Oscar (fish)
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The oscar (Astronotus ocellatus) is a species of fish from the cichlid family known under a variety of common names, including tiger oscar, velvet cichlid, and marble cichlid.<ref name="fishbase">Template:Cite web</ref> In tropical South America, where the species naturally resides, A. ocellatus specimens are often found for sale as a food fish in the local markets.<ref name="kullander"/><ref>Template:Cite web</ref> The fish has been introduced to other areas, including India, China, Australia, and the United States. It is considered a popular aquarium fish in Europe and the U.S.<ref>Keith, P. O-Y. Le Bail & P. Planquette, (2000) Atlas des poissons d'eau douce de Guyane (tome 2, fascicule I). Publications scientifiques du Muséum national d'Histoire naturelle, Paris, France. p. 286</ref><ref name="amcichlidsII"/><ref name="Loiselle">Template:Cite book</ref>
Taxonomy
[edit]The species was originally described by Louis Agassiz in 1831 as Lobotes ocellatus, as he mistakenly believed the species was marine; later work assigned the species to the genus Astronotus.<ref name="florida_museum">Template:Cite web</ref> The species also has a number of junior synonyms: Acara compressus, Acara hyposticta, Astronotus ocellatus zebra, and Astronotus orbiculatus.<ref>Template:Cite web</ref>
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Description
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A. ocellatus examples have been reported to grow to about Template:Convert in length and Template:Convert in weight.<ref name="fishbase"/> The wild-caught forms of the species are typically darkly coloured with yellow-ringed spots or ocelli on the caudal peduncle and on the dorsal fin.<ref name="amcichlidsII"/> These ocelli have been suggested to function to limit fin-nipping by piranha (Serrasalmus spp.), which co-occur with A. ocellatus in its natural environment.<ref name="florida_museum"/><ref name="winemiller">Template:Cite journal</ref> The species is also able to rapidly alter its colouration, a trait which facilitates ritualised territorial and combat behaviours amongst conspecifics.<ref>Template:Cite journal</ref> Juvenile oscars have a different colouration from adults, and are striped with white and orange wavy bands and have spotted heads.<ref name="florida_museum"/>
Distribution and habitat
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A. ocellatus is native to Brazil, Colombia, Ecuador, Guyana, French Guiana, Suriname, Peru, and Venezuela, and occurs in the Amazon River basin, along the Amazon, Içá, Negro, Solimões, and Ucayali River systems, and also in the Approuague and Oyapock River drainages.<ref name="fishbase"/><ref name="kullander">Template:Cite web</ref> In its natural environment, the species typically occurs in slow-moving white-water habitats, and has been observed sheltering under submerged branches.<ref name="amcichlidsII">Template:Cite book</ref> Feral populations also occur in China,<ref>Template:Cite journal</ref> northern Australia,<ref>Template:Cite web</ref> and Florida, USA<ref>Template:Cite web</ref> as a byproduct of the ornamental fish trade. The species is limited in its distribution by its intolerance of cooler water temperatures, the lower lethal limit for the species is 12.9 °C (55.22 °F).<ref>Template:Cite journal</ref>
Reproduction
[edit]Although the species is widely regarded as sexually monomorphic,<ref name="amcichlidsII"/> males have been suggested to grow more quickly,Template:Citation needed and in some naturally occurring strains, males are noted to possess dark blotches on the base of their dorsal fins.<ref name="Loiselle"/><ref name="florida_museum"/> The species reaches sexual maturity around one year of age,<ref name="animaldiversity.org">Template:Cite web</ref> and continues to reproduce for 9–10 years.<ref name="animaldiversity.org"/> Frequency and timing of spawning may be related to the occurrence of rain.<ref>Template:Cite journal</ref> A. ocellatus fish are biparental substrate spawners, though detailed information regarding their reproduction in the wild is scarce.
In captivity, pairs are known to select and clean generally flattened horizontal or vertical surfaces on which to lay their eggs.Template:Citation needed. Smaller females lay around 300–500 eggs, while larger female oscars can lay about 2,500-3,000 eggs.<ref name="animaldiversity.org"/> Like most cichlids, A. ocellatus practices brood care, although the duration of brood care in the wild remains unknown.<ref name="Loiselle"/>
In the aquarium
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Oscar fish can live in the aquarium with almost any type of fish around the same size as it gets, for example any type of cichlids and predatory fish. Template:Citation needed
Food
[edit]Oscar fish are omnivores. Most fish eaten by A. ocellatus in the wild are relatively sedentary catfish, including Bunocephalus, Rineloricaria, and Ochmacanthus species.<ref name="winemiller" /> The species uses a suction mechanism to capture prey,<ref>Template:Cite journal</ref> and has been reported to exhibit "lying-on-side" death mimicry in a similar fashion to Parachromis friedrichsthalii and Nimbochromis livingstonii.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> Wild oscars also consume shrimp, snails, insects and insect larvae, as well as fruits and nuts on a seasonal basis.<ref>Template:Cite web</ref> The species also has an absolute requirement for vitamin C, and develops health problems in its absence.<ref>Template:Cite journal</ref> Captive oscars generally eat fish food designed for large carnivorous fish: crayfish, worms, and insects (such as flies, crickets and grasshoppers).<ref>Template:Cite web</ref>
Territorial behavior
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Oscars will often lay claim to an area of the aquarium and will be very aggressive towards other fish encroaching on their newly established territory inside the aquarium or lake. The size of the territory varies depending on the size and aggressiveness of the fish, and its surroundings. Once the oscar establishes a territory, it will vigorously defend it by chasing away other fish.<ref>Template:Cite journal</ref>
Varieties
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A number of ornamental varieties of A. ocellatus have been developed for the aquarium industry. These include forms with greater intensity and quantities of red marbling across the body, albino, leucistic, and xanthistic forms. A. ocellatus with marbled patches of red pigmentation are sold as red tiger oscars, while those strains with the mainly red colouration of the flanks are frequently sold under the trade name of red oscars.<ref name="tankbusters">Template:Cite book</ref> The patterning of red pigment differs between individuals. In recent years long-finned varieties have also been developed. The species is also occasionally artificially coloured by a process known as painting.<ref>Template:Cite web</ref> Template:Clear