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Bay Clams
Bay Clam Identification


Bay Clam Identification

A number of clam shell features are used to identify clams. Shape and size are usually coupled with exterior and interior design of shells to positively identfy clams.

Know what you’re digging before your shovel starts working! See information about identifying clams by their show.

Quick reference for bay clams of Oregon (pdf)

Commonly Harvested Species

  Gaper clam Butter clam Native Littleneck clam Cockle
Common name Gaper Butter Native Littleneck Cockle
Other names

Empire, horseneck, blue

Scientific: Tresus capax

Beefsteak, Martha Washington, Quahog

Scientific: Saxidomus giganteus

Steamer, native littleneck

Scientific: Leukoma staminea

Heart cockle, Nutall's cockle

Scientific: Clinocardium nuttallii

Key Identification Features

Large gape around neck and concentric shell rings.

Largest common clam in Oregon estuaries.

Commensal pea crab pairs are often found within their mantle.

Identified by its smooth concentric  rings.

Thick and heavy oval shell

Identified by concentric lines and radiating ridges

Longer lived and less abundant than cockles.

Circular in shape.

Identified by their prominent radiating ridges.

Circular in shape.

Common size





Common habitat

High salinity areas of sand or mud.

High salinity areas of sand, mud, gravel, or rock

High salinity areas of sand, mud, gravel, or rock.

High salinity areas of sand.

Further links

How to dig

More about gapers

How to dig

More about butters


How to dig

More about cockles

Other Commonly Harvested Species

soft shell clam
purple varnish clam
rough piddock flat tipped piddock
Common name Softshell Purple varnish clam Rough piddock Flat tipped piddock
Other names

Mud clam, eastern softshell

Scientific: Mya arenaria

Mahogony clam

Scientific: Nuttallia obscurata

Piddock, rock oyster

Scientific: Zirfaea pilsbryi

Piddock, rock oyster

Scientific: Penitella penita

Key Identification Features

Concentric rings and oblong egg shape, slightly pointed at the neck end.

Identified by its varnish like coating and purple interior.

Native to Japan, introduced to Oregon in the 1990s.

Identified by gape at neck end and teeth (for burrowing) at foot end.

Distinguished from the rough piddock by the "callum"- the smooth area on the lower foot area of the shell.

Common size 2-4" 1½-3” 3-5 1½-3”
Common habitat

High to low salinity areas of mud.

Mid salinity areas of sand.

High salinity areas of clay, mud or sandstone. Most common in high salinity portions of bays.

Nearshore rocky areas

Further links

How to dig

More about softshells


More about Piddocks

More about Piddocks


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