Draft Environmental Assesment and Finding of No Significant Impact Gunnision River Activities February 1995

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and Kaeding, 1991) flows have been depleted and the naturally occurring high spring flows have been reduced. The Redlands Diversion Dam has cut off migrations of fish from the Colorado River into the Gunnison. Various sources indicate that the Colorado squawfish and razorback suckers were common in the Gunnison River from the Delta area to Grand Junction (Kidd, 1977; Chamberlain 1946; and Osmundson and Kaeding, 1989). There is no documentation on whether the Gunnison River was ever important habitat for the humpback and bonytail chubs. A fish inventory was conducted in 1992 and 1993 in the Gunnison River upstream of the Redlands Diversion Dam. Five adult Colorado squawfish were collected in 1993 and none collected in 1992. Several other sightings of squawfish were made in this area in 1992 and 1993. No razorback suckers were collected. One humpback chub was collected in 1993. In 1993, eight adult squawfish were captured in the 2.3 mile reach of the Gunnison River downstream from the Redlands Diversion Dam. Five of these fish, along with two additional squawfish captured upstream from the Redlands Diversion Dam, were implanted with radio transmitters and returned to the Gunnison River at three different locations upstream of the dam. Their movements were tracked from April 1993 through July 1994. All seven radiotagged fish moved both upstream and downstream of their release site. A total of 112 individual radio contacts were made periodically with these seven fish between July 20 and August 7, 1993, when spawning might occur. Although no spawning fish were observed or captured during this time, the observed grouping together of these fish upstream from the Redlands Diversion Dam suggests possible spawning behavior. In 1994, 38 individual squawfish were captured in the Gunnison River downstream from the Redlands Diversion Dam, and 14 of these squawfish were recaptured at least once. This indicates a relatively large number of fish that could move upstream through the fish passageway. Other native fish are found in the Gunnison River, including the flannelmouth sucker (Catostous latipinnis) and roundtail chub (Gila robusta), both of which have been declining in the Colorado River Basin and are considered candidate species for listing as threatened or endangered status. The Colorado River cutthroat trout (Oncorhynchus clarki pleuriticus) is also a candidate species but has not been found in the mainstem of the Gunnison River since around 1900 (Wiltzius, 1978). The Gunnison River does have a higher percentage of native fish than most Upper Colorado River Basin rivers (Fish and Wildlife Service, 1994a). One theory is that the Redlands Diversion Dam has served as a barrier to upstream migration of non -native fish and has helped maintain a high percentage of natives. The Gunnison River has relatively high levels of salinity and selenium which are two major factors affecting the water quality in the river. Selenium, which is a trace element and occurs naturally in some of the soils in western Colorado, is also toxic in small concentrations. 22