Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Astronotus ocellatus
(oscar)

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Datasheet

Astronotus ocellatus (oscar)

Summary

  • Last modified
  • 08 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • Astronotus ocellatus
  • Preferred Common Name
  • oscar
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Chordata
  •       Subphylum: Vertebrata
  •         Class: Actinopterygii
  • Summary of Invasiveness
  • Astronotus ocellatus, commonly known as the oscar, is a large, predatory cichlid that is very popular worldwide as an ornamental freshwater fish. It has been introduced to the aquatic habitats of at least 10 co...

  • Principal Source
  • Draft datasheet for peer review

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Pictures

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PictureTitleCaptionCopyright
Astronotus ocellatus (oscar); adult, captive specimen. Suma aquarium, Japan. November 2014.
TitleAdult
CaptionAstronotus ocellatus (oscar); adult, captive specimen. Suma aquarium, Japan. November 2014.
Copyright©harum.koh-2014/Kobe city, Japan/via wikipedia - CC BY-SA 2.0
Astronotus ocellatus (oscar); adult, captive specimen. Suma aquarium, Japan. November 2014.
AdultAstronotus ocellatus (oscar); adult, captive specimen. Suma aquarium, Japan. November 2014.©harum.koh-2014/Kobe city, Japan/via wikipedia - CC BY-SA 2.0
Astronotus ocellatus (oscar); adult, captive specimen.
TitleAdult
CaptionAstronotus ocellatus (oscar); adult, captive specimen.
Copyright©André Karwath aka Aka/via wikipedia - CC BY-SA 2.5
Astronotus ocellatus (oscar); adult, captive specimen.
AdultAstronotus ocellatus (oscar); adult, captive specimen.©André Karwath aka Aka/via wikipedia - CC BY-SA 2.5
Astronotus ocellatus (oscar); adult, captive specimen.
TitleAdult
CaptionAstronotus ocellatus (oscar); adult, captive specimen.
Copyright©Jón Helgi Jónsson (Amything)/via wikipedia - CC BY-SA 3.0
Astronotus ocellatus (oscar); adult, captive specimen.
AdultAstronotus ocellatus (oscar); adult, captive specimen.©Jón Helgi Jónsson (Amything)/via wikipedia - CC BY-SA 3.0

Identity

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Preferred Scientific Name

  • Astronotus ocellatus Agassiz 1831

Preferred Common Name

  • oscar

Other Scientific Names

  • Acara compressus Cope 1872
  • Acara hyposticta Cope 1878
  • Astronotus ocellatus ocellatus Agassiz 1831
  • Astronotus ocellatus zebra Pellergrin 1904
  • Astronotus orbiculatus Haseman 1911
  • Cychla rubroocellata Jardine & Schomburgk 1843
  • Lobotes ocellatus Agassiz 1831

International Common Names

  • English: oscar; velvet cichlid; velvety cichlid

Local Common Names

  • Argentina: acará; carahuazú; caraussú
  • Brazil: acará-açu; acará-grande; acaraú-açu; acaráuaçu; apaiari; apiari; bola-de-ouro; cará; cará pirosca; cará-açu; cará-boi; cará-grande; corró-baiano; corró-chinês; dorminhoco
  • Canada: astronotus
  • Denmark: påfugleøjecichlide
  • Ecuador: vieja
  • Finland: riikinkukkoahven
  • France: cichlidé œil de paon; oscar
  • French Guiana: aluago elselepo; crombier; krobié; masug; paya; rouj
  • Germany: Pfauenaugenbuntbarsch
  • Peru: acarahuazú; carahuazú
  • Poland: pielegnica pawiooka
  • Russian Federation: astronotus
  • Sweden: oscar; påfågelcichlid
  • USA: marble cichlid; red oscar; velvet cichlid

