The rock bass is actually a member of the sunfish family and is not a true bass. Rock bass are fun to catch because they can be caught on many types of baits and lures, and they put up a decent fight on ultralight tackle. Rock bass are known to overpopulate small lakes, making population control measures necessary.
IdentificationAlthough it looks like a cross between a bluegill and a black bass, the rock bass is actually a large and robust sunfish with a deep body; it is less compressed than most sunﬁsh and is more similar to a black bass in shape. The back is raised, and the large head is narrow, rounded, and deep.
The mouth of the rock bass is large in comparison to other sunﬁsh; the upper jaw reaches beyond the beginning of the eye but not to the back of the eye. It has two connected dorsal fins, five to six anal ﬁn spines, and large eyes.
The rock bass is olive brown or bronze on the back and sides, with faint lines of tiny dark marks; the centers of the scales below the lateral line also have dark markings that form 11 or more rows and give the ﬁsh a striped appearance. In some rock bass, the coloring is lighter but consistent underneath, whereas others are silver, gray, or white on the bellies.
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Rock bass are frequently confused with the warmouth (Lepomis gulosus; see: warmouth). Warmouth have teeth on their tongue, whereas rock bass do not. There are also six spines in front of the anal ﬁn of a rock bass, as opposed to the three spines in the warmouth. Rock bass may resemble the mud sunﬁsh as well (see: Sunﬁsh, Mud); rock bass have forked tails and rough scales, whereas mud sunﬁsh have rounded tails and smooth scales.
Size/AgeThe most common size for rock bass is about 8 ounces, although they have been known to reach 3 pounds. Often, rock bass in a particular lake will weigh around a pound, with a few ﬁsh exceeding 2 pounds. As with most sunfish, however, size is extremely variable, and rock bass living in streams are often stunted. The all-tackle record is a 3-pound Canadian fish.
Rock bass can reach a length of 12 to 14 inches but are usually less than 8 inches long. Although aquarium fish have lived for 18 years, those in the wild live 10 to 12 years on average.
Life history/BehaviorRock bass are able to reproduce once they are 2 years old or 3 to 5 inches long; spawning occurs from midspring to early summer, when water temperatures range from 60° to 70°F. Males move into the shallows 3 to 4 days prior to the females’ arrival, to establish territories. They begin building round nests in gravelly or sandy areas near weedbeds or other protection, such as submerged tree trunks, using their pectoral, anal, and caudal ﬁns to fan the gravel for the nests.
Spawning occurs during the day, usually in the morning. The females spawn at least twice, moving from nest to nest and laying from 3,000 to 11,000 eggs in total. The males guard the nests until the eggs hatch and the young swim away, and many males nest a second or even a third time.
Rock bass are a schooling fish and often cluster with other sunﬁsh and smallmouth bass.