Order:	Cypriniformes
Family:	Cyprinidae
Genus and species:	Carassius carassius

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

THE CRUCIAN CARP. PRUSSIAN CARP.

CROWGER. Warwickshire.

Cyprinus	gibelio,	Bloch, Pt. i. pl. 12.
"	"	Gibele Carp,	Penn. Brit. Zool. vol. iii. p. 480, pl. 83.
"	"	Gibel,	FLEM, Brit. An.
"	"	Cuvier, Rčgne An. t. ii. p. 271.

Pennant considers the Crucian Carp as a naturalised species in this country, into which it is said to have been introduced from Germany; but, as in the case of the Common Carp, the country from which the Crucian was brought, and the year in which it was introduced, are both enveloped in obscurity.
The Crucian Carp is found in some of the ponds about London, particularly in the vicinity of the Thames, a few miles upwards to the west of the metropolis ; and the floods that occasionally happen are supposed to be the means by which this species has been carried into the Thames, from whence individuals of large size are sometimes obtained. It is also known to be very common in several counties of England, and probably exists in most of them. This fish spawns about the end of April, or early in May : it is very prolific, and the roe, as might be expected, is in great quantity. Though known to be very numerous in some situations, but little success attends the angler who endeavours to catch them, as they seldom bite freely. They attain considerable size, sometimes weighing a pound, or a pound and a half; in one instance a specimen brought to me from the Thames, in October 1829, weighed two pounds eleven ounces ; but the most common size is about half a pound. The flesh is white and agreeable. This fish is exceedingly tenacious of life. I have known them recover and survive after having been kept out of water thirty hours. The number of fin-rays are -

D. 18 : P. 14 : V. 9 : A. 8 : C. 19. Vertebrę 30.

The length of the head, compared to the length of the head and body without the tail, is as one to four ; including the tail, as one to five; the caudal rays being as long as the head, and one-fifth of the whole length. The body is deepest on the line of the commencement of the dorsal and ventral fins ; and the depth, compared to the whole length, including the tail, is as one to three.
The form of the head obtuse; the mouth and eyes small ; the body rather short and thick : the scales large seven scales in an oblique line between the base of the first dorsal fin-ray and the tubular scale of the lateral line, and six scales below between that and the origin of the ventral fin ; thirty-four or thirty-five scales along the lateral line ; this line descending by a gentle curve from the upper free angle of the operculum below the middle of the body, thence straight to the tail : the pectoral fin commences in a line under the posterior point of union of the operculum with the suboperculum ; the dorsal and ventral fins commence on the same vertical plane ; the length of the base of the dorsal fin nearly equal to the depth of the body; anal fin small, placed in a vertical line half before and half behind the origin of the last ray of the dorsal fin ; the stronger bony ray of the dorsal and anal fin finely serrated, compared with the serrations in the rays of these fins in the Common Carp. The tail forked, divided into two nearly equally rounded halves, the longest rays about one-third longer than the short rays of the middle portion ; the upper part with ten rays, the lower portion with nine.
The top of the head and back olive brown ; the sides lighter in colour; the belly almost white; the whole fish shining with a brilliant golden metallic lustre: irides golden ; cheeks and gill-covers brilliant golden yellow ; the dorsal fin and upper part of the tail, brown tinged with orange ; pectoral, ventral, and anal fins, orange red ; lower part of the tail tinged with the same colour.
This fish has been considered here as the C. gibelio of Bloch ; but in one circumstance it does not agree with his fish. Bloch says the C. gibelio has but twenty-seven vertebrę ; those of C. carassius are stated by Bloch to be thirty, but the specimens examined for the description now given had also thirty vertebrę. The fin-rays agree in number with those of Bloch's gibelio, and do not coincide with the number considered to be present in carassius.