Summary of Invasiveness

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Astronotus ocellatus, commonly known as the oscar, is a large, predatory cichlid that is very popular worldwide as an ornamental freshwater fish. It has been introduced to the aquatic habitats of at least 10 countries, principally because of human-mediated translocation and release. Due to the popular ornamental status of A. ocellatus, it is rarely considered a pest species. A. ocellatus has proven invasive because of wide environmental tolerances, the ability to colonise disturbed habitats, trophic opportunism and fast growth rates. Potential ecological impacts may include resource competition with endemic fish fauna and predation of aquatic invertebrate communities as a whole. Of particular note is the capacity of the species to consume small and moderate sized sympatric fishes due to its large size (up to 450 mm). Research conducted in North and South America has suggested that A. ocellatus may impact negatively on native fish fauna inhabiting similar ecological niches (see Impact section).

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Chordata
  •             Subphylum: Vertebrata
  •                 Class: Actinopterygii
  •                     Order: Perciformes
  •                         Family: Cichlidae
  •                             Genus: Astronotus
  •                                 Species: Astronotus ocellatus

Notes on Taxonomy and Nomenclature

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Astronotus ocellatus Agassiz 1831 was described as Lobotes ocellatus Agassiz 1831and is currently valid as Astronotus ocellatus. However, the Astronotus genus is in need of systematic review. Future studies may reveal that A. ocellatus in the aquarium trade is another Astronotus species, not A. ocellatus (USGS-NAS, 2014).

Description

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A. ocellatus has an oval-shaped, laterally compressed body with a blunt head and large mouth with protrusible jaws. There are 7 pre-opercular pores and the eyes are large with orange/red iris.

The colour varies among natural populations with adults typically dark olive-green to grey to chocolate brown with scattered red-orange irregular spots along flanks, dorsal fin base and opercle margin. There is often a large black spot surrounded by an orange margin the caudal peduncle.

Juveniles are striped with white and orange wavy bands and white spots on the head.

Various ornamental colour varieties have been produced by selective including copper/red and black mottled patterns and also albino forms. Long-finned varieties have also been produced.

A. ocellatus grows to 35-45 cm TL, though usually to 20-28 cm TL. There is no sexual dimorphism.

It has a dorsal fin with 12-14 spines and 19-21 soft rays; anal fin with 3 spines and 15-17 soft rays. It also has dorsal and anal fins with densely scaled bases. The first gill arch is without a lobe; gill rakers short and thick with many denticles; dorsal and anal fins bases densely scaled; many branched rays. There are 31-36 scales on the lateral line and 34-37 scales in the lateral series (Page and Burr, 1991; Froese and Pauly, 2007).

Distribution

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Within the USA, A. ocellatus has been recorded in at least 20 mainland states and also Alaska and Hawaii (USGS-NAS, 2014). The majority of these records describe the collection of single specimens; e.g. Arizona, Arkansas, California, Georgia, Indiana, Louisiana, Maryland, Massachusetts, Minnesota, Mississippi, Nebraska, New Jersey, Ohio, South Carolina, Texas, Virginia, Vermont (USGS-NAS, 2014). It is possible to speculate that these records may describe the collection of single released fish and do not represent established populations (USGS-NAS, 2014). However, many of these collections were not from scientific sampling events, but single specimens collected by recreational anglers. Thus, under these circumstances, it is not possible to determine if established populations of A. ocellatus occur in all US states listed by USGS-NAS (2014).

A. ocellatus was collected on the shoreline of Jewel Lake near Anchorage, Alaska, USA (Alaska Department of Fish and Game, 2002). It is unlikely that the species would survive at such high latitudes, particularly as the collection of fish at this locality occurred “prior to ice formation” on the lake edge. Thus, it is reasonable to assume this “population” in Alaska is no longer present.

The three US states where A. ocellatus is most successfully established are, not surprisingly, the three states where the species has been stocked as a sportfish; Florida, Hawaii and Texas. These records have been collated by USGS-NAS (2014).

