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3 8 8 Recovery of Long-lived Species squawfish caught in substantial numbersdtu:-,;"ratesand the size of ()ccupied range ill ing periods of low flow, when semi-isolated'" 'that if is larger than others. The cR.FP';' pools in the channel were haul seined~ lalso>~/"videdsubstantialdaci for the yeaisf~$'7 interviewed Mr. Sylvan N. Arrowsmith, who 1981; these are summarized in Table I said that he had caught many "white salmon" The same sampling methods were used in .... (75-100 large fish) prior to their legal protec-ous I~cations, including seines, trammel.. tion and ate them in preference to any other and electrofishing. Some methods were I species. Mr. Arrowsmith also reported seeing more efficient, and electrofishing wasc() several (12 or more) in the 13.6-15-9 kg (30- sidered more effective in the Colorado an' 35 pounds) size class that were captured by Yampa rivers than in the Green River, wher seines. turbidity was twice as great or more (U Abundance in the Last Decade Geological Survey records). However, th .', data are the most representative available for comparisons. Summing the four nonoverlap- ping studies in Table 19-1 for each sub-basin, catch per year was 2218 young, 221 juveniles, and 221 adults for the Green River (2.32, 0.23, and 0.23 fish km -.. respectively, for the reaches studied) and 169 young, 36 juveniles, and 59 adults for the Colorado main stem (0.26,0.06, and 0.09 fish km -1, respectively). These values suggest that the Green River sub- basin has about an order of magnitude more squaw fish of each life-history stage than the upper Colorado River sub-basin. Distribution and abundance of Colorado squawfish were poorly understood until sys- tematic surveys of the late 1960s and early 1970S (Holden and Stalnaker 1975a, b). Squawfish are found in small numbers in the main stems of larger rivers of the upper basin, but only the Green and Yampa rivers popula- tion and perhaps that in the Colorado main stem are thought large enough to be of viable, self-sustaining sizes. Although the exact size of the Green River population is unknown, data based on catch Table 19-1. Comparisons of Colorado squaw6sh catch data in the Green and upper main-stem Colorado rivers sub-basins, 1979-1981. , ,'11111111 River Annual catches nl' Author1 River miles Years Young Juveniles Adults "I' ' ,,:-::.'- '1 I , Green River . I' "j'! :1 A Green 22-319 2 2211 202 93 B Green 319-345 1 7 0 16 C White 0-150 1 0 19 39 B Yampa 0-124 1 0 0 73 Colorado River D Colorado -48-241 2 169 36 53 E Gunnison 0-42 2 0 0 6 E Dolores 0-68 1 0 0 0 1 A, Tyus et al. 1982b; B, \v. H. Miller et al. 1982b; C, \v. H. Miller et al. 1982c; D, Valdez et al. 1982b; E, Valdez et al. 1982a.