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fl~wever, intPrme~jiate appearing specimens exist, and it ss unknown <br />,. <br />if trey arc hybrids, int~;rgrades, or e:streme varian`..s of one car more <br />r ,~yytt <br />species (Archer et a1. 1J85). 'Taxonomic SCUUlc7 ~. ~- <br />Gi1r~ (tiiiller 1946, IIoldcn and Stalnsiker 1970, Smith et sl. <br />1879, Smith 1J83, Rosenfeld 1983, 19$6a, I`J86b) contradict each <br />other on same important points; there is presently no consensus <br />about Gila taxonomic relationships. The current classification <br />as separate species is based largely on appearances of only a few <br />specimens (Rosenfeld 1987). <br />riany "intermediate" forms may actually represent only humpback <br />chub, a species which may be morphologically variable ($osenfeld <br />1987). Gila from Black Rocks which were categorized us <br />intermediates between humpback chub and roundtail chub (Archer et <br />al. 1985) were categorized as humpback chubs by using a different <br />analytical technique (Rosenfeld ,198?).- Similarly, Gila <br />specimens from a Green River population possess morphotyges which <br />were perceived as intergrades by Holden and Stalnaker (1.970) but <br />which were thought by another researcher to be humpback chub <br />(Rosenfeld 1987). <br />Morphological variability of Colorado Basin Gi1aH~as <br />hampered studies of humpback chubs because definitive <br />field-identification of adults can be difficult (M.J. Rosenfeld, <br />Univ. of Utah; pers. comm.). A similar lack of reliable taxonomic <br />criteria for specific identification of larval and early-juvenile <br />3 <br />