In Texas, USA, many collection records are based on fish taken by recreational anglers, though according to Howells (1992) there are no known spawning or established populations. Locations in Texas sites where fish were collected included Victor Braunig Reservoir and the San Antonio River near San Antonio (Bexar County), Tom Green County, McLennan County, Freestone County, Mitchell County and Donley County (Howells, 1992; Texas Parks and Wildlife Department, 2001; USGS-NAS, 2014).

A. ocellatus composes a substantial proportion of the recreational fishery catch in some areas of the Everglades, Florida, USA (Fury and Morello, 1994), especially when cold temperatures have been absent for several years (USGS-NAS, 2014).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

ChinaPresentIntroducedMa et al., 2003
PhilippinesPresentIntroducedFroese and Pauly, 2014
SingaporePresentIntroducedNg et al., 1993

Africa

Côte d'IvoirePresentIntroducedWelcomme, 1988

North America

Canada
-OntarioAbsent, formerly presentIntroduced Not invasive Coad et al., 1995; Coker et al., 2001
USAPresentPresent based on regional distribution.
-AlaskaAbsent, formerly presentIntroduced Not invasive Alaska Department of Fish and Game, 2002Jewel Lake near Alaska
-ArizonaPresent, few occurrencesIntroducedWright and Sorensen, 1995Arizona canal near Peoria between 1992 and 1994
-ArkansasLocalisedIntroducedLoe, 2005One fish captured by recreational angler near Hot Springs
-CaliforniaLocalisedIntroducedUSGS NAS, 2014A single specimen was caught in the Kaweah River in Tulare County
-FloridaWidespreadIntroduced Invasive Courtenay and Hensley, 1979a; Courtenay and Hensley, 1979b; Hogg, 1976a; Hogg, 1976b; Rivas, 1965; Courtenay et al., 1974; Courtenay et al., 1984; Loftus and Kushlan, 1987; Courtenay and Stauffer, 1990; Fury and Morello, 1994; Loftus et al., 2004; USGS NAS, 2014Broward, Collier, Glades, Hendry (possibly), Miami-Dade, Monroe, Orange, and Palm Beach counties; including portions of Everglades National Park and Big Cypress National Preserve
-HawaiiPresentIntroduced1952Devick, 1991a; Devick, 1991b; Shima, 1972; Morita, 1981; Maciolek, 1984; USGS NAS, 2014Introduced as a sportfish on Kauai (Nuuanu Reservoir 2 and Wailua Reservoir) and Oahu (Wahiawa Reservoir)
-IndianaPresentIntroduced2008USGS NAS, 2014Single fish caught in Kankakee River
-LouisianaPresentIntroducedUSGS NAS, 2014Single Astronotous sp. caught from “unspecified public water body”
-MarylandPresentIntroduced2003USGS NAS, 2014Single fish collected in a pond near Fort Meade Army Base in Anne Arundel County
-MassachusettsPresentIntroduced1978Hartel, 1992; Cardoza et al., 1993; USGS NAS, 2014Single fish collected by angler in Congamond Lake, Hampden County in 1978; sight record from Hampshire County in 1992; other unconfirmed reports
-MinnesotaPresentIntroducedUSGS NAS, 2014Single fish collected from Simley Pond, Dakota County
-NebraskaPresentIntroduced1998USGS NAS, 2014Single fish collected from pond on North Platte River near Cozad
-New JerseyPresentIntroduced1994USGS NAS, 2014Single fish collected in Millstone River, Somerset County
-OhioPresentIntroduced2000USGS NAS, 2014Single fish collected from near Perrysville in 2000 and in Ohio River at Newburg Landing near Toronto in 2009
-PennsylvaniaPresentIntroducedCourtenay and Hensley, 1979a; Courtenay et al., 1984; Courtenay and Stauffer, 1990; USGS NAS, 2014
-Rhode IslandAbsent, unreliable recordIntroduced1970sUSGS NAS, 2014Two fish collected by angler in a pond in northern Rhode Island
-South CarolinaPresentIntroduced2004USGS NAS, 2014Single fish collected in Edisto River (2004) and Lake Wylie (2010)
-TexasWidespreadIntroducedHowells, 1992; Texas Parks Wildlife Department, 2001; USGS NAS, 2014Donley, Bexar, Tom Green, McLennan, Freestone, and Mitchell counties. Stocked in Tradinghouse Creek Reservoir [Hallsburg, TX], Matagorda Bay, Sabine Lake (estuary), San Antonio Bay (estuary), Aransas Bay, Lower and Upper Laguna Madre, Galveston Bay, Fairfield Reservoir, Braunig Reservoir, Corpus Christi Bay in 1992
-VermontPresentIntroduced2005USGS NAS, 2014Single fish was caught by an angler in Lake Hortonia, Rutland County
-VirginiaPresentIntroduced1987USGS NAS, 2014Single specimen collected from a pond near Virginia beach
-WisconsinPresentIntroducedUSGS NAS, 2014Collected from the inlet of a “hydro facility” on the Yellow River, Burnett County

