Courtesy Tom BanyasDave Whitworth, of Pocatello, Idaho, shows off a large rainbow trout he caught at Mackay Reservoir, which is known for small trout and kokanee.

Dave Whitworth’s goal Nov. 24 was to coax some small fish to take a dry fly.

It ended with a monster trout on the most unlikely of waters.

“I told my son the next day that I can go ahead and die now,” Whitworth said Monday. “I caught the fish of a lifetime, and I know I am never going to catch a bigger trout. It is time to die.”

Whitworth laughs about that quote, but he knows that his late November fishing trip will be forever etched into his memory. “It was really a surprise,” he said.

Whitworth’s day started like most of his weekend days: in the cab of a truck with longtime friend Tom Banyas. The pair fishes together more than 75 days a year and on that cold November Sunday they were looking for late-season, dry-fly action.

They picked the Big Lost River where it dumps into Mackay Reservoir. It is known to most as a place to catch small trout during the summer and kokanee in the winter.

But to Banyas and Whitworth it is a gem, especially when the reservoir is low like it is this year.

“There is a good baetis hatch in the spring and fall,” Whitworth said. “We were hoping we could get in on that, but that doesn’t always happen.”

The sky was clear and the weather was cold and the baetis weren’t popping. They went to their backup plan: fishing midge pupas below strike indicators.

The fishing was poor until they hit the spot where the river’s current starts to die in the reservoir’s pool.

“We just started popping fish back and fourth. Every cast,” Whitworth said. “Those fish were just stacked in there. I know there was one time where Tom caught 15 fish on 15 casts.”

That is a great day.

And it only got better.

“Dave’s strike indicator went down like it was a steelhead,” Banyas said. “That fish came up on it fast and hard. If Dave would have blinked, he would have missed it.”

It was immediately apparent it wasn’t an average fish.

“The fish was too big to jump,” Banyas said. “He raced away from us and we knew it was a big fish.”

After a brief fight, Whitworth laid his hands on the monster rainbow that conservatively measured 34 inches and 14 to 18 pounds.

Why the estimates?

Whitworth didn’t want to lay it on the ground for a measurement and they didn’t have a scale. They snapped a handful of pictures.

“I told Dave that I didn’t think there was a run of steelhead in the Big Lost,” Banyas said. “That is the biggest trout I have ever seen caught and the biggest fish Dave has ever caught.”

Dan Garren, the Idaho Department of Fish and Game’s regional fisheries manager in the Upper Snake Region, was “flabbergasted” by the photo of the toad.

“That is not what we expect to see out of Mackay,” he said. “It’s a total surprise.”

Garren said the fish may have grown large in the river, which is fed by some springs upstream of the reservoir.

Whitworth landed the fish on a No. 14 scud hook, 6-pound test and a 6-weight rod.

And then he released it.

“People said I should have got it mounted,” Whitworth said. “Maybe. But I don’t eat ’em; I release ’em. The neat part of the story is that fish is still swimming in there.”

Banyas said the monster taught him a lesson.

“I would have never ever ever ever thought that we would catch that big of fish there. That leads me to believe there are big fish everywhere,” he said.

Whitworth agrees and said despite his claim that he could die a happy man, he will be out in the coming days looking for a bigger pig.