| Managing
for Blue Ribbon Rainbow trout at Lee's Ferry |
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 Background:
In 1964, the Lee's Ferry tailrace on the Colorado River was given birth
by the completion of Glen Canyon Dam, which impounded Lake Powell. Subsequent
water releases from the bottom of Lake Powell changed the once highly turbid,
warm waters of the Colorado River into a constant cold (46-50°F), clear
flowing river. Shortly after completion of the dam, the Arizona Game and
Fish Department stocked rainbow trout (Oncorhynchus mykiss) in the 15-mile
Lee's Ferry reach and, in 1981, began to manage this section of river as
a Blue Ribbon trout fishery. The trout began to flourish in the Lee's Ferry
reach between 1970-1985 when catches of rainbow trout above 10-pounds were
not uncommon, and angler pressure was relatively low. In 1991, however,
the Bureau of Reclamation implemented the Glen Canyon Dam Environmental
Impact Statement Record of Decision flow regime, which consisted of higher
minimum and more stable flows and allowed for increased trout reproduction
and survival. Under these conditions, a huge population of trout developed
causing individual fish growth rates to decline. Quite simply, there was
a large number of fish competing for limited space and food items, resulting
in a fishery where trout less than 14-inches were dominant.
Arizona Game and Fish Department (AZGFD) has been collecting data on the
trout fishery since the 1970s, and in 2000, began a long-term monitoring
program sponsored by Grand Canyon Monitoring and Research Center (http://www.gcmrc.gov/)
to determine the effects of Glen Canyon Dam operation on the trout fishery
at Lee's Ferry and to make recommendations for improving this fishery.
Since 2000, our data have shown an increase in the general health of all
trout age classes (especially since 2002). This increase in fish health
is usually associated with an increase in growth rates implying improved
fishing conditions in the near future.
Location:
The Lee's Ferry tailrace is located in Marble Canyon, Arizona and covers
the 15-mile section of the Colorado River from Lee's Ferry upstream to
Glen Canyon Dam.
Approach:
 The
Research Branch of the Arizona Game and Fish
Department currently conducts nighttime electrofishing
surveys 3 times per year at Lee's Ferry to
monitor the rainbow trout population. We use
2 - 16-foot inflatable boats with a crew of
3 on each boat. During each sampling trip,
9 fixed sites are sampled along with 27 randomly
selected sites over the span of 3 nights using
an electrofishing system mounted to each boat.
At the fixed sites, individual trout 6 inches
and longer are implanted with tiny microchips,
which allows us to identify individual fish
and gather information such as growth and movement
if the fish is ever captured again. All fish
collected during each sampling trip are measured,
weighed, and checked for sexual maturity. Our
sampling surveys are conducted at night because
fish tend to move towards the shoreline after
sunset, and electrofishing is most effective
in shallow water.
Benefits:
The data collected from each sampling survey enables us to detect changes
in the rainbow trout population over time. From these data, we can take
action to ensure Lee's Ferry remains a world-class fishery. Data are also
used as part of the Glen
Canyon Adaptive Management Program. So come on up folks, the fishing
is great!
For more information
contact:
Joey Slaughter, Arizona Game and Fish Department, 1535 ½ South Milton,
Flagstaff, AZ 86001.
Phone: (928)-226-7677 E-mail: jslaughter@gf.state.az.us |
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