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| Bay Clams |
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 identify clams. From above the sand, clams can also be identified by the hole their neck leaves in the sand as the tide recedes. This is commonly referred to as a show. Each species of clam has a slightly different show that can be identified. The size of the clam and distance from the surface also contributes to its appearance.
Most commonly harvested species | Other commonly harvested species
Most commonly harvested species
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| 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 |
3-6" |
2-4" |
1½-2 ½” |
1½-3”
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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. |
Show |
Produce the largest clam show. Their necks are often visible within the show, as pictured above. |
Usually described as long and narrow, as if a flathead screwdriver had been stuck in the sand. |
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Typically look like two pencil holes next to each other. |
Other commonly harvested species
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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”
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3-5”
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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 |
Show |
Tend to be approximately circular but can sometimes be oblong. |
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