Order:	Cypriniformes
Family:	Cyprinidae
Genus and species:	Tinca tinca

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

THE TENCH.

Tinca	vulgaris,	Cuvier, Règne An. t. ii. p. 273.
"	"	Tench.	Flem. Brit. An. p. 186, sp. 61.
"	"	Tinca	Willughby, p. 251, Q. 5, fig. 1.
Cyprinus	tinca	Bloch, pt. i. pl. 14.
"	"	Tench.	Penn. Brit. Zool. vol. iii. p. 474.
"	"	"	Don. Brit. Fish. pl. 113.

Generic Characters. - To those common to the Gudgeons (Gobio), may be added, that the scales are very small, the mucous secretion on the surface of the body abundant, the barbules or cirri very small.

THE TENCH was known to the older writers, but was not held in much estimation. In the present day it inhabits most of the lakes of the European continent. In this country, though frequent in ornamental waters and ponds, it is but sparingly found in the generality of our rivers. There is some doubt whether, like the Carp, its origin be not foreign, and whether those rivers that can now boast of it are not indebted for it to the accidental escape of fish from the preserved waters of neighbouring gentlemen. In rivers it is mostly in those which are slow and deep, that this fish is found, and in such situations it does not appear to be so prolific as in ponds. In deep pits, from which clay for bricks has been dug out, Tench are often abundant ; broad shallow waters on muddy bottoms frequently produce great quantities ; some very extensive tracts of water a few miles north of Yarmouth in Norfolk, not far inland from a point called Winterton Ness, abound with Tench, which, when removed to stews, feed and thrive on a mixture of greaves and meal till fit for table : their flesh is nutritious and of good flavour.
The Tench appears to decline in numbers in proportion as we proceed northward. In a communication from Carlisle on the subject of fish, obligingly supplied to me by J.C. Heysham, Esq. that gentleman states that the Tench is only now and then taken in the Eden ; and occasionally he has known of one being caught in the Solway Frith. A few Tench exist in preserved waters in the neighbourhood of Edinburgh, but they are not very prolific. In a paper by Mr. Whyte, land-surveyor at Mintlaw, which obtained one of the Highland Society's prizes, it is stated, that in some ponds belonging to Mr. Fergusson of Pitfour, in Aberdeenshire, the Tench thrives well ; and the Carp, although not very prolific, breeds. This is owing, it is said, to a particular softness in the quality of the water where these fish exist; in fact, it is allowed by Mr. Whyte, in allusion to the Carp-ponds, that they are wholly kept up by rain-water, a very different fluid from that produced by the hard springs of the country.*
In Ireland the Tench is noticed as existing in ponds in the counties of Cork, Dublin, and Kilkenny.
Tench are exceedingly tenacious of life ; and experiments have shown that a Tench is able to breathe when the quantity of oxygen is reduced to the five-thousandth part of the bulk of the water : ordinary river water generally containing one per cent. of oxygen. The fact, however, as observed by Dr. Roget, shows the admirable perfection of the organs of this fish, which can extract so minute quantity of air from water, to which that air adheres with great tenacity. This power is strongly illustrated in the instance about to be quoted, which is selected on account of its reference to other points in the history of the Tench.
"A piece of water which had been ordered to be filled up, and into which wood and rubbish had been thrown for years, was directed to be cleared out. Persons were accordingly employed; and almost choked up by weeds and mud, so little water remained, that no person expected to see any fish, except a few Eels, yet nearly two hundred brace of Tench of all sizes, and as many Perch, were found. After the pond was thought to be quite free, under some roots there seemed to be an animal which was conjectured to be an otter ; the place was surrounded, and on opening an en-trance among the roots, a Tench was found of most singular form, having literally assumed the shape of the hole, in which he had of course for many years been confined. His length, from eye to fork, was thirty-three inches; his cir-cumference, almost to the tail, was twenty-seven inches ; his weight eleven pounds nine ounces and a quarter; the colour was also singular, his belly being that of a char, or vermilion This extraordinary fish, after having been inspected by many gentlemen, was carefully put into a pond, and at the time the account was written, twelve months afterwards, was alive and well."**
