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1 <br />METHODS <br />Relative abundance of adult Colorado squawfish and razorback sucker (as <br />described by the catch of fish per unit of sampling effort) was estimated <br />using electro-fishing. Timers on electrofishing units recorded actual <br />shocking time (seconds) during each sampling effort. The number of Colo- <br />rado squawfish or razorback sucker captured (or seen but not captured) per <br />hour of shocking was used as the standard unit of relative abundance. All <br />areas within a reach did not receive equal shocking effort; thus, electo- <br />fishing searches should not be considered systematic. Although both <br />shorelines and all large backwaters of each reach were sampled, those <br />areas where squawfish or razorback suckers were found were subsequently <br />searched more intensively. <br />Radiotelemetry was used to follow movement of adult Colorado squawfish and <br />razorback sucker, as well as to identify the microhabitats used by these <br />fish. Electrofishing and trammel nets were used to capture fish. Fish <br />longer than 550 mm total length (TL) and captured from within the 15-mile <br />reach were surgically implanted with radio transmitters following proce- <br />dures outlined by Tyus (1982). Various sizes of transmitters were used <br />depending on fish size. Battery life of the smallest transmitter was <br />estimated as 150-245 days; the largest, 547-940 days. All captured rare <br />fish were measured to total length, weighed, and had a numbered Carlin tag <br />attached to them. Fish were released at their location of capture 1-2 hr <br />after implantation. The river was searched for radio-tagged fish on a <br />weekly basis. The area routinely searched included the 32.4 miles of the <br />Colorado River between the Grand Valley Diversion and the Loma Boat <br />4 <br />1 <br />1 <br />d <br />1 <br />1 <br />1 <br /> <br />h <br />1 <br />t <br /> <br />11 <br />t <br />t <br /> <br />1 <br />r <br />r