Steamer clams, also called Mya arenaria, soft-shell clams and Ipswich clams, have very thin, fragile shells. Like other clams, they are sold live and should only be cooked and eaten from that state. Test whether a steamer clam is alive by rapping its shell lightly with a finger; if it closes, it is alive. Discard any dead clams immediately, or if you are in a store, report them to the fishmonger. When stored in ideal conditions, steamer clams will stay fresh for about a week to 10 days.
Clear a space at the back of your refrigerator where the temperature is around 36 degrees Fahrenheit.
Place the clams in a box or other container if they did not come in one, then spread them out in a single layer, if possible, between two damp towels and put them in the refrigerator.
Flip the clams over gently every day if they are not in a single layer. Redistribute the weight of the clams so that no clams are constantly bearing the weight of all the others, since the shells are very fragile.
Test the clams for life again just before cooking, using the same method as before. Discard any clams that are no longer living, and do not cook or eat them.
Clams should smell slightly briny, but not decayed or excessively “fishy.” If your clams smell this way, discard them.
If you did not harvest them yourself, examine the tag that should be attached to your bag or container of clams. It will tell you when, where and under what conditions your clams were harvested. Be especially mindful of cooking clams thoroughly. Never serve raw or partially cooked shellfish to pregnant women or anyone with a compromised immune system, including children and the elderly.
Do not store clams on ice. Adding fresh water (such as that from melted ice) will shorten the shelf stability of your clams, according to the website Chow. Additionally, it will be too cold for your clams to survive.