"Tench are said to love foul and weedy, more than clear, water; but situation does not always influence their taste. Tench taken out of Munden Hall Fleet, in Essex, belonging to Mr. Western, which was so thick with weeds that the flew-nets could hardly be sunk through them, and where the mud was intolerably fætid, and had dyed the fish of its own colour, which was that of ink, yet no Tench could be better grown, or of a sweeter flavour; many were taken that weighed nine, and some ten pounds the brace. In a pond at Leigh's Priory, a quantity of Tench were caught, about three pounds' weight each, of a colour the most clear and beautiful, but when some of them were dressed and brought to table, they smelt and tasted so rankly of a particular weed, that no one could eat them. Some that were conveyed alive and put into other water, soon recovered themselves from this obnoxious taint : an experiment that will always answer in this kind of fish, where it is suspected that there is a necessity for cleansing them ; and the circumstance is recited to show that no decisive judgment can be formed from the external appearance of the Tench, however prepossessing it may appear."
As the Tench is one of' our most useful fresh-water fishes, from the ease with which it may be preserved and its increase promoted, the facility of transportation from its great tenacity of life, and the goodness of its flesh, - which is not, however, generally held in the estimation which I think it deserves, - as the Tench is also, like the Carp, one of those species first selected as stock for ornamental waters, I ven-ture to recommend that large and fine fish be chosen as breeders, as the most certain mode of obtaining sizeable fish for table in the shortest space of time. Two males to one female, or not less than three to two, should be the proportion of the sexes ; and from the pond, which is found by experiment favourable for breeding, the small fish should be in part withdrawn from time to time, and deposited elsewhere to afford more space for all. The male of the Tench is recognised by the large size of the ventral fins, which reach far enough to cover the vent, and are deeply concave internally : in the females the ventral fins are smaller, shorter, and less powerful.
In other fishes, besides occasional external sexual distinctions in particular species, it may be stated as a general law, that in the males the head is sharper and longer; the latter effect being produced by a greater backward dilatation of the operculum, and the body less deep in proportion to its length than in the females, the abdominal line nearly straight, in accordance with the general law, that in males the respiratory cavity, and in females the abdominal cavity, has the greater proportional size. In measuring the length of the head with reference to the length of the body, the sex causes little or no difference, the female obtaining in depth what is wanting in length; her shorter body and head afford the same comparative proportions.
The Tench spawns about the middle of June, with some variation depending on the season. Willughby says it happens when wheat is in blossom. Such coincident circumstances in the seasonal progress of animals and vegetables particularly deserve to be studied, recorded, and remembered: they may be made subservient to many useful purposes ; one, which has a direct reference to fishing, will serve as an illustration. Some London friends, who are enthusiastic fly-fishers, know exactly when to leave home and find the Mayfly on the water in different counties of England by the flowering of certain shrubs and plants in the neighbourhood of London.
The female Tench, when ready to spawn, is usually attended by two males, who follow her from one bunch of weeds*** to another, upon which the ova are deposited; and so engrossed are they at this time in the fulfilment of the Divine command, that I have frequently dipped out all three fish by a sudden plunge of a landing-net. The ova are very numerous, Bloch says near three hundred thousand in a fish of four pounds' weight. The food of the Tench consists of the various soft-bodied animals which inhabit fresh-water, with some vegetable matter, as the contents of the intestines seem to indicate ; and the best bait for them is the dark red meadow-worm, which they take very readily early in the morning throughout the summer. They are said to bury themselves in soft mud during winter, and certainly move very little in the colder months of the year.
The length of the head, compared to the length of the head and body without including the caudal rays, is as two to seven ; the depth of the body compared to the length of the head and body as one to three; the head rather large and blunt; the mouth small, with a very small barbule at each corner; the tongue short; the lips flesh colour; the eyes small, the irides golden yellow ; a row of mucous pores down the preoperculum, and thence taking a direction towards the mouth. The body covered with small scales, about forty-eight, in an oblique row between the base of the dorsal fin and the origin of the ventral. The fin-rays in number are

