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MINNOW FAMILY, CYPRINIDAE
<br />Girard)
<br />ith short, deep, and thick
<br />dorsal and anal f ins, and
<br />ong the lateral line. The
<br />14 gill rakers (usually ] 0
<br />'living fish range in color
<br />and belly are generally
<br />igin, originally given to a
<br />now also applied to a
<br />ante to the wide caudal
<br />nd thicktail. Gila is after
<br />first fish referred to this
<br />sti River in New Mexico
<br />~ghout the Central Valley
<br />ibutary to San Francisco
<br />Salinas rivers. If thicktail
<br />iuey floor.
<br />~teresting minnows, since
<br />emely rare. What little is
<br />1t, ranging in length from
<br />98 percent of the fish in
<br />ndant in lowland lakes,
<br />wavy run-off, the surface
<br />Stine, and stout, hooked,
<br />ws, probably feeding on
<br />occasionally hybridized
<br />as a separate species.
<br />ugh to be sold in the San
<br />ig the most abundant in
<br />ins, 1973). However, the
<br />ough, near Rio Vista, in
<br />ieither the extensive fish
<br />rtment of Fish and Game
<br />Delta-Mendota Canal by
<br />ecluct by the California
<br />acy have turned up any
<br />is of the Sacramento and
<br />d, pers. comm.). At the
<br />rn the fully protected list
<br />to preserve them in case
<br />status by being unable to
<br />,particularly the removal
<br />xion in stream flows, the
<br />~f exotic predators and
<br />ilz and Simons, 1973.
<br />Bonytail, Gila elegans Baird and Girard
<br />173
<br />Systematic note. The bonytail is one member of a complex of closely related
<br />Gila species and subspecies that inhabit the Colorado River system. Miller (1946)
<br />thought that the forms could best be placed in two species: G. cypha, the bizarre
<br />humpback chub of the Grand Canyon, and G. robusta, the Colorado chub, with four
<br />subspecies: G. r. robusta, G. r, elegans, G. r, seminuda, and G, r, intermedia. The
<br />different forms presumably evolved, in isolation, to meet special ecological conditions
<br />in the Colorado system's varied waterways: G, cypha for the swift and turbulent water
<br />of the Grand Canyon; G, robusta, with the exception of G. r, elegans, for the quiet
<br />pools and slower moving waters of the main tributaries; and G, r, elegans for the fast
<br />waters of the main river. A careful systematic review of these forms by Holden and
<br />Stalnaker (1970), however, revealed that G. cypha has hybridized with G. robusta in
<br />recent years and questioned its validity as a species. On the other hand, their analysis
<br />confirmed the previous conclusion of Minckley and Deacon (1968), that G. r. elegans
<br />deserved full species status as G. elegans. The work of Vanicek and Kramer (1969),
<br />which indicated that G. elegans and G, robusta are ecologically and reproductively
<br />segregated, tends to support this conclusion.
<br />Identification. Bonytails are readily recognized by their extremely narrow caudal
<br />peduncles with deeply forked tails, their fine, embedded scales (75 to 88 along the
<br />lateral line), and their small, flattened heads with small, elliptical eyes. There is usually
<br />a conspicuous hump behind the head. Scales maybe lacking on the dorsal and ventral
<br />surfaces, as well as on the caudal peduncle. Dorsal and anal rays number 10 to 11;
<br />pelvic rays, 9 to 10. The pharyngeal teeth (2,5-4,2) are closely spaced, compressed,
<br />and hooked. The color of the back and sides ranges from dusky green to metallic blue,
<br />with fine speckling, while the belly is silvery to white. Breeding males become reddish
<br />morphologyhof the adult s ande beart ae fully lcl se re~mblancel to young Colorado
<br />squa wf ish.
<br />Names. Elegans means elegant. Members of the Colorado Gila complex are
<br />commonly referred to by nonichthyologists as Colorado chubs, Other common names
<br />for bonytail include Gila trout and Swiftwater Colorado Glib.
<br />Distribution. Bonytails are found throughout the Colorado River and its larger
<br />tributaries, mostly in the main channels. In California they ate (were) found only in
<br />the Colorado River where it borders the state.
<br />Life History. Bonytails are usually considered to be primarily inhabitants of the
<br />swifter waters of the large rivers of the Colorado system. This conclusion is based on
<br />thew streamlined morphology. The fine, deeply embedded scales, narrow caudal
<br />peduncle, and nuchal hump are all considered to be Swiftwater adaptations (La Rivers,
<br />_~
<br />F,. - ~.... ,> ~~
<br />Figure S5. Bonytail, 30 cm SL, Green River, Wyoming.
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