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

Whitefishes

Coregonidae

THESE are freshwater fishes which in the southern parts of their range live in cold water lakes, and elsewhere in rivers and even in brackish waters. In the British Isles they are confined to a few northern and western lakes with a single marine relative in the North Sea, probably extinct in British waters. Their general appearance is herring-like, the relatively large silvery scales on the body, scaleless heads, and centrally sited dorsal fin all contributing to this impression. The presence of an adipose fin just in front of the tail, however, betrays their affinity with the salmonid fishes.
All whitefishes have relatively small heads, small toothless mouths, moderate eyes, pectoral fins placed low down, rather deep bodies, flattened from side to side, pelvic fins with a long fleshy scale in the axil, and deeply forked tails. The lateral line is very noticeable and runs along the mid-line of the sides.
The whitefishes are well known for their complicated variation both within and between the species. Despite extensive research systematists are in no way agreed as to the way in which this variation should be interpreted.
Whitefishes are a diverse group spread throughout the northern land masses of Europe, Asia and North America. The bulk of the populations live in the northern parts of the U.S.S.R. and central Europe, where they form important commercial fisheries and where extensive research has been undertaken into their ecology and racial differences, and some forms have been cultivated. Throughout this vast range, isolated populations have become environmentally modified, and now exhibit considerable divergence from their parent stocks. Elsewhere, principally in small lakes, hybridisation is presumed to have occurred between distinct forms which in some cases have themselves later disappeared, leaving an intermediate form whose parentage may be further obscured by environmental change. The net result has become a 'puzzling web of closely related populations' (Svardson).
The identification of whitefish populations still presents many problems, as the limits of variation of the ancestral species are not well understood. Further, the fact that study of the ecology of the populations might help to unravel the tangle of relationships was not fully appreciated until the late 1930s. Within recent years relatively detailed studies of some of the European (including British) populations have shed some light on the problem. Current practice has been to regard the number and size of the gill rakers as a primary taxonomic character, with the shape and position of the maxillary bones, and the ecology of the population considered as valid secondary features. Unfortunately even amongst the workers employing these criteria there is no broad measure of agreement as to the constitution of each species. In addition, the validity of gill raker counts implies that a sufficient sample of specimens be examined, that the data be statistically examined, and that a high degree of accuracy be maintained in the counts. It has not always been possible to attain these ideals. This, and the natural difficulty of the group, has led to considerable confusion between authors as to the variation between species, their distribution, and most of all, the names to be employed for the several populations.
Six species of whitefish have been recognised by Dr E. Dottrens (1959), and two additional northern European forms by Dr Gunnar Svardson (1957). Unfortunately these authors do not agree as to the names to be adopted for the five species they recognise in common. As the work of both authors has been widely used in Europe, and some of their nomenclature has been adopted in Britain, the table below is given to try to relate the name to the differing forms known in Europe.

DOTTRENS	SVARDSON	NAMES IN EUROPE
C. acronius Smitt	C. pidschian (Gmelin)	Kilch
C. fera Jurine	C. nasus (Pallas)	Sandfelchen, Grosse Marane
C. lavaretus (Linnaeus)	-	Balchen
C. wartmanni (Bloch)	C. lavaretus (Linnaeus)	Blaufelchen
C. macrophthalmus Nusslin	C. oxyrinchus (Linnaeus)	Schnepel, Gangfisch
C. albula (Linnaeus)	C. albula (Linnaeus)	Kleine Marane
-	C. peled (Gmelin)	(Found only in Finland and parts of Sweden)

Another worker in Europe, Dr Matylda Gasowska (1965), differs in detail from both these authorities. Her studies on the British Isles populations seem to be leading to a more acceptable solution to the taxonomic problems posed by these populations, and they are, with reservations, accepted here. Dr Gasowska, however, recognises several of the populations as having subspecific rank, a view which is not adopted here, and which it is feared is likely to cause confusion amongst non-taxonomists. In the present state of whitefish taxonomy it is more advisable to indicate the wider relationships between populations, accepting the fact that each population may be somewhat different, without trying to impose a rather arbitrary nomenclatural system that cannot satisfactorily cope with situations of this complexity.

Order:	Salmoniformes
Family:	Salmonidae
Genus and species:	Coregonus oxyrinchus

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

Houting

Coregonus oxyrinchus (Linnaeus, 1758)

NAMES Fr. Outil, Corégone; Du. Houting; Ge Elbschnepel; Da. Snaebel.

