work also suggests that the A. oregonensis/A. kennerlyi clade is highly divergent from the clade that A. beringiana belongs to.

photograph


Please contact The Xerces Society for information on how to obtain permission to use this image.

life history

The western floater inhabits muddy or sandy habitats in rivers and lakes. It prefers middle to high elevation watersheds. Its reproductive biology and host fish are unknown. High population densities have been observed.

distribution

The western floater is a northern species and can be found in watersheds of Oregon, Washington, Alaska, British Columbia and Alberta. It is also found on coastal islands of British Columbia and in the Peace River, which is inside the Arctic watershed.

threats

The western floater has not been subject to as many threats as species with more southerly or coastal ranges in more heavily impacted areas. It is still common and abundant in the northern parts of its range. Threats to populations in the Columbia River in Washington may include land use, water diversion, pollution, dams, and invasive species.

references

Chong, J.P., J.C. Brim-Box, J.K. Howard, D. Wolf, T.L. Myers, and K.E. Mock. 2008. Three deeply divided lineages of the freshwater mussel genus Anodonta in western North America. Conservation Genetics.

Nedeau, E., A.K. Smith, and J. Stone. 2005. Freshwater Mussels of the Pacific Northwest. Pacific Northwest Native Freshwater Mussel Workgroup, Vancouver, Washington. 45 p

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