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272 MUELLER ET AL. TABLE l.-Source, rearing conditions, testing conditions, number, length, and weight of razorback suckers used in poststocking dispersal experiments. Sources are as follows: ONFH = Ouray National Fish Hatchery, BCMP = Boulder City Municipal Ponds, and WBNFH = Willow Beach National Fish Hatchery. Length (mm) Weight (g) Rearing Source type Test site N Mean Range Mean Range ONFH Pond Reservoir 30 358 335-402 718 610-925 ONFH Pond Small backwater 30 438 394-483 735 520-1,018 BCMP Pond Large backwater 30 357 327-400 474 360-670 WBNFH Raceway Large backwater 30 319 304-346 358 290-460 All surveys were conducted weekly by motor- ized boat or raft. Reservoir tests extended up the San Juan River 15 km and throughout the 95 km of Lake Powell. Surveys for the small-backwater experiment extended from the town of Green Riv- er, Utah, and the confluence of the Colorado and Dolores rivers downstream to Lake Powell, a total distance of nearly 350 km. Limited access to these remote reaches prevented complete coverage on a weekly basis and only, one survey was conducted in Cataract Canyon. Large-backwater surveys were conducted weekly by two survey crews using jet boats. Surveys extended over the 90-km reach of Colorado River between Davis Dam and Lake Havasu. Signal locations were triangulated and co- ordinates determined by global positioning sys- tems (GPS). Distances fish traveled were calcu- lated from GPS coordinates and existing river- reservoir navigational maps (Baars 1987; Fish-n- Maps Company 1991). Experimental procedures were similar for all tests, and fish were tracked for 28 d. Contact was lost for several fish, and data analysis was limited to just those fish we were able to track for a min- imum of 14 d. Results Reservoir Fish were detected 145 times during the first month, and all had left the release site within 5 d. Initial dispersal was rapid, and fish were found along shore and in open water. Within 3-4 d, fish moved toward shore where they were usually (72%) found within 10 m of shore and in vege- tative or rocky cover. Individual behavior was id- iosyncratic; some wandered whereas others be- came sedentary in coves. However, all were found in protective cover during daytime surveys. Over- all movement was minimal (<0.1 km/week) by week 3. Acclimated fish dispersed an average of 3.3 km, whereas reference fish dispersed 4.3 km from the release site (Table 2). Maximum dispersal distances were 12.4 for reference fish and 11.1 km for acclimated fish. Small Backwater All study fish left the release site within 5 d, and downstream movement of both groups aver- aged 5 km/d during the first week. Twenty (8 ac- climated and 12 control) fish were detected 2 weeks after release, accounting for 70 contacts. TABLE 2.-Number of and mean and standard deviation of distance moved by razorback suckers under different test conditons; N is the sample size; P-values represent comparisons between control and site-acclimated fish at each location. Site and test type N Distance Mean SD P Reservoir 0.3599 Control 8 -4.3 2.5 Site-acclimated (2 d) 11 -3.3 2.7 Small backwater 0.9850 Control 12 -68.1 24.9 Site-acclimated (2-3 d) 8 -71.6 33.9 Large backwater, pond reared 0.6472 Control 13 -6.6 8.4 Site-acclimated (2 d) 15 -8.8 11.6 Large backwater, flow conditioned 0.1406 WBNFH/control 15 -0.2 3.3 WBNFH/site-acclimated (7 d) 15 -3.6 6.9