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collected since 1993 (Bestgen et al. 2002). Only in 1994 (0.80 fishlhr) and 1996 (0.16 fishlhr) were catch rates of razorback sucker larvae higher than the 2001 rate of 0.13 fish/hr. The 2001 capture rate was also similar to the CPUE of 0.1] fish/hr found in the middle Green River in 2000 (N = 82 razorback larvae in 95 samples, 89 of which were collected after capture of the first native sucker larvae). A continued increase in capture rates of razorback sucker larvae over time may indicate increased reproduction by remaining wild and stocked razorback suckers in the Green River system. However, these data must be interpreted cautiously and only after severa] additional years of sampling because capture rates fluctuate dramatically over time. Temperature monitoring. Temperature differences between the Green and Yampa rivers in Echo Park are potentially important because of potential for cold shock of Colorado pikeminnow larvae drifting from the Yampa into the normally colder Green River. Warmer water temperatures in the Green River also increase the likelihood of spawning by rare native fishes upstream of the Yampa River. Temperature data gathered in the Green and Yampa rivers in Echo Park were compared to determine if temperature differences fall within recommended constraints that the Green be no more than about 50C colder than the Yampa River (Muth et a!. 2000). In 2000 (Fig 4.), water temperatures in the Green were relatively cool and exceeded 20C for only a couple of days. Average water temperature in the Green River from I June to 30 September was 17.0oC compared to19.70C in the Yampa River for the same period (Tab]e 2). In 2001 and 2002 (2002 through mid-July only), water temperatures in the Green River were considerably warmer and averaged 190C in each year (Figs. 5 and 6). Water temperatures in the Yampa River in 200] and 2002 (through mid-July) averaged 20.5 and 21.50C, respectively. In only four instances (twice in 2000, once each in 2001 and 2002) did water temperatures exceed the recommended maximum summer difference of SOC and none were within the period when Colorado pikeminnow were drifting downstream from the Yampa River. In 2002, summer water temperatures in the Green River upstream of the Yampa River were likely the highest observed since F]aming Gorge Reservoir filled. VII. . Recommendations: Continue to sample early life stages of razorback sucker and Colorado pikeminnow annually at these sites. This information is critical to establishment oflong-term data that can guide informed management decisions regarding population viability and recovery. Data were also used to monitor effects of F]aming Gorge flows and water temperatures in relation to endangered fish reproduction in spring and summer. This information can also be used to make real-time recommendations for flow and temperature regimes for Flaming Gorge Dam during the critical time of reproduction for endangered Colorado pikeminnow. Sampling may also need to be expanded to assess reproduction by razorback suckers in the Yampa River. FY 2002 Annua] Report 22fPage - S