IDENTIFICATION The houting, in common with other members of the salmon family, possesses a dorsal adipose fin. Its deep, rather flattened body, small head, and feeble, practically toothless jaws set it apart from its other relatives which are likely to be found in the sea or in estuarine conditions. It can be distinguished from the smelt, with which it shares this habitat, by its having no large teeth in the jaw, and jaws which do not reach to the eye, by having a scaly pointed flap of skin at the base of each pelvic fin, and above all by the long, fleshy snout.
Its coloration is greeny-grey on the back, with silvery sides and belly. The tip of the snout and of the dorsal fins is blackish, the fins are otherwise clear. It grows to 20 in (50 cm).
D. 12-15; A. 12-15; lateral line 80-90; vertebrae 53-60.

BIOLOGY This is the sole marine and estuarine whitefish in the North Sea basin. In the Baltic basin several forms of this species living in rivers and lakes are named; their precise identification is a matter of difficulty, and their inclusion here is not practical.
The houting in the North Sea is typically estuarine, only rarely moving into fully marine conditions as a stray. Its food consists of small planktonic animals, chiefly crustaceans. It migrates upriver in the autumn, and it is an autumn-winter spawner.
Extremely little has been recorded of the biology of the North Sea population, probably because over the years it has declined greatly in numbers. There is every reason to suspect that in the southern North Sea this fish is now extinct.
The pollan, the skellies and the gwyniad are all thought to be forms surviving from a common oxyrinchus-type ancestor.

DISTRIBUTION

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

Houting (Freshwater)

Coregonus lavaretus (Linnaeus, 1758)

Powan -- Loch Lomond, L. Eck [C. clupeoides clupeoides Lacépède, 1803]; Skelly -- Haweswater, Ullswater, Red Tarn [C. clupeoides stigmaticus Regan, 1908]; Gwyniad -- Llyn Tegid (Lake Bala) [C. clupeoides pennantii Valenciennes, 1848].

IDENTIFICATION Thirty-five to thirty-nine fairly long and well-developed gill rakers. The head is conical, the snout bluntly rounded with the lower jaw included within the upper, i.e. the mouth is ventral (Figs. 64, 65). The maxillary bone reaches to the front of the eye or only just past it.The dorsal, pectoral and pelvic fins are large and conspicuous when compared with other British species.

The back is bluish or dark green, often very dark. The dorsal, anal and tail fins are dark; the tips (sometimes to half their lengths) of the pectoral and pelvic fins are dusky.
It grows to 18 in (46 cm) and a weight of 2 lb (907 gm).

BIOLOGY As this whitefish is the most tolerant to warm water conditions, it is accordingly very widely spread in western Europe, and is the only whitefish to be found in shallow lakes. Breeding takes place from October to January, and it spawns on the outer edge of the shallows around the shore. In deeper, colder (European) lakes spawning may not take place until the summer months, but in these cases it occurs in deep water.
In Loch Lomond the powan range over the whole lake. They spawn in early January, although some may spawn in December and the season may extend to March. Spawning takes place on certain gravelly shallows, usually those off headlands and on offshore banks and reefs. The water temperature at the time of spawning is close to 6 °C (43 °F). Hatching takes place in sixty to seventy days, the fry being about 12 mm in length at hatching. Little is known of their early life, but at two years old they are more than 6 in (15 cm) long; fish between three and four years old vary in length from 10 to 13½ in (26-34 cm). They may live up to ten years.
In Ullswater the growth rate is similar but in their first year they attain 2½ in (6 cm); in their second year 8 in (20 cm). Members of this population grow to 16 in (41 cm) and a weight of 1½ lb (670 gm).
The food of this whitefish consists of a mixture of planktonic and bottom-living forms. There is a suggestion that the smaller specimens feed exclusively on bottom fauna and the largest take planktonic crustaceans. The bottom fauna eaten consists mostly of insect larvae, and crustaceans such as Gammarus and Asellus.
The skellies feed mainly on the plankton, particularly during the summer months, when they are found round the edges of the weed beds. Their diet is mostly composed of crustaceans, chiefly Cladocera (Daphnia and Bosmina) and copepods (Cyclops). Insects, particularly midge larvae, are also eaten. Some bottom-dwelling animals are eaten, especially molluscs (Lymnaea), insects and the isopod crustacean Asellus. From November to May bottom-dwelling organisms are of the greater importance.
This whitefish appears to live more continuously near the bottom than others, and shoals of the larger fish approach the surface whilst feeding on the plankton which also rises towards the surface at night-time.

