The rock bass has a very deep, laterally compressed body. Its distinguishing features are a red to orange eye and 5 to 7 spines in the anal fin. Less colorful than the pumpkinseed and bluegill, rock bass are golden brown to olive with silvery white undersides. They are capable of changing rapidly to silver or blackish. It is carnivorous, and its diet consists of smaller fish, insects, and crustaceans. Adults feed most heavily in the evening and morning. They are affiliated with the sunfish family.
When water temperatures reach 60-70 degrees in the spring, rock bass move to very shallow areas to spawn. Males build circular nests females will approach only when ready to spawn, the male watching closely until eggs are deposited, fertilizing them as soon as they are extruded. Though females immediately leave the nest, males remain to guard the eggs.
The rock bass prefers clear, rocky, and vegetated stream pools and lake margins. They can often be seen in groups near other sunfishes such as smallmouth bass and pumpkinseeds. During the winter, rock bass move to deeper water, where they enter a condition of semi-hibernation.
Rock bass are native to the St Lawrence River and Great Lakes system, the upper and middle Mississippi River basin in North America from Québec to Saskatchewan in the north down to Missouri and Arkansas, and throughout the eastern U.S. from New York through Kentucky and Tennessee to the northern portions of Alabama and Georgia and Florida in the south.