The New International Encyclopædia/Salmon
SALMON (OF., Fr. saumon, from Lat. salmo, salmon, leaper, from salire, Gk. ἅλλεςθαι, hallesthai, to leap). A large fish (Salmo salar) of the northern oceans, ascending rivers annually to spawn. The name ‘salmon’ is also used for other more or less closely related species, and it gives the name to a family, the Salmonidæ, to which salmon, trout, whitefish, and various related forms of fishes belong. Although a small family, comprising less than 100 species, this group stands first in popular interest from almost every point of view. The following are the chief external characters of the salmon family: Body oblong or moderately elongate, covered with cycloid scales of varying size. Head naked. Mouth terminal or somewhat inferior, varying considerably among the different species, those having the mouth largest usually having also the strongest teeth. (See illustration under Fish.) Maxillary provided with a supplemental bone, and forming the lateral margin of the upper jaw. Pseudobranchiæ present. Gillrakers varying with the species. Opercula complete. No barbels. Dorsal fin of moderate length, placed near the middle of the length of the body. Adipose fin well developed. Caudal fin forked. Anal fin moderate or rather long. Ventral fins nearly median in position. Pectoral fins inserted low. Lateral line present. Outline of belly rounded. Vertebræ in large number, usually about 60. Skeleton not strongly ossified. The stomach in all the Salmonidæ is siphonal, and at the pylorus are many (15 to 200) comparatively large pyloric cæca. The air-bladder is large. The eggs are usually much larger than in fishes generally, and the ovaries are without special duct, the ova falling into the cavity of the abdomen before exclusion. The large size of the eggs, their lack of adhesiveness, and the readiness with which they may be impregnated, render the Salmonidæ peculiarly adapted for artificial culture.
The Salmonidæ belong to the order of Isospondyli, the most primitive and least specialized of the orders of Teleostei or bony fishes. In their group, these fishes represent a high degree of development, adaptation to swift rivers and the need of complex instincts. The Salmonidæ are peculiar to the North Temperate and Arctic regions, and within this range they are almost equally abundant wherever suitable waters occur. Some of the species, especially the larger ones, are marine and anadromous, living and growing in the sea, and ascending fresh waters to spawn. Still others live in running brooks, entering lakes or the sea when occasion serves, but not habitually doing so. Still others are lake fishes, approaching the shore or entering brooks in the spawning season, at other times retiring to waters of considerable depth. Some of them are active, voracious, and gamy; while others are comparatively defenseless, and will not take the hook. They are divisible into 10 easily recognized genera—Coregonus, Argyrosomus, Plecoglossus, Brachymystax, Stenodus, Hucho, Oncorhynchus, Salmo, Cristivomer, and Salvelinus.
The Atlantic salmon (Salmo salar) is the most familiar, although commercially not the most important of the various species properly called salmon. It is the only black-spotted salmonoid found on the Atlantic seaboard of America. (For illustration, see Colored Plate of American Food Fishes, accompanying article Fish as Food.) In Europe, where black-spotted trout (Salmo fario) and salmon trout (Salmo trutta) also occur, the true salmon may be distinguished by the fact that the teeth on the shaft of the vomer mostly disappear with age. From the only other species (Salmo trutta) positively known which shares this character, the salmon may be known by the presence of but 11 scales between the adipose fin and the lateral line.
The salmon of the Atlantic is, as already stated, an anadromous fish, spending most of its life in the sea, and entering the streams in the fall for the purpose of reproduction. The time of running varies much in different streams and also in different countries. As with the Pacific species, these salmon are not easily discouraged in their progress, leaping cascades 10 or 12 feet in height, and other obstructions; or, if these prove impassable, dying after repeated fruitless attempts. The young salmon, or ‘parr,’ is hatched in the spring. It usually remains about two years in the rivers, descending at about the third spring to the sea, when it is known as ‘smolt.’ The dusky cross-shades found in the young salmon or parr are characteristic of the young of nearly all the Salmonidæ. In the sea it grows much more rapidly, and becomes more silvery in color, and is known as ‘grilse.’ The grilse rapidly develop into the adult salmon; and some of them, as is the case with the grilse of the Pacific salmon, are capable of reproduction. After spawning, the salmon are very lean and unwholesome, in appearance, as in fact, and are then known as ‘kelts.’ The Atlantic salmon does not ascend rivers to any such distances as those traversed by the quinnat and the blue-back; its kelts for the most part survive the act of spawning. As a food-fish, the Atlantic salmon is similar to the quinnat salmon, although rather less oily. The average weight of the adult is probably less than 15 pounds. The largest one recorded was taken on the coast of Ireland in 1881, and weighed 84¾ pounds.
