The brook trout (Salvelinus fontinalis) is an iconic species among fly anglers and cold-water conservationists in eastern North America. This fish registers as a powerful symbol for its beauty and its imagery in art and literature. Its presence also tells us a great deal about the health of the larger environment. When an angler has a brook trout in hand, there is confidence that the water is close to pristine. Besides being an important indicator species, the brook trout, with its gold and reddish markings and its camouflaged green and black back, is one of the most beautiful freshwater fish...