Mactromeris polynyma is a large marine bivalve mollusk in the family Mactridae, commonly known as a surf clam. It is distributed in cold and temperate coastal waters of the North Pacific, particularly along the coasts of northern Japan, the Russian Far East, Alaska, and the Bering Sea. The genus name Mactromeris derives from Greek maktra (“kneading trough” or “large shell”) and meris (“part”), referring to shell morphology within the mactrid clams, while the species epithet polynyma comes from Greek roots meaning “many names,” likely reflecting historical taxonomic confusion from multiple regional identifications. This species is often confused with the Sakhalin surf clam (Spisula sachalinensis).

Mactromeris polynyma inhabits sandy or mixed substrates in subtidal zones, where it lives buried beneath the sediment surface and feeds by filter feeding, drawing in seawater to extract phytoplankton and organic particles. Its thick, robust shell and large muscular foot enable it to burrow efficiently in high-energy coastal environments. As a food source, the edible portions consist primarily of the adductor muscles, siphons, and mantle tissue. The clam is consumed steamed, boiled, grilled, or incorporated into soups and mixed seafood preparations in northern Pacific coastal cuisines. In Japanese cuisine, while the Sakhalin surf clam is prized for its raw texture in sushi, the Arctic surf clam is usually cooked.

Nutritionally, the flesh is high in protein and contains essential amino acids, trace minerals such as iron, zinc, and selenium, and marine-derived omega-3 fatty acids. Like other filter-feeding bivalves, it may accumulate environmental contaminants or marine biotoxins under certain bloom conditions, though properly monitored commercial harvesting reduces this risk. Bioactive compounds include taurine and small bioactive peptides, as well as glycogen reserves that contribute to its slightly sweet flavor when cooked.