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1 1 1 1 1 1 1 1 1 precluded direct observation of egg deposition, however, there is substantial evidence that Colorado squawfish and other squawfish species require cleaned cobble surfaces for egg adhesion (Burns 1966, Hamman 1981, Patton and Rodman 1969). Hamman (1981) also noted that hatching occurred on cobble surfaces. Spawning of Colorado squawfish at a time when sediment transport is reduced c (Figure 9) tends to support this need. Colorado squawfish spawning behavior may be divided into two p'nases: 1. Aresting-staging phase in pools or large shoreline eddies where the fish may find suitable resting and feeding habitat between spawning forays or where males may gather around females until they are ready to deposit eggs; 2. Adeposition-fertilization phase on cobble bars, where males and females congregate, females deposit eggs and males fertilize them, Breeding adults occupied pools and/or eddies with an average depth and velocity of about 7.0 ft and 1.0 f/s respectively, and cobble bars with an average depth and velocity of 3.0 ft and 2.0 f/s respectively (Table 4). FWS data (Tyus et al. 1987) and CDOW-NPS data (Wick et al. 1983) indicate that Colorado squawfish spawning activity in the Yampa River occurs in the lower 32 miles, particularly in a reach extending from Warm Springs Rapid (1L*1 4. 1) upstream to the vicinity of Harding Hole (RM 20), Repeated captures of ripe fish between RM 15 and RM 18.3 suggests that actual deposition and fertilization of eggs may be concentrated in this area. This portion of the Yampa Canyon (stratum 1, Figure 3) differs from other sections in that large, deep pools and eddies are intermingled with runs and cobble bars. The latter habitat is dominated by gravel, cobble, and boulder substrates. A total of 290 Colorado squawfish were collected by FWS at the two confirmed spawning sites in the Yampa and Green rivers during spawning period, 20