8138

• UCREFRP Catalog Number: 8138
• Author: Utah Division of Wildlife Resources, Arizona Game and Fish Department and The National Park Service.
• Title: Glen Canyon National Recreation Area Utah/Arizona\
• USFW Year: 1996.
• Copyright Material: NO

perennial tributaries. Red shiner established a marginal reservoir population
but are found much more often in the flowing water than in the lake.
Native fish species were displaced by habitat loss and alteration, as well as
competition/predation with introduced nonnative fishes. Bonytail is the
native species believed to be in the most peril of imminent extinction because
they are virtually eliminated in the upper basin. In the upper basin, less
than ten confirmed bonytails have been caught in the last 15 years. Bonytail
were reported in Lake Powell soon after closure of Glen Canyon Dam, however,
annual gill-net surveys conducted by UDWR have failed to produce any bonytail
in the last 20 years. The last known bonytail taken from Lake Powell was in
May 1985 by an angler near Wahweap Marina.
After Glen Canyon Dam started backing up the waters of the Colorado River,
Colorado squawfish became part of the fish fauna of Lake Powell. Since 1963,
squawfish in Lake Powell have been declining. There have been no reports of
squawfish in the lake since 1977. Before that,, squawfish were reported to
have been taken by anglers and in annual gill-net surveys conducted by UDWR.
Colorado squawfish are believed to still inhabit the inflow area of the
Colorado River. Young-of-the-year squawfish have recently been found in both
the San Juan and Colorado River inflow areas of Lake Powell.
Very few humpback chubs have been found in Lake Powell. Annual gill-netting
surveys conducted by UDWR have captured only three humpback chubs within Lake
Powell in the last 20 years (1 in 1972 and 2 in 1975).. It is presumed that
humpback chubs are not present in the lake at this time, however, unidentified
species were collected by seines and light traps by BIO/WEST in the
Colorado inflow. There are currently no reports of large numbers of humpback
chubs in any of the other Colorado River impoundments.
Small numbers of razorback suckers have persisted in Lake Powell since the
closure of the Glen Canyon Dam. From 1911 to 1991, eight razorback suckers
have been caught throughout Lake Powell by UDWR in annual gill netting
surveys. Inflows of the San Juan, Dirty Devil, and Colorado rivers are areas
that hold larger numbers of fish. In 1987, the BOR and UDWR captured, tagged,
and released 12 razorback suckers in the inflow of the San Juan River. The
next year four more were caught with six recaptures. Additional efforts
produced 14 razorbacks of which 11 were removed for broodstock. Similar
numbers have been observed by researchers in Dirty Devil and Colorado River
inflows.
Flannelmouth suckers are relatively uncommon in lakes and reservoirs, however,
they have persisted in low numbers in Lake Powell. Flannelmouth suckers are
probably the only native fish to inhabit the main body of Lake Powell in
detectable numbers. Annual gill-net surveys conducted by UDWR have
consistently produced flannelmouth suckers. However, there has been a
declining trend in the population. At this time, reproductive recruitment has
not been documented in Lake Powell. Flannelmouth suckers are found in the
flowing Colorado, Escalante, Dirty Devil, and San Juan rivers and inflow
zones. Flannelmouth suckers are also found below the dam in the Lees Ferry
reach. The confluence of the Paria River provides important spawning habitat
for flannelmouths below the dam and in the Grand Canyon.
13