The pink salmon are found in the waters along the Pacific Coast from the Columbia River to the Bering Sea but are most abundant in southeastern Alaska, where they spawn by the millions each year.' This part of Alaska is composed of a narrow strip of continental land that is bordered by a large and broken chain of mountainous islands which protect it from the sea. Owing to the temperate climate and heavy rainfall in the region (see fig. 1) most of the islands and mainland shore are covered with dense growths of timber (spruce, hemlock and cedar) and are drained by hundreds of streams that range in size from brooks to small rivers. These streams may be separated into two groups: first, those originating in lakes, and second, those originating in mountain slopes or watersheds with little or no storage capacity. The former have a more or less steady flow, for the lakes act as reservoirs for the melting snow and rainfall, whereas the latter being fed mainly by surface run-off, have an 1 For a detailed description of the life history of the pink salmon, see Davidson ('34) and Pritchard ('39).