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I I I I I I I I I I I I I I I I I I I VII. Fish & Wildlife Service Monitoring Recent biological and geomorphology studies have documented changes in physical processes and native fish populations related to the modification of the natural snowmelt hydro graph due to the construction of reservoirs upstream of the Colorado-Utah State line. These changes have reduced the ability of the Colorado River to move sediment and rework the river channel (pidick 1999). It is generally accepted that these reservoirs have altered stream flows of the Colorado River and have caused changes in the amount, diversity and quantity of habitat used by the endangered Colorado River fish. In compliance with the Recovery Program RIPRAP, monitoring of embeddedness of gravel and cobble substrates in the upper Colorado River was initiated. Twelve measurements were taken at each of 15 sites (eight in the IS-mile reach; seven in the 18-mile reach) on seven dates in 1996 (three during runoff; four during baseflow) and five dates in 1997 (three during runoff, two during baseflow). Rock sizes were generally larger lower in the channel at base flow elevations than higher in the channel margin inundated during runoff. Additionally, average rock size was slightly larger in the 18-mile reach than in the IS-mile reach, but only at base flow locations. Spring runoff flows in both the 15- and 18-mile reaches were sufficient in both years to mobilize the bed in many areas. In addition, runoff flows during 1995 (prior to sampling) produced widespread mobilization of the bed. Average rock sizes changed significantly between 1996 and 1997 at several of the sampling sites. Mean depth to embeddedness (distance from the top of rocks in the surface layer down to the point where rocks are embedded in fine sediment) ranged from 80 to 171 mm; the adjusted mean of the samples was 125 mm in 1996 and 123 mm in 1997. The mean number of 'free rocks' (those making up the layer above the level of embeddedness) ranged from I. I to 4.3; the adjusted mean was 1.9 rocks in both years. Riffles had slightly greater depths to embeddedness than did runs. For other comparisons, depths to embeddedness were found to be similar between the 15- and 18- mile reaches, between 1996 and 1997, and between runoff and baseflow periods. Rates of sedimentation were low during summer and fall following runoff and depth to-embeddedness remained fairly constant through the base flow period. The two years of initial sampling represents a period of time when both reaches were freshly cleaned of fine sediment and the data should provide a good baseline for future monitoring. In addition, the USFWS also conducted its Standardized Monitoring Program. The following excerpt is from the 1998 Standardized Monitoring Program. "In 1998. a second mark-recapture study was begun to monitor the status of this dynamic population - this time a three-year effort is planned instead of a four-year effort. In 1998. the same protocol was used as before: three passes, or capture efforts. were made through the upper reach and two passes through the lower reach. With each pass, trammel-netting of backwaters, andjlooded canyon mouths was used to capture fish during the run-offperiod. In the upper reach, captures were as follows: first pass. 32 fish; second pass. 67 fish; third pass, 43 fish. In the lower reach: first pass, 31 fish; second pass. 65 fish. Results of the first year of data collection have proved interesting. To begin with, there has been additional recruitment of sub-adults from year.classes following the 1985-1987 year-classes that were previously described, i.e., in the lower reach, a fair number offish in the 350-450 mm size 12