A great experiment is afoot and afin to try and keep the right kind of fish in Fish Lake.

A great experiment is afoot and afin to try and keep the right kind of fish in Fish Lake.

Thousands of Rogue River spring chinook salmon about 10-plus inches long are patrolling the waters of Fish Lake, and wildlife biologists hope they are feeding on the lake's more populous yet unwanted denizens — nonnative tui chub and fathead minnows.

For the past 15 years, the chubs and minnows have outcompeted stocked trout for food and space. It reached a point where their presence has altered trout-stocking programs and stunted the popular trout fishery there.

The hope is that excess Rogue springers now locked in the lake can tap into their predatory selves and turn chub from invader to dinner, while growing into fat "trout" that will make Fish Lake's faithful feel happier about their catches.

"We are looking for a fish that can take advantage of those chub," says Dan VanDyke, the Oregon Department of Fish and Wildlife's Rogue District fish biologist and the architect of the experiment.

The first 50,000 springers were stocked as fingerlings in this High Cascades lake off Highway 140 in 2009, followed by 30,000 more last June. Another 50,000 are planned for this summer, VanDyke says.

The 2009 fish were just starting to get close to the 8-inch legal size last fall, so they ought to run around 10 inches now — if they're feeding on the chub as VanDyke hopes they are.

"This year and next year will tell us whether those chinook are surviving and if they can feed on the chub and fathead minnows," VanDyke says. "Then we'll have some answers to some of our questions."

Anglers, too, can help.

VanDyke wants to hear from those catching these chinook to garner angler input on what they look like and even taste like.

And while they're at the cleaning station, anglers could become armchair surgeons by cutting open and examining the chinooks' stomachs to look for signs of chub as grub.

"This would be a great way to add to the diversity of angling opportunities there," VanDyke says.

The chinook experiment is just the latest change in lake management that has occurred in Oregon because some nitwit decided to use chub as trout bait and ended up infecting a waterway.

Newspaper accounts show that tui chub, which are native to Klamath Lake, showed up in Fish Lake in the mid 1940s and over-ran the lake in no time, much as they did at Diamond Lake.

Diamond Lake was poisoned in 1954 to kill off the chub, and that treatment lasted until they reappeared in the early 1990s. Diamond was poisoned again in 2006, then restocked in 2007. It is now the Northwest's best trout-fishing lake.

Fish Lake? Not so much.

"I consider it a mini Diamond Lake, with an unfortunate twist," VanDyke says.

The unfortunate twist is that Fish Lake is loaded with springs, which make it impervious to poisoning with rotenone. ODFW poisoned Fish Lake with rotenone in 1951, but enough chub survived in the springs to repopulate the lake.

Similar efforts in 1966, 1976 and 1985 failed, as well, so rotenone is off the table as a chub solution at Fish Lake.

The invaders have remained populous enough that ODFW quit stocking fingerling trout there in 1997 because they didn't survive. The 8-inch legals stocked there now keep the fishery going, but at a much more expensive rate.

In 2007, the Forest Service began an aggressive netting program that removed close to a million chub through last fall. That netting program will sunset after this year.

The Oregon Fish and Wildlife Commission last year changed the bag limit at Fish Lake to allow spring chinook to be part of the trout limit here.

Even if the chinook take off, they are not a panacea.

There is no expectation that schools of chinook will reverse the chub dilemma, VanDyke says.

"Any benefit for chub removal would be icing on the cake," he says.

Also, these land-locked springers will never grow to the size of the real McCoys now headed upstream in the Rogue.

Though they may live as long as six years, the chub diet doesn't match krill and other ocean foods for packing on the pounds.

"We don't really know how big they're going to get," VanDyke says. "I'd certainly think we'll see some fish getting to be a couple of pounds each."

VanDyke, who is something of a trout bum himself, caught a few undersized ones trolling last year.

And he has a little advice for budding chinook anglers in Fish Lake.

"Trolling is the way to catch chinook in lakes," he says. "Got one on an orange Flatfish."

Reach reporter Mark Freeman at 541-776-4470, or email mfreeman@mailtribune.com.