They were originally found in abundance in most spring-fed streams of northeastern Iowa, although some fishery investigators believe they were wholly restricted to the Upper Iowa River drainage. Natural reproduction of brook trout is presently limited to two small streams in Jackson and Clayton counties. Future expansion of brook trout populations into other streams will probably be dependent on transplanting fish from existing populations, or more likely, wild brook trout from other states that can be stocked in our streams. The dorsal fin has ten rays and is also strongly mottled. The vomer is trough-shaped, with the teeth restricted to the front portion.
Brook trout feel soft to the touch because of the very small scales that cover the entire body.
About 230 occur along the lateral line, and they are more deeply embedded than other trout in the genus Salmo. Wild brook trout at spawning time are among the most beautiful of all fishes. The sides of the fish often have numerous red and pale yellow spots, with each spot sometimes surrounded by a blue-colored circle. Brook trout spawn from late October to November. Redds or nests are constructed by females in clean gravel areas, often near the headwaters of spring-fed streams.