By Jon Little
(Published June 8, 2000)
Yellow perch look cute. They're small and lack the fangs of northern pike.
But, like pike, perch are invasive predators. And they're scaring the tar
out of state fisheries biologists.
Perch aren't native to Alaska and, once introduced, could easily devastate
salmon-producing streams by gorging themselves on eggs and fingerlings, say
biologists who six weeks ago discovered a lake full of the harmless-looking
fish in Nikiski.
"We don't have to amplify our concern on this one," said Mike Bethe, area
management biologist. "On a one to 10 scale, it's a 10."
The state plans to poison the unnamed, private lake a little later this
summer, hoping to wipe out the perch that have devoured just about all other
fish in the lake and now are cannibalizing themselves. Nicknamed "Perch
Lake" on Department of Fish and Game memos, it will be poisoned a second
time in the fall to make doubly sure all the perch die.
The 14-acre lake is in a secluded area near Nikiski's Island Lake
The lake is landlocked, so in theory no perch should have migrated into
other ponds or
streams, Bethe said. But biologists want to know for sure, and have asked
the public to help. Bethe said he wants to hear from anyone who has caught
or transplanted perch in other Nikiski lakes.
He explained that he's not a fish cop and isn't looking to bust anyone. He
said he just wants to make sure perch don't reach salmon streams, the way
northern pike have in some areas.
Perch are extremely well adapted to northern waters, they reproduce quickly
and thrive in places with water conditions similar to the Kenai Peninsula,
While perch in the Lower 48 eat minnows, sunfish and other small species,
about the only food available to them in Alaska is either salmon species or
themselves, biologists say.
"Our concern is these fish can be introduced into the Kenai, the Kasilof,
the Swanson, the Chickaloon - virtually any system that supports salmon," he
That possibility should alarm anyone who takes part in, or profits from, the
region's multimillion-dollar sportfishing or commercial fishing industries,
It's illegal to stock non-native fish in Alaska, but planting exotic fish
species into small lakes is a snap. Mail order companies will sell popular
sportfish such as largemouth bass, muskies from Minnesota, walleye and
rainbow trout. Perch fingerlings can be bought by the pound from one
Web-based mail order company.
"All it takes is a bucket," Bethe said. "You take a half dozen perch and
toss 'em in a lake. A couple of years later, you've got a fishery in your
It was a fluke that Fish and Game even heard of this stocked lake. Bethe
said an anonymous caller asked a biologist if it was OK to stock a private
lake with northern pike. The biologist said no, then asked why. The caller
explained that the lake needed another predator to thin out its teeming
Biologists rounded up a gillnet and quickly confirmed their fears. They
netted several perch that ranged from 2 to 4 years old, Bethe said.
He said the department will spend $10,000 to rid the lake of perch. If they
find perch in other lakes, they'll have to go after those, too, he said. But
he hesitated to guess what it might cost to rid a river system or a series
of connected lakes of an invasive predator.
"Financially, this has scary implications for us," said Larry Marsh, a state
biologist working on the project.
Much of the money spent on this single lake will be spent on a ton of a
common fish poisoning compound called rotenone.
While rotenone was at the center of a botched fish poisoning effort in a
popular Oregon trout fishing lake recently, biologists say the Nikiski lake
is much smaller and the type of rotenone they will use is environmentally
"Given the nature of this lake - it's real small, real shallow and is
landlocked - the decision to approach this with chemical treatment was
relatively easy," Bethe said.
Derived from the roots of certain South American plants, rotenone affects
fish on a cellular level, making it impossible for them to get the necessary
oxygen. It breaks down rapidly, and a treated lake is considered back to
normal within a year, according to the Oregon Department of Fish and
Wildlife, which proposes using the chemical to rid 3,000-acre Diamond Lake
of another pest species.
Dave Rutz, chief sportfisheries biologist for northern Cook Inlet, is a
proponent of rotenone. Rutz has watched northern pike, a fierce, toothy
predator that can reach 30 pounds, slowly take over Matanuska-Susitna lakes
and streams. "One of the things that needs to be done is jump on this right
away," he said.
Pike were introduced to the Susitna Valley a couple decades ago in Bulchitna
Lake, southeast of Skwentna. A flood in the late 1970s or early '80s briefly
opened a link to other lakes, hastening the inevitable spread. They've since
used the Susitna River as a highway of sorts, darting into sloughs and
Anglers also stocked pike in Mackey Lake in the early 1970s, and that
population has quietly spread into Soldotna Creek, a Kenai River tributary,
and swam up the river to reach Moose River, a key silver salmon spawning
Bethe said all it would take is a flood, and Nikiski's perch population
could find its way to a lake connected to the nearby Swanson River system,
which supports silver and other salmon species.
"The last thing we want to see is these perch scattered around our lakes,"
"That would be just like a buffet," Marsh said.
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