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capable of providing continuous information on the movement of fish immediately downstream and immediately upstream of the diversion dam. This technology allowed researchers to determine if atransmitter-tagged Colorado pikeminnow had passed the diversion dam. A SRX 400 receiver and three-element directional antennae were used to locate fish from boats. An aluminum-jon boat with a 65- horsepower jet drive facilitated up- and downstream travel to monitor movements of transmitter-tagged fish following release. Pertinent data collected for each fish contacted were code, power level, date, time of day, river mile, general habitat type, and surface water temperature. The numbers of fish by species and age category (sub-adult and adult) were recorded on field data sheets at the end of each sample effort. The unique PIT- tag identification code, serially-numbered Floy® tag, or external fin clip was recorded for each fish tagged or marked. Effort was recorded in seconds which was later converted to hours electrofished. All fish collections were accompanied with detailed information regarding sample number, location, date, time of day, water temperature, and voltage and amperage output of electrofishing equipment. All Colorado pikeminnow collected were initially checked for a PIT tag, weighed (g), and measured (total length [mm]). Colorado pikeminnow not previously captured were PIT tagged. All Colorado pikeminnow were released alive. Fishery data recorded in the field were later stored in the database management system, DBASE IV+, to facilitate access and analyses as well as to provide data compatible with the computer system and format used by the Interagency Standardized Monitoring Program database. RESULTS AND DISCUSSION Marking and Recapture Field work to PIT tag native fishes, floy tag some nonnative fishes (carp and white sucker), and fin clip salmonid fishes (rainbow and brown trout) began 3 April 1998. Prior to runoff and the GVIC Diversion Dam being inundated by spring runoff flows, eight different days (7.11 hours of electrofishing) were spent collecting fish to mark between 3 and 27 April (Table 1; Appendix Table B.1.). A total of 744 native fish were PIT tagged and 114 nonnative fish were Floy~ tagged. Twelve salmonids and 21 hybrid suckers were fin clipped. Unfortunately, only one day (0.77 hours of electrofishing) was dedicated to sampling upstream of the diversion dam for marked fish prior to the diversion dam being overtopped by early spring runoff flows sometime during the week of 26 April to 2 May (Figure 3). None of the 167 native and nonnative fish collected upstream of the diversion dam on that date (27 April) had been marked previously (Table 1: Appendix Table C.1.). Fish sampling was suspended during runoff. Following spring runoff, electrofishing was resumed 17 July to capture fish downstream of the diversion dam. Initially, between 17 July and 20 August, a total of 384 native fish were PIT tagged, along with 56 nonnative fish that were floy tagged, and three salmonids and 11 hybrid suckers that were fin clipped. Between 24 and 28 August, 424 native fish and 13 nonnative fish were fin clipped; another 33 fish were