Animal Diversity Web

Ge­o­graphic Range

Rock bass (Am­blo­plites ru­pestris) are dis­trib­uted 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)

• Biogeographic Regions
• nearctic
  • introduced
  • native

Habi­tat

Rock bass are found in­hab­it­ing aquatic bio­mes such as rivers, streams, lakes, and ponds. These aquatic bio­mes are fresh­wa­ter, often heav­ily veg­e­tated to pro­vide cover from preda­tors. These fish also thrive in bio­mes with tem­per­a­tures rang­ing from 10 to 29 de­grees Cel­sius. Rock bass are most com­monly dis­trib­uted in re­gions that sup­ply a habi­tat of rocky or sandy char­ac­ter­is­tics in clear water. In re­gions where rock bass are in­tro­duced such as Eu­rope, ecol­o­gists have found their habi­tats to be slightly dif­fer­ent from North Amer­i­can res­i­dents. Rock bass dis­trib­uted in Eu­rope pre­fer sim­i­lar habi­tats, but avoid areas of fast mov­ing water. (Kot­te­lat and Frey­hof, 2007; Page and Burr, 1991)

• Habitat Regions
• freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Range depth

  1.2 (low) m

  3.94 (low) ft

Phys­i­cal De­scrip­tion

Rock bass are part of genus Am­blo­plites, mean­ing “blunt shield,” and the species name ru­pestris refers to their pref­er­ence for being “among the rocks.” Sim­i­lar to other sun­fish, rock bass can be dis­tin­guished by the five to seven spines lo­cated on the anal fin along with nine to eleven soft anal rays. Rock bass also have spines lo­cated on their much larger dor­sal fin, with 10 to 13 spines and 11 to 13 soft dor­sal rays. Rock bass have dis­tin­guish­able dark spots on each scale that are aligned in rows around the lat­eral line, con­tin­u­ing down to­wards the ven­tral side. 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 ven­tral side. Their fins have a yel­low­ish brown tint, with a black spot on the tip of the gill plate. They are rel­a­tively 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)

• Other Physical Features
• ectothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes alike

• Range mass

  3 (high) kg

  6.61 (high) lb

• Average length

  20 to 25 cm

  in

De­vel­op­ment

Three to four days after spawn­ing, the eggs begin to hatch. At hatch­ing, the mean length of rock bass lar­vae is about 5.5 mm. As the lar­vae grow, melanophores (con­nec­tive-tis­sue cells con­tain­ing melanin, which gives them their color) also begin to de­velop at about 6.8 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. As the mat­u­ra­tion cycle of the lar­vae con­tin­ues, 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)

Re­pro­duc­tion

Rock bass are polyg­y­nan­drous, in which both fe­males and males have mul­ti­ple mates dur­ing the breed­ing sea­son. Rock bass spawn in the spring and, in some cases, spawn again in the early sum­mer with an­other mate. When at­tract­ing a mate, male rock bass find a suit­able area and build a nest. Cir­cling in­side the newly pre­pared 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 si­mul­ta­ne­ously re­lease their sperm and eggs into the nest. The fe­male's role in spawn­ing is over after they re­lease eggs and they are able to leave the nest and mate with an­other male, al­though they some­times choose to re­main near the ex­te­rior of the nest. Male rock bass guard and pro­tect the nest using cir­cling be­hav­iors until the fry hatch. (Buy­nak and Mohr Jr, 1979; Gross and Now­ell, 1980)

• Mating System
• polygynandrous (promiscuous)

Sim­i­lar to the spawn­ing cycle of small­mouth bass, rock bass spawn in areas of shal­low water. 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 reach sex­ual ma­tu­rity 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 fer­til­iza­tion by the male, the newly spawned eggs are guarded by male rock bass in the in­te­rior of the nest, which con­sists of a 20 to 30 cm area. While guard­ing the eggs, males turn darker in 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 fry leave the nest ap­prox­i­mately 9 to 10 days after hatch­ing. Ap­prox­i­mately 33% of rock bass nests are un­suc­cess­ful due to pre­da­tion. (Gross and Now­ell, 1980)

• Key Reproductive Features
• seasonal breeding
• sexual
• fertilization
  • external
• oviparous

• Breeding interval

  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 show parental care 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 in hopes of reach­ing a goal of max­i­mum fit­ness. 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

Lifes­pan/Longevity

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)

