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As discussed in this section, Colorado squawfish migrations have been observed for a hundred years, and we have documented travels of hundreds of kilometers in which adults utilize habitats in fall-spring in flatwater sections of rivers, but migrate to whitewater canyons to spawn in summer. Constructions of dams in the upper Colorado River basin, including Flaming Gorge Dam on the upper Green River, and Taylor Dram Dam on the White River, have blocked passage of migrating Colorado squawfish, as evidenced by the ~.~ ~e sr {nM?bw~''~I congregation of the fish below these obstructions..~ix-~ng spawning season. These dams have not been fitted with passageways for fish (Vanicek~tartinez). The only passage feasibility study conducted for Colorado squawfish was by the Army Corps of Engineers (ACE) in 1986, for the Redlands Diversion Dam on the Gunnison River. The lower Gunnison was historical habitat for the Colorado squawfish, and FWS participated with ACE (1986) to evaluate the feasibility of retrofitting the dam with a passageway as a means of re-establishing connection with parts of their historic range. This work has been placed on co-ticer-v~ s Z~.J 1 lL-sl hold, because of the high cost of the passageway structure, and }a-c~c~€- -1}} ~1D1 (~ /~ t / ~ ~ ~ R a' ~A1MQ.r~~7, CTl S~"`) {-tih- Ih.'~'e9~-f ~uVlhlbaw~l`~'~-r. l 1'G, we.a recd~e ~.~ ) ~= a~ ~1 #l c d~~~ ~S w.~ i ~. It may be. possible to construct fish passageways for migrating Colorado usL I-k~ Pr°~°~ squawfish. However, no passage facility has ever been constructed for~the ~fIQ ~~ species, and loss of fish below barrier dams by increased fishing pressure, or ! attrition, has, sooner or later, disrupted fish migrations. Construction of passageways without fish to use them means that new migrations would have to be established, if possible (no knowledge exists to do this). Another problem with passageways is the need to pass not only adults, but younger life stages 27