STURGEON (Acipenser), a small group of fishes, of which some 20 species are known, from European, Asiatic and North American rivers. The distinguishing characters of this group are dealt with in the article FisH. Most of them pass a great part of the year in the sea, but periodically ascend large rivers, some in spring to deposit their spawn, others later in the season for some purpose unknown ; a few are confined to fresh water. None occur in the tropics or the southern hemisphere. By a decree of Edward II., English sturgeons are the property of the king.
Sturgeons are found in the greatest abundance in the rivers of southern Russia, more than io,000 fish being sometimes caught at a single fishing-station in the fortnight of the up-stream migration, and in the fresh waters of North America. In Russia the fisheries are of immense value. Early in summer the fish migrate into the rivers or towards the shores of fresh-water lakes in large shoals for breeding purposes. The ova are small and numerous. The growth of the young is rapid. After the sturgeon attains maturity, growth continues for some years, but slowly. Some attain great age, and von Baer stated that observations made in Russia indicate that the Hausen (A. huso) may attain an age of between 200 and 30o years. Sturgeons ranging from 8 to I I ft. in length are by no means scarce, and some species grow to a much larger size. Sturgeons are ground-feeders. The more important species are: I. The common sturgeon of Europe (A. sturio) occurs on all the coasts of Europe, but is absent from the Black sea. It is not rare on the coasts of North America. It reaches a length of 1 2 ft., and is always caught singly, or in pairs. The form of its snout varies with age (as in the other species), being much more blunt and abbreviated in old than in young examples. There are 11-13 bony shields along the back and 29-31 along the body.
2. A. guldenstildtii is one of the most valuable species of the rivers of Russia; it inhabits the Siberian rivers also, eastwards as far as Lake Baikal. It attains the same size as the common sturgeon, and abounds in the riv ers of the Black and Caspian seas.
3. A. stellatus occurs in abun dance in the rivers of the Black sea and of the Sea of Azov. It has a long and pointed snout, like the sterlet, but simple barbels without fringes. Though growing only to about half the size of the preceding species it is of no less value, its flesh being more highly esteemed and its caviare and isinglass fetching a higher price.
4. The sturgeon of the great lakes of North America (A. rubicundus) has been made the object of a large industry at various places on Lakes Michigan and Erie. The sturgeons of the lakes are unable to migrate to the sea, but those below the Falls of Niagara are great wanderers.
5. A. huso is recognized by the absence of osseous scutes on the snout and by its flattened, tape-like barbels. It is one of the largest species, reaching the length of 24 ft., and a weight of 2,000lb. It inhabits the Caspian and Black seas, and the Sea of Azov. Its flesh, caviare and air-bladder are of less value than those of the smaller kinds.
6. The sterlet (A. ruthenus) is one of the smaller species, which inhabits both the Black and Caspian seas.
The family Acipenseridae includes one other genus, Scaphir hynchus, the shovel-head or shovel-nosed sturgeon, distinguished by the long, broad and flat snout, the suppression of the spiracles, and the union of the longitudinal rows of scales posteriorly. All the species are confined to fresh water. One of them is common in the Mississippi and other rivers of North America, the other three occur in the larger rivers of eastern Asia.