BEMIDJI, Minn. – Every fall, about the time most outdoors enthusiasts across the Northland put away their rods and reels and set their sights on hunting, Steve Young gets serious about fly fishing.

There’s rarely a warning. Not with pike. When a striped bass attacks a topwater fly, you often see a boil or a swirl before the toilet flushes. Snakeheads will track a foam frog and wake the surface ...