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

THE GWYNIAD.

SCHELLY. Cumberland. - POWAN. Perthshire.

Coregonus	fera ?	Cuvier, Règne An. t. ii. p. 307.
"	" ?	Nilsson, Prod. p. 16, sp. 4.
"	" ?	Jurine, pl. 7.
Salmo	lavaretus,	Gwyniad,	Penn. Brit. Zool. vol. iii. p. 419, pl. 73.
Coregonus	"	"	Flem. Brit. An. p. 182, sp. 50.

Generic Characters -- Body in appearance herring-like ; with two dorsal fins, the first higher than long, the second adipose ; the scales large ; the mouth small, sometimes with minute teeth on the jaws or tongue, or both.

THE species of the genus Coregonus are numerous in Europe, and several of them are so similar to each other, that, without the power of comparing those of this country with foreign specimens, an appropriation of synonymes is at least doubtful. Some authors have even considered the Vendisse of Lochmaben as the same with the Powan of Perthshire, the Schelly of Cumberland, the Gwyniad of Wales, and the Pollan of Ireland : but it will be found that this is not the case ; and, from recent observation, there is now reason to believe that the Pollan of Ireland is distinct from the two species of Coregonus found in Great Britain.
The Gwyniad of Wales was formerly very numerous in Llyn Tegid, (Fair Lake,) at Bala, until the year 1803, when Pike were put into the lake, which have very rnuch reduced their numbers. Pennant considered the Gwyniad as the same with the C. fera of the Lake of Geneva, following in this the opinion of Willughby ; and in the manuscript notes of a fishing tour in Wales, by two excellent fishermen, who had also pursued their amusement abroad, an opinion is given to the same effect. Our Gwyniad bears a close resemblance to the figure of C. fera in the illustrations to M. Jurine's Memoir on the Fishes of Lake Leman : his description I have not seen. The British fish accords also with the short description of the C. fera in Professor Nilsson's Prodromus of the Fishes of Scandinavia. It also resembles the S. Wartmanni of Bloch, pt. iii. pl. 105 ; but is decidedly distinct from his S. lavaretus, pt. i. pl. 25, which is the C. oxyrhinchus of Cuvier and NiIsson.
The Gwyniad is very numerous in Ulswater and other large lakes of Cumberland, where, on account of its large scales, it is called the Schelly. Dr. Heysham, the natural historian of Cumberland, and Pennant also, in his British Zoology, have recorded that many hundreds are sometimes taken at a single draught of the net. They are gregarious, and approach the shore in vast shoals in spring and summer. Pennant says, they die very soon after they are taken out of the water, are insipid in taste, and must be eaten soon, for they will not keep long. The poorer classes, who consider, and even call them the Fresh-water Herring, preserve them with salt. The fish is not unlike a Herring in appearance, and the Welsh term Gwyniad has reference to their silvery white colour. They spawn towards the end of the year, and the most usual length of the adult fish is from ten to twelve inches.
The length of the head is about one-fifth of the whole length of the fish ; the depth of the body rather exceeding the length of the head : the dorsal fin commences about halfway between the point of the nose and the end of the fleshy portion of the tail ; its longest ray one-third longer than the base of the fin, and equal to three-fourths of the depth of the body : the adipose fin rather nearer the end of the tail than the posterior edge of the dorsal fin ; the pectoral fins narrow, pointed, and a little shorter than the head, inserted low down on the body: the ventral fins arising in a line under the middle of the dorsal fin ; the ventral axillary scale one-third the length of the fin : the anal fin commences half-way between the origin of the ventral fin and the end of the short middle rays of the tail, and ends of the same plane with the adipose fin; the longest anterior ray about equal to the length of the base of the fin ; the other rays diminishing gradually: the tail forked. The fin-rays in number are --

D. 13 : P. 17 : V. 11 : A. 16 : C. 19.

The head is triangular ; the snout rather truncated ; the jaws nearly equal, the lower just shutting within the upper; a very few minute teeth on the tongue only ; the eyes large, the breadth more than one-fourth of the length of the head ; the form of the body very like that of a Herring ; the dorsal and abdominal lines but moderately convex ; the scales large ; the lateral line very near the middle of the side. The irides silvery, the pupils dark blue ; the upper part of the head and back dusky blue, becoming lighter down the sides, with a tinge of yellow ; cheeks, gill-covers, lower part of the sides and belly silvery white ; all the fins more or less tinged with dusky blue, particularly, towards the edges.
According to Mr. Thompson of Belfast,* the Pollan, or Lough Neagh Coregonus, differs from the Gwyniad of Bala in the following particulars : in the snout not being produced ; in the dorsal fin being, nearer the head ; in having fewer rays in the anal fin, and in its position being rather more distant from the tail ; in the dorsal, anal, and caudal fins being of less dimensions ; in the third ray of the pectoral fin being the longest, the first being of the greatest length in the Gwyniad; and in the ventral axillary scale being longer. The numbers of the fin-rays in the Pollan are --

