Order:	Cypriniformes
Family:	Cobitididae
Genus and species:	Noemacheilus barbatulus

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

THE LOACH, LOCHE, OR BEARDIE.

Cobitis	barbatula,	Linnĉus. Bloch, pt. i. pl. 31, fig. 3.
"	"	Loche,	Penn. Brit. Zool. vol. iii. p. 379.
"	"	Bearded	Loche	Don. Brit. Fish. pl. 22.
"	"	"	Flem. Brit. An. p. 189, sp. 69.

Generic Characters - Head small ; body elongated, covered with minute scales, invested with a thick mucous secretion ; the ventral fins placed far back, in a line under a small dorsal fin ; mouth small, without teeth ; upper lip furnished with six barbules, four of them in front, and one at each corner; gill-openings small ; branchiostegous rays 3.

THE LOACH is not uncommon in our rivers and brooks ; but its habit of lurking under stones often prevents its being observed. Mr. Neill says it is also frequent in the Waters of Leith, and other rivers of Scotland in general; and Dr. Rutty includes it in his Essay towards a Natural History of the County of Dublin. The Loach delights in small, shallow, clear streams, and swims rapidly when disturbed by moving the stone under which it secretes itself As they are difficult to catch from their slimy smoothness and activity, country boys are in the habit of surrounding any small pool, known to contain some, with a bank of clay, and then making sure of them by lading out the water.
Mr. Booth, in his Analytical Dictionary, considers that our term Loche is derived from the French locher, to be uneasy ; alluding to the restless habits of the species of this genus, and their almost constantly moving from place to place. They are said to be particularly restless before and during stormy weather, and have been preserved in vessels, like the Leach, as living barometers,* from a notion that certain movements and alterations of position or situation indicated particular changes about to take place in the weather.
The species of this genus are remarkable in having six barbules about the mouth. Fishes thus provided are known to feed at or near the bottom of the water ; and it has been stated in this work, at page 22, that those species which reside constantly so near the bottom as to acquire the name of ground-fish, have a low standard of respiration, and a high degree of muscular irritability. In the animals possessing this duration of the power of muscular contractility, as the Eels, flat-fish, and many others, there is reason to believe there exists also great susceptibility of any change that occurs in the electrical relations of the medium in which they reside : the restless movements of Eels and other ground-fish during thunder receive at least a probable explanation in the belief that no alteration in the weather takes place without some previous change in the electrical state of the atmosphere, which, by quality or quantity, may affect the water.
The Chinese, who breed and rear great quantities of Gold Carp, find that thunder does them harm, and even sometimes kills them. Pennant says, Lobsters fear thunder, and are apt to cast their claws on a loud clap. These effects may be referred to spasmodic action of the muscles induced by electrical influence. If fishes of opposite habits, such as surface-swimmers and ground-fish, are put together into the same vessel of water, and a slight galvanic discharge passed through the fluid, the ground-fish with the lowest degree of respiration will be the most agitated.
Worms and aquatic insects are the food of the Loach. It spawns in March or early in April, and is very prolific, but seldom exceeds four inches in length. The flesh is accounted excellent; and in some parts of Europe these little fishes are in such high estimation for their exquisite delicacy and flavour, that they are often transported with considerable trouble from the rivers they naturally inhabit to waters contiguous to the estates of the wealthy. Linnĉus, in his Fauna Suecica, says that Frederick the First, King of Sweden, had them brought from Germany, and naturalized in his own country.
Some peculiarities in the skeleton of the Loach will be pointed out after the description of its external appearance.
The length of the head compared with the length of the body alone is as one to four ; the depth of the body is to the length of the head and body, without the caudal rays, as two to eleven ; the nose is rounded, pointing downwards ; the top of the head flat ; the nostrils double, the most anterior tubular, the second pierced in a depression just before the eye ; the lips large : the mouth small, placed underneath, the lower jaw the shortest ; the form and situation of the mouth very similar to that of the Barbel, with four barbules or cirri over it on the upper lip in the front, and one at each lateral angle: the eye small ; the body elongated, smooth, covered with a mucous secretion, rounded in form before the dorsal fin, compressed behind it: the dorsal fin commences half-way between the point of the nose and the end of the fleshy portion of the tail ; the ventral fins under the dorsal ; 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 slightly rounded. The fin-rays in number are -

D. 9 : P. 12 : V. 7 : A. 6 : C. 19 : vertebrĉ 36.

The head, body, and sides are clouded and spotted with brown on a yellowish white ground ; the belly and under surface white or yellowish white ; all the fins spotted with dark brown, the dorsal fin and the tail the most so ; the irides blue.
I am indebted to the kindness of Mr. George Daniell for the knowledge of two peculiarities in the structure of the bones of the Loach, which are represented in the vignette, and also for the use of a skeleton to draw and describe from.
Attached to each outer side of the first and second vertebrĉ is a hollow sphere of bone of equal size, between which, on the upper surface, the vertebrĉ are distinctly seen; but the union of the two spheres underneath hides the vertebrae when looked towards from below. These circular bones, which are hollow, and the smooth insides of which can be seen through a horizontally elongated aperture that exists on the outer side of each, - these bones are analogous to the scapulĉ, to their outer surfaces the bones of the proximal extremity of the pectoral fins are articulated, and the fin moved by powerful muscles, which assist in producing the rapid motion observable in this little fish. Another peculiarity existing in the upper surface of the head, is the want of union in the two parietal bones at the top ; a deficiency which has been noticed by the late Rev. Lansdown Guilding to occur in the Iguana tuberculata, or common Guana,** and to which aperture that lamented naturalist applied the term foramen Homianum, in honour of Sir Everard Home, observing that the opening did not afford a passage to any nerve or blood-vessel. This peculiarity in the Loach, it will be observed, is another instance of a relation in structure between the fishes and reptiles, some of which have been already adverted to at page 40.
The vignette exhibits a magnified representation, four times larger than the natural size.

