os·car 
(ŏskər)
(ŏskər)n.
A freshwater cichlid (Astronotus ocellatus) native to South America, having a spot at the base of the tail and often kept in home aquariums.
[Perhaps from the name Oscar, given to the fish as a pet or familiar name after New Latin ocellātus, the fish's specific epithet, from Latin ocellātus, having little eyes (from the spot at the base of its tail ); see OCELLATED.]