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:

The ark shell Anadara satowi is native to the Northwest Pacific, ranging from Hong Kong, China to Hokkaido, Japan (Huang 2001; Academy of Natural Sciences of Philadelphia 2010; Museum of Comparative Zoology 2010).

North American Invasion History:

Invasion History on the West Coast:

In the Northeast Pacific, A. satowi is known only from an empty shell found in Quilcene, Washington, in the Hood Canal (Puget Sound), near the Washington State Shellfish Laboratory. The shell could have been discarded from the laboratory, or else introduced with plantings of Pacific Oysters (Crassostrea gigas) from Japan (Hanna, 1966, cited by Carlton 1979).


Anadara satowi, an ark shell, is a marine bivalve with a thick, strongly ribbed shell. The hinge line bears numerous teeth, arranged in a line on both valves. Both valves have prominent beaks which almost come into contact. The shell is heart-shaped in a side view. Ark shells can occasionally attach to rocks and shells with byssus threads (genus characteristics, Morris 1975). The shell superficially resembles that of A. ovalis in photographs, and is covered with brown periostracum, but may reach a larger size (90+ mm) (Natural History Museum Rotterdam,  Anadara satowi, like A. ovalis, has hemoglobin in its blood, and has red blood and tissues (Ohnoki et al. 1973).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Mollusca
Class:   Bivalvia
Subclass:   Pteriomorphia
Order:   Arcoida
Family:   Arcidae
Genus:   Anadara
Species:   satowi


Anadara nipponensis (Pilsbry, 1901)
Scapharca satowi (Dunker, 1882)

Potentially Misidentified Species



Anadara satowi an ark shell, is a suspension-feeding marine bivalve found in muddy, subtidal environments ( It may occasionally attach to rocks and shells with byssus threads.



Trophic Status:

Suspension Feeder



General HabitatUnstructured BottomNone
General HabitatOyster ReefNone
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Vertical HabitatEndobenthicNone

Tolerances and Life History Parameters

Broad Temperature RangeNoneCold temperate-Warm temperate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

Anadara satowi, an ark shell, is known as an introduced species only from a single dead shell on the West Coast, and has had no known impacts outside its native range.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NWP-3b None 0 Native Estab
NWP-3a None 0 Native Estab
NWP-2 None 0 Native Estab
NEP-III Alaskan panhandle to N. of Puget Sound 1966 Def Failed
P290 Puget Sound 1966 Def Failed
NWP-4b None 0 Native Estab
NWP-4a None 0 Native Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Academy of Natural Sciences of Philadelphia 2002-2024a Malacology Collection Search. <missing URL>

Academy of Natural Sciences of Philadelphia 2006-2014b OBIS Indo-Pacific Molluscan Database. <missing URL>

Carlton, James T. (1979) History, biogeography, and ecology of the introduced marine and estuarine invertebrates of the Pacific Coast of North America., Ph.D. dissertation, University of California, Davis. Pp. 1-904

Hanna, G. Dallas (1966) Introduced mollusks of Western North America, Occasional Papers of the California Academy of Sciences 48: <missing location>

Harvard Museum of Comparative Zoology 2008-2021 Museum of Comparative Zoology Collections database- Malacology Collection. <missing URL>

Huang, Zongguo (Ed.), Junda Lin (Translator) (2001) Marine Species and Their Distributions in China's Seas, Krieger, Malabar, FL. Pp. <missing location>

Morris, Percy A. (1975) A field guide to shells of the Atlantic, Houghton-Mifflin, Boston. Pp. <missing location>

Ohnoki, Shiro; Mitomi, Yoshitada; Hata, Ryuichiro; Satake, Kazuo (1973) Heterogeneity of hemoglobin from arca (Anadara satowi,/i>) molecular weights and oxygen equilibria of Arca Hb I and II, Journal of Biochemistry 73(4): 717-725