By P. J. Reay
Body elongate, subcylindrical. Lower jaw protruding beyond upper; teeth absent or restricted to vomer. Single dorsal and anal fins elongate and separate from the rorked caudal fin; pelvic fins absent. Small cycloid scales present but inconspicuous; body may be covered in oblique skinfolds (plicae) between dorsally positioned lateral line canals and ventrolateral skin-folds. Swimbladder absent. Dorsal surface variable in colour, but underside white and sides silvery.
Restricted to the shallower sand and fine gravel areas of the continental shelf from littoral to offshore (e.g. central North Sea) habitats. Often extremely abundant. Typically feed on zooplankton, but one genus is piscivorous. Spawning seasons vary, but it is assumed that all species lay demersal adhesive eggs which attach to sand-grains. Larvae and post-larvae are planktonic and may dominate the ichthyoplankton particularly in spring. Adults and juveniles alternate between active feeding in the water mass by day, and inactivity within the substrate by night; they may also enter the substrate during the daytime, and hardly leave it at all during the winter months. Schooling behaviour is well developed. Migrations are probably restricted to local diel and seasonal movements. Used for bait and food on a small scale in many areas, but the major fisheries are for fishmeal and up to 1 million tonnes per annum are currently being landed from the North Sea (predominantly by Denmark). Important also as a source of food for piscivorous fish, birds and mammals.
Genera 5; in Clofnam area 3.