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137, 139, and 151) were within 4 miles (RM 229.2-225.0) of each other, and three fish (Codes 147, 152, and 156) were within 1.3 miles (RM 222.0-220.7) of each other. However, five of these fish (Codes 137, 140, 151, 152, and 156) dispersed downstream shortly thereafter and it is uncertain if this was a "pre-spawning congregation." No other aggregations ofradio-tagged Colorado pdceminnow were detected in the river during the remainder of the study. The individual contacts and movements during 2001 and 2002 for the 19 adult Colorado pikeminnow radio tagged in 2001 aze provided in Figures 5, 6, 7, and 8. Some of the most revealing information documented during this study was the movement of several radio-tagged Colorado pikeminnow into two irrigation canal systems that divert water from the Colorado River. The Government Highline Canal is presently unscreened and, therefore, fish had free access to the canal throughout this study. The GVIC Canal was unscreened until Apri12002. Of 10 Colorado pikeminnow radio-tagged in 2001 that moved downstream to the Government Highline Dam during 2001, five entered the canal system, whereas the other five continued downstream over the dam (Appendix E). During this period when the five Colorado pikeminnow entered the canal, approximately 70% of the flow volume of the Colorado River was being diverted into the canal (personal communication, Bob Norman, Bureau of Reclamation, Grand Junction). Two of the five that entered the canal were detected moving up-canal (Codes 78 [0.5 mile] and 154 [0.1 mile]) during tracking. The five fish that passed over the diversion dam in 2001 remained an average of 18 days (8-23 days) upstream from the diversion dam following stocking compared to 27 days (20-82 days) for the five fish that entered the canal (Table 2). Downstream movement ofradio-tagged fish either over the Government Highline Dam or into the canal occurred between 24 May and 11 August of 2001. Nine of these fish (Codes 78, 137, 138,143, 145,146,153,154, and 155) moved downstream between 24 May and 11 July, the period which corresponded with spawning for this species (see Figure 9; Appendix F). The average TL of Colorado pdceminnow that moved downstream over the Government Highline Dam in 2001 and into the canal was 631 mm (n=10; range=529-741 mm). This length was essentially identical and was not statistically different (t- statistic=0.11, F=0.915, df17) than the size of the nine Colorado p~eminnow that remained upstream of the diversion dam (mean TL=634 mm; range of 550-727 mm). If a mix of smaller adult Colorado p~lceminnow (e.g., 450-500 mm) could have been captured, radio tagged, and relocated during this study along with larger adult fish (> 500 mm), we could have tested the hypothesis that smaller Colorado pikeminnow would have remained in the upstream reaches where they were released and were better suited to establish residency than ]anger fish. 23