E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Nuttallia obscurata Reeve, 1857
Dark Mahagony Clam; Purple Mahogany-Clam; Purple Varnish Clam
Family: Psammobiidae
Photo of species

© Mark Biagi  Email the photographer   (Photo ID #13230)

E-Fauna BC Static Map
Distribution of Nuttallia obscurata in British Columbia
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Species Information

This is an easily recognized introduced species of clam that is abundant within its introduced ranged, and is often noticed along the beach because of the uniform purple colour of the inside of the shell. It is the only species of clam that looks like this. The outside of the thin flat oval shell has a thick shiny brown coating (periostracum) which typically peels off, and resembles old varnish. “Varnish clams grow to at least 64 mm total length, and a maximum weight of approximately 45 g” (Department of Fisheries and Oceans 1999).

Biology


Diet:

Varnish clams are both filter feeders and also utilize pedal feeding (collecting organic destritus from sediment using their foot) (Department of Fisheries and Oceans 1999).

Reproduction:

Varnish clams are described as synchronous broadcast spawners with pelagic larvae; however, season of spawning, length of the larval period, and the season in which they become settled is unkown (Department of Fisheries and Oceans 1999).

Predators:

Predators include moon snails (Euspira lewisi), gulls, crows and oystercatchers. Dungeness crab, Cancer magister and red rock crab, Cancer productus are also reported to prey on this species (Dudas et al. 2005).

Habitat


This species is found in mid-tidal areas, in mud, sand, or mixed gravel-sand (Dinnel and Yates 2000). It is common near freshwater run-offs and seeps in British Columbia (Mills 2002).

Distribution

Global Distribution

Native to Korea, China, and Japan. This is a recently introduced species in British Columbia that was probably introduced in the Vancouver area through ballast water from trans-oceanic transport vessels (Department of Fisheries and Oceans 1999; Dinnel and Yates 2000).
Distribution in British Columbia

This species is found along the south coast, to the tip of Vancouver Island; there is one record from the north coast (Gillespie et al. 2007).

Comments


This is an introduced, invasive species in BC. Varnish clams are hosts to juvenile pea clams (Pinnixia faba) (Department of Fisheries and Oceans 1999).

Surf Scoters and White-winged Scoters have been observed feeding on the purple varnish clams (Ryder 2007)

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
UnlistedUnlistedUnlistedUnlisted
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Notes

Since the introduction of this species to BC in the 1990's, a fishery has been established, and these clams are marketed under the name 'savory clam'.

Other marine species that are cultured or harvested in BC are listed here.

Additional Range and Status Information Links

Additional Photo Sources

Species References

Department of Fisheries and Oceans. 1999. Varnish Clams. DFO Science Stock Status Report C6-13. Department of Fisheries and Oceans, Canada.

Dinnel, P.A. and E. Yates. 2000. Biological and ecological assessments of Nuttallia obscurata inel, P.A. and E. Yates. 2000. Biological and ecological assessments of Nuttallia obscurata in North Puget Sound. Journal of Shellfish Research 19: 630.

Dudas, Sarah E., Iain J. McGaw and John F. Dowera. 2002. Selective crab predation on native and introduced bivalves in British Columbia. Journal of Experimental Marine Biology and Ecology 325 (1): 8-17.

Gillespie, Graham E., Antan C. Phillips, Debbie L. Paltzat and Tom W. Therriault. 2007. Distribution of Non-indigenous IntertidalSpecies on the Pacific Coast of Canada. Fisheries and Oceans Canada, Nanaimo.

Ryder, J. M. 2007. Scoters and other birds feeding on purple varnish clams: Some observations at Spanish Banks, Vancouver, British Columbia. British Columbia Birds 16: 24-27. Available online.

Mills, Claudia. 2002. Nuttallia obscurata, the purple varnish clam or the purple mahogany-clam. University of Washington. Available online.

Additional Useful References:

Harbo, Rick M. 2001. Shells & Shellfish of the Pacific Northwest. A Field Guide. Harbour Publishing, Madeira Park, BC.

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 2022-06-30 3:04:59 PM]
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