STURGEON, stetion, a family (Acipen seridce) of fishes, now generally considered to constitute, with or without the paddle-fishes (Polyodontidce) the distinct order Chondrostei. Formerly the sturgeons were classified as carti laginous ganoids, an arrangement which ichthy ologists no longer find adequate. This group is considered to be one of the primary divisions of the Tel and the modern sturgeons to be the degenerate descendants of the more highly developed extinct forms. This degeneracy is expressed in the deficiency of the skeleton in numerous respects.
The sturgeons are bulky fishes of elongated form. The snout is conical and tapering. The mouth, which is small, toothless and protractile, is situated on the under surface of the muzzle, and is preceded by four tentacle-like filaments or barbules. The eyes and nostrils exist at the sides of the snout. The head is completely in vested by ganoid plates, some of which are median, while on the body these plates are ar ranged in five longitudinal rows with smaller plates between. The tail is heterocercal, or un equally lobed, and is provided with bony spines along its upper margin. A single dorsal fin is present and placed far back, as are also the anal and ventral fins. Spiracles or apertures for the admission of water to the gills exist on the upper aspect of the head. The opercula or gill-covers are of large size, but imperfectly os sified and the branchiostegal rays are wanting. There are four pairs of gills and a pair of pseudobranchim on the opercu4a. The internal skeleton is chiefly cartilaginous, though the weak maxillary, premaxillary and dentary bones, serving as supports for the jaws, are ossified as are also the cerato-branchials. A persistent notochord is surrounded by partly segmented cartilaginous vertebra. A remarkable feature of the shoulder-girdle is the presence of an in terclavicle. Among features of the soft anat omy are to be noted the presence of an elaborate spiral valve in the rectum, of pyloric caeca, of a large swim-bladder communicating with the oesophagus by a duct but without any highly vascular respiratory area, of several series of valves in the bulbus arteriosus, or base of the aorta, and of distinct funnel-shaped oviducts. All of these characters separate the sturgeons from the more highly specialized spiny-rayed fishes. Two to four genera and from 20 to 50 species have been recognized by different au thors, the disparity arising from the great changes undergone by these fishes in the course of their growth. All are found in the northern
hemisphere and most of the species are anadro mous, living in the sea except at the time of reproduction, when they migrate up the rivers to fresh water for the purpose of spawning.
The latest authorities on the North Ameri can species give six as belonging to our fauna, five of the genus Acipenser, and one of Scaphi rhynchops. All of them are of more or less importance as food fishes. The common stur geon (A. sturio) is common to the Atlantic coasts of the United States and Europe. This and the related species are distinguished by minute characters in the shape, sculpturing, number etc., of the large shields, the propor tions of snout, fins and other similar characters for which the reader is referred to the literature cited. On our coasts the common sturgeon is found from New England to the Carolinas, entering rivers in the spring. In the Delaware River they appear in April and remain until September, the eggs being deposited during the early summer, being forced out by the female as she rubs her belly over rocks, stubs or other hard objects to which the eggs adhere after their immediate fertilization by the male. They are blackish in color, very glutinous, about a ninth of an inch in diameter and their number very great, not less than one to two and one-half millions being produced by each large female, and the ovaries at the time of maturity are so bulky that they constitute fully one-third of the fish's weight. Although so large the stur geon feeds almost entirely on small mollusks, annelids, crustaceans and dead animal matter which it digs from the mud with its pointed snout, detects with its sensitive tentacles and sucks in with its small toothless mouth; to a great extent it is a scavenger. At times small fishes are also devoured in considerable quan tities and that it may display considerable agil ity is attested by its occasional leaps from the water. The sturgeon reaches a length of from 5 to 10 feet, and a weight of 500 pounds, though examples of that size are now exceedingly rare. Formerly this fish was exceedingly abundant, a fact frequently mentioned by colonial and other early writers.