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Goggle eye

Ambloplites rupestris

What do they look like?

Similar to other sunfish, rock bass have five to seven spines on their anal fin along with nine to eleven soft anal rays. Rock bass also have spines on their much larger dorsal fin, with 10 to 13 spines and 11 to 13 soft dorsal rays. Rock bass have dark spots on each scale aligned in rows around the lateral line, continuing down towards their belly. Starting with their back, rock bass are dark green or brownish, fading to a lighter green, and slowly fading to whitish green or yellow towards their belly. Their fins have a yellowish brown tint, with a black spot on the tip of the gill plate. They are fairly small, averaging about 20 to 25 cm long and very rarely reach one kilogram, although the largest recorded rock bass was 3 kg. Rock bass have large mouths and bright red eyes, which give them the nickname “redeyes.” (Kottelat and Freyhof, 2007; Page and Burr, 1991)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    3 (high) kg
    6.61 (high) lb
  • Average length
    20 to 25 cm

Where do they live?

Rock bass (Ambloplites rupestris) are found throughout North America. They are native to the North Atlantic region of the United States and the St. Lawrence, Great Lakes, Hudson Bay, and Mississippi River drainages, as well as northern to southern Georgia and northern Alabama and Missouri. Rock bass thrive in areas of the east-central part of the United States. Although they are native to these areas, many introductions have been made. From 1889 to 1936, the United States Fish Commission introduced rock bass to Atlantic drainages and some western states. Rock bass were introduced to areas of the Atlantic drainages, from New Hampshire, south to the Roanoke River in Virginia and North Carolina. As for the western states, rock bass have made it to states such as California, Washington, Colorado, and even Wyoming. Rock bass have also been introduced in other regions. In Europe, rock bass were introduced in countries such as England and France in the 1880’s. (Kottelat and Freyhof, 2007; Page and Burr, 1991)

What kind of habitat do they need?

Rock bass are found in freshwater areas in rivers, streams, lakes, and ponds. These areas often have many aquatic plants to help them hide from predators. They thrive in areas with temperatures ranging from 10 to 29 degrees Celsius. Rock bass are most commonly found in rocky or sandy areas with clear water. Rock bass introduced to Europe have similar habitats, but avoid areas of fast moving water. (Kottelat and Freyhof, 2007; Page and Burr, 1991)

  • These animals are found in the following types of habitat
  • freshwater
  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • Range depth
    1.2 (low) m
    3.94 (low) ft

How do they grow?

Three to four days after spawning, the eggs begin to hatch. At hatching, rock bass larvae are about 5.5 mm. By about 6.9 mm, the larvae begin to develop caudal fin rays, and dorsal, anal, and pectoral fin rays at about 8.6 mm in length. Finally, pelvic fin rays begin to develop at about 13.5 mm in length. By the first year, young rock bass grow to about 5 cm in length, reaching 10 cm by year two, and up to 18 cm by year three. (Buynak and Mohr Jr, 1979)

How do they reproduce?

Both females and males have multiple mates during the breeding season. Rock bass spawn in the spring, but they sometimes spawn again in the early summer with another mate. When attracting a mate, male rock bass find an area and build a nest. Circling inside the new nest, the male awaits a mate. Without courtship displays, the female enters the nest and joins the male in his circular behavior. Both the female and male release their sperm and eggs into the nest. After releasing eggs, the female's role is over and she is able to leave the nest and mate with another male, but she sometimes stays near the exit of the nest. Male rock bass guard and protect the nest using circling behavior until the eggs hatch. (Buynak and Mohr Jr, 1979; Gross and Nowell, 1980)

Similar to the spawning cycle of smallmouth bass, rock bass spawn in shallow water areas. The spawning cycle of rock bass occurs in the spring and into the summer months of June, as the water temperature reaches between 13 to 15 degrees Celsius. Rock bass are ready to breed at about 2 to 3 years of age. Male rock bass prepare the nest for spawning. Their nests are circular bowl-shaped depressions, approximately 20 to 30 cm in diameter. Using their tail, male rock bass are able to clear areas of debris to produce their nest. Without male courtship, females enter the newly-made nest and spawn, releasing approximately 500 to 5,000 eggs depending on the female's size. After the eggs are fertilized, they are guarded by male rock bass inside the nest. While guarding the eggs, males become a darker color and continue their circling behavior, which helps protect the eggs from predators. The eggs begin to hatch 3 to 4 days after spawning and the young leave the nest about 9 to 10 days after hatching. Approximately 33% of rock bass nests are unsuccessful due to predation. (Gross and Nowell, 1980)

