7384

• UCREFRP Catalog Number: 7384
• Author: Tyus, H. M.
• Title: Colorado Squawfish.
• USFW Year: n.d.
• USFW - Doc Type: Vernal, Utah.
• Copyright Material: NO

Environmental change in the Colorado River Basin since the turn of the
century has been dr matic, and far too rapid for genetic adaptation by its
~6~s~
native fish fa aq indicated in Figure ~, much of the Colorado River has
been significantly altered by mainstream impoundments, diversions, and other
water resources projects. The lower Colorado River has been converted from a
natural, fluctuating, turbid system into a modified (dammed) channel. Native
fishes there have been largely extirpated from the main stream Colorado River,
and replaced by a new fauna of 44 or more introduced forms, of which 20 or
more are abundant locally or regionally (Hinckley 1982). The 1up er Colorado
0.~-~-- ~rl k~~21~'7
River Basin has also been altered, but ~e~mainstream~thabitat remains.
m„ e ~ boo v-~,1 ~s BF
Although over 42 species have been introduced into the upper basin (Tyus et al
1982a),'populations of endemic fishes remain in areas wffhich have been least
affected.
be.- s~¢ct F~ ~
Loss of reproducing populations of .endemic fishes in the Green River has
been primarily attributed to conversion of riverine habitai_to...artifieial
impoundments, replacement of warmwater habitats to cold tailwaters, and
migration barriers (Holden and Wick 1982, Seethaler 1978, Tyus 1984, Vanicek
~~ ~~
1967). l~r-a insidious effects ;n~ntroduction of non-native species ~
and ~^ '' '^ `F '"' _y water manirrpulations from water projects are more
difficult to document (or prove) b~~ ~k7 ~~ ~+~ ~~
`~~o c~s CE, ~ v' ~ b ~ ~"~ ~ I o -~t e- ~ ~~ ~ h,~ a ~ '~ L r v ~
-~~~h`S`
With the passage of the ESA, federal and state agencies were provided with
n Z`~ policy initiatives and funding to protect and recover populations of
n an eyed Colorado River fishes, including the Colorado squawfish. Federal
e d g
who wCrL
agencies, ~wrequired to consult with the USFWS regarding the effects of
18