* The Lake Loche of the European Continent, Cobitis fossilis of authors, is in an old Continental Naturalist's Miscellany called Thermometrum vivum.
** Zoological Journal, vol. i. p. 130.

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

LOACH.

Local names: Beardie, Bearded Loach, Loche, Groundling, Lee Loach, Spined Loche, Ground Gudgeon, Loach, Loch Loche, Stone Loach, Tommy Loach, Tommy Loych, Tommy Lurcher. French: Loche, Frauche. German: Steinbeisser, Schmerlein, Grundling. Italian: Barbatello.

IT is not uncommon in our rivers and brooks. From its slimy smoothness and activity it is very difficult to catch. We Winchester boys used to spear this fish on the Itchen with an ordinary fork tied on to the end of a stick, and then pickle him with the minnows. It forms an excellent bait for eels, and Mr. Thames Trout will sometimes take him, if he is properly and artistically spun.
The Loach is a veritable hermit ; he lives in brooks and small streams, and always under the stones. If the Loach risks the end of his nose beyond his hiding-place, it is only immediately to go back again, or to seek another place. The Loach is probably nocturnal in its habits. He grows to be about as big as a gudgeon. He is very quick in his movements when frightened, and lives probably on little insects and other creatures found among the moss and weeds of the brooks. Their great enemy is probably eels. Nothing whatever is known of their spawning time. I should be too pleased to have any remark on this subject.

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

Stone Loach

Noemacheilus barbatulus (Linnaeus, 1758)

NAMES Fr. Loche franche; Du. Bermpje; Ge. Bartgrundl; Da. Smerling; Sw. Grönling.

IDENTIFICATION An elongate, scaleless fish, with a moderately laterally compressed body, and six barbels around the mouth, four under the tip of the snout, and a pair at the corners of the mouth. The lateral line is well developed anteriorly. The fins are rather rounded, the dorsal set well back, its origin slightly in front of the pelvic fin base. No spine under the eye.
Colour very variable; usually a dull yellow-brown with dark brown, irregular patches, ventrally creamy yellow. The dorsal, tail and pectoral fins are spotted, the tail fin with a light margin. It grows to a length of 5 in (12.5 cm), usually around 3 in (7.6 cm).
D. 9-11; A. 7-9.

BIOLOGY The stone loach lives mainly in the clear water of small streams, occasionally on the shore-line of lakes, and also in brackish lagoons in the Baltic. It occurs from sea-level to altitudes of 1250 ft (381 m). It is found on sandy, muddy or stony bottoms, and lives under the larger stones or in dense weed, often together with other loaches, bullheads and (in winter) minnows. It emerges at night or on dull days to forage. The stone loach spawns from April to June, the eggs being shed amongst gravel and weed. The eggs are dirty white in colour, 1 mm in diameter, and hatch in fourteen to sixteen days at a temperature between 12 and 16 °C (54-61 °F). The newly hatched fry are 3 mm long, and grow quickly; at five weeks, when they are ½ in (1.5 cm) long, the barbels first become visible. The growth of the stone loach in the Lake District has been analysed, and the mean length at the end of each year of life was found to be: 3ĵ in (8 cm) in the first year; 4 in (9.9 cm) in the second year; 4ĵ in (10.8 cm) in the third year; 4½ in (11.4 cm) in the fourth year and 4½ in (11.5 cm) in the fifth year.
The male stone loach has a longer, more pointed pectoral fin than the female, but the difference is not clear-cut. In the breeding season males have minute papillae on the pectoral fin; in fish over 3 in (8 cm) long they are always present, although difficult to see except in spring. Most stone loach mature in their first year, but slow-growing individuals may not spawn for the first time until their second year.
It feeds almost entirely on bottom-living invertebrates. Chironomid larvae are a major item of diet, ephemeropteran and plecopteran nymphs making up the remainder of the bulk of the food. Other less important foods include crustaceans (Gammarus), Cladocera (Chydorus, Eurycerus and Alona) ostracods and copepods, worms and leeches, and occasionally molluscs. Feeding is less intense from November to January, at least in northern waters.
The stone loach has no direct economic importance. Occasionally it is eaten by trout, pike and eels, when young by bullheads, and by a number of birds (dippers and greenshanks) and mammals (water-shrews and otters). It is fairly sensitive to pollution and its presence or absence can be used as an indicator of river pollution.

DISTRIBUTION

Eastwards to the Caspian basin.