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al. 1988). All of the preceding results are in direct conflict with outputs of IFIM (Bovee 1981) modelling of simulated nursery habitat near Ouray, Utah (calibration flow 3283 cfs). Although peaks and dips in model output (weighted J~ usable area) made acceptable flows difficult to determine, flow levels in ~J j~ ~ ~~ which recruitment, growth, and habitat was maximized (1600-1900 cfs) in the G~~~e ~ ~ ~ ~ previous field studies, was the lowest level predicted by the model (WUA e ~" v~- ti r~~~ a~'~ ~ b nearest 0). Subsequent evaluations of model use and outputs revealed that the ~ appropriate for this application. (refer to ft Collins) Oi E~ ~i fivQ, - SQR. ~c. Gati ~,,`~~ ~~~ e~~c ~ s _~ rg u r ~ ~ .Nti In arriving at out interim instream flow recommendation for release from ~~v~~, ti~~~ ~Y 1l ~ ~~~~,~, Flamin Gore we also had to ons der to eratu{~ j of f ct§ on the small 'r-~Q,, ~~''~,,y' `~j C~ L -}Y'Z t'e~~s ,NIX'S ~'b~ ~~ZGG~ ~ro~~~~ -~e M~edcl ~-,z~ ~R- Wxs ~~~~h~~s w/ l~~kw~~,- WD~.~ Y larvae, because increased flows of colder water also lowered average ~*,~~~,~- w/~~tN4c, ~t,S P PP y I`1 ~~lr ~e51. ~~rL tem eratures in the u er Green River (above Desolation Can on). We noted a v J ,~`5 ~, A temperature differential of lOC at the junction of the Green and Yampa Rivers ~.t\\ t ~~t~4C~~\ in Echo Park in 1983, whereas in best years the temperature differenctial was D~''- V~Q~~ o~ ~~p, ~\~~~~ usually less than 2 C (1979x0, 1980=1.5, 19811.5; Tyus et al 1987). Berry 1„" ~ t ~ G~ ~ ~ .(1988), demonstrated adverse effects of 10-15C cold shock could adversely ~` ~ ~J~ `;~f~ affect young Colorado squawfish larvae {14 d, TL 9 +0.3mm). No effects were ~ Q 1 ` 1 noted for larger, 40 day-old fish (24.4 +0.4mm). These colder temperatures ~Q~ ~ ~ti l1 '~ uring the larval drift period (soon after spawning) could be implicated in w `~` the partial loss of the 1983 year class. However, temperatures in~1984 did not \~ V~~~ approach this differential (range ), and do not explain the loss of that ri~ year class. Also, loss occurred in the lower Green River downstream of the Gray Canyon spawning area--locations not affected by low temperatures from the dam, but affected by high discharge as was the upper river. Temperatures in the few backwaters observed during `FWS fall sampling in 1984 av~ertaged 22.8 C, Q,ti1, a-~ ~ G r2 cL ~l'i4. (,.. l ~ e~ ~~ ~ l ~~- ,~~ ~~ ~ coti ~.,,.,~ t~.~ ~.~~~ ~T~ ~Ot"Y S ~ 1 ~~J~ ~ s ~o w~ ~o.~.~-e ~ e(l~ v~~ ~-e~ s zle ~~ ~~-1 ~ ~