D. 14 : P. 16 : V. 12 : A. 13 : C. 19. Vertebræ 59.

In the stomach of a Pollan I found one example of a species of Gammarus..
The vignette is a view of Whitewell, in the Forest of Bowland, Yorkshire.

* Reports of Proceedings of the Zoological Society of London for 1835, p. 77.

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

Coregonus albula (Linnaeus, 1758)

IDENTIFICATION Thirty-four to fifty-two long gill rakers. The head is pointed, with a conical, rather sharp snout and a mouth which opens on the upper side of the head (Fig. 66). The lower jaw fits into a shallow groove in the upper. The back is a dark greeny-blue, the sides and belly whitish. The pectoral, dorsal and tail fins are dusky, but not conspicuously so, at their tips. Grows to about 14 in (35 cm).

BIOLOGY Little is known about the biology of this whitefish in British waters. It appears to remain in deep water most of the time, only entering shallow water when spawning in winter (November to January). Spawning usually takes place close inshore on hard or rocky bottoms in water of 2½-5 fathoms (4.5-9 m). It is a relatively small species, reaching about 12 in (30 cm) in four or five years, but some European populations are stunted and are mature at a length of 4 in (10 cm) and an age of three years.
Its food is dominantly planktonic, but in winter a substantial part of its diet is formed by bottom-living organisms such as insect larvae, molluscs and fish eggs.
In Lough Neagh, the pollan is said to prey extensively on the planktonic crustacean Mysis relicta, but Regan reports that they also feed on unspecified insect larvae, shrimps, bivalve molluscs and the young of other fishes. This population is also said to come inshore during the warmer months of the year. This is the one whitefish which is commercially exploited and has been for many years; during the summer months it is caught and marketed in Belfast and elsewhere in Ulster. Some used to be sent to northern England for sale, but this market seems to exist no longer.

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

THE VENDACE, OR VENDIS.

Coregonus	WilIughbii,	Vendace, Jardine.
		Vangis and Juvangis, Penn. Brit. Zool. vol. iii. p. 420.
		Vendace, Knox, Trans. R. S. E. vol. xii. p. 503.

