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I I I I I I I I I I I I I I I I I I I Green River were connected to the mainchannel until at least early July in 1993 and early August in 1995, but habitats were disconnected from the mainchannel as early as mid June in 1994 (R. T. Muth and E. J. Wick, personal observations). The effects of spring through early summer flow and sediment-transport regimes in the middle Green River during 1993-1996 (related to timing and magnitude of peak releases from Flaming Gorge Dam and peak flows in the Yampa River) on physical conditions at the primary razorback sucker spawning area in the Escalante reach will be evaluated in a Ph.D. dissertation being prepared by E. J. Wick. Low reservoir levels in Lake Powell during spring and early summer 1993 resulted in flowing, lotic conditions throughout the Colorado River inflow, whereas. in 1994 and 1995, non-flowing, more lentic conditions existed in the Colorado River inflow as far upstream as Palmer Canyon (RK 312.8) or Gypsum Canyon (RK 314.4). Daily water temperature data for 19 May-7 July 1995 inside Millard Canyon (at about 10 and 200 m from mouth) and in a flooded wash at Bonita Bend are presented in Appendix C. At all three sites. water temperatures over each day typically fluctuated 10C or less; daily fluctuations were greatest inside Millard Canyon at the site about 200 m from mouth and least in the flooded wash at Bonita Bend (wash was shaded by overhanging bank vegetation). Water temperatures inside Millard Canyon ranged from 14 (29 May) to 200C (27-29 June) at the site about 10 m from mouth and, after first inundation by mainchannel Green River water on 21 May, 12 (17 June) to 220C (3 July) at the site about 200 m from mouth. Water temperatures in the flooded wash at Bonita Bend ranged from 15 (29 May) to 180C (2 July) and were influenced by mixing with mainchannel water. Fish Collections: 1993, 1994 (Objectives 1-4), and 1995 (Objective 1) Floating quatrefoil light traps (Southern Concepts, Inc.) with 2 or 4-mm wide fish-entry slots and 1.6-mm mesh. 1-m deep X 3-m long seines were used to collect fish. Preliminary results of the laboratory study to evaluate effectiveness of several types of light traps indicated that the trap designed by Southern Concepts, Inc. would effectively sample razorback sucker larvae. light traps were usually deployed overnight (set near sunset and retrieved before sunrise), and seining was conducted during daylight. All juvenile Colorado squawfish collected were examined for presence of latex marks (mark-recapture study conducted by USFWS and LFL in the middle and lower Green River; 1994 and 1995 only), measured to the nearest mm total length (TL), and released alive near point of capture. In 1994. fish in light-trap samples with high numbers of sucker larvae were anesthetized in a 100 mgll solution of MS-222 (concentration used was based on preliminary results of laboratory experiments). Sucker larvae in those samples were identified and measured to the nearest mm TL alive in the field under a stereo-zoom dissecting microscope. and selected specimens were placed in styrofoam coolers with aerated water and taken to the LFL for rearing. Other fish collected were killed with an overdose of MS-222, preserved in 100% ethanol or 10% formalin, and taken to LFL for processing. In the laboratory, preserved fish were identified to species, endangered fish were measured to the nearest mm TL. and other fish were grouped by 5-mm TL intervals. Time light traps were set during darkness was recorded for each sample, and catch per effort (CPE) for each species was computed as number of fish per 10 h. Similarly, area seined was measured for each sample collected in 1994 and 1995, and CPE for each species was computed as number of fish per 10m2. For comparison with other studies in the upper Colorado River basin, the geometric mean of sample CPE's (GMcPE) for each species was calculated to determine catch rates. 4