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this length range were estimated to have been harvested in 1980. This represented twice the number of brown trout captured during the 1980 spawn- ing migration. Evaluation of Spawning Habitat One of the major limiting factors in controlling the number of fish in any population is spawning habitat. In the Blue River, 1.8% of the total study area was usable brown trout spawning habitat. The majority of the riverine substrate was comprised of small boulders and cobble (100-300 rom diameter). Much of the brown trout spawning habitat was confined to small areas along streambanks. All spawning habitat appeared to be utilized, in- cluding areas that were considered marginal. Evaluation of Angler Use and Harvest Dillon Reservoir has received high fishing pressures since 1975 (Sealing and Bennett 1980, Davis 1982). Angler hours per season have ranged 128,000- 283,000, or 96-212 angler hoursjha/yr. This may not appear to be very high until the actual area of the reservoir utilized by anglers is considered. The majority of the fishing pressure was exerted by shore anglers. Combin- ing the length of the reservoir shoreline, 41.6 km, and the average distance an angler casts a line, 20 m, the actual area utilized for fishing was 82 ha. Adjusted angler hours per hectare per season ranged 1560-3451, which is very heavy fishing pressure. The percentage of brown trout in the total harvest of all species from Dillon Reservoir from 1975-1980 ranged 2.4-6.0% (Sealing and Bennett 1980, Davis 1982). The high, 6.0%, occurred in 1978 during a severe drawdown. The percentage of brown trout in the total harvest has varied from 1% over a 20-year period in LacLeman, Switzerland (Laurent 1972), to 47% over as-year period in Castle Lake, California (Wales 1946). Hansen (1952) reported that brown trout provided 42% of the annual trout harvest from Pathfinder Reser- voir, Wyoming. CONCLUSIONS 1. The number of large brown trout captured was less in 1980 than in 1979. 2. Mean weight and length of brown trout were less in 1980 than in 1979. 3. The number of brown trout in the Blue River spawning migration has declined since 1977. 4. Brown trout growth and condition declined between the ages of 2-4 years and then began to increase. 5. All available spawning habitat in the Blue River contained at least one brown trout nest. 6. Spawning substrate and water parameters in the Blue River were typical of brown trout spawning habitat. 45