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New rainbow trout chomping on chub at Diamond Lake

Predatory fish draw cheers, interest from area fishermen

There's a new trout in town at Diamond Lake, and the tui chubs that actlike they own the place ought to start watching their dorsal fins.

Newly introduced trout from a strain of Klamath Basin rainbows are ekingout a living among the millions of chubs clogging Diamond Lake ­ inpart because these trout make no bones about eating small chubs.

These predator trout show the most promise for growing big fish for anglersin a lake so overwhelmed by the illegally introduced chubs that other troutgenerally starve or get caught before reaching 12 inches long.

Since first introduced two years ago, the new trout have not just survivedwhere standard rainbow have failed. They've grown from three inches to 18inches or more in those two years, and are quickly becoming known as thenew jewels in Diamond Lake's once outstanding trout fishery.

They're like little assassins, said Jay Carter, a Medfordfishermen who recently visited the Douglas County lake. I've caughta couple and found chubs in their stomachs. You see those chubs in theirbellies, and you feel bad about killing the trout.

Carter shouldn't feel bad at all, says Dave Loomis, an Oregon Departmentof Fish and Wildlife biologist managing the lake.

The predator trout can eat just enough chubs to grow to appreciable size,but not enough to slow the spread of the dastardly chubs.

They don't out-compete (chubs), just compete with them, Loomissays. These fish aren't the answer for solving the chub problem. SoI just tell people, hey, just enjoy them.

Loomis says the only long-term solution for returning Diamond Lake toits old place as Oregon's top trout lake is to chemically treat it to killall the fish ­ chubs and trout ­ then re-stock it with new rainbows.

The ODFW continues to pursue this option, and the agency hopes an EnvironmentalImpact Statement studying the possible effects of chemical treatment canbegin next year.

In the meantime, the predatory trout are making a splash in a lake nowknown more for its millions of chubs than for the thousands of happy fishermenthat once flocked to its high Cascades waters.

Tui chubs are natives of the Klamath Basin and have been illegally introducedinto Diamond Lake since the 1940s by unwitting fishermen who used them asbait.

At first, the chubs caused less of a problem because the original troutfirst stocked in Diamond Lake back in 1910 were chub-eating rainbows broughtin from the Klamath Basin as well.

The Klamath trout held their own for a decade, but the chubs eventuallytook over Diamond. The ODFW chemically treated the lake in 1954 and re-stockedit with rainbows.

In the '60s, the ODFW switched its trout plants from the spring-spawningKlamath trout to a strain of trout that spawns in the fall. These trout,called the Oak Springs strain because their eggs come from theOak Springs Hatchery, proved to grow quickly by dining on Diamond's vastinsect population.

The Oak Springs trout were considered better at that time because, asfall spawners, they were silvery and fleshy to catch in summer. The Klamathtrout, as spring spawners, were often dark and ugly during early summer.

The Oak Springs rainbows, of which 400,000 are planted annually, faredso well in Diamond Lake that it was the most-visited trout lake in Oregonin the '60s and '70s. But tui chubs were found again in the lake in 1992,and the trout fishing has spiraled downward ever since.

The Oak Springs trout tend to feed on insects and not chubs, so theirgrowth rates have crashed now that millions of chubs have nibbled the lake'sonce-abundant insects to very depressed numbers, Loomis says.

Now, the Oak Springs trout are a skinny 9-11 inches long and so starvedthat they are easily caught. Between hooking mortality and anglers keepingtheir limits, the lake is basically fished out of these smalltrout by mid-summer each year, Loomis says.

As a stop-gap, Loomis in 1995 convinced the ODFW to plant 12,000 rainbowfingerlings spawned from wild trout in the Klamath Basin's Williamson River­ a strain known for eating chubs.

The fish have since grown to 16-20 inches long, while the Oak Springstrout either died or grew to just 9-11 inches in the same period. The Williamsontrout have clipped adipose fins, which differentiate them from the Oak Springsfish.

Another 50,000 Williamson rainbow fingerlings were stocked last month,and plans are to stock 50,000 more each of the next two years.

The ODFW is closely monitoring the trout to ensure that they don't strayout of Diamond Lake and into downstream reservoirs and eventually into theNorth Umpqua River, where some fear they might feed on or cross-breed withnative cutthroat trout or steelhead.

So far, Loomis says, no evidence of straying has occurred.

The Williamson trout have been a godsend because they are producing thelarger trout that bring many anglers back to Diamond Lake, says Rick Rockholtof Diamond Lake Resort, whose $4 million business last year was down $750,000­ all attributed to the drop-off in trout fishing.

stocking Oak Springs and Williamson trout, the lake now has a two-tieredfishery ­ a large number of small trout anyone can catch, plus a splatteringof big Williamson rainbows that serious fishermen tend to focus on.

There's a lot of fishermen who would rather catch one, two, orthree Williamson River fish a day than a `limit' (of five trout),Rockholt says. But if you bring your grandkids here, you want actionthat's fast.

And the more people who can enjoy the new predator trout, the better.In fact, anglers who used to rely on PowerBait, cheese balls or tiny fliesare now using lures meant to imitate small chubs.

I've never seen Rapala (lures) being sold here before at DiamondLake, Loomis says. Now they're right up there on the wall withthe Flat Fish and PowerBait.

Rockholt believes the Williamson rainbows are only a short-term answerto growing bigger trout. Left untreated, the lake eventually will boasta chub population that will out-compete even the most shark-like rainbowsand the trout fishery will be history, he says.

If the fishery crashes, Rockholt says, this place willbe a tough sell.