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Post spawning migration of the Colorado squawfish coincided with the near baseflow conditions, ranging between approximately 1,400 cfs to 325 cfs (Figure4, from Tyus and Karp 1989, and Appendix 1). The upstream movement of squawfish during low flow conditions presents the potential problem of barriers to fish passage through Cross Mountain Canyon and the Maybell Diversion. Telemetry records of 13 fish (from a total of 165 Colorado squav-lfish as defined by Tyus 1990, irving and Modde 1994, Wicket al. 1983, and Wick and Hawkins 1989) were observed to move to the spawning site in the Yampa River and migrated upstream through Cross Mountain Canyon. In addition, 8 of these 13 fish also moved above the Maybell Diversion. The actual movement of Colorado squawfish through Cross Mountain Canyon occurred at flows of 324 cfs or greater (Figure 5). Actual fish movement through the Maybell Diversion was observed at even lower flows (Le. 177 cfs). Timing of fish movement was related more to the hydrograph than to specific calendar dates (Appendix 1). For exa(T1ple, during low flow years fish were more likely to spawn earlier and return e'arlier than during high flow years when spawning and return migrations occur later in the calendar year. Although it was possible to identify that fish could move through Cross Mountain Canyon and Maybell Diversion at flows of between approximately 350 and 200 cfs, respectively, we were unable to identify whether these in-channel obstacles were barriers to fish migration at lower flows. Humpback chub Spawning of humpback chub occurs during the descending limb of the hydrograph, usually during the months of May and June (Figure 6, from Tyus and Karp 1989) (Tyus et al. 1987, and Karp and Tyus 1989). As with Colorado squawfish, the relationship of spawning seemed more related to the hydrograph than specific flows or dates. Fish in spawning condition were collected between RM 12 and 40 in shoreline eddy and run habitats. Average temperature during the spawning period was 190C, ranging between 14.50 and 23.00C (Karp and Tyus 1990). Little evidence exists that fish in the Yampa River migrate long distances to spawning sites. However, two humpback chub were collected during the descending limb of the hydrograph in the lower 9 miles of the Little Snake River in 1995 (Fish and Wildlife Service and Colorado State University, unpublished data). Although secondary reproductive characteristics were not present on either fish (Le. tubercles or pigmentation) at the time of capture, these fish remained in the Little Snake River until the baseflow period, after which they moved to RM 36 and RM 41 in the Yampa River. This pattern of movement is consistent with humpback chub in the Colorado River that occupy the mainsteffi river during the nonreproductive period and enter the Little Colorado River to spawn (Valdez and RyeI1995). 11