The structural differences between the three American graylings are so slight that they would be scarcely recognized by the lay angler, therefore a general description will probably answer. It is a slender, gracefully formed fish, with a body about five times longer than its depth, and rather thin, or compressed, on the order of the lake herring or cisco, or the Rocky Mountain whitefish. From this slight resemblance there is an erroneous notion quite current in Montana that it is a cross between the whitefish and the trout.
Characteristic Feature
Its characteristic feature is the tall dorsal fin, beautifully decorated with a rose-colored border, and oblong spots of various sizes of rose-pink ocellated with blue, green or white. The height of the fin is about one-fourth the length of the fish; I have several specimens of fins that are four inches tall, from fish not more than sixteen inches long.
Coloration
When first out of the water the grayling might be compared to a fish of mother-of-pearl, owing to the beautiful iridescence, wherein are displayed all the colors of the spectrum in subdued tints of lilac, pink, green, blue and purple, with the back purplish gray, and a few dark, small spots on the forward part of the body. The graylings are closely allied to the trout family, having an adipose second dorsal fin.
Its Peculiar Eye
The eye of all graylings is peculiar, the pupil being pyriform or pear-shaped. In all illustrations of American graylings that I have seen, except photographs, the artist has drawn the pupil perfectly round, as in most fishes. The only exception is that of the painting of the Montana grayling, by A. D. Turner, that accompanies the magnificent work, "Forest, Lake and River," by Dr. F. M. Johnson.
Food and Haunts
The grayling having but few teeth, and those small and slender, its food consequently consists of insects and their larvæ. It prefers swift streams with sandy or gravelly bottom, and loves the deep pools, where it lies in small schools. Occasionally it extends its search for food to adjacent streams strewn with small rocks and bowlders. Its maximum weight is one and a half pounds, very rarely reaching two pounds.
Comparative Abundance