Spiny and soft parts of the dorsal fin are broadly connected with only a shallow notch between the lobes. Body color is golden green on the sides and back with faint wavy olive blotches evenly spaced along the sides. There are five olive green bars radiating backward from the eye, and one forward to the end of the snout. The tail fin in young smallmouth is distinctly tri-colored with a black vertical bar separating the yellowish fin base. Pyloric caeca are not forked in contrast to forked pyloric caeca in the closely related largemouth bass.
Smallmouth bass are omnivorous in the food items that they consume.
In the larger cool, clear interior streams of northeast Iowa smallmouth bass is the dominant predator, feeding mostly on fish, crustaceans and larger aquatic and terrestrial insects. Food habit studies have revealed that forage fish were present in 40 percent of the stomach samples, crayfish in 30 percent and insects in 20 percent. Where crayfish are abundant, they frequently comprise over two-thirds of the food. Newly hatched smallmouth consume copepods and cladocerans but begin to forage on insects when about one-half inch long. Smallmouth bass spawn in Iowa during the early part of May as water temperatures exceed 60' F. Preparatory to the spawning ritual, parent spawners move up larger streams, eventually reaching small tributaries where the actual spawning occurs.