Blue Tilapia
Oreochromis aureus
Oscar
Astronotus ocellatus
About
A big, bold cichlid of slow Amazon rivers, the oscar typically reaches about 24 cm long, though the largest grow to 45.7 cm and can weigh up to 1.58 kg.
Also known as: astronotus ocellatus, marble cichlid, red oscar, velvet cichlid
- Length
- 24 cm · max 45.7 cm
- Weight
- max 1.6 kg
- Temperature
- 22–25 °C
How to tell it apart
Other dark cichlids share these same slow rivers. Check the base of the tail: the oscar's rounded black spot there, rimmed in orange like a false eye, is the mark to look for.
Appearance
Wild oscars are darkly coloured, with a bright orange rim along the edge of the gill cover and on the lower sides of the body. Several yellow-ringed spots, called ocelli, mark the dorsal fin and the base of the tail. This fish can change its colour quickly, which it uses during territorial standoffs with other oscars. Young oscars look nothing like adults: they are striped with wavy white and orange bands and have spotted heads.
Habitat
It lives in slow-moving, silty rivers of the Amazon basin, sheltering under submerged branches, and also turns up in quiet, shallow mud- or sand-bottomed canals and ponds. It needs warm water, generally between 22 and 25°C, and does poorly anywhere the water turns cold.
Behaviour
An oscar will claim a patch of habitat as its own and defend it vigorously, chasing off other fish that come too close. The size of the territory it holds depends on the fish's own size and how aggressive it is.
Diet
The oscar is an omnivore. In the wild it mainly hunts slow-moving catfish, using a strong suction bite to pull prey in, and also eats shrimp, snails, insects and their larvae, along with fruit and nuts when in season. It has even been seen lying on its side, apparently playing dead, a trick that may help it ambush prey.
Breeding
Oscars are biparental substrate spawners: a mated pair chooses and cleans a flat surface, lays their eggs there together, and both parents care for the resulting brood. Spawning may be timed to coincide with rainfall.
Is it dangerous?
harmless
Did you know?
The orange-ringed spot near the oscar's tail may work as a decoy eye, drawing bites from fin-nipping piranhas away from its real head.
Log it in Into the Blue
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