The family Ammodytidae, commonly known as sandeels or sand lances, comprises a group of marine bony fishes characterized by their elongated shape and burrowing habits. The scientific name Ammodytidae derives from the Greek ‘ammos‘ (sand) and ‘dytēs‘ (diver), referring to their characteristic behavior of diving into sandy seabed sediments. This family is mainly found in temperate and cold waters of the Northern Hemisphere, in both the Atlantic and Pacific Oceans. They inhabit shallow coastal areas, sandbanks, and continental shelves, where they find shelter and food. They are highly abundant in certain regions, playing a crucial role in marine ecosystems as a primary prey for numerous predators.
Members of the sandeels have long, slender, laterally compressed bodies, with lengths varying by species but typically ranging from 10 to 35 cm. Their heads are pointed, with small mouths lacking prominent teeth, adapted for capturing small planktonic organisms. They do not have a swim bladder, which allows them to quickly burrow into the sand when threatened. Their coloration is usually silvery on the sides and darker on the back, providing effective camouflage. Morphologically, a distinctive feature is the presence of a single long, continuous dorsal fin and an equally elongated anal fin, both without spines. These structures give them agility for fast swimming near the seabed and through sediments.
Sandeels feed mainly on plankton, especially copepods and crustaceans, though some species also include small fish and other microscopic organisms in their diet. They feed continuously during the day, swimming in tight schools in open waters in search of food concentrations. In adverse conditions or when food is scarce, they tend to burrow into the sand, conserving energy and avoiding predators. Due to their abundance, these fishes are a crucial food source for many seabirds, pelagic fish, and marine mammals, such as cod, tuna, salmon, and puffins, which depend heavily on sandeels at certain times of the year.
Currently, about 30 species are recognized within the family Ammodytidae, distributed across several genera, with Ammodytes, Hyperoplus, and Gymnammodytes being among the best known. These species are primarily found in the North Atlantic, North Sea, Baltic Sea, North Pacific, and parts of the Arctic. An interesting fact about these fishes is their significant indirect economic importance, as their abundance influences the health and population of commercially valuable predators. In some Northern European countries, they are also harvested for fishmeal production used in aquaculture. Another notable trait is their gregarious behavior and ability to form dense shoals, making them highly visible during feeding and reproductive migrations. Their life cycle is strongly influenced by water temperature and the availability of suitable sandy habitats for shelter.