Central America and Caribbean

Puerto RicoWidespreadIntroduced1950-1974Lee et al., 1983; Erdsman, 1984; USGS NAS, 2014Tortuguero Lagoon, Loiza Reservoir, Las Curias Reservoir, Guajataca Reservoir, La Plata Reservoir, Comerio Reservoir, Cidra Reservoir, Bayamon Reservoir and Aibonito farm pond

South America

ArgentinaWidespreadNative Not invasive Silvano and Begossi, 2001Native to the Amazon River Basin
BrazilPresentSilvano and Begossi, 2001; Latini and Petrere, 2004Native to the Amazon River Basin. Introduced to River Doce State Park southeastern Brazil
ColombiaWidespreadNative Not invasive Kullander, 2003
French GuianaWidespreadNative Not invasive Boujard, 1992
PeruWidespreadNative Not invasive Kullander, 1986
VenezuelaAbsent, unreliable recordNative Not invasive Robins et al., 1991Reported as unreliable by Froese and Pauly (2014)

Europe

GermanyPresentIntroduced Not invasive NOBANIS, 2013; Froese and Pauly, 2014
ItalyAbsent, formerly presentIntroduced Not invasive Froese and Pauly, 2014Not established
PolandPresentIntroducedSolarz, 2005Current status unknown

Oceania

AustraliaPresentPresent based on regional distribution.
-New South WalesEradicatedIntroduced2011 Not invasive RiotACT, 2014Single fish removed from ornamental pond in Canberra during summer. Species would not survive over winter at this latitude/locality
-QueenslandWidespreadIntroduced Invasive ACTFR, 2014Common in rivers and ponds in the Ross River drainage around Townsville; also found around Cairns
GuamAbsent, reported but not confirmedIntroducedWelcomme, 1988Said to be established but current status unknown

History of Introduction and Spread

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Within Australia, successful introductions of A. ocellatus were first recorded at two locations in Queensland (northern Australia) in 1998. It has been recorded within the Ross River around Townsville and creeks around Cairns (Corfield et al., 2008). A single specimen was collected in an ornamental pond in the Australian Capital Territory in 2011 (RiotACT, 2014). This fish was collected during summer and would not have survived the temperate winter.

A. ocellatus was first stocked in Florida, USA, in southeastern Dade County in the late 1950s with stock from an aquarium fish farm (Courtenay et al., 1974; Courtenay and Hensley, 1979a; Courtenay and Stauffer, 1990). Also during the 1950s, attempts were made to popularize the species as a  sportfish under the name "velvet cichlid" (USGS-NAS, 2014). It is established in ponds and canals in southern Florida in Broward, Collier, Glades, Hendry, Miami-Dade, Monroe, and Palm Beach counties, including portions of Everglades National Park and Big Cypress National Preserve (Rivas, 1965; Courtenay et al., 1974, 1984; Hogg, 1976a, b; Courtenay and Hensley, 1979a, b; Loftus and Kushlan, 1987; Courtenay and Stauffer, 1990; Fury and Morello, 1994; Loftus et al., 2004). A. ocellatus was first sighted at the Anhinga Trail in Everglades National Park, USA, in the late 1980s (Loftus and Kushlan, 1987) and reportedly was introduced to the park by way of the South Florida Water Management District's Canal L31W (USGS-NAS, 2014). It has been collected in other Florida counties but is not known to be established. These include the Indian River drainage, Brevard County, Pasco County, St. Johns River drainage Volusia County, Alachua County, University of Florida campus and Bay County (Hill and Cichra 2005; USGS-NAS, 2014).

