CLUPEIFORM

any member of the order Clupeiformes, containing some of the world's most numerous and economically important fishes. The order includes more than 400 species, about 20 of which provide more than one-third of the world fish catch. They are by far the most heavily exploited of all fish groups. Most clupeiforms are small marine fishes, under 30 centimetres (12 inches) in length, slender, streamlined, and rather non-specialized in body form; a few species exceed 50 centimetres in length. The wolf herring, Chirocentrus dorab, is exceptional in size among the clupeiforms; this species reaches 3.6 metres (12 feet). Authorities disagree on many aspects of the classification of the order Clupeiformes, which is usually described as including more families than are treated in this article. In a sweeping revision of the bony fishes, the ichthyologists P.H. Greenwood of Great Britain and Donn E. Rosen, Stanley H. Weitzman, and George S. Myers of the United States have restricted the order to the families Clupeidae (herrings, sardines, and allies), Engraulidae (anchovies), Chirocentridae (wolf herrings), and Denticipitidae, a single, little known African species. The last two families are of purely scientific interest; the dominant members of the order, in abundance and therefore in economic importance, are the herrings, sardines, pilchards, menhadens, sprats, anchovies, and anchovetas. Other fish groups formerly included in the Clupeiformes are the tarpons and bonefishes; salmons, trouts, and pikes; and bony tongues and mormyrs. Most clupeiforms inhabit more or less offshore open waters in abundant schools. Although usually considered pelagic (inhabiting the open ocean), in relation to distribution and life history, they are closer to the neritic (coastal) fauna because they do not usually occur in the really open parts of the oceans; rather, they stay close to shore and in bays. Even the truly pelagic and migratory species spawn close to shore. The geographical distribution of the order is limited mainly by temperature and salinity. About 70 percent of the species occurs in tropical waters, only few visiting subtropical regions. More than 20 species are limited to purely boreal and subarctic distribution. Remarkably few species are found in the Southern Hemisphere. In relation to salinity clupeiform fishes represent a fairly mixed group: most of them, approximately half of the living species, are wholly marine; a smaller part are anadromous (living in the sea but entering freshwater to breed); and nearly the same number are wholly freshwater fishes. The order includes some marine genera with large numbers of species, such as Sardinella and Harengula, which together comprise more than 60 genera and nearly 220 species. There are fewer anadromous clupeids, about 10 genera with 40 species, distributed mostly in temperate regions, but some in subtropical areas. Freshwater clupeiform fishes include 31 species in 16 genera, most of them limited to the tropics. Nine genera with 15 species inhabit the rivers and lakes of Central and West Africa; six species are distributed in freshwaters of the Indo-Malayan Archipelago and Australia; two genera with four species occur in freshwaters of India; some species of the genera Sigualosa and Dorosoma occur in Central America; and single species of otherwise marine genera are found in the Amazon River (Rhinosardinia amazonica), in the rivers of Borneo (Ilisha macrogaster), and in freshwater lakes of the Philippines (Harengula tawilis). A few other species occasionally occur in freshwater. Of the families and subfamilies of the Clupeiformes, the subfamilies Dussumieriinae (round herrings), Clupeinae (typical herrings), and Pristigasterinae, and the family Chirocentridae are purely marine; the Denticipitidae and Pellonulinae are limited to freshwater; the Alosinae (shads and alewives) and Dorosomatinae (gizzard shads) are anadromous, freshwater, brackish, or marine; and the Engraulidae are brackish or marine. any member of the order Clupeiformes, a group of bony fishes that includes some of the most numerous and heavily exploited of fishes, such as the herring, anchovy, and sardine. More than half of the 400 species of clupeiforms, found mainly in the tropics, are marine; the rest are divided equally between freshwater and anadromous species. Clupeiform fish are usually small, less than 30 cm (12 inches) in length, with slender, streamlined bodies. Only a few species exceed 50 cm (20 inches), although one wolf herring (species Chirocentrus dorab) reaches 3.6 m (12 feet) in length. Characteristic features include an internal passage between the inner ear and the swim bladder, peculiarities of the skull relating to the lateral lines and their connection to the ear, and certain features of the tail (caudal) skeleton. The body of most clupeiforms is keeled on the bottom. This shape prevents the ventral portion of the fish from being in shadow against the light backdrop of the sky, which would make it an easy target for a predator from below. The dorsal fin may be located anteriorly, posteriorly, or centrally on the back. Those species with the best-developed lateral line system and an anterior dorsal fin are the strongest swimmers and undertake the longest migrations. Newly hatched larvae differ in shape from the adults. They are long and wormlike, with the dorsal fin always placed posteriorly. All marine species feed on plankton. Many species change their feeding habits seasonally, while all herrings and some other forms are known to cease feeding altogether during the breeding season. In general, clupeiforms feed intensively in summer, after spawning, but less in the spring before the spawning season. Almost all clupeiforms are schooling fish. In large schools the bigger individuals remain toward the bottom, allowing light to filter down through the massed fish. At the approach of a predator all the fish clump together. Although there are no particular leaders, the entire school turns as though it were one organism. The leading fish remain there and have first access to new food sources. The schools tend to remain in deep water during the day and migrate vertically to the surface at night, following the movements of the plankton. The majority of marine clupeiforms lay their eggs in shallow, inshore waters. Freshwater and anadromous forms choose shallow lakes and the beds of slow-moving rivers. The eggs are usually free-floating, although some genera, such as Clupea and Pomolobus, have sticky eggs that adhere to gravel or plants. The eggs of freshwater species usually sink to the bottom. Additional reading P.H. Greenwood et al., Phyletic Studies of Teleostean Fishes with a Provisional Classification of Living Forms, Bull. Am. Mus. Nat. Hist., 131:339455 (1966), contains the classification that is used in this article. Different classifications and arrangements are in: L.S. Berg, Classification of Fishes, Both Recent and Fossil, Trav. Inst. Zool. Acad. Sci. U.S.S.R., vol. 5, no. 2 (1940; reprinted in book form, 1947), Russian and English texts; Leon Bertin and Camille Arambourg, Super-ordre des tlostens (Teleostei), in P.P. Grass (ed.), Trait de zoologie, vol. 13, fasc. 3, pp. 22042500 (1958); P.J.P. Whitehead, A Contribution to the Classification of Clupeoid Fishes, Ann. Mag. Nat. Hist., Series 13, 5:737750 (1962); H.S. Clausen, Denticipitidae, a New Family of Primitive Isospondylous Teleosts from West African Freshwater, Vidensk. Meddr. Dansk Naturh. Foren., 121:141151 (1959), the first scientific description of an unknown and evolutionary important Clupeiformes family; M.B. Schaefer, Men, Birds and Anchovies in the Peru Current: Dynamic Interactions, Trans. Am. Fish. Soc., 99:461467 (1970), an evaluation of the most abundant species resources; A.J. Mansueti and J.D. Hardy, Development of Fishes of the Chesapeake Bay Region: An Atlas of Egg, Larval, and Juvenile Stages (1967); E.K. Balon, First Catches of Lake Tanganyika Clupeids (kapentaLimothrissa miodon) in Lake Kariba, Bull. Fish. Res. Zambia, 5:175186 (1971), an account of successful artificial introduction into a new area; and A.N. Svetovidov, Fauna of the U.S.S.R., Fishes, vol. 2, no. 1, Clupeidae (1963; originally published in Russian, 1952), a good source of biological and morphological data with an extensive bibliography.