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Aspinall Unit did not adversely affect the endangered fishes in the Gunnison River because their numbers had already been reduced by a variety of factors-- particularly the blockage of movement into the Gunnison River by the Redlands Diversion Dam. However, there is a remnant population of Colorado squawfish in the Gunnison River above the Redlands Dam. It is not known whether the fish moved above the diversion dam during the relatively short periods (due to dam maintenance or other activities) when upstream movement is possible or whether they were spawned above the diversion. If spawning is being attempted in the Gunnison River, the reduced temperatures (even though the reduction is small) would decrease the probability that it would be successful. Further, the reduced temperature would decrease the probability of success if future reintroduction efforts are directed at the Gunnison River. Colorado River temperatures are essentially unchanged by the Aspinall Unit. Therefore, water temperature changes as a result of the Aspinall Unit probably did-not affect the endangered fishes in the mainstem Colorado River. Sediment Load It is unknown how the reduced sediment load has affected the endangered fishes. Reduced sediments have affected the Gunnison River (e.g. the armored bottom in many areas [Sanford and Ward 1983]), but because the fish were already greatly reduced before Aspinall was completed, it is unlikely that the sediment changes caused their decline. However, the changed substrate may affect the success of future reintroductions. The primary effect of reduced sediment levels involves the maintenance of backwaters in the lower Colorado River, an important habitat for young-of- the-year Colorado squawfish. However, the sediment load of the Colorado River 23