It’s been more than a decade since Montana Fish, Wildlife and
Parks rolled out a proposal to purge non-native fish from alpine lakes above
the South Fork Flathead River drainage, for the purpose of restoring and
protecting native westslope cutthroat trout populations for the long haul, and
now it has the markings of a significant success story.
The proposal was met with criticism and controversy, partly
because it involved poisoning wildly popular alpine lake fisheries with a
natural toxin called Rotenone that deprives fish of their ability to process
oxygen. But state fisheries officials persisted with multiple approaches to
assuaging public concerns, and the 10-year project won approval and got
underway in 2007.
The project involved “treating” 21 alpine lakes with a
documented presence of non-native Yellowstone cutthroats and rainbow trout,
along with hybridized west slope cutthroats. Because the lakes have outlets
draining into the South Fork, the main concern was that hybrid cutthroats, or
non-native fish, would gradually leak into the broader South Fork, presenting a
long-term threat to the widely recognized stronghold for native westslope
cutthroats in Montana.
Every fall, one lake after another were treated and then
re-stocked with genetically pure west slope cutthroats. Only two more lakes
remain: the 51-acre Handkerchief Lake on the Flathead Nation Forest, set for
fall of 2016, and the largest lake on the list, the 148-acre Sunburst Lake in
the Bob Marshall Wilderness in the fall of 2017.
Matt Boyer, the state’s lead biologist for the project, says
the effort has proven to be biologically successful and general public
acceptance has come about.
“I don’t think opportunities like this are exceedingly
common, to have the opportunity to restore a native fish assemblage on such a
large landscape,” Boyer said.
“Here in the Flathead, we’re in a fortunate position that we
still have some fairly robust cutthroats populations in terms of genetics,” he
said. “When you take a step back, where are you going to focus your limited
conservation dollars? The Flathead rises to the top because you still have
largely intact, genetically pure populations … The land is healthy, with intact
watersheds that are protected as wilderness. You are working with a landscape
that has many functioning ecological aspects. You don’t have a whole myriad of
issues that are broken. You can walk right in and get the job done.”
Boyer says the overall cost of the 10-year project, largely
coming from Bonneville Power Administration fisheries mitigation funding, comes
to about $3 million. An additional $1 million from the same funding source has
gone toward development of the Sekokini Springs conservation fish hatchery (see
related story http://www.cbbulletin.com/435727.aspx) located just off the North Fork Flathead River over the last
decade. Sekokini Springs has provided critical support to the alpine lakes
The Sekokini hatchery and alpine lakes work are intended to
mitigate impacts on fisheries caused by construction of Hungry Horse Dam on the
South Fork Flathead River in the 1950s. Ironically, the dam has turned out to
be one of the main protections for native fisheries in the South Fork. While
other branches of the Flathead River system have been invaded by non-native
species, and dams have caused significant harm to fisheries around the world,
Hungry Horse Dam has prevented an incursion of non-native lake trout from
migrating into the South Fork from Flathead Lake.
Most of the lakes on the western flank of Glacier National
Park have been occupied by lake trout that moved upstream through the North
Fork Flathead River over decades, but native fish in the South Fork drainage
above Hungry Horse Dam were protected from that threat. The South Fork’s native
fish, however, were exposed to the introduction of non-native species by humans
— first by Yellowstone cutthroat and rainbow trout being packed in on
livestock, and later by aerial deliveries to the alpine lakes that pepper the
higher elevations above the drainage.
“They got there through legacy stocking programs dating back
to as late as the 1920s,” Boyer said. “It was during a time when there was not
awareness or knowledge of native fish conservation … It was sort of the Johnny
Appleseed approach to fisheries management.”
Native fisheries conservation evolved into the realm of
genetics, with biologists like Boyer recognizing that hybridization of native
fisheries would eventually have a pernicious effect of exterminating the
species that were best suited to survive in the environments they have occupied
The alpine lakes project was aimed at putting the brakes on
that happening: “At the end of the day, you have native self-sustaining trout
populations spread out over an enormous watershed,” Boyer said.
It has worked as planned.
“We’re seeing effective chemical restoration” where Rotenone
was used in 15 of the lakes, while genetic “swamping” — overwhelming a lake
with stocking of native fish — has been successful in four of six lakes where
that method was used.
There has been continuous before-and-after monitoring for
effectiveness of the work at each lake. “We’re evaluating the success of
Rotenone, and we’re assessing the success of genetic swamping,” Boyer said.
But even before work at the first lake started, Montana
Fish, Wildlife and Parks did extensive research into the potential impacts of
Rotenone on amphibians, aquatic insects and other elements of the natural
alpine lake habitat. It is notable that this extensive research was done prior
to the project’s initiation to assess risks to amphibians, even though Rotenone
has been used for decades to manage fisheries, usually for the purpose of
curbing undesirable fish populations.
“Scientifically, we went to the nth degree to document
before-and-after conditions,” Boyer said. “To date, we have not seen negative
effects to those non-target species.”
Boyer says any measures that would be harmful to an aquatic
habitat for native fish would be grounds for the entire project to be scrapped.
“That is so important to this project … we would be harming
the food sources for the species we are trying to help,” he said.
The social side of the project was also critical. Many
anglers had considerable reluctance about anything that would kill off quality
fisheries; genetics aside, it didn’t make sense to kill good-looking alpine
lake fish, whether they be hybrid “cut-bows,” rainbows, or Yellowstone
And that led to a major policy element for the project to
proceed. “We made the promise to the public to restore these to quality
fisheries again,” Boyer said, adding that re-stocking efforts have involved
putting multiple age classes back into the lakes to ensure “there would be
catchable fish right away.”
That came to be true. Maybe fishing was different on the
lakes initially, but quality angling opportunities came back.
Montana Fish, Wildlife and Parks also committed to an
“adaptive management” approach, taking input at formal annual meetings to
evaluate the work that was underway. Boyer said there was intense interest at
the start that gradually declined as the results came in.
Another big accomplishment, he said, is that the alpine
lakes will have self-sustaining native fish populations, not relying on
continuous fish stocking.
The overall effort provides conservation for fisheries that
“now represent more than 50 percent of the remaining west slope cutthroat
populations in Montana,” Boyer said. “It is the stronghold … The waters above
the (Hungry Horse) dam now contains the largest, intact native fish assemblage