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verify age and growth determinations from scale analysis. Calculation of fishery statistics was computed using Fire I, a computer program designed by Hesse (1977). Length-weight relationships, backcalcul- ated growth, condition (K), length frequency, and mean weight and length per age group were among the computed statistics. Lee's corrected formula was used to determine length-weight relationships, and condition(K) was deter- mined using total length. Analysis of Spawning Habitat The Blue River study area was divided into 25 150-m-long sections. Aver- age width and total area of spawning habitat were estimated in each section. Three indicators were used to identify spawning habitat: 1) presence of suit- able gravel, 2) presence of brown trout nests, or 3) presence of spawning brown trout. Total area, mean current velocity and mean depth were calculated for each identified spawning site. Substrate samples were collected from 23 spawning sites to determine size range and percentage composition of gravel utilized for nest construction. Each sample was collected using a 305-mm-diameter pipe, which was driven approximately 75 mm into the substrate. Substrate within the pipe was removed and stored in plastic bags. Each sample was air dried and separated into size groups described by Cummins (1961). Percentage composition by size group was calculated by weight. Measurements taken on individual trout nests included length, width, depth of depression, water depth, current velocity and distance from cover. Dimension of redds and number of nests per redd could not be determined be- cause it was not known whether the nests in one area were constructed by one or several females. Determination of the Effect of Harvest A stratified random sampling creel survey modeled after one designed by Neuhold and Lee (1957) and described by Sealing and Bennett (1980) was used to estimate angling pressure and total number of brown trout harvested from Dillon Reservoir in 1979 and 1980. The creel survey was conducted from Memorial Day through Labor Day each year between the hours of 6:00 A.M. (0600) and 9:00 P.M. (2100). A creel survey also was conducted from dark to dawn during September-October 1980 to estimate brown trout harvest at night. RESULTS Age, Growth, Condition, Sex Ratio and Number of Brown Trout in the Spawning Migration, 1979-1980 Age group III was the most abundant group collected from the spawning migration (Fig. 1). Length-frequency distribution (Fig. 2) verified age groups determined from scales. Otolith analysis was also used for verifica- tion; 97% of the cases compared were in agreement. Average lengths and weights of aged fish (Table 1) in 1979 were larger than in 1980 (independent sample t-test indicated a significant difference for both lengths and weights, P < 0.001). 38