A. ocellatus was introduced into Hawaii, USA, in 1952 for purposes of recreational fishing (Devick, 1991a, b). Hawaii's Division of Fish and Game made additional reservoir stockings in 1958 with the species being stocked on the islands of Kauai (Nuuanu Reservoir 2 and Wailua Reservoir) and Oahu (Wahiawa Reservoir) (Brock, 1960; Shima, 1972; Morita, 1981; Maciolek,1984; Devick, 1991a, b). The original source of the fish stocked in Hawaii was stock obtained from Steinhart Aquarium in San Francisco, USA (Brock, 1960).

During 1992, A. ocellatus was stocked in Tradinghouse Creek Reservoir (Hallsburg), Matagorda Bay, Sabine Lake (estuary), San Antonio Bay (estuary), Aransas Bay, Lower and Upper Laguna Madre, Galveston Bay, Fairfield Reservoir, Braunig Reservoir and Corpus Christi Bay, in Texas, USA (USGS-NAS, 2014).

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Brazil Brazil 1960-1979 Froese and Pauly (2014); Latini and Petrere (2004) Introduced to Brazil (River Doce State Park southeastern Brazil)
China Thailand 1990 Froese and Pauly (2014); Ma et al. (2003)
Hawaii California 1952 Yes Froese and Pauly (2014)
USA South America 1952 Hunting, angling, sport or racing (pathway cause) Yes Froese and Pauly (2014); USGS NAS (2014); USGSNAS (2014)

Risk of Introduction

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A. ocellatus is a popular ornamental species (Rixon et al., 2005; USGS-NAS, 2014). Researchers have speculated that the release of unwanted ornamental fishes is the most likely explanation for the nonindigenous populations in Australia and some states in the USA (Courtenay and Stauffer, 1990; ACTFR, 2007; USGS-NAS, 2014).

There is the potential for the natural dispersal and anthropogenic translocation of introduced populations of A. ocellatus and this is more likely to occur in areas that contain multiple populations and/or larger and widely distributed populations. However, natural dispersal of populations of A. ocellatus may be constrained by salinity and temperature tolerances.

A. ocellatus has been widely dispersed in the USA as a sportfish (USGS-NAS, 2014). The species now composes a substantial proportion of the recreational fishery catch in some areas of the Everglades (Fury and Morello, 1994). Therefore, as A. ocellatus is considered a desirable sportfish by sections of the general public there is the potential for the species to be deliberately spread by recreational anglers (USGS-NAS, 2014).

Habitat

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Native populations of A. ocellatus are found in floodplains and swamps of slow moving rivers among woody debris (sunken branches and logs). Introduced populations occupy similar areas and also thrive in artificial ponds, lakes and reservoirs (ACTFR, 2007; Froese and Pauly, 2014; USGS-NAS, 2014).

The capacity of the species to tolerate hypoxic conditions allows it to inhabit stagnant ponds and colonise degraded waterways (Corfield et al., 2008).