The salmon is found in Europe between the latitudes of 45° and 75°. In the United States it is now rarely seen south of Cape Cod, although formerly the Hudson and numerous other rivers were salmon streams. The land-locked forms of salmon, abundant in Norway, Sweden, Maine, and Quebec, which cannot, or at least do not, descend to the sea, should probably not be considered as distinct species. Comparison has been made of numerous specimens of the common land-locked salmon (Salmo salar, var. sebago) from the lakes of Maine and New Brunswick with land-locked salmon (Salmo salar, var. hardini) from the lakes of Sweden, and with numerous migratory salmon, both from America and Europe. While showing minor distinctions, especially in size and habit, they are structurally identical. The differences are not greater than would be expected on the hypothesis of recent adaptation of the salmon to lake life. We have, therefore, on our Atlantic coast but one species of salmon (Salmo salar).
The numerous other species of the genus Salmo are usually known as ‘trout,’ although, except for the better development of the vomer and greater backward extension of the series of teeth upon it, there is no technical character of any importance to distinguish the Atlantic salmon from the true, or black-spotted trout. But the salmon reaches a larger size than any of these, and it is regularly anadromous. On the other hand, the running of trout up the rivers to spawn is irregular, and most individuals are land-locked, as are also certain dwarf varieties of the salmon (as the Sebago salmon and the ouananiche of Saint John's River, Quebec).
Most trout, however, enter the sea when they can. These sea-run individuals often grow large and look like salmon, and, like the salmon, they enter the rivers to spawn. They do not, however, ascend the streams with as much energy, nor do they go as far, the instinct in these respects being much less perfect. To the large species entering the sea, intermediate in structure between trout and salmon, the name ‘salmon-trout’ is applied in England. The species so named (Salmo trutta) is considered by some as doubtfully distinct from the ordinary brown trout of Europe (Salmo fario). Other species which may be properly called salmon-trout, having the size, appearance, and habits of Salmo trutta, are the steelhead of California and Oregon (Salmo Guirdneri), the kawamasu of Japan (Salmo Perryi), and the mykiss of Kamchatka (Salmo mykiss). These differ in no important respect from ordinary black-spotted trout, and the young in the rivers are known as ‘trout.’ Indeed, it is not certain that the various species of trout are not originally land locked salmon-trout, and it is probable that a change of environment of relatively few years might transform the one into the other. This remark does not apply to the red-spotted forms known as ‘charr’ in England and as ‘brook trout’ or ‘speckled trout’ in America. These belong to a distinct genus, Salvelinus. See Trout.
The salmon of the Pacific diverge considerably from the Atlantic salmon, and still more from the forms called ‘trout.’ The six known species of these fishes are placed in a distinct genus, Oncorhynchus, which agrees with Salmo in general characters, and in the structure of its vomer, but differs anatomically in the increased number of anal rays, branchiostegals, pyloric cæca, and gill-rakers. The species of Oncorhynchus differ, further, in their highly specialized reproductive instincts, all individuals, male and female, dying after spawning. The character most convenient for distinguishing Oncorhynchus, young or old, from all the species of Salmo is the number of developed rays in the anal fin. These in Oncorhynchus are 13 to 20, in Salmo 9 to 12.
The species of Oncorhynchus, anadromous salmon confined to the North Pacific, was first made known in 1768 by that most exact of early observers, Steller, who described and distinguished them with perfect accuracy, under their Russian vernacular names. These Russian names were in 1792 adopted by Walbaum as specific names in a scientific nomenclature; and the six species of Pacific salmon may be called: (1) Quinnat, Chinook, or king salmon (Oncorhynchus tschawytscha); (2) red salmon, blueback, or sukkegh (Oncorhynchus nerka); (3) silver salmon or coho (Oncorhynchus kisutch); (4) dog salmon, calico salmon, or haiko, the saké of Japan (Oncorhynchus keta); (5) humpback or pink salmon (Oncorhynchus gorbuscha); (6) masu (Oncorhynchus masou) of Japan. These species, in all their varied conditions, may usually be distinguished by the characters given below.
