WSP07295 - Laserfiche WebLink

Home Browse Search

prior to the 1960's. 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. Only 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. There has been no successful reproduction of the endangered fish detected above the Redlands Diversion Dam in recent years. 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. The furthest upstream movement was into an area upstream from the Uncompahgre River confluence and the city of Delta. The habitat quality for endangered fish declines upstream from Delta, due possibly to colder waters released from the Aspinall Unit and due to the presence of the Hartland Diversion Dam, another barrier to fish migration. 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 later 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 (Carostous 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. 28