7822 - Laserfiche WebLink

Home Browse Search

DISTRIBUTION AND LIFE HISTORY OF MAJOR FISHES • Colorado Squawfish Distribution and abundance Colorado squawfish were captured throughout a major portion of the study area. Adult Colorado squawfish had widespread distribution, probably a reflection of their predatory nature and specific requirements for different habitats at different times of the year. Juvenile and YOY squawfish exhibited a less widespread distribution, which was prob- ably attributed to an affinity for more localized habitats. Investigations over the past 2-1/2 years indicated adult Colorado squawfish inhabited approximately 360 miles of the mainstem Green River, 150 miles of the White River, (Miller et al. 1982a) and 107 miles of the Yampa River (Miller et al. 1982b). Colorado squawfish were collected in 200 miles of the mainstem Colorado above Lake Powell and from the lower 30 miles of the Gunnison River. No squawfish were captured in the Dolores River. Standardized sampling indicated 41 percent of the adult squawfish collected from the main Colorado were from a 50-mile reach between RM 125 and 175, the section of river between Grand Junction downstream to the head of Westwater Canyon. Black Rocks, a unique 1-mile reach within this section, accounted for 36 percent of all adults captured. In the Green River and its tributaries, adult Colorado squawfish were more prevalent in those reaches having a moderate gradient and less incised channel, and less abundant in canyon reaches. Reaches between Split Mountain Gorge (RM 320) and the head of Desolation Canyon (RM 212) and from the lower end of Gray Canyon (RM 132) to the confluence of the Green and Colorado Rivers produced 90 percent of the adult Colorado squawfish catch (Table 2). From 1979 to 1981, 30 adult and 7 juvenile Colorado squawfish were tagged in the Green River within 3 miles of the mouth of the White River. This represents 29 percent of all Colorado squawfish tagged from 300 miles of the Green River (Miller et al. 1982b). Table 2 also demonstrates the occurrence of more large fish at the upstream river locations and smaller YOY fish in the lower section. This information supports the upstream spawning movement theory and downstream YOY drift theory, which are covered in more detail in the ' section on Migration and Movement. 7