Cape Cod Clams by their Shells

Clams - The All Purpose Bivalve


The shore is home to many different types of shellfish. Only some of them are edible! Clams are not the only delicious thing you can take home from the sand, but some things look like clams that aren’t, and some shellfish you must not eat!

Here is a photo guide to common edible shellfish of Cape Cod and environs and their inedible (or nasty!) relatives.

Cockle. The cockle is not considered a clam on Cape Cod, but it is edible. They are steamed, then eaten. Most people find the taste disagreeable. It is something like licorice with added gasoline and dirt. The Irish refer to cockles as “famine food,” meaning cockles are eaten only when nothing else is left.

Ribbed Mussel
Ribbed mussel.
Not a clam. Do not eat ribbed mussels. They are OK for seagulls, but will make a person sick. Blue mussels have shells without ribs, they’re known as moules in French, and are delicious. They were once common on the East Coast of the US, are now rare. Scientists believe a pathogen has killed most Atlantic blue mussels


This carnivorous predator kills shellfish of all kinds. Its shells are distinctive for having a domed dorsal surface, and a ventral surface that extends only halfway to the shell’s edge. This species is an aggressive nuisance and its shells have replaced almost all others. When these shells are broken, their edges are razor-sharp like chunks of volcanic rock: watch your feet. Whether the oversupply of cowries is related to nitrogen seawater contamination is not known.


Cowries on Beach
Too many cowries. Almost all the shells you see here are cowrie shells. This is an ecosystem out-of-balance, but the cause is not easy to identify. Overabundance and scarcity of shellfish can be a natural phenomenon, changing by the year.

Hard shell clams: littleneck, cherrystone, quahog Hard-shell clams: These are fine to eat!

From left to right: a littleneck, a cherrystone and a quahog.

These are all actually of the quahog clam species, graded by size, the littleneck the smallest, the cherrystone next, and the quahog the largest. Littlenecks and cherrystones are often served raw.

Clam Relative sizes

Relative sizes. Some good things come in small packages.

Steamer ClamSteamer clam: This is one of the best clams to eat! The size is less important, although legal-to-keep steamers should be at least double the size of the hole you make with you fingers showing “OK.” Best way to identify a steamer: the soft shell. It’s so brittle, it’s easy to a steamer clam shell yourself by accident. Dig with care! It’s best not to eat a steamer with a broken shell.

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