The quinnat salmon (Oncorhynchus tschawytscha) has an average weight of 22 pounds, but individuals weighing 70 to 100 pounds are occasionally taken. It has about 16 anal rays, 15 to 19 branchiostegals, 23 (9+14) gill-rakers on the anterior gill arch, and 140 to 185 pyloric cæca. The scales are comparatively large, there being from 130 to 155 in a longitudinal series. In the spring the body is silvery, the back, dorsal fin, and caudal fin having more or less of round black spots, and the sides of the head having a peculiar tin-colored metallic lustre. In the fall the color is often black or dirty-red. and the species can then only be distinguished from the dog salmon by its technical characters.
The blue-back salmon (Oncorhynchus nerka) usually weighs from five to eight pounds. It has about 14 developed anal rays, 14 branchiostegals, and 75 to 95 pyloric cæca. The gill-rakers are more numerous than in any other salmon, usually about 39 (16 + 23). The scales are larger, there being 130 to 140 in the lateral line. In the spring the form is plumply rounded, and the color is a clear bright blue above, silvery below, and everywhere immaculate. Young fishes often show a few round black spots, which disappear when they enter the sea. Fall specimens in the lakes are bright red in color, hook-nosed and slab-sided, and bear little resemblance to the spring run. Young spawning male grilse are also peculiar in appearance, and were for a time considered as forming a distinct genus. This species appears to be sometimes land-locked in mountain lakes, in which case it reaches but a small size, and is called ‘koko’ by the Indians.
The silver salmon (Oncorhynchus kisutch) reaches a weight of three to eight pounds. It is silvery in spring, greenish above, and with a few faint black spots on the upper parts only. In the fall the males are mostly of a dirty red. The dog salmon (Oncorhynchus keta) reaches an average weight of about nine pounds. In spring it is dirty silvery, immaculate, or sprinkled with small black specks, the fins dusky. In the fall the male is brick-red or blackish, and its jaws are greatly distorted. The humpback salmon (Oncorhynchus gorbuscha) is the smallest of the species, weighing from three to six pounds. Its scales are much smaller than in any other salmon. In color it is bluish above, the posterior and upper parts with many round black spots. The masu (Oncorhynchus masou) is thus far known only from the rivers of Northern Japan. It is very much like the humpback salmon, but may be known at sight by the absence of black spots on its tail.
The blueback abounds in Fraser River and in all the streams of Alaska; the silver salmon in Puget Sound; the quinnat in the Columbia and the Sacramento; and the dog salmon in some of the streams to the northward and especially in Japan. All of the five American species have been seen in the Columbia and Fraser rivers; all but the blueback in the Sacramento, and all in waters tributary to Puget Sound. Only the quinnat has been noticed south of San Francisco, as far as Carmelo River. The king salmon and blueback habitually ‘run’ in the spring, the others in the fall. The usual order of running in the rivers is as follows: tschowytscha, nerka, kisutch, gorbuscha, keta. The economic value of the spring-running salmon is far greater than that of the other species, because they can be captured in numbers when at their best, while the others are usually taken only after deteroration. To this fact the worthlessness of Oncorhynchus keta, as compared with the other species, is partly due. Its flesh at the best, however, is soft and mushy.
The habits of the salmon in the ocean are not easily studied. King salmon and silver salmon of all sizes are taken with the seine at almost any season in Puget Sound; this would indicate that these species do not go far from the shore. The king salmon takes the hook freely in Monterey Bay, both near the shore and at a distance of six to eight miles out. We have reason to believe that these two species do not necessarily seek great depths, but probably remain not very far from the mouth of the rivers in which they were spawned. The blueback and the dog salmon probably seek deeper water, as the former is seldom taken with the seine in the ocean, and the latter is known to enter the Straits of Fuca at the spawning season, therefore coming in from the open sea. The run of the king salmon begins generally at the last of March; it lasts, with various modifications and interruptions, until the actual spawning season, August to November, the time of running and the proportionate amount in each of the subordinate runs varying with each different river. In the Sacramento the run is greatest in the fall, and greater in the summer than in spring. The spring salmon ascend only those rivers which are fed by the melting snows from the mountains, and which have sufficient volume to send their waters well out to sea. Those salmon which run in the spring are chiefly adults (supposed to be mostly four years old). It would appear that the contact with cold fresh water, when in the ocean, in some way causes them to run toward it, and to run before there is any special influence to that end exerted by the development of the organs of generation. High water on any of these rivers in the spring is always followed by an increased run of salmon. The manner of spawning is probably similar for all the species. Usually the fishes pair off; the male, with tail and snout, excavates a broad, shallow ‘nest’ in the gravelly bed of the stream, in rapid water, at a depth of one to four feet; the female deposits her eggs in it, and after the exclusion of the milt the pair cover them with stones and gravel. They then float down the stream tail foremost, never swimming down stream or making any effort to reach the sea. In the course of from a day to a week or two all of them, both males and females, die, regardless of the distance of their spawning beds from the sea. The young hatch in from 120 to 180 days.
