Mallotus villosus is a small pelagic fish species in the family Osmeridae, commonly known as capelin. It is widely distributed in cold and subarctic waters of the North Atlantic and Arctic Oceans, as well as parts of the North Pacific. The genus name Mallotus derives from Greek roots possibly referring to “woolly” or “soft,” while the species epithet villosus is Latin for “hairy,” likely referencing the fine scale texture or breeding characteristics of the fish. Capelin is a key forage species in marine ecosystems and plays a central role in the diets of larger fish, seabirds, and marine mammals.

Mallotus villosus forms large schools in open ocean and coastal waters, migrating seasonally to spawn along shorelines and shallow seabeds. During spawning, the fish deposit adhesive eggs on sand or gravel substrates, often in massive numbers. The species is relatively small, typically reaching lengths of 15–20 centimeters, with a slender, silvery body adapted for pelagic life. Its abundance and reproductive strategy make it an ecologically significant link in marine food webs.

Capelin is consumed in several regional cuisines, particularly in northern Europe, Iceland, Canada, and Japan. In Japanese cuisine, it is closely associated with roe-bearing forms known as shishamo, which are grilled whole and eaten with the eggs intact. The fish may also be dried, smoked, or fried, and its roe is valued for its texture and flavor. In other regions, capelin is processed into fish meal and oil, though it is also eaten directly as a small whole fish.

Nutritionally, Mallotus villosus is rich in high-quality protein and contains significant amounts of omega-3 fatty acids such as EPA and DHA, which contribute to cardiovascular and neurological health. It also provides vitamins such as B12 and D, as well as minerals including selenium and iodine. The roe is particularly nutrient-dense, containing lipids, phospholipids, and fat-soluble vitamins. Bioactive compounds include marine peptides and fatty acids that have been studied for anti-inflammatory and metabolic effects.