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Ouananiche — Part 3
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Among the various more or less tangible forms that may be recognized, 3 distinct series appear which have been regarded provisionally by us as distinct species. These have been termed the cut-throat trout series, the rainbow trout series, and the steelhead series, each of which has been sufficiently characterized in the key on page 163.
The steelhead, or gairdneri series, is found in the coastwise streams of California and in the streams of Oregon and Washington, below the great Shoshone Falls of Snake River. In the lower course of the Columbia and in neighbouring streams they are entirely distinct from the cut-throat or clarkii series, and no one would question the validity of the 2 species. In the lower Snake River and in other waters east of the Cascade range, the 2 forms or species are indistinguishable, being either undifferentiated or else inextricably mixed.
The rainbow forms are chiefly confined to the streams of California and southern Oregon. The cut-throat forms are found from Humboldt Bay northward in the coastwise streams of northern California, Oregon and Washington, and all the clear streams on both sides of the Rocky Mountains, and in the Great Basin and the headwaters of the Colorado. Along the western slope of the Sierra Nevada there are also forms of trout with the general appearance of steelheads, but with scales intermediate in number (in McCloud River), or with scales as small as in the typical cutthroat (Kern River). In these small-scaled forms more or less red appears the lower jaw, and they are doubtless what they appear to be, really intermediate between clarkii and gairdneri. A similar series of forms occurs in the Columbia basin, the upper Snake being inhabited by clarkii and the lower Snake by clarkii and gairdneri, together with a medley of intermediate forms.
It seems not improbable that the American trout originated in Asia, extended its range southward to the upper Columbia, thence to the Yellowstone and the Missouri via Two-Ocean Pass; from the Missouri southward to the Platte and the Arkansas, thence from the Platte to the Rio Grande and the Colorado, and then from the Colorado across the Sierras to Kern River, thence northward and coastwise, the sea-running forms passing from stream to stream as far north as the Fraser where the Kamloops trout would mark one extreme of the series, and re-entering as a distinct species waters long occupied by typical clarkii.
The various forms of cut-throat trout have usually been regarded merely as subspecies of the species originally described as Salmo clarkii, but as none of them is really known to intergrade with any other we now think it best to consider them all as distinct species. Most of them certainly are good species while a few others may prove wholly undefinable.
a. Black spots almost as numerous on the head as on the posterior part of the body.
b. Scales usually about 160 to 170.
c. Spots rather large, irregular and profusely scattered, usually none on the belly.
d. Red marks under dentary bones always present.
e. Black spots encroaching somewhat on belly; .....Clarkii
ee. Black spots not encroaching on belly; ................lewisi
dd. Red marks under dentary bones obsolete or nearly so; gibbsii
cc. Spots rather large, sparsely scattered, some on belly and lower side of head; ..............henshawi
bb. Scales very small, about 200 transverse series; tahoensis
bbb. Scales large, usually about 145. Body profusely but finely spotted, the spots numerous both anteriorly and posteriorly; virginalis; jordani; bathoecetor
aa. Black spots placed chiefly on posterior half of body.
f. No black spots except on tail; .............declivifrons
ff. Black spots on body.
g. Scales not very small, about 160; spots of moderate size (Rio Grande Basin); ............spilurus
gg. Scales very small, about 180.
h. Spots rather large; lower fins distinctly red, rarely orange.
i. Spots very numerous; a red lateral band (Colorado Basin); pleuriticus
ii. Spots less numerous, none anteriorly (Waha Lake); bouvieri
iii. Spots few and large, chiefly on the tail (Arkansas and Platte rivers); . .......stomias
hh. Spots all small; lower fins bright yellow; a yellow lateral shade (Twin Lakes, Colorado); ........macdonaldi