Order:	Acipenseriformes
Family:	Acipenseridae
Genus and species:	Acipenser sturio

William Yarrell (1836) in "A History of British Fishes":

THE COMMON STURGEON

Acipenser	Sturio,	Common Sturgeon,	Linnæus. Bloch, pt. iii. pl. 88.
Sturio,		The Sturgeon,	Willughby, p. 239, P. 7, fig. 3.
Acipenser	Sturio,	Common Sturgeon,	Penn. Brit. Zool. vol. iii. p. 164, pl. 22.
"	"	L' Esturgeon,	Cuvier, Règne An. t. ii. p. 379.
"	"	Common Sturgeon,	Don. Brit. Fish. pl. 65.
"	"	Sturgeon,	Flem. Brit. An. p. 173, sp. 30.
"	"	Common Sturgeon,	Jenyns, Man. Brit Vert. p. 493, sp. 182

Generic Characters. -- Body elongated and angular, defended by indurated plates and spines, arranged in longitudinal rows ; snout pointed, conical; mouth placed on the under surface of the head, tubular, and without teeth.

ALL the remaining portion of the British Fishes to be yet described belong to Cuvier's division called Chondropterygiens, or Cartilaginous Fishes, the skeletons of which are made up of cartilage, and not, as in the divisions of Acanthopterygiens and Malacopterygiens, made up of true bone. The earthy matter in the hard parts of these fishes is smaller in quantity, is deposited in grains, and does not assume the form, as in other fishes, of distinct osseous fibres.
In the fishes of the families contained in this order, there are several interesting peculiarities. Some have their gills free, like those of ordinary fishes ; there are others in which the gills are fixed by having their outer edges, attached to the skin. Several of them bring forth their young alive in a manner very different from any of the true bony fishes ; while some, and these the last in the series, want that degree of organization in the bones of the upper jaw observable in those generally which have been hitherto described, but of which two or three examples of deficiency by malformation have been figured.

This order may be said to be further distinguished by including within its limits fishes exhibiting in certain points of their structure the highest as well as the lowest degrees of organization observable throughout the whole class. These different peculiarities will be pointed out on arriving at the different genera in succession.
The Sturgeon, the first of the cartilaginous fishes, allied to the Sharks in the elongated form of its body, resembles other fishes in having the gills free, and in being oviparous. It is caught occasionally on various parts of our coast, most frequently in the estuaries, or but a short distance up rivers ; Very seldom taken in the open sea, where it is believed to inhabit deep water, beyond the reach of nets, and is not, that I am aware, ever caught upon the fishermen's lines. Dr. Neill says that one or two are generally taken every summer about the mouth of the Almond or of the Esk, where they get entangled in the Salmon nets, and when of large size frequently doing the fishermen considerable damage by tearing their nets. They are otherwise harmless. One caught in a stake net near Findhorn in Scotland in July 1833, measured eight feet six inches in length, and weighed two hundred and three pounds.
The Sturgeon is occasionally taken on the East coast, and frequently brought to the London market from various localities. When caught in the Thames, within the jurisdiction of the Lord Mayor, it is considered a Royal Fish ; the term being intended to imply that it ought to be sent to the King, and it is said that the Sturgeon was exclusively reserved for the table of Henry the First of England.
On our Southern coast, Colonel Montagu mentions one taken in the estuary at Kingsbridge ; and Mr. Couch enumerates three instances at different periods of different years; one in the Tamar in June, one at Plymouth in August, and one near the Eddystone in January. In September 1802, a specimen, eight feet long, and weighing one hundred and ninety-two pounds, was caught in a weir below the castle at Shrewsbury. The largest specimen taken in this country is probably the fish recorded by Pennant, which was caught in the Esk, and weighed four hundred and sixty pounds.
In Ireland the Sturgeon has been taken on the south, the east, and the north coasts.
In the northern parts of Europe this fish is much more numerous than with us, and extensive fisheries are established for its destruction. Caviar is made of the roe of the female ; isinglass is obtained from the dense membrane forming the air-bladder ; and the flesh, besides being preserved by salting and pickling, is in request for the table while fresh, being generally stewed with rich gravy, and the flavour considered to be like that of veal. The flesh, like that of most of the cartilaginous fishes, is more firm and compact than is usual among those of the osseous families.
The Sturgeon, as has been before observed, is oviparous, spawning in winter. It has been frequently remarked that Sturgeons of very small size are seldom seen : by the kindness of Mr. George Daniell, however, I possess a small specimen, only twelve inches long, that is quite perfect, and exhibits all the characters of the mature fish. "It is presumed that the young, as soon as they escape from the eggs, which the female deposits in fresh water, descend immediately to the sea, and do not visit the places of their birth again till they come in their turn to deposit their spawn." The Sturgeon is said to subsist on small fishes ; from the structure of the mouth it probably feeds also on any soft substance that it finds at the bottom.
The body is elongated; from the shoulders backward somewhat pentagonal in shape, with five longitudinal rows of flattened plates, with pointed central spines directed backwards, one row, larger than the others, along the ridge of the back, one row on each side, and another along the edge of the abdomen in a line from the pectoral fin to the ven-tral on each side ; the flattened plates are marked with radiating striæ. The nose is long and pointed ; the forehead with a longitudinal depression ; the crown of the head ele-vated, the occiput rising into a sharp keel: the mouth placed on the under surface of the head, rather wider than long, with a projecting rim ; no teeth within: about half-way between the mouth and the end of the nose, are four cirri ranged in a line across ; the eyes small; the operculum hard and strong, covered with striæ radiating from a centre; dorsal fin placed very far back, but little in advance, of the line of the anal fin : tail forked ; upper lobe much the long-est, and pointed. The fin-rays in number- - -

