On a chilly April morning, Gunwoo Yoon, his wife and two sons joined about 100 other anglers at Prairie Lakes in Cedar Falls. They were fishing for trout, and plenty were available as the Iowa Department of National Resources did its annual stocking of the lake. Hundreds of trout gushed from a tank truck through a pipe into the lake. “We moved last year to Cedar Falls, and it was the first time that we went fishing at the trout stocking event,” Yoon, a University of Northern Iowa assistant professor of marketing, said. “It was a super family-oriented fishing event, so we were there.