The bull trout
, technically not a true trout but a char, chills in some of North America's coldest freshwater bodies. Classified as vulnerable by IUCN, the these Rocky Mountain and U.S. Pacific Northwest residents require even summer water temperatures to remain below 58 degrees Fahrenheit (14.5 Celsius). And because some migrate from lakes back into smaller streams to spawn, bulls also need large, interconnected, unobstructed waterways.
Climate change and shifting snowfall patterns may make many U.S. western waters lower, slower, and warmer--meaning far fewer places where the beleaguered bull can survive.
Because the bull trout likes its water not just cold but very clean, the fish serves as a canary in a coalmine for overall watershed health, so the fish's current troubles have many conservationists concerned.
Photograph by Guido Rahr III, AP