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4 Timing of sampling Intensive sampling was conducted during spring, summer, and fall. The schedule was based on daily minimum water temperatures obtained from the U.S. Geological Survey (USGS) Maybell gage operator. Sampling was initiated within 5 days after daily minimum water temperatures reached a threshold temperature for 3 consecutive days. The threshold temperature for each season was: 1) spring (high flow) -- > 120C, 2) summer (decreasing flow) -- > 190 C, and 3) fall (base flow) -- C 1500. The spring sampling temperature of 120 C was selected because according to . USGS records it usually coinsided with peak runoff flows. The runoff period is critical because of stress from high velocity and low temperatures. The summer sampling temperature of 190 C is prior to spawning of Colorado squawfish in • Yampa Canyon. Sampling during the summer would allow annual comparisons of numbers of spawning fish in the spawning area each year. Sampling above Yampa Canyon was also conducted to determine if mature squawfish were present in the . upper Yampa during spawning. The fall sampling temperature of 150 C was based on USGS flow records which indicated that base flow usually occurred at this time. Previous experience indicated that catch rates are higher between 120 and 180 C. The base flow period is considered a critical period because of habitat limitations associated with low flow levels. Intensive sampling was conducted during the three seasons at all three upstream sites; Lilly Park, Sunbeam, and Juniper Springs. Intensive sampling at the fourth site, Yampa Canyon, occured only in the summer during the spawning period. Intervening sampling was conducted at upstream areas during all three . seasons and within Yampa Canyon during the summer. Special sampling (angling) was conducted in the summer and fall during times of clear water.