  • How often does reproduction occur?
    Rock bass reproduce in the spring but it is not uncommon for rock bass to spawn a second time in the early summer.
  • Breeding season
    Rock bass spawn in the spring and summer.
  • Range number of offspring
    500 to 5000
  • Range time to hatching
    3 to 4 days
  • Average time to independence
    9 to 10 days
  • Range age at sexual or reproductive maturity (female)
    2 to 3 years
  • Range age at sexual or reproductive maturity (male)
    2 to 3 years

Male rock bass care for the eggs by fanning the nest with their pectoral fins and guarding and protecting the nest by using circling behaviors after spawning with the female. These behaviors continue for several days, protecting the offspring from predators. After females lay eggs in the nest, their parental effort is complete. (Buynak and Mohr Jr, 1979; Gross and Nowell, 1980)

  • Parental Investment
  • male parental care
  • female parental care
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • male
    • protecting
      • male
  • pre-independence
    • provisioning
      • male
    • protecting
      • male

How long do they live?

Rock bass have an average lifespan of about 5 to 8 years in the wild. This average is obviously influenced by the level of predation and food supply in the environment. It has been reported that the maximum lifespan of a rock bass in captivity was 18 years. (Patnaik et al., 1994)

How do they behave?

During spawning, male rock bass do not eat. Male rock bass guard the nest of the newly spawned eggs. This nest becomes their home range, spanning between 20 and 30 cm in diameter. To protect the nest from predators, they perform circling behaviors. Males are very aggressive during spawning season. When faced with an intruder, they race towards it with spread gill flaps or display an open mouth. In the winter months, rock bass can be found in schools and slowly go their separate ways as spring approaches for spawning activity. (Gross and Nowell, 1980)

  • Range territory size
    20 to 30 cm^2

Home Range

Besides the nest territory that males defend, no other home ranges have been reported. (Gross and Nowell, 1980)

How do they communicate with each other?

Fish use chemical signals to communicate and perceive their environment. Such chemical signals are used for locating prey, identifying opposite sexes, identifying other species, identifying predation threats and how to avoid them, recognizing their young, signaling for migration, and even identifying where they are in their habitat. Rock bass also use their sense of touch by using their large, bass-like mouths. These fish also use their large eyes, or “goggle eyes,” which is another one of their common nicknames. (Ross, 2013)

What do they eat?

Rock bass have a varied diet which includes the plants found in their habitat. Rock bass also prey on small crustaceans like crayfish, insects such as small larvae, and smaller fish, including smaller individuals of their own species. (Kottelat and Freyhof, 2007; Page and Burr, 1991)

  • Animal Foods
  • insects
  • aquatic crustaceans

What eats them and how do they avoid being eaten?

Predators of rock bass include of other, larger adult rock bass, northern pike, muskies, walleyes, largemouth bass, and even humans. These predators prey on adult and young rock bass. To avoid these predators, rock bass depend on their coloration, which helps them stay camouflaged in their environment. (Angermeirer, 1992)

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

Rock bass feed on insects, aquatic crustaceans, and smaller fish. As a result, they help keep the population sizes of their prey in check. Rock bass may also host parasites including anchorworms, which embed into the skin of the fish and damage and shorten the lifespan of rock bass. (Causey, 1957; Kottelat and Freyhof, 2007; Page and Burr, 1991)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host

Do they cause problems?

Environmental impacts may result from sport fishing for rock bass and other species. For example, pollution from boats, such as oil and gas leaks, as well as littering by sportsman can be expensive due to efforts to clean up after them. (Dayton, et al., 1995)

How do they interact with us?

Rock bass, along with other bass species, such as smallmouth bass, largemouth bass, and spotted bass, are all sport fish. With tournaments and even recreational events, bass fishing has become a multi-billion dollar industry. For example, 33 million people of age 16 and older engage in the activity of fishing and spend 48 billion dollars a year to do so. These sportsmen spend this money on fishing guides and services, equipment, apparel, licenses, restaurants, gas, boats, and more. Fishing also supports 828,000 jobs in the United States; many of these jobs involve fishing for species such as rock bass. (Schramm Jr., et al., 1991)

Are they endangered?

Introduced into many drainages in the United States, rock bass have flourished in their environments. Rock bass are successfully surviving in their environments and are listed as a species of "least concern" on the IUCN red list. Rock bass do not require any special monitoring or conservation management plans because of their population stability. However, as a sport fish, they are managed to some extent. (NatureServe, 2013)


Brendan Schnell (author), Radford University, Karen Powers (editor), Radford University, Leila Siciliano Martina (editor), Animal Diversity Web Staff.