From some measurements, and other particulars in my note-book, I have great reason to believe that specimens of C. carassius have been more than once brought to me from the Thames ; but not at that time contemplating the want of them for the present purpose, the specimens were not preserved. In order, however, that other inquirers may identify this species should it occur, a reduced figure of C. carassius, from Bloch, pl. 11, is here supplied as a vignette. The fin-rays are -

D. 21 : P. 13 : V. 9 : A. 10 : C. 21. Vertebrę 30.

The length of the head is to the depth of the body as one to two, and to the whole of head, body, and tail, as one to five ; the depth of the body compared to the whole length, as two to five : the tail nearly square at the end.
Several authors have wholly omitted the gibelio in their systematic works ; others have considered it as a distinct species ; and some have supposed it only a variety of carassius. The most obvious points of distinction between these two fishes are, in C. gibelio, depth of body compared to the whole length as one to three ; depth of body not equal to twice the length of the head ; tail forked. In C. carassius, depth of body compared to the whole length as two to five , depth of body equal to twice the length of the head ; tail nearly square. The length of the head, compared to the whole length of the fish, is the same in both, viz. as one to five. Dr. Turton, in his British Fauna, has described the carassius, p. 108, sp. 119. Mr. Pennant and Dr. Fleming have described the gibelio.

Frank Buckland (1880) in "Natural History of British Fishes":

CRUCIAN CARP.

(Carassius vulgaris.)

German : Die Karausche; French : Le Carassin

The Crucian Carp is another kind of Carp (see Prussian Carp).

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

Crucian Carp

Carassius carassius (Linnaeus, 1758)

NAMES Fr. Carassin; Du. Kroeskarper; Ge. Karausche; Da. Karuds; Sw. Ruda.

IDENTIFICATION The body is hump-backed, especially so in old specimens, which have a 'heavy' look. The mouth is moderately small and terminal, the head about a quarter of the body length. No barbels at mouth. The dorsal fin is long, with a strong, lightly serrated third spine; the anal fin short with six to eight (exceptionally) branched rays and a strong, lightly serrated spine. Twenty-six to thirty-one gill rakers on first gill arch. Grows to an average of 10 in (25 cm), and a maximum of 20 in (51 cm). The British record fish weighed 4 lb 11 oz (2.12 kg).
In colour, olive green, or reddish brown on the back, paler with a brassy tint on the sides, with a rounded dark spot, indistinct in old specimens, near the base of the tail. The pectoral, pelvic and anal fins are a bright reddish bronze.
D. III-IV/14-21; A. III/6-8; lateral line scales 32-5; transverse scales 7-8/5-6; pharyngeal teeth four each side (Fig. 69).

BIOLOGY A fish found in still waters and less commonly in slow-flowing rivers in the lowlands. It is very tolerant of low oxygen conditions and lives in marshes with only occasional pools of open water, and in small ponds.
The Crucian carp breeds from May to June, occasionally to July, in several isolated spawnings. There is no apparent segregation by size in the spawning shoals, and fish of all ages spawn together. The eggs are golden, from 1.4 to 1.7 mm in diameter, and adhere to the vegetation. They hatch in five to ten days depending on the temperature, and the alevins measure about 4 mm in length. This fish's rate of growth varies greatly depending on the habitat; many in small pools are several years old and only 2-3 in (5-7.5 cm) in length. In large waters, however, the growth rate lies between the following figures: one year old, 1¼-1½ in (3.0-3.7 cm); second year, 2-2½ in (5.4-6.6 cm); third year, 3-3¾ in (7.6-9.7 cm); fourth year 3 ¾-5 in (9.6-12.9 cm); fifth year 4½-5¾ in (11.6-14.4 cm). Populations have been studied in which the growth rate is half as great again as in these figures.
Little has been recorded concerning the food of this species. It is said to eat both plants and animals, the latter being more important.
The Crucian carp is of considerable economic importance in eastern Europe, and is raised in fish farms, and released in poor-quality artificial waters to be cropped later. It is also a valuable angling fish, not least for its ability to thrive in places where few other species could survive. It makes an attractive aquarium fish, and quickly becomes surprisingly tame. It has been widely introduced both in the British Isles and Europe.

DISTRIBUTION

Eastwards to the U.S.S.R.