7722

• UCREFRP Catalog Number: 7722
• Author: Smith, G. R.
• Title: Notes and Keys for Identification of Upper Colorado River Basin
• USFW Year: 1983.
• Copyright Material: NO

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Alternate key to Gila robusta complex, for field use

la. Dorsal and anal fins each with 9 rays, head large/fins small,

no hump ........................ Gi la robus ta

lb. Do~sal or anal fin with 10 or 11 rays, or head small or fins
large or hump behind head, or just questionable..... 2.
2a. Dorsal fin 'rays 10 and anal rays 11, minimum depth of caudal
peduncle stepped into dorsal or anal fin base with
dividers goes 3 to 4 times, prominent but g~adual
hump behind head ~.............Gila' elegans
2b. Dorsal fin rays 9 or anal rays 10 (or both) ~ or__caud.;tl. peduncle
thicker than 1/3 D orA fin base, ar hump other than
above ............=cypha or problem specimens........3
3a. Dorsal rays 9 and a'nal rays 10', abrupt hump behind head,
snout overhanging short lower jaw, head small and
concave above, eyes small and depressed, fins large,
. . "d" GOl .'h
. . . . . . '. . . .'. . . . . . . . . .-. . . . . . . . goo ~ c~p ~

3b. Any exception to the above .........hybrids or oddballs ....4.
4a. Dorsal rays 9, anal rays 9 or 10 .~................'..........S
'4b. Dorsal rays 10 or 11, anal rays 10 6r 11 .................:..6
Sa. Head and lower jaw large, fins small, peduncle thicker
than 1/3 anal or dorsal fin base, no hump except
in very large specimens, eye large, scales aligned
evenly ("normally") .............. Gila robusta
5b. Opposite to Sa and having an abrupt hump .. Gila cypha
5c. Distinct mixture of Sa and 5b, or borderline conditions
on all of the characters ...Hybrids: robusta X cypha
Ga. Smaller than 20 cm total length ............................7
6b. Larger than 20 cm total length ..............................8
7a. Caudal peduncle goes into' dorsal or anal fin base less than
2.5 times, D=lO A=ll, eye diameter greater than 2/3
caudal peduncle depth ........ Gila elegans
7b. Caudal peduncle thicker than above, eye smaller, A=lO..~a
7c. Mixture of characters in 7a and 7b..Hybrids:s:ypha X elegans
8a. Caudal peduncle more than 1/3 anal and dorsal bases, hump
abrupt or at least steepl snout overhanging short
lower jaw, eye depressed, A=lO .. Gila cypha
8b. Caudal peduncle less than 1/3 dorsal and/or anal base, snout normal,
hump gradual, eye round, A=lO or 11.. Gila elegans
8c. Hixture of characters in 8a & 8b or borderline in all.'EYEha X elegan~