Angermeirer, P. 1992. Predation by rock bass on other stream fishes: experimental effects of depth and cover. Environmental Biology of Fishes, 34/2: 171-180.

Beckman, W. 1943. Further studies on the increased growth rate of the rock bass Ambloplites rupestris (Rafinesque), following the reduction in density of the population. Transactions of the American Fisheries Society, 72/1: 72-78.

Beckman, W. 1941. Increased growth rate of rock bass, Ambloplites rupestris (Rafinesque), following reduction in the density of the population. Transactions of the American Fisheries Society, 70/1: 146-148.

Bergman, R. 1942. Fresh Water Bass. New York: Penn Publishing Corp.

Bowers, G. 1903. U.S. Fish Manual. Washington D.C.: Government Printing Office.

Buynak, G., H. Mohr Jr. 1979. Larval development of rock bass from the Susquehanna River. The Progressive Fish Culturist, 41/1: 39-42.

Carlander, K., R. Cleary. 1949. The daily activity patterns of some freshwater fishes. American Midland Naturalist, 41/2: 447-452.

Causey, D. 1957. Parasitic Copepoda from Louisiana fresh water fish. American Midland Naturalist, 58/2: 378-382.

Dayton, P., S. Thrush, T. Agardy, R. Hofman. 1995. Environmental effects of marine fishing. Aquatic Conservation: Marine and Freshwater Ecosystems, 5/3: 205-232.

George, E., W. Hadley. 1979. Food and habitat partitioning between rock bass (Ambloplites rupestris) and smallmouth bass (Micropterus dolomieu) young of the year. Transactions of the American Fisheries Society, 108/3: 253-261.

Gerber, G., J. Haynes. 1988. Movements and behavior of smallmouth bass, Micropterus dolomieu, and rock bass, Ambloplites rupestris, in southcentral Lake Ontario and two tributaries. Journal of Freshwater Ecology, 4/4: 425-440.

Gross, M., W. Nowell. 1980. The reproductive biology of rock bass, Ambloplites rupestris (Centrarchidae), in Lake Opinicon, Ontario. Copeia, 1980/3: 482-494.

Kottelat, M., J. Freyhof. 2007. Handbook of European Freshwater Fishes. Switzerland: Kottelat, Cornol.

NatureServe, 2013. "Ambloplites rupestris" (On-line). The IUCN Red List of Threatened Species. Accessed April 03, 2014 at

Near, T., J. Koppelman. 2009. Centrarchid Fishes: Diversity, Biology and Conservation. United Kingdom: Blackwell Publishing.

Noltie, D., M. Keenleyside. 1986. Correlates of reproductive success in stream-dwelling male rock bass, Ambloplites rupestris (Centrarchidae). Environmental Biology of Fishes, 17/1: 61-70.

Page, L., B. Burr. 1991. A Field Guide to Freshwater Fishes of North America North of Mexico. Boston, MA: Houghton Mifflin Company.

Patnaik et al., 1994. Ageing in fishes. Gerontology, 40: 113-132.

Petrimoulx, H. 1983. The life history and distribution of the Roanoke bass Ambloplites cavifrons cope, in Virginia. American Midland Naturalist, 110/2: 338-353.

Probst, W., C. Rabeni, W. Covington, R. Marteney. 1984. Resource use by stream-dwelling rock bass and smallmouth bass. Transactions of the American Fisheries Society, 113/3: 283-294.

Roe, K., R. Mayden, P. Harris. 2008. Systematics and zoogeography of the rock basses (Centrarchidae: Ambloplites). Copeia, 2008/4: 858-867.

Ross, S. 2013. Ecology of North American Freshwater Fishes. California: The Regents of the University of California.

Sabat, A. 1994. Costs and benefits of parental effort in a brood-guarding fish (Ambloplites rupestris, Centrarchidae). Behavioral Ecology, 5/2: 195-201.

Schramm Jr., H., M. Armstrong, N. Funicelli, D. Green, D. Lee, R. Manns Jr., B. Taubert, S. Waters. 1991. The status of competitive sport fishing in North America. Fisheries, 16/3: 4-12.

University of Michigan Museum of ZoologyNational Science Foundation

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Schnell, B. 2014. "Ambloplites rupestris" (On-line), Animal Diversity Web. Accessed March 02, 2024 at

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