In the depths of Lake Superior is a variety of the Great Lake trout known as the Siscowet (_Cristivomer namaycush siskawitz_), remarkable for its extraordinary fatness of flesh. The cause of this difference lies probably in some peculiarity of food as yet unascertained. =The Ayu, or Sweetfish.=—The ayu, or sweetfish, of Japan, _Plecoglossus altivelis_, resembles a small trout in form, habits, and scaling. Its teeth are, however, totally different, being arranged on serrated plates on the sides of the jaws, and the tongue marked with similar folds. The ayu abounds in all clear streams of Japan and Formosa. It runs up from the sea like a salmon. It reaches the length of about a foot. The flesh is very fine and delicate, scarcely surpassed by that of any other fish whatsoever. It should be introduced into clear short streams throughout the temperate zones. [Illustration: FIG. 79.—Ayu, or Japanese Samlet, _Plecoglossus altivelis_ Schlegel. Tamagawa, Tokyo, Japan. ] In the river at Gifu in Japan and in some other streams the ayu is fished for on a large scale by means of tamed cormorants. This is usually done from boats in the night by the light of torches. =Cormorant-fishing.=—The following account of cormorant-fishing is taken, by the kind permission of Mr. Caspar W. Whitney, from an article contributed by the writer to _Outing_, April, 1902: Tamagawa means Jewel River, and no water could be clearer. It rises somewhere up in the delectable mountains to the eastward of Musashi, among the mysterious pines and green-brown fir-trees, and it flows across the plains bordered by rice-fields and mulberry orchards to the misty bay of Tokyo. It is, therefore, a river of Japan, and along its shores are quaint old temples, each guarding its section of primitive forest, picturesque bridges, huddling villages, and torii, or gates through which the gods may pass. The stream itself is none too large—a boy may wade it—but it runs on a wide bed, which it will need in flood-time, when the snow melts in the mountains. And this broad flood-bed is filled with gravel, with straggling willows, showy day-lilies, orange amaryllis, and the little sky-blue spider-flower, which the Japanese call chocho, or butterfly-weed. In the Tamagawa are many fishes: shining minnows in the white ripples, dark catfishes in the pools and eddies, and little sculpins and gobies lurking under the stones. Trout dart through its upper waters, and at times salmon run up from the sea.