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Pest fish profiles
Astronotus ocellatus - Oscar
Detailed
information
Synonyms
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Classification
Taxonomic description
Appearance and size
Diet
Reproduction
Natural & introduced distribution
Habitat
Ecological tolerances
Ecological impacts
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Glossary
References
Contact details
Common names:
Oscar.
aquarium trade, especially copper/red and black mottled patterns
and even albino forms.
Synonyms:
Lobotes ocellatus (Agassiz 1831)
Acara ocellatus (Agassiz 1831)
Cychla rubroocellatus (Jardine 1843)
Heros altifrons (Kner 1863)
Astatheros altifrons (Kner 1863)
Cichlasoma altifrons(Kner 1863)
Acara compressus (Cope 1872)
Acara hypostica (Cope 1878)
Astronotus ocellatus zebra (Pellegrin 1904)
Astronotus orbiculatus (Haseman 1911)
Diet:
Omnivorous though predominantly carnivorous. Feeds mainly on
aquatic and terrestrial insects, crustaceans and small fish (Soares et
al. 1986; Honebrink 1990). Will eat other small invertebrates
(molluscs) (Soares et al. 1986; Consoli et al. 1992), also fruits,
benthic algae and water plants (Soares et al. 1986) and small
vertebrates, e.g., lizards (Fury and Morello 1994) and even small
birds (A. Webb, pers. obs.).
Reproduction:
Oviparous, substrate spawners with biparental care; females lay
between 200 and 2000 eggs.
Classification:
Order Perciformes
Suborder Labroidei
Family Cichlidae
Tribe Tilapiini
Genus Astronotus
Species ocellatus
Oscars reach maturity at about 12 cm TL and are relatively long
lived (10 to 20 years) (Robins 2007). Spawning is temperature
dependant and may be restricted to warmer months (>25°C) in
higher latitudes within its native or introduced range. Sexual
maturation is reached in approximately one year and individuals
may be reproductively active for up to 9-10 years (Pinto-Paiva and
Hilton Nepomucenko 1989). The species is territorial and
dominance hierarchies are established through agonistic displays.
Success in such interactions is positively correlated with larger
body size (Beeching 1992). After protracted courtship, males and
females form breeding pairs. Adhesive eggs are laid on a cleaned
flat rock, on woody debris or in a shallow pit excavated in substrate
(gravel), the number of eggs positively correlated with female body
size (Beeching 1992). Both parents defend the nest site. Eggs hatch
in 3-4 days and parents move fry to another shallow pit in substrate
where they remain for 6 to 7 days. Both parents continue to guard
fry for several weeks (Baerends and Baerends-Van Roon 1950;
Fontinele 1951).
Taxonomic description:
Dorsal fin with 12-14 spines and 19-21 soft rays; anal fin with 3 spines
and 15-17 soft rays.
Appearance & Size:
Grows to 35-45cm TL, though usually to 20-28cm TL. No sexual
dimorphism; slender, laterally compressed, oval-shaped body with
blunt head and large mouth. Grows to 35-45cm TL, though usually
to 20-28cm TL. No sexual dimorphism; slender, laterally
compressed, oval-shaped body with blunt head, large mouth and
protrusible jaws and 7 pre-opercular pores. Eyes are large with
orange/red iris. Dorsal fin with 12-14 spines and 19-21 soft rays; anal
fin with 3 spines and 15-17 soft rays. Dorsal and anal fins with
densely scaled bases (Froese and Pauly 2007).
During aggressive interactions, oscars may change colour individuals that are startled or defeated in combat may assume a
darker, almost black colouration with irregular white banding,
including a band arching over the head posterior to the eyes.
Beeching (1995) suggested that such a colour pattern may provide
crypsis to avoid detection and further attack by disrupting the
visual borders of the fish. Beeching (1995) also noted that the
pattern closely resembled that of juvenile oscars. He referred to
Zaret (1977) who suggested that adoption of juvenile patterning
may inhibit parental cannibalism - and therefore might effectively
inhibit aggression of attacking conspecifics.
