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.L Colorado squawfish that were captured at Yampa River spawning <br />sites apparently returned to spawn in the same area in subsequent <br />years (Tyus 1985a, Wick et al. 1985}. The species may use learning, <br />genetic memory, or olfaction to relocate specific sites (Tyus <br />1985c). An orientation mechanism of scent imprinting may be used- <br />perhaps similar to those used by salmonids (Wick et al. 1983}. <br />Colorado squawfish spawned in canyon areas that receive freshwater <br />input from seeps;-they may use the odor of groundwater to identify <br />potential spawning habitats (Tyus 1985a, 1985c). Colorado squawfish <br />may return to the same spawning areas simply because other suitable <br />areas are not available, their yearly return could indicate a <br />learned behavior (Archer et'al. 1985). <br />Not all adult sized Colorado squawfish in the Green River <br />-Sub-basin undertake springtime migrations (Wick. et aI. 1983, Tyus <br />and McAda 1984). Nonmigrants may be immature (Tyus and McAda 1984}; <br />if so, they would not be expected to undertake migrations that <br />appear sexual in nature. One possibility is that nonmigrants spawn <br />in place.- Another possibility is that some adults may spawn one <br />year and "recondition" the next (Wick et al. 1983). Or perhaps lack <br />of proper environmental.-stimuli during some years may preclude <br />pre-spawning gonadal development. Some distances between "home <br />ranges" and spawning sites are so large that simple logistics make <br />L~~~ yearly spawning seem unlikely (Martinez 1986). <br />Long distance movements and aggregations by Colorado squawfish <br />are rare in the Colorado River in contrast with observations of the <br />Green River system (Archer et a.l. 1985). Aggregations of adults <br />8 <br />