The Salmoniformes

The Fish Shop

The Order of the Salmoniformes consists of three Families that have representatives in the European (including British and Dutch) fresh water, being: the Pike family (Esocidae), the Smelt family (Osmeridae) and the Salmon family (Salmonidae):

Salmonidae Osmeridae Esocidae

The Salmonidae

The Fish Shop Salmoniformes
The Salmon The Sea Trout The Brown Trout The Grayling
The Houting The Powan The Gwyniad The Vendace

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

Salmons, Trouts, Grayling, Charrs and Whitefishes

Salmonidae, Thymallidae and Coregonidae)

A DIVERSE group of mainly freshwater or anadromous fishes. All possess a distinct rayless, fleshy, adipose fin on the back between the dorsal fin and the tail; the pelvic fins are abdominal in position, and the teeth are well developed in the jaws, except in the whitefishes.
Many of the salmon-like fishes are of great economic importance. The salmon is a valued food fish and Atlantic populations are heavily exploited, as are the Pacific saImons, Oncorhynchus elsewhere. Salmon, various trouts and some charrs are highly regarded as anglers' fishes and possess considerable value from this aspect, as well as being good to eat. Local fisheries also exploit populations of whitefish.
Members of the salmon family are widespread and as a result of their migratory habits have penetrated into many waters in which they have become landlocked. Due to the remarkable plasticity of the family, many of its members have diverged considerably from their parent stock and have been recognised as distinct species. The status of some of these forms is still a matter of discussion, and particularly in the case of the whitefishes, Coregonus, and the charrs, Salvelinus, scientific opinion is divided as to whether they should be recognised as distinct species, subspecies or merely races. In addition even the less variable species, like the salmon and trout pass through a number of developmental stages, in which their coloration and in some respects their body proportions change. The trout, in particular, also shows considerable variation in body form and coloration, depending on its migratory (sea trout) or non-migratory (brown trout) habit. For a long time these two forms, along with others, were considered to be distinct species. This variability sometimes leads to confusion between the species. Wheeler presents several keys that have been devised with these problems in mind to help identification of these fish at all stages of their lives. The one presented here distinguishes the Salmonidae, Thymallidae and Coregonidae from their marine relatives the Osmeridae and Argentinidae.

A. Salmon-like fishes with an adipose fin between the dorsal fin and the tail; a fleshy, pointed flap above the pelvic fin base; freshwater and anadromous.
Salmons, Trouts, Charrs and Whitefishes
AA. Fishes with an adipose fin between the dorsal fin and the tail; no fleshy, pointed flap above the pelvic fin base; marine, one species in estuaries, occasionally into freshwater.
Smelts and Argentines
Fig. 55

The following notes are divided under three headings, based firstly on size (juveniles which are often closely similar-Key 2), and secondly on habitat (freshwater-Key 1, marine and estuarine-Key 3).