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Freshwater
  Secondary/tolerated habitat Harmful (pest or invasive)
  Secondary/tolerated habitat Productive/non-natural
Reservoirs Secondary/tolerated habitat Harmful (pest or invasive)
Reservoirs Secondary/tolerated habitat Productive/non-natural
Rivers / streams Principal habitat Harmful (pest or invasive)
Rivers / streams Principal habitat Natural
Rivers / streams Principal habitat Productive/non-natural
Ponds Secondary/tolerated habitat Harmful (pest or invasive)
Ponds Secondary/tolerated habitat Productive/non-natural

Biology and Ecology

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Genetics

The diploid/haploid chromosome numbers are 48-48/24 (Kornfield, 1984; Klinkhardt et al., 1995; Arkhipchuk, 1999; Froese and Pauly, 2014).

Reproductive Biology

A. ocellatus reaches sexual maturity at about 12 cm TL and may live from 10-20 years (Robins, 2007). Fish mature at approximately one year and may be reproductively active for up to 9-10 years (Pinto-Paiva and Hilton Nepomucenko, 1989). Spawning is temperature dependant and may be restricted to warmer months (>25°C) in higher latitudes within its native or introduced range (ACTFR, 2007).

A. ocellatus is an oviparous substrate spawner with biparental care (Beeching, 1992). After a 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 and both parents defend the nest site (Beeching, 1992). Fecundity is 300-2000 progeny per spawning (ACTFR, 2007). Eggs hatch in 3-4 days and parents move fry to another shallow pit in substrate where they remain for 6-7 days. Both parents continue to guard fry for several weeks (Baerends and Baerends-Van Roon, 1950; Fontinele, 1951).

Physiology and Phenology

Juvenile fish are striped with white and orange wavy bands and white spots on the head. Zaret (1977) suggested that such a colour pattern may promote crypsis and assist the avoidance of predation and parental cannibalism.

Research has been conducted on the species behaviour in the laboratory. A. ocellatus is territorial and dominance hierarchies are established through agonistic displays. Larger body size is correlated with success in agonistic interactions (Beeching, 1992).

During agonistic interactions fish that are startled or defeated in combat may assume an almost black colouration with irregular white banding, including a band arching over the head posterior to the eyes (Beeching, 1995). Colour pattern may prevent further attack by disrupting the visual borders of the fish and therefore potentially making the fish more cryptic (Beeching, 1995).

A. ocellatus has the capacity to endure extremely hypoxic conditions. It is speculated that these adaptations evolved because A. ocellatus migrates from the main rivers into the Amazonian floodplains when water levels are high to breed. The Amazonian floodplains are rich in organic material and consequently there are large fluctuations in oxygen concentrations and hypoxic waters are common. Research has suggested that several fish species, including A. ocellatus, use multiple adaptive strategies to survive hypoxia and even anoxia (Almeida-Val and Hochachka, 1995; Muusze et al., 1998). Strategies include substantial metabolic depression, increased use of anaerobic metabolic pathways (Muusze et al., 1998; Almeida-Val et al., 2000; Chippari-Gomes et al., 2005) and increased respiration/ventilation (Chippari-Gomes et al., 2005; Scott et al., 2008).

Nutrition

A. ocellatus is omnivorous though predominantly carnivorous. Feeds on small fish, aquatic and terrestrial invertebrates, including crayfish, worms, insect larvae and molluscs, and even small vertebrates (Soares et al., 1986; Honebrink, 1990; Consoli et al., 1991; Fury and Morello, 1994; Froese and Pauly, 2014). May also consume fruits, benthic algae and water plants (Soares et al., 1986).

A. ocellatus consumed Gambusia sp. and goldfish in laboratory experiments (Beeching, 1992; 1997).

Environmental Requirements

A. ocellatus is considered a hardy and undemanding ornamental species and is maintained in aquaria with very general environmental requirements.

It has broad temperature tolerances, though higher temperatures are required for reproduction. Reported critical thermal minimum of 12.9°C Shafland and Pestrak (1982), though temperatures of greater than 25°C may be required for spawning (ACTFR, 2007). Lowe-McConnell (1987) reported water temperature ranges of 23-34°C in rivers and pools within the Amazon basin where A. ocellatus occurs.

