7818

• UCREFRP Catalog Number: 7818
• Author: Stalnaker, C. B. and P. B. Holden
• Title: Changes In Native Fish Distribution In The Green River System, Utah-Colorado
• USFW Year: 1973
• USFW - Doc Type: Utah Academy Proceedings
• Copyright Material: YES

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CHANGES IN NATIVE FISH DISTRInUTlON
IN TilE GREEN RIVER SYSTEM, UTAII-COLORADO

Clair B. Stalnaker and Paul n. Holden
Utall Coopulltive Fisleery Unit
Uta" State U"iversity

Introdue-tion

The Colorado River System is one of America's most unique natural
river system:.. Historically, this system was comprised of large warm-w:ller
rivers flowing thron;h ueserls. Steep canyons filled with torrential rapids
and swift water given to sudden and drastic changes in volume and tur-
bidity were charJ(teristic. The native fish fauna of the Colorado River was
likewise extrclllely unique, pos~cssing one of the highest degrees of
endemism found in an~' of our river systems. The endemic fishes were of
two types; small fish fou.d in limited ranges in the lower Colorado B:lsin
and large-rivl?r fish found in the 1Il:linsteearn of the brger rivers throug.11Out
the basin, p:Hliwbrly the Glcen River system. This latter group induues
l'tyc1IOChcill/s It/elliS, the ('olondo squ:Jwfish (North America's larc;est
minnow); Gila C}'{1h.l, t h,~ Il'lIll pf'ack chub, and Xyrallchcll teXGllllS, the
humpback SUd,~1 (1Il'lll l1.nln:( alllilptl~1 bUll1rcJ bJcks hypothc:.izcd to be
an adaprJti\'1l fOl S\\,lt"-W;tf..:e cn...ir,JlIlll,:nts); Gila elcg,7IIs, the bOnjlail
chub, slllw:ing stlt:,;!il:ili,',j lOt.tj,!lolll;:Y aJ'lplcd for swift water; G:la
robusto, the [Oulldtail l'hllb (a more robw,t ruinnow of the upper p"rLi of
the basin); Cllm{olJlIi.; !Ilripillllis, the l1ann~lmollth suck~1 (the most
COllll1ll'lO .:ntlcmic fi,hl; ;md GUOS{(IIIIlIS ,iiscuuvius, thc biu,~heaJ sucker
(foulId as two PUIYIWlJph:; In the Colorado Basin).
Today much uf lli:: (\,Iur;\(!o River System is composed oflargl' reser-
voirs that fill the c.wyum. Very hale l'rigillaleivcr IS left, especially in the
Ivwer bilsin. This IiJ:; haa ,J proliounccu effect on the nalive fish fauna
where urastic reductions in Jlsleibulion are the general rule. :\Iiller (1961)
and Mincklcy and D~.l':\'li (I <)0>)) documcnled the (kcreasc in nativc fishes
in tbe lower basin. ~lany of lhe small endemics ;lre either extinct or found
ie. vcry limited areas, afler. one slHillg. The large I1sh for the n~OSl part Jre
extremely rare if not extinc t ill the lower uasin.
The upper Co!ondo River OJsin, induding the Green River system,
now relllains the last stronghold of the large river endemic fishcs. Much of
the upper basin stili flows frce, but two major reservoirs built in the 1960's
. are present. Fl~ming Gorge Rescrvoir is located on the upper Green Rh'er.
the major tributary of the Colorado. Lake Powell, behind Glen Canron
Dam. is just upriver from Marble and Grand canyons.

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