7147 - Laserfiche WebLink

Home Browse Search

, . 220 TRANS. AMER. FISH. SOC., 1975, NO.2 part of 4 are characterized by low gradient and sandy bottoms. The remainder of the basin has high gradients and gravelly bot- toms interspersed with areas of sand. MATERIALS AND METHODS Fish sampling in the upper and middle Colorado basins was conducted from 1967 to 1973. Gill nets, seines, electrofishing, and hook and line were used. Intensive sampling was conducted near Echo Park at the confluence of the Green and Yampa Rivers in 1968-70. The lower Green River was sampled 1968-71, the upper Colorado River primarily in 1971, Glen Canyon just below Glen Canyon Dam in 1967 and 1970, and Marble and Grand Canyons on three float trips, 1970-72. The latter area was the least intensively studied due to the high cost. Also, the large amount of floating algae, the daily 120-150-cm fluctuations of river level, and deep, swift channels made sampling the main channel extremely dif- ficult. Emphasis was placed on seining shallow areas for juvenile fish, indicators of recent reproduction. Most fish were returned to the river Ull- harmed, although rare forms dead in gill nets, and occasional specimens from throughout the basin were preserved. All preserved fish were placed in the fish col- lection of the Utah Cooperative Fishery Unit al Utah State University. Nomencla- ture follows that recommended by Bailey et al. (1970) except for the humpback chub complex (Gila cypha). Reasons for listing these fish as a complex and not a species were given by Holdcn and Stillnaker (1970). Fish abundancc was recorded in relative terms to better cxpress population status. Definitions of terms follow: Abundant: The species was collected at will with standard equipment and little ef- fort. Several age groups were present indi- cating stable reproducing populations. Juvenilcs were readily taken in one or more habitats by seine. Common: The species, especially juve- niles, was readily collected. Usually more than one age group was rcpresented, sug- gesting reproduction ill the area. Rare: The species was collected sional1y but with no certainty regard effort expended. Occasional: Occurrence of the i was due to stocking or movement ir area during a particular season, S1 winter. The species was usually fm low numbers. Failure to collect a species in a: did not necessarily mean it was abse suggested it was very rare. SPECIES ACCOUNTS Table 1 summarizes the distributio abundances determined by this surV( Salmonidae Rainbow trout-Salmo gairdneri ardson. Rainbow trout werc collee arcas 1, 2, 3, 9, 11, and 12. Their encc was due to planting by govcr agencies. Rainbow were also fou Rock Creek, a tributary to the River, in Desolation Canyon, in 1967, and 1973. The source of these fish known; flash Hoods and angling pI greatly reduced this population 1969-72. Tapeals Creek in Grand ( supporled a self-sustaining rainbow population fished by hikers and boal An interesting seasonal variation oc in areas 2 and 3. Hainbow were co in the cold (10-15 C) Green River the mouth of the warm (16-22 C) , River during summer months. In and fall, 1970, when lIw Yampa Riv. cool, they were caught in areas 2 ; apparently moving down the Green, ing favorable habitat. Some may alst movecl down froll! the headwaters Yampa or up from Jones Hole Cn tributary to the Grecn. Brown trout-Salmo trutta Lin Brown (rout were collected in areas and 10. Originally introduced, most brown trout in the study area were They were more COflllllon than rain) arcas 2 and 3 ill su Illmer months, PI' duc to greater tolerance of higher ICI tures and turbidity (Embody 1922). Cutthroat trout-Salmo clarki