Order:	Cypriniformes
Family:	Cyprinidae
Genus and species:	Leuciscus idus

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

THE IDE.

Leuciscus	idus,	Cuvier, Règne An. t. ii. p. 275.
"	"	Jenyns, Syst. Cat. p. 26.
Cyprinus	"	Linnæus. Bloch, pt. i. pl. 36.

Generic Characters - The anal fin short, as well as the dorsal, but without strong rays at the commencement of either ; no barbules at the mouth.
The species of the first section of this sub-genus, instituted by Klein, have the dorsal fin over the ventral fins.

ACCORDING to Mr. Stewart, this species was taken at the mouth of the Nith by the late Dr. Walker ; and a figure from Meidinger's plate, which Cuvier considers a better representation than that in Bloch's work, is introduced here, with a short description to assist in identifying this species at any future time.
Bloch says this fish is distinguished by the bulky character of the body, and by the anal fin having thirteen rays. It was first described by Gesner, and is found in Pomerania, Westphalia, Sweden, Norway, Denmark, and Russia. It is an inhabitant of large rocky lakes, from which it seeks its way into rivers in the months of April or May, to deposit its spawn in running water among stones. It feeds on worms and herbage, like the other species of the genus, but grows slowly. The flesh is said to be white, tender, and of good flavour.
The head is large, and appears somewhat truncated ; the muzzle blunt ; the mouth small, without teeth, as is the case also with the other species of this extensive family , the upper jaw rather the longest ; the eye of moderate size ; the dorsal line convex ; abdominal line almost straight ; the scales of the body large ; the lateral line curved in its descent from the upper edge of the operculum to the centre of the body: the fin-rays in number are -

D. 10 : P. 17 : V. 11 : A. 13 : C. 19 : Vertebræ 41.

In colour the irides are straw yellow, the pupils black ; forehead, nape, and back, very dark bluish black ; the sides bluish grey ; the belly white : pectoral fin orange; ventrals immediately under the dorsal fin, red in the middle, the first and last rays white ; base of the anal fin white, the other part red ; dorsal fin and tail grey, all the rays branched.

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

Ide or Orfe

Leuciscus (Idus) idus (Linnaeus, 1758)

NAMES Fr. Ide mélanote; Du. Winde; Ge. Orfe, Aland; Da. Rimte; Sw. Id.

IDENTIFICATION The body is relatively thickset and humped behind the head; the snout is blunt and the mouth distinctly oblique. The dorsal fin is sited behind the level of the pelvic fins; both dorsal and anal fin are short, the anal fin being longer based. The dorsal fin has a convex free edge, the anal a straight to concave free edge. Pharyngeal teeth in two rows, of three and five, cylindrical, smooth and not serrated (Fig. 69). Average length 12-17 in (30-43 cm); in eastern Europe they may reach 40 in (102 cm) and a weight of 13-17 lb (6-8 kg).
The adults’ back and upper sides are greyish black, the lower sides and belly silvery. All but the dorsal fins are reddish. The golden variety (the orfe), kept in ponds, is a pale yellow to orange fish, often with dark patches.
D. III/8; A. III/9-10; lateral line 56-61; transverse scales 8-9/4-5.

BIOLOGY Common in slowly flowing and still waters in north western and central Europe, it is found also in brackish waters in the Baltic. It is found in shallow water, but seems to prefer deeper waters in which it remains throughout the winter. The ide spawns in April and May in weedy and sandy areas, the eggs attaching themselves to plants in the shallows. The males in particular are more brightly coloured in spring-time. Maturity is attained in the third or fourth year at around 6 in (15 cm). The growth rate varies with locality, 2 in (5 cm) in the first year, 4 in (10 cm) in the second, and 5 in (13 cm) in the third, being average in favourable localities. The ide lives for twenty or more years in continental waters.
Its food consists mainly of insect larvae, adult insects, particularly mayflies, and bottom-living invertebrates including snails, bivalves and crustaceans. In places in eastern Europe the ide is fished for commercially; elsewhere it is a reasonable angler’s fish and will take a fly. The golden variety is often stocked in private and municipal lakes.

DISTRIBUTION

East to U.S.S.R. Introduced to Britain.