Colour varies greatly among natural populations - adults typically
drab and cryptic: dark olive-green to gray to chocolate brown in
base color with a mottling of some or all of these colors, with
scattered red-orange irregular spots along flanks and dorsal fin
base. A large black spot surrounded by an orange ring present on
either side of the base of the upper caudal peduncle. Juveniles are
striped with white and orange wavy bands and white spots on the
head. Several colour varieties produced by selective breeding for
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Pest fish profiles
Astronotus ocellatus – Oscar
World distribution:
Figure 1: World wide distribution of Oscar.
Native and introduced distribution:
Native to South America: Venezuela, Peru, Colombia, Bolivia,
Ecuador, Brazil, Guyana, Argentina and Paraguay. Mainly found
in mid to upper reaches of rivers and tributaries of the Amazon
Basin; from the Orinocco River to Rio Paraguay.
The Oscar is hypoxia tolerant and can survive severe hypoxia
(dissolved oxygen < 0.4 mg/l) and even 4 hrs of complete anoxia at
28°C (Muusze et al. 1998). The species can tolerate low
temperatures, with a critical thermal minimum of 12.9°C (Shafland
and Pestrak 1982). The critical thermal maximum is not known,
although Lowe-McConnell (1999) reported water temperature
ranges of 23 to 34°C in rivers and pools within the Amazon basin
where oscars occur. pH tolerance range is not known, though its
preferred range appears to be pH 6-8 (Froese and Pauly 2007). The
species probably does not tolerate pH below this range as it does
not occur in the black water (acidic) rivers in the Amazon basin.
Critical salinity tolerance range for the species is unknown. Based
on its distribution, in the mid and upper reaches of rivers in the
Amazon basin, the species is probably stenohaline (limited salinity
tolerance).
Introduced to at least 12 countries and territories including
Australia (Cairns and Townsville, north Queensland) and
continental USA (Florida) - (reported from 9 other states but not
established) and Hawaii (Fuller et al. 1999).
Table 1: Introduced range of the Oscar.
Country
Established
Australia
yes
Canada
?
China
?
Guam
yes
Italy
no
Ivory Coast
?
Philippines
?
Poland
?
Puerto Rico
yes
Singapore
yes
USA (Florida, Hawaii)
yes
Ecological impacts:
Largely unknown. Latini and Petrere (2004) reported a significant
decrease in species richness and diversity of lake fish fauna in southeastern Brazil following the introduction of oscars along with
peacock cichlids and red piranha that are non-indigenous to the
region. Robins (2007) expressed concern that the spread of
introduced oscars in southern Florida may have a negative effect on
native sunfishes which have similar habitat and ecological needs.
From: Fuller et al. 1997; Froese and Pauly 2007
Habitat:
Inhabits floodplains and swamps of slow moving rivers; usually
found among woody debris (sunken branches and logs) which
provide cover.
Ecological tolerances:
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Glossary
Agonistic
display
Anal
Cannibalism
Carnivorous
Caudal
Conspecifics
Crypsis
Dimorphism
Dorsal
Fry
Hypoxia
Lateral
Omnivorous
Opercular
Oviparous
Posterior
Protrusible
Stenohaline
The type of display fish make when they threaten with combat.
(Fin) beneath the body, behind anal opening.
Predation of an animal by a member of its own species.
An animal that eats other animals.
Towards the tail.
Members of the same species.
The ability of an organism to avoid observation.
Sexual differences in size.
Situated near to or on the back.
Newly hatched or born fish.
An inadequate supply of oxygen to the tissues.
Situated at or extending to the side.
Eating both plant and animal matter.
Situated near or related to the gill cover.
Egg laying.
Towards the back, behind.
Capable of extending forward.
It can tolerate only a narrow range of salinities, opposite to
euryhaline.
