Rock bass are native to the Great Lakes region, the Mississippi Valley, and certain streams on the east side of the Alleghany Mountains. They were imported into Germany and other European countries in 1883.

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Throughout most of the northeastern U.S. and adjacent southern Canada; south to Missouri, northern Alabama, and northern Georgia, west to Saskatchewan and eastern Dakotas. Introduced in many places on Atlantic slope south to Roanoke River, Virginia, and west of native range in Missouri, Arkansas, northeastern Oklahoma, southeastern Kansas, and some western states (Lee et al. 1980, Page and Burr 1991).

Adult rock-bass usually weigh between 1/2 and 3/4 pounds, occasionally reaching 1 pound, and they have been recorded to weigh 3 pounds. The young grow slowly, averaging 2 inches in length during the first six months. Their dorsal fin is much larger than the anal, with 11 spines and 10 rays; the anal fin has 6 spines and 10 rays. Adults are olive-green on the top, greenish-silvery on the sides and white on the belly. Young are often blotched with black, while adults have a dark spot at the base of each scale, forming stripes. (Bowers, 1903).

Range mass: 0 to 1300 g.

Average mass: 0 g.

Length: 22 cm

Rock bass occupy large lakes, reservoirs, and ponds in the midwest and Mississippi Valley, and they are also found in streams east of the Alleghany Mountains. Rock bass, in the winter months, can be found under ice, yet they can stand a summer temperature as high as 88 degrees F. Though sometimes found in muddy bayous and in waters with decaying vegetation, rock bass thrive best in clear, pure waters well stocked with aquatic plants and small crustacea. (Bowers, 1903).

Aquatic Biomes: lakes and ponds; rivers and streams

Habitat Type: Freshwater

Comments: Most common in clear, silt-free rocky streams (Page and Burr 1991). Prefers small, cool, weedy lakes or littoral regions of larger lakes, and streams with typically rocky, always silt-free substrates, permanent flow, low turbidity, and extensive cover (Lee et al. 1980). Mostly inactive in deeper water in winter. Spawns in shallow water in shallow depression made by male in areas as diverse as swamps and gravel shoals; nests may be close together (Scott and Crossman 1973).

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

The main source of food of this species is aquatic plants. They also feed on small crayfish, minnows, tadpoles, worms, and insects. The food of the young consists of minute animals, mainly crustacea and insects, and also vegetation. Some rock bass become cannibalistic in early life, with the larger eating the smaller. (Bergman, 1942).

Comments: Major foods are crayfish, aquatic and terrestrial insects, and fishes (Manooch 1984). Young eat cladocerans, chironomid and neuropteran larvae, and terrestrial insects. Adults take aquatic insects, crustaceans, mollusks, and small fishes (Sublette et al. 1990).

Adults often aggregate.

Average lifespan

Status: captivity: 7.0 years.

Average lifespan

Status: captivity: 12.0 years.

Average lifespan

Status: wild: 18.0 years.

Spawning occurs in spring and early summer, requiring a temperature above 10 degrees celsius. Males make nests in the sand or gravel at a depth of about 1.8 meters. The male cleans the gravel with his caudal fin and tail until every particle is bright. The nest is usually 30 cm in diameter. In the act of spawning, the male and female cross the nest, their stomachs close together, the male a little behind the female, and simultaneously void the eggs and eject the milt. The real act of spawning takes a minute or less. After the female lays the eggs, the male guards the nest. The female may lay 2000 to 10,000 eggs depending on her size. The hatching period takes from one to three weeks. Upon emerging, the young rise in a school and hover over the nest for several days before scattering. The male continues to guard the young during this period. They become sexually mature between 3 and 5 years of age. (Bowers, 1903; Bergman, 1942).

Spawns in late spring and early summer; eggs hatch in 3-4 days at 20-21 C; sexually mature at age II-IV (Becker 1983, Scott and Crossman 1973).

There are 9 genera and 30 species in the bass and sunfish family. Rock bass are one of the most abundant fish in the United States. Their adaptability to extreme temperatures has made their introduction to new areas easier than most other fishes. They have been successfully introduced into the western states of California, Washington and Utah. They have also been transplanted into England, France, Germany, and Finland. The artificial breeding of rock bass, by taking and impregnating the eggs, has not been successful. The eggs can only be stripped with great difficulty, and it is necessary to kill the male to obtain the milt. Also, obtaining the eggs and milt at the same time is difficult. Interruption or handling, even during spawning, prevents the discharge of eggs or milt. Artificial ponds for bass are very common in the midwest and southern states. The water must be at least 6-10 feet deep. (Bowers, 1903).

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

All bass are fine game fishes, with tournaments being held regularly. Because there are so many bass fisherman their abundance is vital. The indirect value of bass fishing in rural districts, in the expenses of visiting sportsman is immense. Bass fisherman spend billions of dollars each year on guides, accommodations, gas, outdoor clothing, meals, tackle, bait, boats, motors, and permits. Their contribution to the economy is more than sportsmen spend on football and baseball combined. It is estimated that 85 percent of licensed anglers fish for bass. (Bauer, 1955)

Comments: Ambloplites cavifrons and A. ariommus formerly were included in this species.

Roe et al. (2008) noted that morphological, mitochondrial, and allozyme characters do not allow discrimination between A. rupestris and A. ariommus within the Interior Highlands; this may indicate that A. ariommus never occurred west of the Mississippi River, or it could indicate that if A. ariommus occurred in these drainages, it has now become introgressed with A. rupestris (Roe et al. 2008).