ing 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
