The appearance of adult brook trout in fresh waters varies from place to place and with age and sex of the fish, but is usually distinct from all of its relatives. The back is green to dark brown or nearly black. The sides are green to brown with pale spots and small, distinct, red spots surrounded by bluish halos. The belly can be white to yellow in females or deep orange to red in males. The front edges of the lower fins are black with white borders.
Colors become more pronounced as spawning time approaches.
Brook trout that go to sea become silvery and lose much of their distinctive marking, but the white leading edges of the lower fins and the red spots on the sides are often visible. Upon returning from the sea, they revert to their usual appearance in fresh waters. Brook trout flesh ranges from white to orange, pink, and red, depending on the diet and physical condition of the fish. Brook trout spawn in the fall, usually from September to November, in shallow, gravel-bottomed streams and, occasionally, in lakes. The female digs and cleans a shallow nest or read in the gravel and covers her 3 to 5 mm diameter eggs after they have been shed and fertilized.