• Range lifespan
  Status: captivity

  18 (high) years

• Average lifespan
  Status: wild

  5 to 8 years

• Average lifespan
  Status: captivity

  7.0 years

  Max Planck Institute for Demographic Research

• Average lifespan
  Status: captivity

  12.0 years

  Max Planck Institute for Demographic Research

• Average lifespan
  Status: wild

  18.0 years

  Max Planck Institute for Demographic Research

Be­hav­ior

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 a ter­ri­to­r­ial in­truder, they race to­wards it with spread op­er­cles 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)

• Key Behaviors
• natatorial
• motile
• territorial
• social

• 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)

Com­mu­ni­ca­tion and Per­cep­tion

Fish use chem­i­cal sig­nals to com­mu­ni­cate and per­ceive their en­vi­ron­ment. Rock bass use chemore­cep­tion for a num­ber of com­mu­ni­ca­tion and per­cep­tion tasks. These tasks con­sist of lo­cat­ing prey, iden­ti­fy­ing op­po­site sexes, iden­ti­fy­ing other species, iden­ti­fy­ing pre­da­tion threats and how to avoid these preda­tors, dif­fer­en­ti­at­ing be­tween their young, sig­nal­ing for mi­gra­tion from oth­ers, and even iden­ti­fy­ing where they are in com­par­i­son to their habi­tat. Rock bass use tac­tile char­ac­ter­is­tics or the sense of touch with body parts such as their large, bass-like mouth and even vi­sual char­ac­ter­is­tics such as their big eyes or “gog­gle eyes,” which is an­other com­mon nick­name of rock bass. (Ross, 2013)

• Communication Channels
• visual
• tactile
• chemical

• Perception Channels
• visual
• tactile
• chemical

Food Habits

Rock bass prey on var­i­ous aquatic species such as plants lo­cated around their highly veg­e­tated habi­tat. Rock bass also prey on small crus­taceans like cray­fish, in­sects such as small lar­vae, and smaller fish, in­clud­ing those of their own species. (Kot­te­lat and Frey­hof, 2007; Page and Burr, 1991)

• Primary Diet
• carnivore
  • eats non-insect arthropods
• omnivore

• Animal Foods
• insects
• aquatic crustaceans

Pre­da­tion

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 cryp­tic col­oration, stay­ing cam­ou­flaged in their en­vi­ron­ment. (Anger­meirer, 1992)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • northern pike (Esox iucius)
  • muskies (Esox masquinongy)
  • walleyes (Sander vitreus)
  • largemouth bass (Micropterus salmoides)
  • humans (Homo sapiens)

Ecosys­tem Roles

Rock bass feed on in­sects, aquatic crus­taceans, and smaller fish. As a re­sult, the pop­u­la­tions of these or­gan­isms are sup­pressed so that their pop­u­la­tion den­si­ties are at an ac­cept­able level. Rock bass are also hosts in their ecosys­tems. Cope­pods, a small group of crus­taceans that have a par­a­sitic role with rock bass, such as an­chor­worms, de­pend on rock bass. An­chor­worms are ex­ter­nal par­a­sites that embed into the skin of the fish and dam­age and ul­ti­mately de­crease the longevity of rock bass. (Causey, 1957; Kot­te­lat and Frey­hof, 2007; Page and Burr, 1991)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Rock bass, along with other bass species, such as small­mouth bass, large­mouth bass, and spot­ted bass, are all sport fish. With com­pet­i­tive tour­na­ment events and even recre­ational events, bass fish­ing has evolved into 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)

• Positive Impacts
• food
• ecotourism

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

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 take an eco­nomic toll on the ef­forts to main­tain clean and healthy ecosys­tems. (Day­ton, et al., 1995)

Con­ser­va­tion Sta­tus

In­tro­duced into many drainages in the United States, rock bass have flour­ished in their en­vi­ron­ments. As a means of con­ser­va­tion, 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. Even though they are not a fish many peo­ple pre­fer to eat, there are slot lim­its (re­quired lengths) on dif­fer­ent bod­ies of water, which reg­u­late whether peo­ple can keep these sport fish. Also, ar­ti­fi­cial nests and nurs­ery/ar­ti­fi­cial ponds are man­age­ment tools de­vel­oped to main­tain pop­u­la­tions of rock bass. (Na­ture­Serve, 2013)

• IUCN Red List

  Least Concern

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Con­trib­u­tors

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

Ref­er­ences

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 www.​iucnredlist.​org.

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.