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| NAS - Nonindigenous Aquatic Species |
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Common Name: Japanese littleneck
Synonyms and Other Names: Manila Clam, Japanese Cockle, Japanese Carpet Shell
Taxonomy: available through 
Identification: Elongated oval strong radial ribs. Ribs are stronger at posterior end. Exterior color varies from gray to brown, often with streaked patterns, occasionally with angular pattern similar to the native littleneck. Short siphons with split tip. Interior of shell often has purple or yellow coloration; inside edge is smooth to the touch (Harbo 1999). Valves are more oblong than the Native Littleneck's (Protothaca staminea): more pointed at the narrow end and more squared at the broad end. (Yates 1998).
Size: To 3" (7.5 cm).
Native Range: Japan, Korea and China, with natural range expanded by cultivation.
Nonindigenous Occurrences:
54°N-37°N; Central northern coast of British Columbia to Elkhorn Slough, California (Harbo 1999).
Stocked in the Salton Sea of California in 1955 but excessive silt destroyed the population (Hanna 1966).
Ecology:
Buried to 4" (10 cm) in gravel-sand-mud, high intertidal (Harbo 1999). Lives near the surface on muddy sand or pea gravel beaches. Abundant in sheltered bays; high intertidal to shallow subtidal. Can tolerate crowded conditions and lives high up on the beach above the reach of most predators (Yates 1998).
Live span can reach 8 - 14 years (Harbo 1999).
Means of Introduction: Species was introduced accidentally with Pacific oyster seed from Japan (Harbo 1999).
Status:
Established.
Impact of Introduction: Limited spatial competition with native clams.
Remarks: This is the only clam for which there has been extensive development of aquaculture in recent years in British Columbia and Washington State (Harbo 1999).
References
Hanna, G.D. 1966. Introduced mollusks of western North America. Occasional Papers of the Cal. Acad. of Sciences. 48:108 pp.
Harbo, Rick M. 1999. Shells & Shellfish of the Pacific Northwest :270 pp.
Yates, Steven M. 1998. Marine Wildlife: From Puget Sound Through the Inside Passage :262 pp.
Other Resources:
Fish Stocks of the Pacific Coast - Invertebrates - Manila Clam
Guide to the Exotic Species of San Francisco Bay
Washington Dept. of Fish and Wildlife - Shellfish
Author: Nancy Elder
Revision Date: 11/9/2007 Citation for this information:
Nancy Elder. 2009. Venerupis philippinarum. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
<http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=150> Revision Date: 11/9/2007
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