A. ocellatus is likely to be stenohaline, though critical salinity tolerance range is unknown. Based on its distribution (mid and upper reaches of rivers in the Amazon and Orinoco basins) the species is highly likely to have limited salinity tolerance (ACTFR, 2007; Froese and Pauly, 2014).

A. ocellatus is reported to be highly hypoxia-tolerant (Muusze et al., 1998), and may utilise surface respiration to help mitigate hypoxia (Kramer and McClure, 1982). Muusze et al. (1998) reported that the species may reduce its metabolic rate in hypoxic conditions. It can survive severe hypoxia (dissolved oxygen < 0.4 mg/l) and even 4 hrs of complete anoxia at 28 °C (Muusze et al., 1998).
 

Climate

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ClimateStatusDescriptionRemark
Af - Tropical rainforest climate Preferred > 60mm precipitation per month
Am - Tropical monsoon climate Preferred Tropical monsoon climate ( < 60mm precipitation driest month but > (100 - [total annual precipitation(mm}/25]))
As - Tropical savanna climate with dry summer Preferred < 60mm precipitation driest month (in summer) and < (100 - [total annual precipitation{mm}/25])
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
BS - Steppe climate Tolerated > 430mm and < 860mm annual precipitation
BW - Desert climate Tolerated < 430mm annual precipitation
Cf - Warm temperate climate, wet all year Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Preferred Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
4 25

Water Tolerances

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ParameterMinimum ValueMaximum ValueTypical ValueStatusLife StageNotes
Dissolved oxygen (mg/l) 0.4 Harmful Muusze et al., 1998
Hardness (mg/l of Calcium Carbonate) 5 19 Optimum Froese and Pauly, 2014
Salinity (part per thousand) Optimum Freshwater only - ACTFR, 2007; Froese and Pauly, 2014
Water pH (pH) 6 8 Optimum Froese and Pauly, 2014
Water temperature (ºC temperature) 22 25 Optimum Shaftland and Pestrak, 1982; Lowe-McConnell, 1987; Riehl and Baensch, 1991; ACTFR, 2007
Water temperature (ºC temperature) 12.9 34 Harmful

Means of Movement and Dispersal

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Natural Dispersal (non-biotic)

Further spread of A. ocellatus by natural dispersal may occur (e.g. flooding), though is most probable in areas with substantial populations. For example A. ocellatus was established in Miami-Dade County, southeastern Florida, USA, since late 1950s, but began to expand range greatly in late 1970s and early 1980s (Hogg, 1976b; Courtenay and Stauffer, 1990; Fury and Morello, 1994).

The limited salinity tolerance of A. ocellatus renders the species unlikely to disperse between sites where migration spanning brackish or marine water is required.

High hypoxia tolerance may allow this species to readily colonise and migrate within degraded waterways often associated with urban areas.

Intentional Introduction

A. ocellatus may be intentionally introduced to aquatic habitats as unwanted ornamental fishes. Although A. ocellatus is a very popular ornamental species it is not an ideal fish species for many hobbyists due to its large size (i.e. regularly up to 30 cm in home aquaria) and piscivorous nature (i.e. not ideal for the standard ‘community’ aquarium with many different fish species as A. ocellatus will readily consume smaller fish). USGS-NAS (2014) speculated that because of these two biological traits A. ocellatus is more likely to be released into natural waterways than many other ornamental fish species “by aquarists loathe to kill their unwanted pets”. This potentially accounts for the numerous instances of single specimen records from both temperate and subtropical states in the USA and Australia (RiotACT, 2014).

A. ocellatus has been widely dispersed in the USA as a sportfish (USGS-NAS, 2014). The species now composes a substantial proportion of the recreational fishery catch in some areas of the Everglades (Fury and Morello, 1994). Therefore, as A. ocellatus is considered a desirable sportfish by sections of the general public there is the potential for the species to be deliberately spread by recreational anglers (USGS-NAS, 2014).