References
Baerends, G.P. and Baerends-van Roon, J.M., 1950. An introduction to the study of the ethology
of cichlid fishes. Behaviour Supplement 1: 1-242.
Honebrink R., 1990. Fishing in Hawaii: a Student Manual. Education Programme. Division of
Aquatic Resources, Honolulu, Hawaii.
Beeching S.C., 1992. Visual assessment of body size in a cichlid fish, the oscar, Astronotus
ocellatus. Ethology 90: 177-186.
Latini A.O. and Petrere M. Jr., 2004. Reduction of a native fish fauna by alien species: an example
from Brazilian freshwater tropical lakes. Fisheries Management and Ecology 11: 71-79.
Consoli R.A.G.B., Guimaraes C.T., do Carmo J.A., Soares D.M. and dos Santos J.S, 1992.
Astronotus ocellatus (Cichlidae: Pisces) and Macropodus opercularis (Anabantidae: Pisces) as
predators of immature Aedes fluviatilis (Diptera: Culicidae) and Biomphalaria glabrata
Lowe-McConnell R.H., 1987. Ecological Studies in Tropical Fish Communities. Cambridge
University Press, Cambridge, NY.
.
(Mollusca: Planorbidae). Memorias do Instituto Oswaldo Cruz 86(4): 419-424
Muusze B., Marcon J., van den Thillart G., Almeida-Val V., 1998. Hypoxia tolerance of Amazon
fish. Respiratory and energy metabolism of the cichlid Astronotus ocellatus. Comparative
Biochemistry and Physiology Part A 120: 151-156.
Fontinelle O., 1951. Contribucao para o conhemencimento do biologia do apaiari, Astronotus
ocellatus, em cativiera. Apparelhode reproducao. Habitos de desova e prolificidade. Revista
Brasilieira do Biologia 11: 467-484.
Froese R. and Pauly D. (Eds.), 2007. FishBase [online] version (01/2007). Available from:
www.fishbase.org {Accessed April 2007}.
Pinto Paiva M. and Hilton Nepomucenko F., 1989. On the reproduction in captivity of the oscar,
Astronotus ocellatus (Cuvier) according to the mating methods (Pisces-Cichlidae). Amazoniana
10(4): 361-377.
Fuller P.L., Nico L.G. and Williams J.D., 1999. Nonindigenous Fishes Introduced into Inland
Waters of the United States. American Fisheries Society Special Publication 27. AFS, Bethesda,
Maryland, USA.
Robins R.H, 2007. Biological Profiles: Oscar. Education webpage for Ichthyology at the Florida
Museum of Natural History. Online: www.flmnh.ufl.edu/fish/ {Accessed May 28, 2007}.
Shafland P.L. and Pestrak J.M., 1982. Lower lethal temperatures of fourtenn non-native fishes in
Florida. Environmental Biology of Fishes 7(2): 149-156.
Fury J.R. and Morello F.A., 1994. The contribution of an exotic fish, the Oscar, to the sport
fishery of the Everglades water conservation areas. Proceedings of the Annual Conference of
Southeastern Association of Fish and Wildlife Agencies 48: 474-481.
Soares M.G.M., Almeida R.G. and Tunk W.T., 1986. The trophic status of the fish fauna in Lago
Camaleao, a macrophyte dominated floodplain lake in the middle Amazon. Amazoniana 9(4): 511526.
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Created by A. Webb, M. Maughan and M. Knott
© ACTFR, James Cook University, 2007
For further information please contact [email protected], tel: 07 4781 4262
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Other information sheets available:
Spotted tilapia – Tilapia mariae
Oscar – Astronotus ocellatus
Burton’s haplochromis – Haplochromis burtoni
Mosquitofish – Gambusia holbrooki
Guppy – Poecilia reticulates
Swordtail – Xiphophorus helleri
Platy – Xiphophorus maculates
Three-spotted gourami – Thrichogaster trichopterus
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