Laserfiche WebLink
<br />'. . <br /> <br />~'J <br /> <br />. <br /> <br />. <br /> <br />~ <br /> <br />e <br /> <br />.- <br /> <br />.. <br /> <br />",.,..~_.-....._-_..,.,-,... .....---.---"..,-.... <br /> <br />e <br /> <br />to have occurred in Dinosaur National Monument prior to impound- <br />ment except the humpback chub, which was never common here, were <br />readily collected from the river in this lower area of the Monument. <br />Several species (in addition to rainbow and brown trout) were col- <br />lected that were not taken in the five pre-impoundment collections. <br />These were mountain whitefish, Utah chub, creek chub, white sucker, <br />and green sunfish. With the exception of mountain whitefish, these <br />species are l:Iet exotics. The occurrence of these fishes probably reflects <br />the more intensive sampling efforts in the present study rather than <br />any change in fish populations. Miller (1964) has reported finding <br />creek chub at Echo Park in 1963 and green sunfish at Island Park in <br />1962. <br />The humpback chub, whose taxonomic status needs further study <br />(Smith, 1960), was collected only in 1963, the first year of this investi- <br />gation. Three specimens were collected. One was taken at Echo Park <br />and was apparently a bona fide humpback chub. The other two were <br />extremely humped forms which closely resemble Gila cypha. One was <br />taken at Island Park and the other at Swallow Canyon, above Dinosaur <br />National Monument. Little is known of the morphological variability <br />of G. robusta or G. cypha, and the identification of these two specimens <br />remains tentative. <br />Although Azevedo (Unpublished fishery management report, Bu- <br />reau Sport Fisheries and Wildlife), Hagen (1962), and Hagen and <br />Banks (1963) reported taking humpback chubs in Dinosaur National <br />Monument before closure of Flaming Gorge Dam, none of these fish <br />was positively identified. Many of the problems related to the question <br />of the pre-impoundment distribution of the humpback chub will <br />remain unsettled until its taxonomic status is better understood and <br />criteria for positive identification are established. Humpback chubs <br />were listed, however, among the fishes collected by Gaufin, Smith, and <br />Dotson (1960) in the reservoir basin (above the present study area) <br />before inipoundment. <br />On the basis of numbers of fishes taken in the present study, the two <br />most abundant species in the Green River in Dinosaur National Monu- <br />ment were redside shiners and speckled dace, while the species com- <br />prising the greatest biomass was the flannelmouth sucker. Smith <br />(1960) reported that the redside shiner was the most common species <br />in Flaming Gorge Reservoir basin prior to impoundment, and that the <br />speckled dace was the most abundant native species. <br />The primary factor responsible for the major change in the fish <br />fauna in this area was most likely the change in water temperature <br />imposed by the dam. Since impoundment, water temperatures at least <br /> <br />312 <br /> <br />'.. " <br /> <br />to <br /> <br />, <br /> <br />, <br /> <br />'l' <br />