PONCA CITY, Okla. (AP) — The light bulb came on for Keith Lawrence several years ago during a fishing trip to Canada with his father for walleye and pike.

Lawrence had bought a local coil-spring tool to hold open the mouth of a fish while removing fishing hooks, a handy gadget when dealing with toothy fish.

But the fish-mouth spreader didn't work very well. The coil spring tool either provided too much pressure for small fish or not enough for big fish.

"It was ineffective," Lawrence said. "I thought there has got to be a better way to do this."

The Ponca City real estate agent then came back...