Biologists: Efforts appear promising
By Jessianne Castle EBS ENVIRONMENTAL & OUTDOORS EDITOR
BOZEMAN – Last
summer, 22 fluvial Arctic grayling were pulled out of a small mountain stream
just 30 miles south of Big Sky. Once measured and tagged, they were released
back into the waterway that bares their namesake.
Just three
years earlier, some of those very fish made their first journeys through the
water as tiny fry, when tens of thousands of eggs were incubated and then hatched
in the upper reaches of Grayling Creek. Together, with juvenile Westslope
cutthroat trout, the fish set about recolonizing their historic waters.
The 2018 capture,
which also counted 440 Westslope cutthroat trout, will be replicated this
summer and is an effort to understand whether fish restoration has been
successful on Grayling Creek, a stream that flows through Yellowstone National
Park and is just one of numerous park restoration projects. Researchers hope to
better understand the successes of the restoration effort by looking at the
population size, age and size of the fish, and whether they are naturally
reproducing.
The work on
Grayling Creek is what fisheries biologist Colleen Detjens described as a “huge
restoration effort” during Yellowstone National Park’s 2019 annual spring
angling meeting on April 29.
Beginning in
2012, restoration efforts saw to the development of a barrier that would
prevent non-native fish from swimming upstream into the upper reaches of the
river, as well as the still controversial treatments of Rotenone, a piscicide
that kills gilled aquatic species. This was followed by several years of
grayling and Westslope reintroductions.
Native
grayling, Westslope cutthroat trout and Yellowstone cutthroat trout are endemic
to many of Montana’s waters, but are now imperiled by the threat of thriving
non-native species such as rainbow or brook trout. These non-native fish were
stocked in many park and state waters during an era when management objectives
prioritized sportfishing and the impacts of non-native species weren’t well
understood.
The
discussion of Grayling Creek was just one topic on the agenda during the
angling meeting, which was held in Bozeman on April 29 at the Hilton Garden Inn.
Approximately two dozen individuals were in attendance, and they heard from
several presenters about the Yellowstone Native Fish Conservation Program.
In
Yellowstone Lake, suppression of lake trout continues in light of historic
Yellowstone cutthroat trout decline. Last year, staff fished 6,000 miles of
gillnet on a nightly basis as a form of passive capture technique. Assessments
indicate that mature adult lake trout are becoming less common in the water
system, though young lake trout are still common.
“The
world-wide range for this fish—Yellowstone cutthroat trout—is in Yellowstone
Park. So [Yellowstone Lake] is very important for the fish’s longevity and
existence,” said fisheries biologist Phil Doepke. “We don’t suspect the
gillnets are going to remove all the lake trout from the system, so we’re doing
other research trying to find out other ways of removing lake trout from the
system.”
Many of
these alternative methods target lake trout eggs, and include sucking up the
eggs from the lake bottom, killing the eggs with Rotenone, and killing the eggs
using organic material such as dead lake trout that were caught in the gillnets
or the application of a soy and wheat gluten pellet. According to Doepke, this
latter method has proved most successful in early testing.
Doepke said the
pellet—known as a carcass analog pellet—effectively kills the eggs within a
matter of days as it breaks down in the water, and after approximately 30 days
the pellets are fully dissolved. Further research will reveal the impacts of
nutrients being added into the water system from the pellets and whether this
is a safe option for lake trout removal.
On the Upper
Gibbon River, staff will complete a third year of Rotenone treatment this
summer and will reintroduce native fish in the fall. Unlike most reintroduction
efforts that involve incubating the eggs within the river, fish introduced in
the Gibbon River system are more mature so that common loons have something to feed on when they arrive in
the spring.
“We’re
trying to balance a bunch of different resource issues to make it the best
thing it can be,” said fisheries supervisor Todd Koel.
Within the
Lamar drainage, which includes Slough, Soda Butte and Buffalo Fork creeks, biologists
have recently completed an assessment of rainbow and Yellowstone cutthroat
trout migration, as well as inventoried for hybridized rainbow-cutthroat. The
results indicate that hybrid trout are present far up the Lamar River.
Overall,
park staff continue to brainstorm how best to combat these hybridized trout,
which pose a risk to the genetic purity of the Yellowstone cutthroat.
Discussions center around how to effectively identify hybrids and whether selective
removal and mandatory fish kills for anglers can be effective.
“During the
summer there’s quite a lot of people [on the Lamar River and Slough Creek] so a
lot of these fish are being caught numerous times,” Detjens said. “If we can
get anglers to help us remove those hybrids and recognize hybrids and also help
us remove the rainbow trout, that’s going to be a huge help toward our
management goals.”
As a final
note, fisheries technician Drew MacDonald added that the National Park Service
is going to begin intensive surveys for aquatic invasive species such as zebra
and quagga mussels this year. In past years, the surveys were conducted by
Wyoming Game and Fish. In addition to adding intense watercraft inspections, he
said the park has implemented a ban on watercraft with sealed internal water ballast
tanks that make decontamination difficult.
An
additional fisheries meeting was held in West Yellowstone on April 30, in Cody,
Wyoming, on May 7, and in Jackson, Wyoming, on May 8. The fishing season in
Yellowstone will open on Saturday, May 25.
For more information visit nps.gov/yell/learn/fisheriesscience.htm.
