7625

• UCREFRP Catalog Number: 7625
• Author: Stone, R. C., L. Fields and K. Miller.
• Title: Lake Powell Post Impoundment Investigations.
• USFW Year: 1964.
• USFW - Doc Type: Progress Report No. 2,
• Copyright Material: NO

.

-l]-

over the e:1tire reserrOir, and ranked first in i:nportance in the 02.S3 diet.

In 1964 they We:-8 ccr;lple~01y a':Jse:-,:~ f:G:n fish collectiOrls ar:d. ',!e:"e ;'8.:-.k:2d

last in tr.e food studies. The indi.cated div81'ge;lce i~l gro\..1:h rates for

the bass planted in 1963 a~d in 196~ may be a consequence of this lack of

small forage species. The reservoir 3.9pearS to have no substitute in its

natural fa~na at this time for these fish.

The three prim3.ry species 'w"hich have declined are the plains red s~liner

Nctropis lutrensis, the fathead minnow Pi~ephales promelas, and the western

:i.osqui tofish Gar.:bus::.a af::ir.us. The fathead ~1i:1nOH was commo;), in this locale

of the Colorado River a:ld 1 ts tribu~~aries before i::1pOUlldment, inllabi tit:,;

clear and muddy waters. It increased in numbers, although probably not

spectacularly in 1903. It is not k:l0~;n to do Hell in large lentic

environments. The western gambusia was rare in this vicinity before the

reservoir, but exploded to abu~da~t populatio~s durins, the f:rst su~~er of

impou:1d:;-;ent. Gambusia ",:ere cO:1sidered as inr.e.biting Lake Head i:;. its es.rly

years.. but are nm.... not knO\m there. It. probably suffered g.::-eatly f1'o7.'. ba:3s

predation late in 1963. The lake has very little of the shelter common l~

environments whicf'. are f':i'forable to it. The plains red. shiner ',"'1S not

described in Utah before 1963.. but is comhon in the 10'.o.'er Colorado River

and its tributaries. T!lis spec ies also exploded in lStJ3 and vlas very

abum:.ant allover tte reservoir. DJring 1964 it appeared to be :a0st

frequen~ in the extrer.--le upper reaches of the reservoir, but \-;8os sti 11

much less important tha:1 in 1%3. 1':one "were observed ill the l'J\{C'l' n':J~'l'\r\.\L'.

It apparently has maintai:oled popu1atic;;s to d:.J.te in reser/airs or th.:; 1c'.....cr

Colorado River system.

FOOD !1.AIH'IS

Lc~~,~e:;:Guth 3ass

Fifty-two large:noJuth bass stom2.cns were examined and separated i:1to