Spirinchus lanceolatus, commonly known as the shishamo, is a small anadromous fish species in the family Osmeridae. It is endemic to the Northwestern Pacific, specifically restricted to the coastal waters and rivers of southeastern Hokkaido, Japan. The genus name Spirinchus is derived from Greek roots, likely referencing features of the fish’s slender body form, while the species epithet lanceolatus comes from Latin lanceolatus, meaning “lance-shaped,” describing its narrow, elongated body. The common name Shishamo comes from the Japanized form of the Ainu words susu, meaning "willow", and ham, meaning"leaf". Like other smelts, it is characterized by a translucent, silvery appearance and a delicate structure.

Spirinchus lanceolatus occupies both marine and brackish environments and migrates into estuaries and freshwater systems to spawn, making it ecologically important in coastal food webs. It feeds on plankton, small crustaceans, and other microscopic organisms, serving as prey for larger fish, birds, and marine mammals. The species has experienced population declines in parts of its range due to habitat alteration and environmental pressures, and it is considered of conservation concern in some regions.

As a food source, shishamo smelt has been traditionally harvested in limited quantities and consumed whole due to its small size. It may be eaten grilled, fried, dried, or used in small fish preparations similar to other smelt species. Outside of Japan, the capelin (Mallotus villosus) is often marketed as shishamo as the population of true shishamo is limited. The flesh is soft and mild in flavor, with edible bones when cooked appropriately.

Nutritionally, Spirinchus lanceolatus provides protein, omega-3 fatty acids, and micronutrients typical of small marine fish, including calcium when consumed whole with bones. Bioactive compounds include marine lipids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are associated with cardiovascular and neurological health. Because of its ecological sensitivity and limited availability, it is not a major industrial food source, and its use is generally restricted to local or traditional contexts.