BELGRADE, Minn. (AP) — Dennis Bertram worked the curved blade in an unhurried rhythm, releasing thin curls of redwood. The emerging decoy lost its band-saw edges while old-time country played on the radio.

A self-taught carver and retired heavy equipment operator, Bertram, 62, has never figured how long it takes to finish a decoy.

A half-dozen rest on a workbench among chisels, knives, and patterns cut from Wheaties and Coke boxes. Some decoys are just taking shape, others have galvanized tin fins or wood-burned scales. When he gets tired of one thing, he moves to the next.

“One thing nice about carving, you don’t have to go to the blueprints and see if you’ve got it right or not,” Bertram told the St. Cloud Times.

Bertram has been carving for 35 years and spearing for 40. He tests every decoy in the water to see if he’s got it right. The trickiest part is getting the right amount of lead in the right spot.

He’s given up on some, and then fished them out of the garbage and kept working until, immersed, they’ll cruise slowly around the hole in the ice.

“He’s kind of one of the granddaddies of Minnesota carvers because he’s spent so much time in the fish house. He knows as much about northern pike and their habits as (Babe) Winkelman and (Al) Lindner know about walleye,” said Rod Osvold. “He makes one of the best swimming decoys in the United States.”

Osvold founded the National Fish Decoy Association 18 years ago, initially to support a decoy show in Perham. That endeavor has grown to include a Saturday show in Little Falls, where Bertram will be among 20 fish decoy carvers.

Bertram makes about 100 decoys a year. He brings about 50 to the show. Ninety percent of his customers are fishermen; the rest are collectors. Neither needs to look for the “D.B.” he wood-burns on the bottom of each decoy.

“Everyone knows him as Big-Lips Bertram,” Osvold said.

Each of Bertram’s decoys has an open mouth and giant lips. That includes his most popular, the 11-inch red-and-white; his second-most-popular, the 11-inch perch; and all of the variations, which include a four-headed model designed to tell which color is hot.

The effect can seem cartoonish.

But it works.

“I tell everybody they’re guaranteed. If you don’t get any fish off them, you bring them back, Bertram said.

Osvold said no matter if a decoy goes down a hole in the ice or on a display shelf, it must work.

“The fishermen and the collectors both look for the same thing: It’s got to be a usable, functional, working fish,” Osvold said. “It’s got to work. That’s the key. From there it evolves into art.”

Bertram started carving decoys because the biggest ones available commercially were only 6 or 8 inches long. He figured he could catch bigger fish with bigger decoys. A 22-inch red-and-white was hot on Mille Lacs this year. The largest: a 39-inch red-and-white made to attract sturgeon.

One of his earliest designs, smooth and torpedo-shaped with a flat tail, juts from a top-shelf box in his workshop. The first models, he said, “looked kind of like a bowling pin with some thumb tacks for eyes.”

He’s stuck with redwood, which sometimes turned up as scrap lumber on job sites.

As Bertram’s designs evolved, he set in glass eyes, surrounded by a starburst paint pattern. The tails of the red-and-whites developed a bit of a curve; their grooves are carved, not wood-burned. The tin fins are set into a groove and affixed with glue. The whole decoy gets up to six coats of oil paint — that’s the one step done in batches. A pile of decoys, lead intact, dries as it awaits paint.

Bertram’s decoys are made to withstand strikes.

Some of the results hang on the wall in the small room where he displays his finished work. Others appear in photographs — fish in one hand, decoy in the other.

While some spearers see one 20-to-25-pound northern in their lifetime, Osvold said Bertram has seen hundreds. At the Minnesota Fishing Museum in Little Falls, a 20-minute film condenses six hours of footage — some of what Bertram captured over a six-year span doing what he calls watch-and-release winter fishing.

Working construction gave him winters off. Some years, he’d spear every day of the season, mostly on lakes near Melrose. He carved year-round. It was an escape during the summer, when he’d put in 12-hour days in a backhoe, watching the workers below and the power lines above.

Carving was more of a chore for Bob Halvorson, 75, of New London, who has seven or eight Bertram decoys in his current collection.

Starting at about age 12, he drilled eye holes and did some sanding for his father, who produced a couple thousand a year under the name Cy’s Decoys and sold them to hardware stores. Turned out he had more appreciation than aptitude for carving.

“A lot of these guys make decoys but they do it the easy way. He’s carving them by hand,” Halvorson said. “Dennis isn’t just a craftsman. He’s a spearfisherman, too. He uses what he works with.”

Halvorson uses the Bertram decoys, along with the ones his father made back in the ‘50s and ‘60s. But he tells Bertram all the fish he catches are off his father’s.

When Bertram goes spearing, he takes a dozen decoys into the house and has another dozen in the truck.

“Without a doubt, if I’ve got that gut feeling there’s a fish out there, I don’t play my decoys much but I’ll switch ‘em a lot so I have a lot of decoys in the house all the time. Sometimes, that’s just what it takes, taking one out and putting a different one down,” Bertram said. “I tell everybody red-and-white is definitely the place to start.”

But he’s learned that what works changes from day to day, even on the same lake.

“On the right day, every one is going to work,” Bertram said. “I don’t feel my decoys have changed much over the last 10 years. I still make red-and-whites. They sell. They work, and people are happy with them.”

Dennis Bertram, 62, carves out a fish decoy in his workshop Tuesday, Feb. 24, 2015, in Belgrade, Minn. Bertram has been carving decoys for 35 years and spearing for 40, creating decoys from two inches long to almost 40 inches long. (AP Photo/St. Cloud Times, Jason Wachter) NO SALES

Dennis Bertram, 62, starts to carve a fish decoy in his workshop Tuesday, Feb. 24, 2015, in Belgrade, Minn. “One thing nice about carving, you don’t have to go to the blueprints and see if you’ve got it right or not,” Bertram told the St. Cloud Times. (AP Photo/St. Cloud Times, Jason Wachter) NO SALES