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I [I 384 Recovery of Long-lived Species females) are also used to determine sex, the percentage of females increases from 7% (ripe fish only) to 20% (ripe, plus fish identified by secondary sex characters as females; Tyus and Karp 1989). Growth rates for fifty-nine tagged adults subsequently recaptured in the Green River (range 48.2-77.0 cm TL) averaged 11.2 mm per year (Tyus 1988). Colorado squawfish have been aged to eleven years by examination of scales (Seethaler 1978), but more recent re- sults using otoliths and vertebrae (conducted by D. Schultz, \v. L. Minckley, and myself) suggested ages for wild Green River adults from seven to thirty years. Foods and feeding Adult Colorado squawfish are PlSClvores (Vanicek and Kramer 1969; Minckley 1973; Holden and Wick 1982), although some other foods are also consumed. Large fish have been caught with various baits, including Mor- mon crickets (Anabrus migratorius; Tyus and Minckley 1988) and carcasses of mice, birds, and rabbits (Beckman 1953). I have also inter- viewed fishermen who caught adults on hooks baited with earthworms, night crawlers, cut bait of sucker flesh; chicken, moose, and sage grouse livers; and various artificial lures, in- cluding spinners, plugs, and spoons (E. Wick, M. Hughes, J. Johnson, and L. Masslich, pers. comm.). W. L. Minckley (pers. comm.) saw a large brood fish at Dexter National Fish Hatchery, New Mexico, consume young Amer- ican coots (Fulica americana). This voracious appetite was further illustrated by a large indi- vidual that surfaced and proceeded to strike my plastic float and take it underwater. Reproduction Colorado squawfish make extensive migra- tions, and homing of adult fish of 100 km and more (Fig. 19-3) to spawning sites was docu- mented through radio-tracking and repeated recaptures of the same fish (Wick et al. 1981, 1983, 1985; Tyus 1985, 1990; Tyus et ale 1987; Tyus and Karp 1989). Large size pre- sumably aids in undertaking long movements, which must require significant energy expen- ditures: The strategies involved are not fully understood, but habitat selection and recruit- ment success (fitness) are no doubt important. Migration is a logical adaptation of intermon- tane desert fishes to seasonally low discharges and is related to selection of opdmal spawn- ing sites as well (G. R. Smith 198Ib). Only isolated captures of ripe squawfish were reported from the Green River in the late 1960S (Vanicek and Kramer 1969) and early 1970S (Holden and Stalnaker 1975b; See- thaler 1978). More detailed studies in the 1980s, however, indicated that reproductively active adults seek faunally depauperate white- water canyons for deposition of gametes in summer. Two major migrations and spawning areas have been identified by tracking radio- tagged fish (Fig. 19-3). One migration to Yampa Canyon (Yampa River km 0-32) was identified in 1981 and studied annually through 1988 (Tyus et a1. 1982b; Wick et al. 1983; Tyus and McAda 1984; Tyus et al. 1987; Tyus and Karp 1989). The other migra- tion, to Gray Canyon of the Green River (km 232-256), was suspected in 1982, but in- sufficient fish were radio-tracked to confirm it until 1983 (Tyus 1985). The area was mon- itored continuously from 1983 through 1988 (Tyus 1990), and ripe adults have been caught at both sites each year. Successful reproduc- tion was confirmed by collection of larvae im- mediately downstream, but not upstream, in both areas, from 1980 to 1987 (Haynes et al. 1984; Tyus et a1. 1987; Nesler et a1. 1988). It is possible that other spawning sites exist, in- cluding one in Labyrinth and Stillwater can- yons of the lower Green River (Tyus et al. 1987). If so, few radio-tagged fish used them and the populations are presumably small. Homing behavior was inferred from long- distance movement patterns and recaptures