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<br />The roundtail is restricted to the Colorado River Drainage. In Wyoming it is
<br />common in the Green River and the Little Snake River drainages, mostly in larger
<br />rivers, but occasionally in smaller streams. It is sometimes abundant in lakes; for
<br />example, Burnt Lake near Pinedale.
<br />This species is adapted by its streamlined form, relatively narrow caudal
<br />peduncle and strongly forked tail, to the strong current of the Green and Colorado
<br />rivers, which it apparently prefers.
<br />As in the other species of this genus, the adhesive eggs are broadcast near
<br />shore. Citing Jonez and Sumner (1954), Sigler and Miller reported that in Lake
<br />Mohave, Nevada, this species spawned on a gravelly shelf in water up to 30 feet
<br />deep. Several males attended a single female; the eggs were broadcast and adhered
<br />to rocks. Spawning occurs in late spring, undoubtedly later at higher elevations.
<br />The roundtail feeds on insects and some algae. From its relatively large size,
<br />large mouth and strong swimming habits, this species might be expected to be
<br />predaceous on smaller fish, but there is no evidence for this assumption.
<br />
<br />Several morphological forms of the Gila robusta complex occur in the Colorado River
<br />drainage (Miller, 1946; LaRivers, 1962; Holden, 1968). In smaller streams and apparently in
<br />slower-water habitats in the Green and Colorado rivers proper, there is a more robust,
<br />fully-scaled form with a somewhat deeper caudal peduncle and with usually 9 dorsal rm rays.
<br />This is the form which predominates in the smaller tributary streams of the upper Colorado and
<br />Green river systems, and was called Gila robusta robusta by Miller and by LaRivers. Holden
<br />(1968) concluded that this form is specifically distinct, calling it Gila robusta, the roundtail. In
<br />swifter water habitats in the large rivers, there is found a more streamlined form of this
<br />complex, with imbedded scales, a narrower caudal peduncle, a moderate nuchal hump, and
<br />usually 10 dorsal fin rays. This form was called Gila robusta elegans by Miller (op. cit.) and by
<br />LaRivers (op cit.), but Holden gave it specific rank, as Gila elegans. An extreme, even bizarre,
<br />form with an exaggerated nuchal hump occurs in the lower Green and Colorado rivers. This
<br />form was named Gila cypha by Miller (1946). Holden (op. cit.: 35) believed that he could
<br />demonstrate intergradation between Gila elegans and Gila cypha, and said "present information
<br />suggests these two forms are only subspecifically separated."
<br />
<br />Bonytail
<br />
<br />Gila elegans Baird and Girard
<br />
<br />Gila elegans. Cope, 1872: 441 (Fort Bridger, forks of Green River).
<br />
<br />Body form similar to that of the preceding species except that there is a pronounced
<br />nuchal hump which is uniform from the head to the back; depth of the caudal peduncle less
<br />than in Gila robusta; lateral line scales 75-99; dorsal rays 9-11, usually 10; anal rays 9-12,
<br />Usually 10; pharyngeal teeth usually 2,5-4,2.
<br />Color dusky above, grading to a white belly. Breeding males become red.
<br />Distinguished from the round tail by the nuchal hump, the narrower caudal peduncle, and
<br />the (usually) larger number or dorsal and anal fin rays.
<br />Size usually 8-10 inches, sometimes to as much as 17 inches.
<br />
<br />elegans: "elegani:."
<br />
<br />The bony tail occurs in the Colorado and Green rivers where it is adapted to
<br />the torrential canyon waters. It was collected in Wyoming before the construction
<br />of the Flaming Gorge Reservoir but probably no longer occurs in the state in the
<br />absence of suitable habitat, and with the Flaming Gorge Dam acting as a barrier to
<br />its upstream movement.
<br />The biology of the bony tail is quite similar to that of the round tail with,
<br />probably, some modifications in adaptation to a somewhat swifter-water habitat.
<br />
<br />The different morphological forms of the roundtail-bonytail complex are discussed under
<br />the preceding species.
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