Biologist Laura Jackson wants all of you happy Diamond Lake trout anglers to do yourself a favor and start keeping more of the fat rainbows you catch up there.

Biologist Laura Jackson wants all of you happy Diamond Lake trout anglers to do yourself a favor and start keeping more of the fat rainbows you catch up there.

After all, the fishery you save might be your own.

Oregon's hottest trout-fishing lake of 2010 has close to a half-million trout under the ice heading into the Saturday, April 23, spring trout opener, and that's simply too many rainbows to keep Jackson comfortable.

The Oregon Department of Fish and Wildlife biologist is in charge of the 5-year-old reclamation of the lake, which was rescued from a tui chub invasion that once ruined the trout fishery and damaged the lake's overall health.

One lake-poisoning and four years of fabulous fishing later, the sheer tonnage of rainbows there is so great it is almost too much. In trout terms, the rainbows might soon start altering the lake the way chubs did in the 1990s.

"The biologist part of me is concerned that having too many holdover fish could alter the (lake's) ecology," Jackson says.

That's why Jackson has scaled back this year's fingerling plant from 315,000 to 200,000, in part to make up for the roughly 76,000 trout that anglers caught — and then released — at Diamond Lake last season.

As crazy as it sounds, that means fishermen need to stop releasing so many trout. You need to do your civic duty and keep a legal stringer of fat trout for your barbecue and smoker every time you visit this lake.

"To me, it's a safer bet for people to harvest these fish," Jackson says. "That would help lessen the fear of having too many fish."

Anglers will start helping ease Jackson's fears April 23, but they will do so in snowshoes instead of boats.

The lake is currently under about 20 inches of semi-slush and another five inches of ice, so opening-day anglers likely will be fishing through the ice.

Diamond Lake Resort will rent out augers and snowshoes, and they'll sell Sno-Cat rides for those wanting access to what little open water is available at the lake's north end and around Short and Silent creeks, says Steve Koch, the resort's general manager.

State law requires that ice-fishing holes be no bigger than 12 inches in diameter. The resort's augers drill 8-inch-wide holes. And that will set up another weird conundrum.

"You have to teach people how to get an 18-inch fish out of an 8-inch hole," Koch says. "You got to really tire them out."

Anglers never seem to tire of the Diamond Lake story, which adds better chapters year after year.

Following the 2006 rotenone treatment and the restocking of the lake, the trout fishery and the lake's ecology have been fantastic. Water quality has been very good, zooplankton and insect levels remain excellent and fish growth rates have been off the charts.

Anglers last year had a catch rate of 3.5 fish per trip. That's more than twice the 1.7 fish per trip in 2008, which had been the best in Diamond Lake's post-chub era.

Creel surveys show anglers caught nearly 205,000 trout last year, keeping 128,000 and releasing more than 76,000.

Jackson says she figures about 20 percent died from hooking and handling. But the rest survived and left the lake so lousy with trout that estimates of up to a half-million fish — with probably none under 11 inches — now cruise beneath the ice.

"We're saying over 400,000 is probably a safer number," Jackson says. "Regardless, that's a huge number of fish."

The state's management plan focuses on keeping a quality fishery and healthy water. That means fish mass of less than 100 pounds per surface acre. More than that could mean too much pressure on zooplankton, which could eventually lead to toxic algae blooms like the ones triggered in the past by chub.

The lake measured out at 100 pounds of trout per acre last fall, Jackson says. Even though water quality is good and the lake's insect load remains high, Diamond Lake did have a toxic algae bloom last year.

"I want to bring that (fish mass) down a little bit more under 100 pounds," she says.

So help her out and turn a few more eyes into X's this year.

It's not that anglers don't like to eat these trout. They are known as great tasting and the cleaning stations buzzed all year with the sound of filleted-out carcasses running through the grinders.

The problem was that anglers didn't catch their limit and leave. They culled their catch, releasing 14- and 16-inch fish while targeting what seemed to be a limitless supply of 18- and 19-inchers that weighed 3 pounds or more.

"That's what anglers told us they were doing," Jackson says.

The limit remains five trout over 8 inches, but only one can be more than 20 inches.

Jackson hopes you get that stringer of beauties and bring them home.

"We should have a tremendous catch rate this year," she says. "Fishing is going to be phenomenal."

Reach reporter Mark Freeman at 541-776-4470, or email