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r ~ <br />accompanied by delayed reproduction would favor large adults.\ Rinne et al. <br />(1986) cited slow growth (3.2 cm in 9 years) and long life in ~ha-tchery- ~'`~~ <br />reared Colorado squawfish, and speculated that a 2.75 m specimen might be 50 <br />years of age. n the Green River. Seethaler (1978) indicated that Colorado <br />squawfish Less than 428 mm were immature, and fish over 503mm TL (n=147) were <br />mature. Aowever, he examined only one mature female. In our work on the <br />spawning grounds of this species from 1981-1985, we found 7 ripe females <br />~cea~- ~,--~¢st, o~ser~~~~swJ wL <br />(ave=710 mm TL), and 120 ripe males (ave=559 mm TL)~ speculat~,,as did <br />Vanicek (1967), that females grew larger, and were perhaps alder//than males <br />(Tyus et al 1987). (Unfortunately, the rarity of females (7/127=0.06), only <br />about 6x in the above case, suggests differential mortality for these large <br />fish, and is a potential cause for concern.) <br />Growth rates for 59 tagged adult Colorado squawfish that were subsequently <br />recaptured in the Green River averaged 11.2 mm/yr, SD=10.2 (Tyus 1988). <br />Colorado squawfish have been aged to 11 years by the scale method (Seethaler <br />1978), and more recently, preliminary results from aging work using otoliths <br />and vertebrae (conducted by D.S. Schultz, W.L. Hinckley, and myself}, <br />suggested maximim ages for Green River wild fish ranging from 14-31 pears. <br />Migration has been implicated as a major adaptation to dry seasons in the <br />intermountain desert fishes, and related to selection of spawning sites (G. <br />Smith 1981). Colorado squawfish make extensive use of migration, and homing of <br />adult fish to desirable spawning sites a hundred km and more have been <br />documented through radiotracking, and repeated recaptures of the same fish <br />(Tyus 1985, Tyus et al 1987, Wick et al 1983). Attainment of large size <br />6 <br />