7343

• UCREFRP Catalog Number: 7343
• Author: Vanicek, C. D. and R. H. Kramer
• Title: Life History of the Colorado Squawfish,
• USFW Year: 1969
• Copyright Material: YES

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Mlld,- ill United SIIII,'., "i A"If'rim
T'L\NS,\CTlII~, "'" TII~; A\IU:IL\!\ FISIIEHIES
YoL <)H, No.2, April 1%<)
Pl'. ]<)3 2UH

:-;IIUETY

Life History of the Colorado Squawfish, Ptyc1wcheilus lucius,
and the Colorado Chub, Gila robusta, in the Green River in
Dinosaur National MOJlument, 1964-19661

C. DAVIIi VANICEK2 AND ROBEHT II, KI:A:\lEH3
Utllh Cooperative Fishery Ullit, Utah State Ullher,~ity, LOgIIII, Utah

ABSTnAr.T
IlI\'estigations of the ecology and life history of the Colurado squawfjsh, I'tychorhcilus lucius,
and thc Colorado chub, Gilu robusta, in thc Green HiVeI' in Dinosaur National MOnUI1lCllt,
Colorado-Utah, were conducted from May 1964, to Octobcr 1%6. A total of 1,469 squawfish
and 2,393 ,chubs was collected with gill nets, seines, fry gear, and an el'~ctrie shocker, The
operation of Flaming Gorge Reservoir (46 miles above the Monument) has reduced the range
of these two species in this area, Age and growth determinations were made from scales from
182 squawfish and 333 chuhs, Both species grew slower in years after resenuir operation began
0%3-1%5) than before 0958-1%2); this reduction in growth rate was related to thp
alteration of seasonal streanHem(leraturc pattern caused hy thes., operations, The honytaii
form of thc Colorado chuh grew faster than the rollndtail fllrm, Lpn~lh-frequelll:Y analyses of
young st]uawfish and chuhs descrihed seasonal growth of the first llm'e year-dasses and pro-
vided evidcnce that these species !'eproduced successfully in Dinosaur National Monument every
yellr .iuoo iWjlOWlUllltilIL. altbouah rt:prouucLioll apparently nin not occur Rhove the mouth 01
the Yampa Hiver in ]964 Rnd 1%6, yeare of hilZh ~lImml'r dischnr!!(J from Lhe dam nnd
resultant lower water temperatures. Time of spawning of the two species varied ant! was relatet!
10 waleI' temperature and re('edin/!: water leveL The roundtail and honytail forms of the
Colorado chub had significantly different length-weight relationships. Squawfish over 200 Illm
total length were entirely piscimwus, while shorter sqllawfish consumed microcrustacealls ollld
aquatic insects, The diet of the Colorado chuh consisted lar:~cly of aquatic and terrestrial insects.

II\THOtJOCTlON
Liule is known about the life history of the
Colorado squawfish, Ptychocheilus lucius, or
the Colorado chub, Gila robllsla, both large
minnows, which are endemic in the Colorado
River drainage (La Hivers, 1962; Sigler allll
Miller, 1963). The squawfish is the largest
native minnow in North America, and has
been reported to have reached sizes of 36 kg
(80 lbs) and larger. Both species are de-

1 This paper is hascd on materials prepan',l for a
thesis submitted to the Graduate School, Utah State
University, in partial fulfillment of the requirements
for the degree of Doclor of Philosophy.
2 Present Address: Department or 13iulogieal Sei-
,mccs, S.lcramento St.lte College, Sacrumento, Cali-
fornia 951\19,
3 Unit Leader, llurcau Sport Fisheries and Wild-
life,

creaslllg in allUndance in their native ranges
because of man's modification of rivers
(Miller, 1961; Minckley and Deacon, ] %3!
and the squawfish has been placed on the
Bureau of Sport Fisheries and Wildlife's lisl
of "Hare and Endangered Fish and \Vildlifl'
Species of the United States:'
I n September 1l)()2. just prior to the
closure of the Flaming Gorge Dam (Figure
1), the Green River and its tributaries from
Pinedale, Wyoming, to a point 7 miles above
the dam site, were treated with rotenone to
eradicate non-game fish populations prepara-
tory to the establishment of a sport fishery
in the new Flaming Gorge Reservoir and its
taihntters (Binns ('I aI., ] lJ6J.). Following
closure of the dam in Novel11her 11)62. ap.
proximately 90 mile!' of the Green River

193