<br />1046
<br />
<br />be shown that Colorado squawfish return to natal
<br />areas for spawning. The similarity oftheir behav-
<br />ior to that of many of other fishes makes it prob-
<br />able that they do so, and this could lead to repro-
<br />ductive isolation and separate genetic stocks
<br />(Leggett 1977; Solomon 1977; Stahl 1987). Spe-
<br />cific migration routes and positive or negative
<br />rheotaxis in homing orientation could be main-
<br />tained in different genetic stocks by homing fidel-
<br />ity (reviewed by Smith 1985). Some genetic in-
<br />terchange between stocks to maintain healthy
<br />levels of genetic variability could be maintained
<br />by movements of fish that "strayed" from one
<br />river to another, and the "strays" noted in my
<br />study may be important for successful evolution
<br />of the species (Baker 1982; Leggett 1984; Quinn
<br />1984). Colorado squawfish movements between
<br />the Green River, its tributaries, and the Colorado
<br />and Dirty Devil rivers may thus be important in
<br />maintaining a diversified gene pool.
<br />Migration and other reproductive behavior of
<br />Colorado squawfish are ostensibly attuned to a
<br />variety of stimuli, including intrinsic mechanisms
<br />and dependable environmental cues. A better un-
<br />derstanding of these mechanisms and cues could
<br />assist management and recovery efforts for this
<br />endangered species. If reproducing stocks are dis-
<br />tinct, as my study indicates, they may be geneti-
<br />cally isolated. Population genetics of the Colorado
<br />squawfish stocks in the Green River basin thus
<br />deserves further attention to aid recovery efforts
<br />for this species. Recovery of the Colorado squaw-
<br />fish to a nonendangered status may require main-
<br />tenance of separate spawning stocks and protec-
<br />tion of present environmental conditions until the
<br />reproductive ecology of the species is better un-
<br />derstood.
<br />
<br />Acknowledgments
<br />This study was funded by the Bureau of Rec-
<br />lamation, and Fish and Wildlife Service, U.S. De-
<br />partment of the Interior. Many government em-
<br />ployees assisted with the collection of data.
<br />Colorado Division of Wildlife, Utah Division of
<br />Wildlife Resources, Bio/West Incorporated, Col-
<br />orado State University, and Bureau of Reclama-
<br />tion employees furnished information. G. B.
<br />Haines aided with statistical analyses. P. B. John-
<br />sen provided helpful information about olfaction
<br />and imprinting. C. A. Karp, J. H. Williamson, A.
<br />A. Echelle, R. T. Muth, T. P. Nesler, and J. C.
<br />Schmulbach improved an earlier draft of the
<br />manuscript.
<br />
<br />TYUS
<br />
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