The salmon of all kinds in the spring are silvery, and the mouth is about equally symmetrical in both sexes. As the spawning season approaches the female loses her silvery color, becomes more slimy, the scales on the back partly sink into the skin, and the flesh changes from salmon-red, and becomes variously paler from the loss of oil, the degree of paleness varying much with individuals and with inhabitants of different rivers. In the Sacramento the flesh of the quinnat, in either spring or fall, is rarely pale. In the Columbia a few with pale flesh are sometimes taken in spring, and a good many in the fall. In Fraser River the fall run of the quinnat is nearly worthless for canning purposes, because so many are ‘white-meated.’ In the spring very few are ‘white-meated,’ but the number increases toward fall, when there is every variation, some having red streaks running through them, others being red toward the head and pale toward the tail. The red and pale ones cannot be distinguished externally, and the color is dependent upon neither age nor sex. There is not much difference in the taste, but there is no market for pale-fleshed salmon.
As the season advances, the difference between the males and females becomes more and more marked, and keeps pace with the development of the milt, as is shown by dissection. The males have (1) the premaxillaries and the tip of the lower jaw more and more prolonged, both of the jaws becoming finally strongly and often extravagantly hooked, so that either they shut by the side of each other like shears, or else the mouth cannot be closed. (2) The front teeth become very long and canine-like, their growth proceeding very rapidly, until they are often one-half inch long. (3) The teeth on the vomer and tongue often disappear. (4) The body grows more compressed and deeper at the shoulders, so that a very distinct hump is formed; this is more developed in the humpback and dog salmon, but is found in all. (5) The scales disappear, especially on the back, by the growth of spongy skin. (6) The color changes from silvery to various shades of black and red, or blotchy, according to the species. The distorted males are commonly considered worthless, rejected by the canners and salters, but are preserved by the Indians. These changes are due solely to influences connected with the growth of the reproductive organs. They are not in any way due to the action of fresh water. They take place at about the same time in the adult males of all species, whether in the ocean or in the rivers. At the time of the spring runs all are symmetrical. In the fall all males, of whatever species, are more or less distorted.
As already stated, the economic value of any species depends in great part on its being a ‘spring salmon.’ It is not generally possible to capture salmon of any species in large numbers until they approach the rivers, and the spring salmon enter the rivers long before the growth of the organs of reproduction has reduced the richness of the flesh. The fall salmon cannot be taken in quantity until their flesh has deteriorated; hence, the dog salmon is practically almost worthless, except to the Indians, and the humpback is little better. The silver salmon, with the same breeding habits as the dog salmon, is more valuable, as it is found in the inland waters of Puget Sound for a considerable time before the fall rains cause the fall runs, and it may be taken in large numbers with seines before the season for entering the rivers. The quinnat or Chinook salmon, from its great size and abundance, is more valuable than all the other fishes on our Pacific coast outside of Alaska taken together. The blueback, a little inferior in flesh, much smaller and far more abundant when Alaska is considered, is worth more than the combined value of the three remaining species of salmon. The pack of blueback salmon for 1903 is valued at $8,000,000, the catch of the quinnat at nearly $4,000,000.
