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to fish, while maximizing el ectrof i shi ng effectiveness. Motorized el ectrof i shi ng jon boats facilitated maneuvering around the plunge pool, into eddy habitats, fast velocities of shorelines, and traveling upstream to sample fish. Because the study area was only 2.3 miles long, the entire reach was sampled during each trip. Information was collected and recorded separately for the 0.1-mile plunge pool and the downstream 2.2-mile reach. The plunge pool was defined as the riverine area immediately downstream of the Redlands Diversion Dam and extended downstream for 0.1 mile. In the 2.2-mile reach, the electrofishing boat was maneuvered downstream slowly in an "S"-shaped manner from one shoreline to the other to sample mid-channel habitats. The numbers of fish by species and age category (young-of-the-year [YOY], sub-adult [JUV], or adult [ADU]) were recorded on field data sheets at the end of each sample effort. Age - class groupings established in 1979-1981 by the Colorado River Fishery Project (CRFP; Miller et al. 1982; Appendix B; Table B.1.) were used. Effort was recorded in seconds which was later converted to hours electrofished. All fish collections were accompanied with detailed information regarding location, date, time of day, habitat type, conductivity, water temperature, and voltage and amperage output of electrofishing equipment. All Colorado squawfish and northern pike that were collected were initially checked for a PIT tag, weighed (g), and measured (total length [TL]). Colorado squawfish and northern pike that had not been previously captured were PIT tagged. All Colorado squawfish were scanned for a coded-nose- wire tag (Northwest Marine Technology) to determine if they were hatchery- produced fish previously stocked in the river. Other native and nonnative fishes collected during this study were not weighed or measured because length and weight data had been recorded for a large number of native and nonnative fishes captured in this reach during 1992 and 1993 (Burdick 1995). All fish were released alive. Data sheets were completed and the elapsed-time clock on the VVP-15 was reset after each sample effort. Hydrological BR Transects Twenty-seven cross sections were surveyed in April 1993 by BR personnel from the Redlands Diversion Dam to the confluence with the Colorado River to describe the geometry and flow characteristics of the river in the 2.3-mile reach. These 27 transects which provided maximum coverage of the reach were integrated into this study. For each of the 27 transects, the mean and maximum water depth and the number of water depths that exceeded 1 foot and 2 feet between 100 and 600 cfs were computed from the HEC-2 (Hydrologic Engineering Center) output. Eleven of the 27 transects that were believed to provide habitat or might have critically shallow water depths during low-flow periods were graphed and further analyzed. A backwater profile was developed using the HEC-2 water surface profile program developed by the U. S. Army Corps of Engineers. This program calculates water surface profiles for steady, gradually varied flow in natural or human-made channels with irregularly shaped cross sections. In essence, the program predicts velocity and maximum depths with various corresponding flows. Staff gages were placed at three different locations in the reach (at RM's 2.7, 1.4, 8