When aggravated by a predator, they, you know, puff up. Some puffers, like the porcupine fish, become a bona fide spike ball, moving through the water seemingly out of control. But if you peer ...

These rare, pint-sized fish are just two of many river-dependent species disappearing where they once flourished, left behind to wade and wander through only occasional pockets of undisturbed habitat.