Key 1. Fishes with adipose fins found in fresh water

A. First dorsal fin base not longer than the head length, the rays not greatly elongate; the last dorsal rays much shorter than the longest ray; sides of body either silvery or dark, usually with spots. B AA. First dorsal fin base longer than the head length, the rays very long; last dorsal rays as long as the longest ray; body silvery with several parallel dark longitudinal lines; dorsal fin with four or five rows of rounded spots between the rays. Grows to 18 in (45 cm). Widespread but local. Grayling (Thymallidae)
B. Teeth in jaws well developed, also on the palate and tongue; scales small to minute, never fewer than nineteen from first dorsal ray base to the lateral line; body rather rounded in cross-section.
Salmons, Trout, etc. (Salmonidae) C
BB. Teeth in jaws minute or absent, none on palate or tongue; mouth rather small; scales large, usually fewer than thirteen between the first dorsal ray base and the lateral line; body rather flattened from side to side. Colour silvery on sides. Alpine and other glacial lakes; in Scandinavian rivers.
Whitefishes (Coregonidae)
C. Scales small, fewer than 150 in a series from head to tail, less than twenty-eight scales from the first dorsal fin to the lateral line; teeth present on or absent from the head of the vomer, in a single, if staggered, row along the shaft of the vomer (Fig. 56). D CC. Scales minute, more than 180 in a series from head to tail; more than thirty scales from the base of the first dorsal fin ray to the lateral line; teeth present on the head of the vomer only, none on the shaft (Fig. 57). F
Fig. 56 Fig. 57
D. The extreme end of the upper jaw reaches well past the level of the bind edge of the eye; caudal peduncle deep; the tail fin only shallowly forked; gill rakers on first gill arch never more than twenty; usually many dark spots on body including the gill covers. E DD. Extreme end of the upper jaw just reaches the level of the rear edge of the eye (Fig. 58); caudal peduncle narrow; tail fin deeply forked (Fig. 59); seventeen to twenty-four gill rakers on first gill arch; scales relatively large, ten to thirteen from the adipose fin to the lateral line (counted in an oblique line). Colour variable, not usually densely spotted; x-shaped black spots on back and sides, not normally below the lateral line, and not more than four or five on the gill cover. Widespread. Grows to 49 in (125 cm) and more.
Salmon Salmo salar
Fig. 58
Fig. 59
E. Scales small, thirteen to sixteen, from the adipose fin to the lateral line in an oblique series; anal fin has seven to eight branched rays; upper jaw reaches well past the hind edge of the eye (Fig. 60). Caudal peduncle deep, tail square cut (Fig. 61). Colour is variable with many rounded dark spots on body including the gill covers; tail fin not heavily spotted to the extreme edge, reddish spots always present on body. Common and widespread; the sea trout may reach 49 in (125 cm), the brown trout usually 14-16 in (35-40 cm).
Trout Salmo trutta
EE. Scales very small, fifteen to sixteen from the adipose fin to the lateral line; anal fin with nine to eleven branched rays; upper jaw reaches to the hind edge of the eye; head small, fitting 4.5 times into the body length, at 10 in (25 cm). Colour very variable, always with dense rounded dark spots on head and body; tail fin densely spotted to the extreme edge, no reddish spots on body; an iridescent band along the sides.
D. 11-12; A. 9-12.
Fig. 60
Fig. 61
Rainbow Trout Salmo gairdneri Richardson, 1836 [= S. irideus]
See Pl. 3 facing p. 126.
U.S.A.: Steelhead or Cut-throat Trout; Fr. Truite-arc-viel; Ge. Regenbogen forelle.
A fish native to north-western America, introduced and artificially stocked throughout Europe, occasionally living wild, but rarely succeeding in establishing itself in numbers. It lives in the same habitats as the brown trout, but can withstand higher temperatures, and is often stocked in lakes and enclosed waters. It grows rapidly by comparison with the native trout, and attains 20 in (50 cm) in its third year. A valuable cultivated food fish which is also appreciated by anglers.
F. Body dark coloured with light spots, pectoral and pelvic fins dark with light edges; head blunt, and body rather thick-set; scales minute, not less than 200 in a series along body, nor fewer than thirty from the dorsal fin origin to the lateral line; teeth on head of vomer (see Fig. 57) separated from rows of palatine teeth by a distinct gap.
Salvelinus spp. G
FF. Body dorsally grey-blue, sides silvery with small black x-shaped spots, pectoral and pelvic fins light; head pointed and laterally compressed; body rather slim; scales small, fewer than 200, usually about 190, in a head to tail series; eighteen to twenty scales between the first dorsal fin and the lateral line; teeth on head of vomer continuous with rows of palatine teeth (Fig. 62).
D. 13-14; A. 12-14; lateral line 180-200.
Fig. 62
Huchen Hucho hucho (Linnaeus, 1758)
A native of the Danube system and its associated lakes, now rather rare. Introduced unsuccessfully to the river Thames in the early twentieth century, to the river Rhine and S.E. France in the 1950s. The adults chiefly eat fishes, but in early life small crustaceans and insects are widely eaten. Spawns from March to May after an upstream migration towards the head waters. A good angling fish, growing to a length of about 49 in (125 cm) and a weight of 40 lb (18 kg) or more.
G. Body colour dark with numerous reddish spots on the back coalescing into light wavy lines; tail and dorsal fins densely marked with small brown spots; fifteen to seventeen gill rakers on the first gill arch; upper jaw reaches well past the hind edges of the eye.
D. 11-13; A. 9-12; lateral line c. 230.

