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15 reaches and all habitats and by collecting physical as well as biological information over the wide range of conditions present in the river. Within each 0.5 mile intensively sampled reach, discrete habitat types were delineated (Figure 2) and fish collections conducted within them, rather than across several habitats. This permitted a delineation of habitat preferences and associated depths, velocities nad substrates. Sampling was not only stratified spatially, but also temporally. Days were subdivided into one a.m. sampling period, one p.m. daylight sampling period, and a darkness sampling period. A midday period of sampling inactivity was reserved for equipment maintenance, travel and personal activities of the crew (Figure 3). Daylight activities were devoted to netting, trapping, electroshocking and physical/chemical measurements. Activities during darkness were devoted to tending nets, traps and some seining. The annual sampling activities were scheduled relative to the spring runoff, with sampling conducted before, during, and after runoff (Figure 3). There was a period of inactivity each year when the river was either frozen or the weather was to severe to safely carry out sampling activities. Physical Measurements Sample sites were precisely located on river maps and aerial photographs. Sketches were made of each 0.5 mile intensively sampled reach illustrating the prevelance and juxtaposition of eight habtitat categories (Table 2). Three cross-sectional depth profiles were recorded at each 0.5 mile intensive section using an electronic depth recorder. Depth profiles were recorded at each end of the 0.5 mile sample sections and at the mid-point of the section. , t ~ Attempts were made to collect fish from every habitat present in a sample reach. The habitat from which each fish sample was collected was described by taking a series of depth and velocity measurements and recording the substrate over which it was found. Bottom substrates were classified according to the following scheme: silt sand gravel rubble boulder bedrock fine gritty material less than 33 mm diameter 33mm to 76 mm 76 mm to 305 mm 305 mm and larger rock outcropping Water quality measurements site. These included dissolved temperatures and conductivity. pH and DO were taken between 10 were taken at each intensive sample oxygen, turbidity, air and water Such variable parameters as temperature, a.m. and 2 p.m. for standardization.