MulletThe common name of the family, sardines, probably derives from the Mediterranean island of Sardinia, around which sardines were once abundant. The body shape and dentition (teeth and bite) of sardine are modified for its carnivorous diet. The fins are used in locomotion as well as providing stability when they rest on the ocean bottom.
They are silvery fishes 30–90 cm (1–3 feet) long, with large scales; relatively stocky, cigar-shaped bodies; forked tails; and two distinct dorsal fins, the first containing four stiff spines. Many have strong, gizzard-like stomachs and long intestines capable of handling a largely vegetarian diet.
Sardines feed almost exclusively on planktonic organisms. Most species, notably the herring family ( Clupeidae ), are filter feeders that open their mouths as they swim. Water is sucked into the mouth and passes through a gill net that retains food particles and expels water and wastes from the other side of the gill. The gill-net mechanism is common to many fish, and sardines share this technique with herrings and some other members of the Clupeidae . Sardines may be either demersal (found on or near the bottom) or pelagic (swimming in midwater). Many species live in large schools.
Sardines, pilchards, and anchovies are closely related. The three families belong to the suborder Clupeoidei . They share certain features: Both dorsal fins usually have spines; the mouth is subterminal (below pointed snout); two separate canals open to the exterior for each eye; no lateral line visible externally; and two occludable (covered) nostrils.
The herrings ( Clupeidae ) are among the more important commercial fishes of the world, and they may already be extinct in many areas where they were formerly fished. Most species feed on plankton; others eat tiny crustaceans or very small fish. Many members of this family spawn vast numbers of tiny, buoyant eggs in shoals near the surface. The larvae are also very small and planktonic. A few species, notably members of the genus Harengula , feed voraciously on smaller fish as they grow larger. Herrings are fished by seining, purse seining with encircling
The family is primarily marine, with species typically occupying both temperate and tropical glasses of water. The most notable member of the family is the Atlantic sardine (Sardina pilchardus). Many other species are found in coastal waters of varying salinities, ranging from brackish water to freshwater. The (freshwater) European pilchard (S. pilchardus) is restricted to the brackish waters of the Baltic Sea, while some other members of the family are found in highly saline environments.