A black bear in Alaska just offered the kind of wildlife scene most people expect from a nature documentary: walking away with an enormous king salmon as if the outcome had never been in doubt. What happened? At Alaska's Herring Cove, an amateur photographer filmed a black bear carrying off a king salmon that, according to Whiskey Riff, locals estimated at nearly 40 pounds. Cindy and I stopped at Herring Cove in Ketchikan, Alaska Thursday and wi…