Brook Trout Salvelinus fontinalis (Mitchill, 1815)
A native of eastern North America, introduced in 1884 to Europe, and later to the British Isles. Although it can be cultivated and stocked, it seldom is in Britain and is rather uncommon. It inhabits streams and cold clear running water, and is best suited to the upper reaches of mountain streams. lts food is similar to that of the brown trout; it breeds during winter and spring. It grows to about 18 in (46 cm), but the length varies with the size of the stream. A popular angling fish, which is also well flavoured.
GG. Body colour dark with light spots on sides, but very few on the back; tail and dorsal fins dark and unspotted; eighteen to thirty gill rakers on the first gill arch; upper jaw reaches only just past the hind edge of the eye, not usually so far. These salmonid fishes are found in Alpine and Arctic lakes, and in far northern waters in rivers and the sea. Numerous local races occur in isolated waters. They grow to a maximum of 3o in (76 cm), freshwater populations usually much less. Charrs Salvelinus alpinus complex

Key 2 Juvenile fishes up to 6 in (15 cm), with adipose fins, found in fresh water.

For simplicity the easily identified grayling and whitefish are omitted; the young in each case closely resemble the adults which are described above and on pages 143 and 145-9.

A. Scales small, but visible with a hand lens or to the naked eye; parr marks (Fig. 63) fairly obvious. B AA. Scales minute, not readily distinguished without a lens; upper jaw reaching to the rear edge of the eye; parr marks on sides indistinct, the back and sides usually dark, with rounded pale, sometimes orange, spots. Charrs and Brook Trout (Salvelinus spp.)
Fig. 63
B. Jaw extending to hind edge of eye; parr marks less distinct; tail fin shallowly forked; caudal peduncle broad; often densely spotted on back and sides. C BB. Jaw extending to mid-point of eye; parr marks prominent, usually ten to twelve in number; tail fin deeply forked; caudal peduncle thin; ten to thirteen scales between the adipose fin and lateral line; adipose fin a uniform grey in colour; usually not densely spotted on back and sides. Salmon parr
C. Adipose fin tinged with red; small black spots on back and sides, but very few below the level of the lateral line; tail fin not spotted. Common and widespread. Trout parr CC. Adipose fin not red tinged; back and sides densely spotted with round black marks which extend heavily below the lateral line, on the tail fin and the adipose fin. Introduced, not widespread. Rainbow Trout parr

Key 3 Marine and estuarine salmonid fishes

A. Jaws small, teeth minute or even absent; snout rather pronounced with a fleshy lobe; body flattened from side to side; scales large, not more than thirteen from dorsal origin to lateral line; body silvery in colour, not spotted. Mainly estuarine, in northern waters only. Whitefishes (Coregonus)
(Beware the Argentines, page 157, which have pointed snouts.)
AA. Jaws large, teeth pronounced; snout rounded, no fleshy lobe; body rounded in cross-section; scales small, nineteen or more from dorsal origin to lateral line; colour dark (or spotted) if silvery. B (Beware the Smelt, page 160, which has no pointed scaly flap above the pelvic base.)
B. Anal fin has fewer than thirteen rays, fin base shorter than the longest ray. C BB. Thirteen or more rays in the anal fin, fin base is longer than the length of the longest ray; scales small, 180-240 in the lateral line; twenty-six to thirty-three gill rakers on the first gill arch. Colour in the sea is silvery with black spots confined to the tail fin, in estuaries darker with dark spots on back, sides and head, but not on belly.
D. 14-16; A. 13-17; vertebrae 69-72.
Hump-back or Pink Salmon Oncorhynchus gorbuscha (Walbaum, 1792)
The back is most strikingly humped in males, which also develop enormously hooked jaws with strong teeth; the arching of the back is, however, noticeable in both females and juveniles. Spawns in estuarine to fresh water, never far upstream. Introduced to the Kola Peninsula (Barents Sea) in the late 1950s, subsequently recorded in numbers on the Norwegian and Icelandic coasts, and in 1960 and 1965 on the British coast (three authenticated, a few ‘possible’ records). Also introduced into Newfoundland waters in 1958. Its natural range is the northern Pacific coasts of Asia and North America, where it is a valuable food fish.

