If you go to Yosemite National Park to catch trout in high-elevation lakes this year, you might want to ask a ranger if the fish are still there before you start climbing. Brook, rainbow, and brown trout there prey on rare yellow-legged frogs, and in order to save the imperiled amphibians, the park has proposed removing them from a dozen such lakes. If, on the other hand, the ranger says the trout are still around, you might want to bring along a green-and-yellow popper.