The fall salmon of all species, but especially of the dog, ascend streams but a short distance before spawning. They seem to be in great anxiety to find fresh water, and many of them work their way up little brooks only a few inches deep, where they perish miserably, floundering about on the stones. It is the prevailing impression that the salmon have some special instinct which leads them to return to spawn on the grounds where they were originally hatched, but there is no evidence of this. It seems more probable that the young salmon hatched in any river mostly remain in the ocean within a radius of 20 to 100 miles of its mouth. These, in their movements about in the ocean, may come into contact with the cold waters of their parent river, or perhaps of any other river, at a considerable distance from the shore. In the case of the quinnat and the blueback, their ‘instinct’ seems to lead them to ascend these fresh waters, and in a majority of cases these waters will be those in which the fishes in question were originally spawned. Later in the season the growth of the reproductive organs leads them to approach the shore and search for fresh waters, and still the chances are that they may find the original stream. But undoubtedly many fall salmon ascend, or try to ascend, streams in which no salmon were ever hatched.
Commercially speaking, the two principal species of Pacific salmon are unquestionably the most valuable fishes in the world. The market value of the entire salmon catch on the West coast of the United States, including Alaska, has reached nearly $20,000,000 annually, and this vast amount is represented chiefly by the two species, the Chinook and blueback, the catch of the four other species being in comparison insignificant. The annual catch of salmon in Puget Sound has reached to more than $4,000,000, and consists chiefly, as in Alaska, of bluebacks. The run of quinnats begins in the Columbia River as early as February or March. At first the fishes travel leisurely, moving up only a few miles each day. As they go farther and farther up-stream they swim rather more rapidly. Those that enter the river first are the ones which will go farthest toward the headwaters, many of them going to spawning beds in the Salmon River in the Sawtooth Mountains of Idaho, more than 1000 miles from the sea. In the Yukon the quinnat ascends to Caribou Crossing, 2250 miles from the sea. Those which go to the headwaters of the Snake River in the Sawtooth Mountains spawn in August and early September; those going to the Big Sandy in Oregon, in July and early August; those going up the Snake River to Upper Salmon Falls, in October; while those entering the small lower tributaries of the Columbia or the small coastal streams spawn even as late as December. Observations made at various places indicate that whatever the spawning beds may be, spawning will not begin until the temperature of the water has fallen to 54° F. If the fish reach the spawning grounds when the temperature is above 54°, they wait until the water cools down to the required degree. The spawning act extends over several days.
It has been often stated and generally believed that the salmon receive many injuries by striking against rocks and in other ways while en route to their spawning grounds, and as a result from these injuries, those which go long distances from the sea die after once spawning. An examination of many salmon at the time of arrival on their spawning beds in central Idaho showed most fishes to be entirely without mutilations of any kind, and apparently in excellent condition. Mutilations, however, soon appeared, resulting from abrasions received on the spawning beds while pushing the gravel about or rubbing against it, and from fighting with each other, which is sometimes quite severe. See illustration under Dog Salmon.
The blueback salmon is found from the coast of southern Oregon northward, especially in the Columbia, Quinialt, and Skagit rivers. It enters the Fraser in enormous numbers, and is by far the most abundant and valuable salmon in Alaska. In the Columbia River it is called ‘blueback;’ in the Fraser it is the ‘sockeye,' ‘sawkeye,’ or ‘sau-qui;’ in Alaska it is the red salmon or ‘redfish;’ while among the Russians it is the ‘krasnaya ryba.’
The death of all the individuals of all the species of the West coast salmon after once spawning is in no manner determined by distance from the sea. The cause is deep-seated in its nature and general in its application, and the same as that which compasses the death of the Ephemera or May-fly after an existence of but a few hours, or of all annual plants at the end of one season.
Bibliography. Consult general authorities mentioned under Fish; especially Günther, Cat-Fishes, British Museum (London, 1866); Day, Fishes of Great Britain, etc. (ib., 1896); Jordan and Evermann, Fishes of North and Middle America, part i. (United States National Museum, Washington, 1896); Jordan and Evermann, Food and Game Fishes of North America (1901); Jordan, Science Sketches (Chicago, 1887); Moser, The Salmon and Salmon Fisheries of Alaska (United States Fish Commission, Washington, 1898).
See Colored Plate of Food-Fishes; Plate of Salmon and Trout.
SALMON AND TROUT (WESTERN)
|1. SALMON-TROUT or STEELHEAD (Salmo Gairdneri).||4. QUINNAT SALMON (Oncorhynchus tschawytscha).|
|2. COLUMBIA RIVER TROUT (Salmo mykiss, var. Clarkii).||5. BLUEBACK SALMON (Oncorhynchus nerka); female.|
|3. HUMPBACK SALMON (Oncorhynchus gorbuscha).||6. BLUEBACK; old male in breeding dress.|