It’s called a plecostumus, and you’ve probably seen one eating algae off the sides of an aquarium. Sometime this winter, for whatever reason, someone in Polson got tired of their pet fish.
“So rather than kill it,” says the Department of Fish, Wildlife & Parks’ Jim Vashro, “they took it down to Flathead Lake and dumped it.”
The lake’s temperature in January was apparently too cold for the plecostumus to survive. Its body washed up on shore where a passerby found it and called FW&P.
Other dwellers of the aquarium world have made their way into Montana waters as well. FW&P has recorded five goldfish introductions, one involving a brown and orange oscar, and two encounters with pacus.
The pacu is a fruit-eating native of the Amazon that happens to resemble a piranha. So when one was caught in Lake Elmo, a popular swimming hole in Billings, “it got everybody excited,” says Vashro.
These days, it’s not former pets, but other non-native fish that have biologists like Vashro all worked up. The offending species are yellow perch, pumpkinseeds, blue gills and northern pike, which are known to eat everything from native trout to baby ducks.
Northern pike were illegally planted in a reservoir near Hot Springs in 1953. Since then, so-called “bucket biologists” have spread pike all over the Flathead. When they showed up in Whitefish Lake in 1977, local anglers posted a reward for information leading to the capture of whomever dumped a bucket of small pike into that fishery.
At the time, pike and other non-native fish were reviled as unwelcome outsiders by the fishing public. Lake trout, kokanee, grayling, whitefish, West Slope cutthroat, rainbow and brown trout were the preferred game fish.
But today, following what FW&P calculates to be more than 400 documented illegal introductions in Montana waters, many anglers have had a change of heart. They’ve become especially enamored of the yellow perch and its cousin, the walleye.
Considered a delicacy by champions and foes alike, walleye are the newest illegal transplant to arrive in the Flathead. It’s against FW&P policy to stock walleye west of the continental divide, because they’re non-native and piscivorous, meaning they eat other fish. As FW&P has learned, when walleye are introduced to a trout fishery, they devour both the trout and other available food sources.
John Wilson, conservation director with Montana Trout Unlimited, points to Canyon Ferry Reservoir south of Helena as an example of what can happen when walleyes begin preying on an established trout population. At first, the walleyes thrive, eating their fill of trout and growing large.
“Then, when the trout are gone, the forage is gone and the walleye will later be gone, unless you want to introduce some other kind of bait fish, which might introduce even more problems,” says Wilson, recalling how FWP tried recently to restore the trout population at Canyon Ferry by dumping thousands of trout fry into the reservoir. When the department went back to check how the new fish were faring, the news wasn’t good.
“It was a buffet bar,” says Wilson, emitting a sad chuckle at the thought of thousands of baby trout being gobbled up by the resident walleye. “Those poor little hatchery trout. They’d never seen a walleye.”
For years, no one fishing in the Flathead ever saw a walleye. But recently, FW&P has found illegal walleye plants in eight lakes west of the divide, including Lake Five on the outskirts of Glacier National Park. Such discoveries have put walleye fishermen on the defensive.
“Walleyes Unlimited is dead-set against bucket biology,” says WU’s Frank Danner. “We want to look at these things and we want to be up front and proud about it. We don’t want to go sneaking around.”
Danner speaks for a lot of fishermen in the Flathead when he complains that fans of perch and walleye are treated like “the orphan step-child” of the fishing community. He says FW&P has “committed itself to protecting [native] West Slope cutthroat and bull trout, but we’d like to have some of those resources.”
Specifically, Walleyes Unlimited wants FW&P to establish and manage walleye fisheries in the Flathead. That’s a notion that has trout fishermen looking up from their fly-tying and speaking out.
Mike Rooney with the Kootenai Valley Trout Club says he likes fishing for walleye, but that doesn’t mean he wants walleye planted in northwest Montana. The region, he says, already has to contend with planted pike, brown trout and other troublesome outsiders. If another non-native species is brought in by FW&P, “There’s always someone out there with a bucket who doesn’t care about what happens long term.”
FW&P’s management of non-native species has involved a lot of trial and error. The most notorious case—the one anglers often bring up when they claim FW&P is the worst bucket biologist of all—involves the introduction of the mysis shrimp to area lakes in the 1960s and ’70s. When the shrimp made their way into Flathead Lake, they interrupted the established food chain and created a crash in the population of kokanee salmon.
“The old fish management was a Johnny Appleseed approach where you just throw fish around and see what happens,” says FW&P’s Vashro. Today, he says, no legal introduction is made without a complete environmental assessment. Vashro keeps an “unauthorized fish introduction database” in his office in Kalispell. He tracks the work of bucket biologists, then “treats” local lakes when illegal intros threaten to significantly alter what FW&P considers to be a stable and healthy fishery.
Treating or “rehabbing” a fishery involves the fish poison rotenone, which is used to kill off unauthorized species. Once all fish are dead, the water is restocked with a varying mix of native cold water species, rainbow trout and kokanee salmon.
Vashro hasn’t used rotenone to stop the spread of walleye into Northwest Montana, but it’s an option he isn’t ruling out. As a warning to would-be bucket biologists, Vashro says, “Don’t do this yourself.” The regional fisheries manager then offers a quip others have used before: “Leave the mistakes to the professionals.”