D. 10 : P. 17 : V. 10 : A. 9 : C. 19.

The dorsal fin commences about the middle of the body, the first ray half as long as the second, which is one-third longer than the whole base of the fin, and more than half as long as the body is deep ; the front line of the fin straight, the upper and hinder edges rounded ; the pectoral fins large and rounded; the ventral fins arise in a vertical line before the commencement of the dorsal, and exhibit the sexual indication already noticed ; the anal fin commences half-way between the origin of the ventral fin and the end of the fleshy portion of the tail ; the caudal rays not so long as the head ; the posterior edge of the tail in young specimens concave, afterwards straight, and finally convex.
The general colour of the body greenish olive gold, lightest along the whole line of the under surface ; the fins darker brown ; the lateral line elevated, distinct, descending by a curve from the top of the operculum to the middle of the body, then passing straight to the centre of the tail.

* The Art of Angling as practised in Scotland, p. 99.
** Daniel's Rural Sports.
*** The broad-leaved pondweed, Potamogeton natans, is in some counties called Tench-weed.

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

Tench

Tinca tinca (Linnaeus, 1758)

NAMES Fr. Tanche; Du. Zeelt; Ge. Schlech; Da, Suder; Sw. Sutare.

IDENTIFICATION The body is thick-set and heavy and is covered with small scales, all smaller than the pupil of the eye and deeply embedded in the skin. The skin is extremely slimy; the slime often masks the scales and always makes lively fish difficult to hold. The mouth is terminal, relatively small and has a single barbel each side at the corner. Both dorsal and anal fins are short based, with not more than nine rays, and are rounded. It grows to an average length of 12 in (30 cm), but may attain 25 in (63.5 cm) and commonly weighs 4 lb (1.8 kg). The British record rod-caught fish weighed 8 lb 8 oz (3.85 kg).
The tench's colour varies with locality. Usually they are dark green, sometimes almost black, but with a golden sheen on the flanks, and bronze ventrally. The fins are always dark. A golden variety is cultivated.
D. III/8; A. III/6-8; pharyngeal teeth usually four on the left, five on the right.

BIOLOGY Tench are fishes of still waters, found mostly in lakes, but occasionally they occur in the lower reaches of rivers, most often in backwaters, oxbow lakes or marshy deltas. They also live in estuarine conditions in salinities of up to ten parts per thousand. Tench are said to overwinter in severe winters by lying dormant in the bottom mud. Their ability to live in still, often poorly oxygenated, waters makes them ideal fish for small ponds and they have been widely introduced by angling and fishing interests in Europe and elsewhere.
The tench eats principally bottom-living animals, chiefly insect larvae such as dragonflies and damsel flies, midges (chironomids), isopod crustaceans like the water slaters (Asellus) and pulmonate molluscs, for example, the pond snails (Lymmaea spp.). It also eats cladocera (water fleas) and copepods, which are chiefly the food of the young fish, along with amphipods, chironomid larvae, and water mites. Only young tench eat substantial quantities of algae. Some plant remains may be found in adult fish guts, but these are probably the result of accidental ingestion.
Spawning takes place from May to July, sometimes even in August, when adhesive eggs are shed over the submerged vegetation at certain sites in the water. The eggs are small (less than 1 mm) and green, and hatch in from six to eight days. Spawning takes place in large shoals when the water temperature has reached 18°C (64°F), usually after a period of hot weather. Tench grow relatively slowly as a rule, but favourable conditions of food and space have a good effect. Normally at one year they average around 1¼ in (3 cm), at two years 2½ in (6 cm), at three, when most males reach maturity they average 3¾ in (9.5 cm) and at four, when the majority of the females mature, the average is 5 in (12.5 cm).
Males that have matured possess a much thickened, strong ray in the external edge of the pelvic fins. This is not particularly distinct in the immature fish.
Tench are widely raised with carp in fish farms, although their poor growth rate makes them a long-term investment. Small local fisheries exist for wild fishes. Tench have considerable value as angler's fishes, particularly as they can be introduced to small, oxygen-deficient waters. Their hardiness and ability to live out of water for some hours helps with these introductions, but their slow growth detracts somewhat from their utility in restocking.

DISTRIBUTION

Eastwards to the U.S.S.R.