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Acclimatization societiesPrincipally Florida and Hawaii (USA) Yes Yes USGS NAS, 2014
Hunting, angling, sport or racingPrincipally Florida and Hawaii (USA) Yes Yes USGS NAS, 2014
Intentional releaseAustralia and USA Yes Yes ACTFR, 2014; USGS NAS, 2014
Pet tradeAustralia and USA Yes Yes ACTFR, 2014; USGS NAS, 2014

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Pets and aquarium species Yes Yes Corfield et al., 2008
WaterWithin River Systems (e.g. Florida) Yes Yes USGS NAS, 2014

Impact Summary

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CategoryImpact
Environment (generally) Negative

Environmental Impact

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Impact on Habitats

A. ocellatus may burrow/modify the substrate during nest preparation when breeding. Corfield et al. (2008) speculated that this behaviour may potentially impact aquatic habitats, native fish and invertebrate communities.

Impact on Biodiversity

Within Florida, USA, A. ocellatus is considered a potential competitor with native centrarchids (sunfishes) for food and possibly for spawning areas (Courtenay and Hensley, 1979a), and as predators on native fishes and invertebrates. Similarly, Robins (2007) opined that the spread of the species in southern Florida may have a negative effect on centrarchids which have similar habitat and ecological needs.

Latini and Petrere (2004) reported a decrease in species richness and diversity of lake fish fauna in south-eastern Brazil following the introduction of A. ocellatus along with other introduced fishes that are non-indigenous to the region.

The behaviour of A. ocellatus may, in some circumstances, increase potential impacts on sympatric fishes. The species is territorial and dominance hierarchies are established through agonistic displays (Beeching, 1992). It is likely this agonistic behaviour will be directed not only at conspecifics but also sympatric fishes. Furthermore, Beeching (1992) found that in the laboratory A. ocellatus can assess the size of other fish visually. Smaller native fishes co-occurring with A. ocellatus are potentially more likely to be targeted and also more vulnerable to agonistic behaviour.
 

Risk and Impact Factors

Top of page Invasiveness
  • Invasive in its native range
  • Proved invasive outside its native range
  • Has a broad native range
  • Abundant in its native range
  • Highly adaptable to different environments
  • Is a habitat generalist
  • Capable of securing and ingesting a wide range of food
  • Benefits from human association (i.e. it is a human commensal)
  • Long lived
  • Fast growing
  • Has high reproductive potential
  • Gregarious
Likelihood of entry/control
  • Highly likely to be transported internationally deliberately
  • Difficult/costly to control

Uses

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Economic Value

A. ocellatus is a popular ornamental species in Australia (Corfield et al., 2008), the United States (Rixon et al., 2005) and worldwide. It is considered of “High” importance as an ornamental fish in Australia, with the volume of fish sold ranked as “Medium” (between 10,000 and 100,000 fish sold annually Australia wide) (Corfield et al., 2008).

Social Benefit

A. ocellatus has been used as a model for behavioural research (Zaret, 1977; Beeching 1992; 1995; 1997).

Uses List

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General

  • Pet/aquarium trade
  • Research model
  • Sport (hunting, shooting, fishing, racing)

Similarities to Other Species/Conditions

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Artificial breeding has produced several colour variants (Axelrod, 1993), and genetic analyses have suggested the presence of “morphologically cryptic species” within Astronotus (Colatreli et al., 2012).

However, A. ocellatus is distinctive and non-native populations are unlikely to be misidentified with sympatric species including other cichlids.

Gaps in Knowledge/Research Needs

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More research needs to be conducted on the impacts of A. ocellatus on ecosystems and resource competition with sympatric fishes.

No data was found on attempts to control introduced populations of A. ocellatus. This is unusual considering the popularity of the species and the frequency of introduction, particularly in the USA. Thus, control strategies are also a research priority.

References

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Links to Websites

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Principal Source

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Draft datasheet for peer review

Contributors

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08/05/2014 Original text by:

Mark Maddern, University of Western Australia, Australia

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