To find and catch river-dwelling fish, you need to think like one. Here’s how

Why is the fish doing that? I wondered. One early piece of fly-fishing advice that stuck with me was to observe moving water before plunging into it. On this summer morning, I was watching a trout near a boulder rise every few minutes. The confusing part was that it was clearly upstream of the boulder—not behind it, where I’d always been told to cast. At that point, I’d spent much more time…