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aggregation of striped bass near Glen Canyon Dam during March, April and May. They were probably attracted to the current created as an average of 20,000 cfs is released from the dam through the penstocks. Large concentrations of striped bass are found each spring at the intake to the Navajo Generating station which draws water from the lake to the power plant. Mature fish remained near these sources of current for weeks or even months prior to spawning (Gustaveson et ale 1984). Individual females may hold eggs for months waiting for appropriate environmental spawning triggers. Once triggered, hormone level causes egg deposition to occur in a matter of a few hours. striped bass river spawning was triggered by a rapid increase in spring runoff from snowmelt. Temperatures from 16-1~ C were suitable for spawning when coupled with a surge in flow. Lake spawning was triggered solely by temperature. Hot, calm spring days can cause an increase in surface temperature of 3-4 C in a one day period. Spawning has occurred between mid April and mid June. Schools of mature striped bass staging near the dam left the area, following a rapid warming period when surface temperature neared 20-21 C, to seek out spawning habitat. They preferred points and coves where depth was 1-10 m. spawning occurs on the surface and usually peaked between 2100 and 2400 h. Intensive study of the prespawning aggregation of striped bass in 1981 determined that some males ripened by mid-April. All were ripe by May 1st. The main school broke up and left the staging area at the dam during the first week of May before any ripe females were collected. Striped bass in spawning condition were collected on 14 May in a gill net in Warm Creek Bay, 19 km above the dam. The fish were collected in 3-6 m of water near a gradually sloping sandstone talus shoreline composed of sand, cobble, and boulder-sized substrate overlain by 2-3 mm of fine silt. On May 22, 1982 striped bass were observed spawning in Warm Creek within 1 km of the 1981 collection site. Activity was 28