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Methods Relative abundance of adult Colorado squawfish and razorback sucker (as described by the catch of fish per unit of sampling effort) was estimated using electrofishing. Timers on electrofishing units recorded actual shocking time (seconds) during each sampling effort. The number of Colorado squawfish or razorback sucker captured per hour of shocking time was used as the standard unit of relative abundance. All areas within a reach did not receive equal shocking effort and thus searches should not be considered systematic. Although both shorelines and all large backwaters of each reach were sampled, those areas where squawfish or razorback suckers were found were searched again more intensively. Radiotelemetry was used to follow movement of adult Colorado squawfish and razorback sucker, as well as to identify the microhabitats used by these fish. Electrofishing boats and trammel nets were used to capture fish. Fish longer than 550 mm total length (TL) and captured from within the 15- mile reach were surgically implanted with radio transmitters following procedures outlined by Tyus (1982). Various sizes of transmitters were used depending on fish size. Battery life of the smallest transmitter is estimated as 150-245 days; the largest, 547-940 days. All captured rare fish were measured to total length, weighed, and had a numbered Carlin tag attached to them. Fish were released at their location of capture. The river was searched for radio-tagged fish on a weekly basis. The area routinely searched included the 35 miles of the Colorado River between the Price Stub Dam (three miles upstream from the upper end of the 15-mile reach) and the Loma Boat Launch, and the lower 2.2 miles of the Gunnison River (the reach downstream from the Redlands Diversion Dam). The search area was expanded downstream to the Utah state line when some fish could not