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, ,!1H ni~"; ill i.....i.~...i., I', f' . l j', , , '1': J.'l .11' 3 86 Recovery of Long-lived Species 1989a; Wick et al. 1983; Haynes et al. 1984; Nesler et ale 1988), and field (Hendrickson and Brooks 1987; Tyus and Haines 1991) and laboratory experiments (unpub. data) suggest active downstream movements for larvae six weeks old and older. Juveniles Juvenile Colorado squawfish from about 60 to 400 mm TL (Tyus et al. 1982b) include age- l to about age-5 fish. Little is known of smal- ler juveniles (size range 100-300 mm) be- cause they are apparently difficult to capture and too small to radio-tag and track. Down- stream concentrations of postlarvae indicate that upstream movement of juveniles must occur to repopulate upstream reaches. Such probably occurs in the late juvenile or early adult stage (i.e., subadult, 30-50 cm TL), as suggested by highest concentrations of these larger juveniles in lowermost sections of the Green River and highest numbers of adults in upstream sections (Tyus et al. 1987). Collec- tions from the White and Yampa rivers (\v. H. Miller et al. 1982a, b) tend to support this hypothesis (Tyus 1986), and such a partial separation of life stages may reduce can- nibalism. Small juveniles are nonetheless sometimes captured in the same backwater habitat used by younger life stages (Holden 1977b; Tyus et ale 1982b), whereas larger juveniles are not uncommon in shoreline habitats similar to those occupied by adults (Tyus et al. 1987). Adults After spawning, adults in the Green River re- turn to the areas they previously occupied in spring (Wick et al. 1983; Tyus and Karp 1989; Tyus 1990), where they also reside in winter (Valdez and Masslich 1989; Wick and Hawkins 1989). There are no indications that adults stray any significant distances from the specific reaches they occupy during the non- migratory period. Large adults used compara- bly large areas of habitat, often moving aboU1 within a 5-km or longer reach of stream it their day-to-day activities. Radiotelemetryoi twenty-two fish (38.5-70.7 cm TL, N = 2325 observations) indicated that they were mOS1 often associated with shorelines (Tyus et al 1984). Comparable data on habitat use wa~ presented by Holden and Wick (1982), Tyus et al. (I982b, 1984), Wick et al. (1983, 1985), and Valdez et ale (1987). Distribution and Abundance General Observations Colorado squawfish were recorded from the Green River as early as 1825, when Colonel W. H. Ashley's party subsisted on fish caught by angling (Morgan 1964). Dellenbaugh (1908) reported their capture during the 1871 Powell Expedition, and D. S. Jordan (1891) caught them near the town of Green River, Utah, in 1889. Residents of Vernal, Utah, re- marked that squawfish were abundant in the Green River; individuals taken there reached a documented 52 pounds (23.6 kg), and a photograph of a large specimen was provided by Vanicek (1967). Seethaler (1978) sum- marized interviews with local people in Green River, Wyoming; Brown's Park, Colorado; and other places, who reported fish of thirty pounds (13.6 kg). He also reported an inter- view with Mr. Rial Chew, who observed a squawfish 5.5-6 ft (1.7-1.8 m) long, caught just below the confluence of the Green and Yampa rivers in 19II in what is now Di- nosaur National Monument, and presented a photograph of a 25-pound (1I.4-kg) adult taken in the same area in 1928. Mr. Chew also said that he caught several of the fish by hand during a flood. Figure 19-4 is a recently discovered photograph of a large specimen captured in the lower Yampa River in the late 1930S (Burton 1987), where the species was, and is, regularly taken. Older residents ofVer- nal and surrounding communities reported