Invasion History

First Non-native North American Tidal Record:
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Leukoma staminea is native to the Northeast Pacific from Baja California to the Aleutian Islands (Abbott 1974). It is a popular edible clam in its native range. A ‘large number’ of this clam (as Tapes staminea) were brought back to Woods Hole in 1885 by G. H. Moore, of the U.S. Fish Commission and were planted ‘in various localities’ around the Commission's Woods Hole station (Galtsoff 1962). However, none of these clams were found in subsequent years. While many attempts were made in the 19th century to introduce Eastern Oysters (Crassostrea virginica), American Lobsters (Homarus americanus), and Blue Crabs (Callinectes sapidus) to the West Coast, this is the only deliberate attempt, that we know of, to introduce a West Coast invertebrate to the East Coast.

North American Invasion History:

Invasion History on the East Coast:

In 1885, G. H. Moore of the US Fish Commission, supervised the transport of a carload of American Shad (Alosa sapidissima) from the East Coast to Oregon and Washington, and in return brought a large quantity of Pacific Littleneck Clams. Many of the clams perished, but those that appeared to be in good condition (several hundred) were planted near the Woods Hole station. Galtsoff (1962) noted that 'Leukoma staminea (as Tapes staminea) apparently did not survive and was never found in Woods Hole waters.'


Leukoma staminea is still widely known under its previous genus Protothaca. It is a roughly oval clam, with its beak nearer to the anterior end. The shell is sculptured with concentric lines and stronger radial ribs, forming beads as they cross. The radial ribs are better-defined in the middle of the shell. The beaks are almost smooth. The ligament is sunken, and not elevated above the dorsal margin. The interior of the ventral margin is slightly crenulated. The siphons are united for their entire length. Adults range from 35-80 mm in length. The color ranges from yellowish or gray in muddy environments to white with geometric blotches or lines on the open coast (Abbott 1974; Shaw 1986: Coan et al. 2000; Coan and Valentich-Scott, in Carlton 2007).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Mollusca
Class:   Bivalvia
Subclass:   Heterodonta
Order:   Veneroida
Superfamily:   Veneroidea
Family:   Veneridae
Genus:   Leukoma
Species:   staminea


Venus staminea (Conrad, 1837)
Venus rigida (Gould, 1850)
Venus pectunculoides (Valenciennes, 1846)
Venus mundulus (Reeve, 1863)
Venus conradi (Römer, 1867)
Venus ampliata (Carpenter, 1857)
Venerupis petiti (Deshayes, 1839)
Tapes tumida (G.B. Sowerby II, 1852)
Tapes diversa (G.B. Sowerby II, 1852)
Protothaca staminea (Conrad, 1837)
Protothaca grewingkii (Dall, 1904)

Potentially Misidentified Species

Leukoma laciniata
Rough Littleneck, Monterey Bay to Mexico

Venerupis phillipinarum
Japanese Littleneck, Native to NW Pacific, introduced, California-British Columbia



Leukoma staminea is a common clam in shallow bays and estuaries. Adults reach 30-60 mm in length. The sexes are separate and spawning occurs from May-September in Alaska, and December-June in Mugu Lagoon, California (Glude 1978; Peterson 1982, both cited by Shaw 1986). Sperm and eggs are released into the water. Fertilized eggs develop into trochophore larvae within 12 hours, and veligers by 24 hours. Larvae settle at about 300 μm, after about three weeks in the plankton. The clams mature in 2-3 years at 22-35 mm, in British Columbia (Quayle 1943, cited by Shaw 1986). Estimated longevity is 7-13 years (Shaw 1986).

Pacific Littlenecks tolerate temperatures from near 0 to 25°C, and salinities as low as 20 PSU. They grow best in coarse sand or gravel, and can be smothered by fine sand or silt. Predators include crabs, starfishes, predatory snails, octopuses, sea otters, and humans (Shaw 1986).




Fishes, Marine Mammals, Birds, Humans


Venerupis philippinarum (Japanese Littleneck)

Trophic Status:

Suspension Feeder



General HabitatUnstructured BottomNone
Tidal RangeSubtidalNone
Tidal RangeLow IntertidalNone
Vertical HabitatEndobenthicNone

Tolerances and Life History Parameters

Minimum Temperature (ºC)0Field (Shaw 1986)
Maximum Temperature (ºC)25Field (Shaw 1986)
Minimum Salinity (‰)20Field (Shaw 1986)
Maximum Salinity (‰)35Field (Shaw 1986)
Maximum Duration21Typical larval duration, British Columbia (Quayle 1943, cited by Shaw 1986).
Maximum Length (mm)60Abbott 1974; Shaw 1986
Broad Temperature RangeNoneCold temperate-Warm temperate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

Leukoma staminea supports commercial fisheries in the northern part of its range and sport fishery in California. An unsuccessful attempt was made to introduce it to the Atlantic at Woods Hole, Massachusetts in 1885 (Galtsoff 1962). This introduction was considered to be a possible vector for the introduction of the Pacific hydroid and medusa Gonionemus vertens to the Woods Hole area: ‘the sand-gravel habitat would be unfavorable for the hydroid, but they were packed in eelgrass or seaweed, G. vertens might have been transported by these shipments’ (Edwards 1976).

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NEP-II Alaska south of the Aleutians to the Alaskan panhandle 0 Native Estab
NEP-III Alaskan panhandle to N. of Puget Sound 0 Native Estab
NEP-IV Puget Sound to Northern California 0 Native Estab
NEP-V Northern California to Mid Channel Islands 0 Native Estab
NEP-VI Pt. Conception to Southern Baja California 0 Native Estab
NA-ET3 Cape Cod to Cape Hatteras 1885 Def Failed
M010 Buzzards Bay 1885 Def Failed

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Abbott, R. Tucker (1974) American Seashells, Van Nostrand Reinhold, New York. Pp. <missing location>

Carlton, James T. (Ed.) (2007) The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon Fourth Edition, Completely Revised and Expanded, University of California Press, Berkeley. Pp. <missing location>

Coan, Eugene V.; Valentich-Scott, Paul (2007) The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon, University of California Press, Berkeley CA. Pp. 807-859

Coan, Eugene V.; Valentich-Scott, Paul; Bernard, Frank R. (2000) Bivalve Seashells of Western North Ameira, Santa Barbara Museum of Natural history, Santa Barbara CA. Pp. <missing location>

Edwards, C. (1976) A study in erratic distribution: the occurrence of the medusa Gonionemus in relation to the distribution of oysters, Advances in Marine Biology 14: 251-284

Galtsoff, Paul S. (1962) The Story of the Bureau of Commercial Fisheries Biological Laboratory Woods Hole, Massachusetts, Bureau of Commercial Fisheries Circular 145: 1-121

Shaw, William N. (1986) Species Profiles: Life histories and environmental requirements of coastal fishes and invertebrates (Pacific Southwest) Common Littlrnrck Clam, Biological Report 82(11.46): 1-11