ABSTRACT
The “ayu” is a salmonoid fresh-water fish widely distributed in this country. Its zone of habitation in the river lies intermediate between that of the yamome (mountain trout) and that of bottom fish, such as carp, funa, and namazu (cat-fish). Where the water of a river has lost much of its purity by its passage through a densely populated district, we find fish for which a muddy bed has an attraction, and, as we ascend the river leaving towns behind and coming to a less peopled area, we enter the ayu zone, where the water is purer and clearer. Tracing the river course further to its source and penetrating into the solitary heart of the mountains, we approach the haunt of the yamome, that hermit of a fish.
