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probabilities of capture tended to remain the same or increase from passes one to three in some reaches, even when fourth pass data were not combined with third pass data. Probabilities of transition.--Transition probabilities (Orij) characterized the annual likelihood that tagged fish would move between the five different Green River Basin river reaches. Estimates of transition probabilities adjusted probabilities of capture because the likelihood of a fish being captured in a given reach was partially a function of its continued presence there (1 - r#,j). Estimates of reach transition probabilities also gave insights into rates and direction of movement of Colorado pikeminnow to and from various reaches, and how those varied with fish TL. In general, §V s for Colorado pikeminnow were low, especially those for non-adjacent reaches (e.g., lower Green River to the White or Yampa River, Table 11). Reaches in the middle of the study area had the most fish moving in. For example, the Desolation-Gray Canyon reach of the Green River was the only reach to have fish moving there from every other reach. The negative slope for 0 covariate TL reflected that transition probabilities among reaches were higher for smaller than larger fish (Fig. 11). Recall that transitions may reflect relatively short- distance movements just across the boundary of one reach to another (e.g., White River mouth to the middle Green River), and thus, may not necessarily reflect a large total distance moved. Average transition probabilities (only non-zero values used) for a fish of average TL moving from the Yampa River (0.027) and the middle Green River reach (0.021) were low, reflecting a relatively high propensity of fish to remain in those reaches (Table 12). The Or from the White River (0.035), the Desolation-Gray Canyon reach (0.050), and the lower Green River reach (0.121) were higher. Mean Otto a particular reach from all other reaches were lower for tributaries at the extremities of the Green River Basin (Yampa River = 0.012, White River = 34