July 2023 - 16

IN THE FIELD
Researchers from the University of Wyoming cast gill nets during fish sampling at New Fork Lakes near Pinedale. (Photo by Travis Neebling/WGFD)
Predators below
the surface
Research shows lake trout have a big impact on the kokanee salmon
population in New Fork Lakes
By Game and Fish Staff
L
ake trout are a favorite sportfish for
many anglers across Wyoming. Their
voracious appetites and potential
to reach trophy sizes make them an
exciting fish to catch. But what happens
when those voracious appetites are turned
toward eating other desirable and managed
fish species?
The Wyoming Game and Fish Department
partnered with researchers at the University
of Wyoming from 2020-23 to study just that.
New Fork Lakes, located near Pinedale, hosts a
robust lake trout population. It also is home to
one of the Game and Fish's primary kokanee
16 | July 2023
broodstocks - a population used to provide
eggs for the state's fish hatcheries. In recent
years Game and Fish monitoring revealed the
kokanee population was in decline, a trend
that jeopardized its ability to meet hatchery
objectives.
" We thought either more people were fishing
for kokanee or lake trout predation was
driving down numbers, " said Travis Neebling,
Game and Fish fisheries biologist.
In 2021 Game and Fish surveyed anglers
at New Fork Lakes to determine if kokanee
were commonly harvested. The results
revealed anglers were primarily targeting
lake and rainbow trout. While some people
fished for kokanee, there was not enough
fishing pressure to cause population declines.
Researchers shifted their focus to lake trout
predation.
UW graduate student Caroline Rosinski,
advised by Dr. William Fetzer, set out to quantify
how many kokanee were eaten by lake
trout each year. In 2020 and 2021, Rosinski,
alongside Game and Fish and UW field crews,
collected lake trout from New Fork Lakes
using gill nets. The team examined stomach
contents to evaluate what lake trout were
eating. A variety of prey types were present,
ranging from invertebrates like midge larvae
and zooplankton to fish species including
kokanee, rainbow trout and mottled sculpin.
Some noteworthy lake trout stomachs

July 2023

Table of Contents for the Digital Edition of July 2023

July 2023 - 1
July 2023 - 2
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