A glut of big walleyes and other alien species are threatening native fish in the West.
by Ted Williams
IN AN EFFORT TO IMPROVE ON NATURE, alien fish have been flung like confetti around the lakes and rivers of the American West (and the world) by bucket biologists, professional and otherwise.
These days the professionals are mostly rehabilitated, the amateurs not so much.
The results of bucket biology have almost always been the same—what a six-year-old would achieve by operating on a Bogdan reel to improve the gear assembly. Native ecosystems have been destroyed, native fish displaced and imperiled. In Montana alone, there have been about 600 confirmed illegal fish introductions in at least 250 waters.
Consider the walleyed pike. Perhaps you’ve not heard that this large, predaceous perch is part of the native-fish complex in Montana east of the Continental Divide. Walleye fishing guide Dale Gilbert and his fellow walleye advocates have “proof”—a unique map Gilbert found in a book titled Biology, Culture, and Management of Walleye and Sauger, published by the American Fisheries Society, that depicts North America’s historic walleye range. On the strength of this map, Gilbert is petitioning Montana Fish, Wildlife & Parks to correct its classification of walleyes from “introduced nonnative” to native because, as he is quoted by the media, “natives get priority as far as management.”
If you’ve not heard that walleyes are native to Montana, perhaps it’s because the claim is BS. The map is wrong. “We’ve looked at this really closely,” says Montana fisheries biologist Eric Roberts. “We talked to our natural heritage folks as well as the national American Fisheries Society. Reviewing all the literature and distribution, we didn’t find any information to indicate the walleyes are native to Montana.”
Walleyes could never have made it over Great Falls. And Yellowstone cutthroat trout, which occurred as far down the Yellowstone as the mouth of the Tongue River, can live only in water with temperature and chemistry incapable of sustaining walleyes. The fact that Yellowstone cutts were there and in other east-slope Montana streams proves that walleyes weren’t.
The first recorded walleye catch in Montana was from Nelson Reservoir in 1922—the result of stocking, apparently by a fishing club. In 1933 the state stocked 300,000 walleyes in the Missouri River near Fort Peck. Since then anglers have unlawfully polluted aquatic ecosystems with the species, further imperiling such natives as federally threatened bull trout and grievously depleted westslope cutthroat trout.
The push by Gilbert and his allies illustrates one of the many dangers of bucket biology—creation of public advocacy for aliens. Now that illegally introduced walleyes have naturalized in reservoirs of the Missouri and Clark Fork Rivers, walleye anglers are fighting modest suppression efforts by Montana and Idaho.
This from David Brooks, executive director of Montana Trout Unlimited: “One potential impact in the Missouri is that in big water years, walleyes spill over dams into the free-flowing river, especially below Holter Dam. The stretch from Helena to Great Falls is a wildly productive tailwater fishery. It sees 12 percent of all trout angling in the state. That’s a huge economic impact. When rivers are flooded in spring, everyone goes there because it’s dam-controlled. There’s some walleye predation on the trout. Now the walleye management tool in that stretch is unlimited take. We would like to see it stay that way.”
But Fish, Wildlife & Parks is being pressured by walleye anglers to reduce walleye kill in this wild trout water. So this year it will propose to change the no-limit walleye reg from Holter Dam to Cascade to 20 fish a day.
“That proposal,” says Roberts, “comes mostly from discussions with our walleye folks. But just because we’ll propose it doesn’t mean it will happen. There will be lots of opportunity for feedback from the public. If the coldwater folks want to maintain that no limit, they’ll certainly have opportunities to comment.”
Why should alien trout get priority over alien walleyes? Maybe because anglers who create illegal fisheries should not be rewarded for their ecosystem vandalism. What’s more, many western still waters are successfully managed for walleyes and not that many wild trout fisheries are as productive as that of the Missouri River.
The river’s dams have pretty much precluded any fishery for native trout. So for anglers who appreciate wild trout, rainbows and browns are about the only opportunity. And at least the trout fishery is planned and managed by professionals. In the human-created alien hell of western water, there’s nothing wrong with managing for fish that don’t belong but have become permanent residents. States, Montana included, manage heavily for both alien walleyes and alien trout.
While the Missouri’s trout are not native, they’re highly valued and able to provide a sustainable fishery. In contrast, introduced walleyes tend to do great for a while but eventually deplete the prey base, grow slowly, and aren’t so desirable to anglers.
“A big objective of our agency is to provide fishing opportunity,” says Roberts. “Nonnative species create that opportunity, and we dedicate a lot of time and resources to that. We also dedicate a lot of time and resources to our native fish.”
To its credit, Montana stocks only still waters. But with the walleye irruption in the Missouri reservoirs, it has been forced to cease stocking fingerling trout—that is, walleye candy. Now it stocks “catchables,” a bit ragged from their long stay in the raceways. “They survive better,” says Roberts. “But costs are higher. The fish need more feed, have to be kept in the hatchery longer, and they require more truckloads.”
There is some spillover of hatchery trout into the river, but Fish, Wildlife & Parks minimizes it by not stocking during the big spring runoff and stocking as far away from the dam as possible.
Illegally introduced walleyes showed up in the Missouri system’s Canyon Ferry Reservoir in 1989, remaining at low levels until 1996, when they reached critical mass. In 1997 Montana attempted to suppress them with gill nets, this to the distress of Walleyes Unlimited and other walleye advocates. The effort proved futile, and since then, all walleye suppression has been by generous catch limits, what Brooks calls “suppression light.”
In 2017 the already prolific walleye population in Canyon Ferry hit a record high, and the state was obliged to increase the 12-fish daily limit to 20 with only one over 20 inches, this also to distress from the walleye faction.
While alien walleyes pose scant threat to native fish in the Missouri system, that’s far from the case in the Flathead Lake–Clark Fork system. In that water, federally threatened bull trout and imperiled westslope cutthroats are being outcompeted and preyed on by alien lake trout. This necessitates lake trout suppression via gill nets.
In 2015 two illegally introduced walleyes turned up in a gill net when Montana was suppressing lake trout in Swan Lake, deep in the Flathead’s critical bull trout habitat. State fisheries biologist Sam Bourret, who did his master’s work tracking origins of introduced fish via microchemistry, compared otoliths from the Swan Lake walleyes to walleyes from 14 popular fisheries in Montana. They were a perfect match for fish from Lake Helena, where Bourret’s analysis showed they’d hatched. The fact that they weren’t progeny of fish hatched in Swan Lake was a relief, and no walleye has shown up in Swan Lake since.
Montana Trout Unlimited is offering a $20,000 reward for information leading to the conviction of the criminal or criminals responsible for the Swan Lake introduction. The state will throw in an additional $15,250, a reward available for convicting evidence for this or any illegal introduction anywhere in the state. (The state contribution includes pledges from angling groups, including Walleyes Unlimited.)
The walleye reg for Swan Lake is mandatory catch-and-kill. Any walleye taken must be reported to Fish, Wildlife & Parks within 24 hours and delivered whole within 10 days.
In 1991 illegally introduced walleyes turned up in 7,500-acre Noxon Reservoir on the Clark Fork. Twenty-one years later, after a popular walleye fishery had developed, Fish, Wildlife & Parks attempted suppression with gill nets and electrofishing. Walleye anglers howled, and the state went to suppression light via no limit.
But some walleye anglers don’t like suppression light either. “We absolutely do not condone illegal introductions, but we also challenge the position taken by Fish, Wildlife and Parks and their loyal supporters that a ready source of walleyes will lead to introductions in other western Montana waters,” contends the Noxon Warm Water Fisheries Association.