D. 35 : P. 28 : V. 24 : A. 23 : C. 125.

The colours of the body are various shades of brown ; the plates nearly white, the belly silvery.
The vignette represents the under surface of the head.

Alwyne Wheeler (1969) in "The Fishes of the British Isles and North West Europe":

Sturgeon

Acipenser sturio Linnaeus, 1758

NAMES Fr. Esturgeon; Du. Steur; Ge. Stör; Da. Stør; Nor. Stør.

IDENTIFICATION This unmistakable fish is unique in the northern East Atlantic. The five rows of large, hard, bony scutes along the body are the most obvious feature; the first row along the centre of the back has from ten to fifteen plates (behind the dorsal fin they are paired); the lateral rows have twenty-six to thirty-six plates, while on the belly there are two rows (usually with between nine and thirteen plates), which merge into a paired central row behind the vent. The snout is long, pointed in the young, broad in adults, and there are two pairs of barbels midway between the snout tip and the mouth. The mouth is ventral, and can project as a short tube. Colour: bluish-black dorsally, lightening on the sides to white ventrally. The dorsal scutes are light in colour. In young fish the scutes are conspicuously light and the fish has a striped appearance. It grows to 11.5 ft (3.5 m) and a weight of 700 lb (320 kg) for females, the males being smaller.

BIOLOGY The sturgeon is a rare visitor to northern European waters. From a once moderate abundance in coastal waters it has practically been exterminated, the only populations existing today in the Atlantic basin being centred on the Rivers Gironde (France), and Guadalquivir (Spain) and Lake Ladoga (U.S.S.R.). Normally a few are caught each year in British waters. The largest recently was taken in 1956; it was 11 ft (3.37 m) long and weighed 142 lb (317 kg).
* The adult sturgeons enter the river mouth in February and March, the males being more numerous and smaller than the females. Spawning takes place well up the branches of the Garonne and the Dordogne, in deep water of 3-4 fathoms (6-8 m) over a gravel bottom. The eggs are large (2.1-2.5 mm) and sticky and adhere to the stones or plants; they hatch in three to seven days at water temperatures of 19-14 °C (66-57 °F) respectively. Thereafter growth is rapid and the young are said to attain 8 in (20 cm) in their first summer. One-year-old fish average 15 in (39 cm) in length. Other European populations, however, do not grow so fast, an annual average of 4 in (10 cm) for the first year of life having been calculated. After spawning, the adults return immediately to the sea, but the young stay in the river and its estuary for up to three years. In the sea, growth is rapid.
Many sturgeon, juveniles and adults, stay within a radius of sixty miles of the Gironde mouth, but the presence of specimens in British waters indicates an occasional wider dispersal; tagged specimens of a related American species have travelled up to 900 miles. It is, however, not proven that British sturgeons are members of the Gironde population, they may derive from the Baltic, or from Spanish, Mediterranean, or even North American sources. In the sea the majority are caught in depths of 11-27 fathoms (20-50 m); exceptionally they are taken down to 38 fathoms (70 m).
Juveniles feed on a wide variety of aquatic life whilst they are in the rivers, mainly insect larvae (chironomids, may-flies, etc.), isopods, gammarids and molluscs. The adults eat molluscs, small fish (gobies and sand eels), polychaete worms, shrimps and isopods at sea, but they do not feed whilst ascending to the spawning grounds. They feed by rooting around in the bottom mud or sand with their broad snouts, detecting food with the sensitive barbels, and picking up edible items with the relatively protrusible mouth.
The eggs from the ripening female form the famous dish caviare; the flesh of large sturgeon is also highly palatable. In good years following the 1939-45 war the production of caviare from the Gironde population totalled three tons annually, and the total annual sturgeon catch amounted to fifty tons. The fishery has, however, to be carefully regulated by means of close seasons and catch limits to prevent over-exploitation. Most of the caviare imported from Russia (industries in the Black, Caspian and Azov Seas) and Persia (Caspian Sea) is prepared from the roe of related species of sturgeon.

DISTRIBUTION

Mediterranean (particularly the R. Po), Black Sea (rare), a related species on the American Atlantic coast.