NOTE A second Pacific salmon, the chum salmon, Oncorhynchus keta (Walbaum, 1792), is also believed to have been introduced to the White Sea. It can be distinguished by its larger scales (125-50), and by having an average of twenty four gill rakers on the first arch. It does not, so far, seem to have spread into the Norwegian Sea and the Atlantic.
C. Scales small, fewer than eighteen between adipose fin and lateral line; teeth on palate run along the roof of the mouth; body colour silvery with dark spots. All northern European coasts. D CC. Scales minute, nineteen to twenty-two between the adipose fin and the lateral line, and 130-40 in the lateral line; tail fin moderately concave; teeth on the vomer confined to the front end and not running along the mid-line of the palate (Fig. 57). Colour on the back dark, with pale yellow spots above the lateral line, orange spots below on a silvery background. Arctic waters, south to Tromsö (Norway) and Iceland.
Charr Salvelinus alpinus
D. Ten to thirteen scales between the end of the adipose fin and the lateral line; seventeen to twenty-four gill rakers on first gill arch; caudal peduncle narrow (fish can be easily grasped here and does not slip through the hand); tail fin fairly deeply notched. Colour silvery with a few dark x-shaped spots, normally none below the lateral line.
Salmon Salmo salar
DD. Thirteen to sixteen scales from the adipose fin to the lateral line; fourteen to sixteen gill rakers on the first gill arch; caudal peduncle wide (fish tends to slip through the hand when grasped by the tail); tail fin is shallowly notched. Colour silvery, but with many dark, rounded, but sometimes x-shaped, spots above and below the lateral line.
Sea Trout Salmo trutta

The Osmeridae

The Fish Shop Salmoniformes The Smelt

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

Smelts and Argentines

Osmeridae and Argentinidae

A. Dorsal fin well in front of the pelvic fin base; mouth small, teeth minute with large, rough-edged scales, when present giving a box-like appearance in cross-section. B AA. Dorsal fin origin over the base of the pelvic fins, or slightly behind it; mouth large, extending at least to the mid-point of the eye, often further. C
B. Eye large, its diameter longer than the length of the snout; mouth small but extending about two-thirds of the distance to the eye; last ray of dorsal fin in front of pelvic fins; deep water, from 50 to 200 fathoms (91-366 m); north and west coasts only; grows to 18 in (45 cm).
Argentina silus
BB. Eye relatively large, its diameter equals the snout length; mouth small, extends only half-way to eye; last ray of the dorsal fin is directly above the pelvic fin base; 35 fathoms (64 m) downwards; all coasts except southern North Sea and Baltic. Grows to 10 in (25 cm).
Argentine Argentina sphyraena
C. Scales large; mouth large, gape extends to behind the eye; teeth large and prominent, particularly on the lower jaw, the palate and the tongue; when fresh, smells strongly of cucumber; inshore waters and estuaries, on all coasts; grows to 18 in (45 cm).
Smelt Osmerus eperlanus

CC. Scales minute; mouth moderately large, gape extending to mid-eye level, teeth minute, none on tongue; the adipose fin is low and square cut. Males have longer pectoral fins and the base of the anal fin is humped; rows of scales above the lateral line and on the belly are pointed and, at spawning go time, swollen into felt-like bands. Olive or bottle green on the back, sides and belly silvery.
D. 12-15; A. 18-22; lateral line c. 200. Capelin Mallotus villosus (Müller, 1777)

An oceanic fish, living in huge shoals in northern seas, coming inshore to spawn on arctic and subarctic coasts and on offshore banks in summer. Frequently stranded on these shores and preyed on by whales, many species of fish, and sea-birds whilst close inshore. Found commonly north of Trondheim Fjord, Norway, and around Iceland, less often south as far as the Faroes and Denmark. Grows to 9 in (23 cm).

The Esocidae

The Fish Shop Salmoniformes The Pike

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

The Pike and the Mud-minnow

Esocidae and Umbridae

Two vastly dissimilar fishes are included in this section; the familiar pike, one of our largest native freshwater fishes, and the mud-minnow, a small Danubian fish, relatives of which have been introduced to western Europe. Both have a single dorsal fin, placed far back directly above the anal fin, conspicuous pores on the head and prominent scales.
The pike is widely distributed across the northern hemisphere, and is found in America with several related species, although the one only is native to Europe. It belongs to the family Esocidae, which can be characterized by its large mouth, broad and flattened snout and large strong teeth.
Mud-minnows are also found in the United States of America, but unlike the pike their distribution is not continuous. The European species is confined to the Danube basin. Mud-minnows belong to the family Umbridae, members of which can be recognised by their short rounded snout, small jaws and relatively small teeth.