BUT little is known of this delicate fish beyond what has been published by Sir William Jardine, Bart. in the third volume of the Edinburgh Journal of Natural and Geographical Science, and by Dr. Knox, in the Transactions of the Royal Society of Edinburgh. Sir William Jardine, in his original communication, considered this species very closely allied to the Salmo albula of Linnæus ; but the difficulty of fixing synonymes satisfactorily from the short descriptions of the older authors has since led to a request from him that the name of our distinguished British naturalist should be attached to it, and I with pleasure adopt the suggestion.
The localities inhabited by this species of Coregonus are as limited as the range of the species last described was shown to be extensive. The Vendace is only known in the lochs in the neighbourhood of Lochmaben, in Dumfries-shire; and in this district some traditions and curious opinions exist regarding it.
"The Vendace is well known," says Sir William Jardine, "to almost every person in the neighbourhood ; and if, among the lower classes, fish should at any time form the subject of conversation, the Vendace is immediately mentioned, and the loch regarded with pride as possessing something of great curiosity to visiters, and which is thought not elsewhere to exist. The story that it was introduced into these lochs by the unfortunate Mary Queen of Scots, as mentioned in Pennant in his description of the Gwyniad, -- and it is likely that his information was derived from this vicinity, -- is still in circulation. That the fish was introduced from some Continental lake, I have little doubt ; but would rather attribute the circumstance to some of the religious establishments which at one time prevailed in the neighbourhood, and which were well known to pay considerable attention both to the table and the cellar. Mary would scarcely prefer a lake so far from even her temporary residence for the preservation of a luxury of troublesome introduction, and leave her other fish-ponds destitute of such a delicacy."
"An idea prevails that this fish, if once taken from the water, will die, and that an immediate return will be of no avail; and it is also believed that it will not exist in any other water except that of the castle loch. These are of course opinions which have gradually, from different circumstances, gained weight, and have at last been received as facts. The fish is of extreme delicacy ; a circumstance which may have given rise to the first notion ; and the introduction of it must have taken place by means of the spawn: the fish themselves, I am confident, could not be transported alive even a few miles. As to the second opinion, they are not confined to the castle loch, but are found in several others, some of which have no communication with that where they are thought to be peculiar."
"In general habits the Vendace nearly resemble the Gwyniad, and indeed most of the allied species of the genus. They swim in large shoals; and during warm and clear weather retire to the depth of the lakes, apparently sensible of the increased temperature. They are only taken with nets, a proper bait not being yet discovered ; and the fact that little excrement is found in their intestines has given rise to another tradition, that they are able to subsist without food. They are most successfully taken during a dull day and sharp breeze, approaching near to the edges of the loch, and swimming in a direction contrary to the wind. They spawn about the commencement of November, and at this time congregate in large shoals, frequently rising to the surface of the water, in the manner of the common Herring, and making a similar noise by their rise and fall to and from the surface. The sound may be distinctly heard, and the direction of the shoal perceived, during a calm and clear evening. They are very productive. The lochs abound with Pike, of which they are a favourite food ; but their quantity seems in no degree to be diminished, notwithstanding that immense numbers must be destroyed. They are considered a great delicacy, resembling the Smelt a good deal in flavour; and though certainly very palatable, the relish may be somewhat heightened by the difficulty of always procuring a supply. During the summer, fishing-parties are frequent, introducing some stranger friend to this Lochmaben whitebait ; and a club, consisting of between twenty and thirty of the neigbouring gentry, possessing a private net, &c. meet annually in July, to enjoy the sport of fishing, and feasting upon this luxury."
The circumstance that this fish is never caught by anglers made a knowledge of its food a matter of interest in several points of view. Dr. Knox ascertained that this consists principally of very minute entomostracous animals, not exceeding seven-twelfths of a line in size. I have been favoured with specimens of the Vendace by Sir William. Jardine and T. S. Bushnan, Esq. which have afforded me several opportunities of examining the contents of the stomach and intestines. The contained mass, which is frequently in considerable quantity, has a brownish yellow colour, appearing slightly granulated to the unassisted eye. A very small portion being placed on a slip of glass, and agitated gently in conjunction with a drop of water, which separates the particles, on placing the slip of glass under a good microscope, two species in various states of perfection are almost constantly found. The vignette at the end of the description of this fish represents these two forms. The first and second figure on the left hand are a back and side view of a species of the genus Lynceus of Muller and others; the third and fourth figures are a back and side view of a species of Cyclops of Muller. On one occasion, I found a very small coleopterous insect, the tough skin of a red worm not much thicker than fine thread, and what appeared to be a portion of the wing of a dipterous insect.
Dr. Knox found that the females of the Vendace were more numerous as well as larger than the males, frequently exceeding eight inches in length ; the males not measuring more than seven inches, which was the length of the specimen here described.
The length of the head compared to that of the body only was as two to seven ; the depth of the body at the commencement of the dorsal fin not quite equal to one-fourth of the length of the body without the caudal rays : the body elegantly shaped ; the convexity of the dorsal and abdominal lines about equal ; the lateral line passes straight along the middle of the side, with six rows of scales in an oblique line between the dorsal fin and the lateral line, and the same number between the line and the ventral axillary scale : the dorsal fin commences half-way between the nose and the origin of the upper caudal rays ; the longest ray double the length of the base of the fin : the adipose fin very near the tail ; pectoral fin not quite equal to the length of the head ; the ventral fin commences in a line under the first ray of the dorsal fin the ventral axillary scale one-third the length of the fin the anal fin commences half-way between the origin of the ventral fin and the end of the fleshy portion of the tail ; the longest ray about equal to the base of the fin : the tail deeply forked ; all the fins large. The fin-rays in number are --

D. 11 : P. 16 : V. 11 : A. 15 : C. 19. Vertebræ 52.

In form the under jaw is the longest ; the mouth small, the opening square ; a few very minute teeth on the tongue only : the breadth of the eye one-third of the whole head, the posterior part of the iris the broadest ; the colour silvery tinged with yellow, the pupil blue : the upper parts of the body of a delicate greenish brown, shading gradually towards the belly into a clear silver ; the dorsal fin greenish brown; the lower fins are all bluish white.