Markings and Coloration The brook trout can be recognized by the wavy lines, or vermiculations, on its dark, olive-green back–the same pattern created when the sun shines through rippled water to cast shadows on the bottom. The result is a camouflage enabling the brook trout to avoid predators from above such as kingfishers and herons. The brook trout also typically has many pale yellow spots and a few small red spots surrounded by blue halos on their sides. They’ve also been described as the only trout with light spots against a dark background, as the brown and rainbow trout have the opposite spotting pattern (dark spots on a paler background). The brook trout’s pectoral, ventral, and anal fins are starkly edged in white, which again is unique among other common trout. The white is the main giveaway. Even when the brook is motionless, the white-edged fins will call your attention to the fish. The highly visible, white-edged fins are a definite disadvantage when it comes to the brook’s predators. Another characteristic is a relatively large head and mouth, and the head may amount to one quarter of the body length on adult fish. During their fall spawning period, the lower flanks of males become brilliant orange and older males may develop a slightly hooked lower jaw. If you are still in doubt after checking all the previous characteristics, feel along the center of the mouth’s roof with your fingertip. The vomerine bone has teeth in a small cluster at its forward end. If you find teeth all along the roof of the mouth, you didn’t catch a “brookie”. Because...