Ecological Risk Screening Summary - Oscar (Astronotus ocellatus) - Uncertain Risk

Species that are considered uncertain risk need a more in-depth assessment beyond the Risk Summary to better define the species’ risk to U.S. environments.

Oscar (Astronotus ocellatus) is a cichlid native to much of South America. Extremely tolerant to low oxygen conditions, this species prefers slow-moving waters where it feeds on fruits, small fish, crayfish, worms and insect larvae. Under the right conditions this omnivorous fish can grow to a large size. A. ocellatus is common in the aquarium trade, and is used as a game and commercial fish for human consumption. It is reportedly affected by a number of bacterial and parasitic infections. Numerous A. ocellatus specimens have been taken from waterbodies across the contiguous United States. Most of these introductions likely resulted from aquarium releases, although, in Florida, the species was deliberately stocked as a sport fish in the 1950s. This species is now established in ponds, rock pits, and canals in southern Florida, and in Hawaii and Puerto Rico. Distribution and abundance in Florida varies with prevalence of cold temperatures. A. ocellatus has expanded its range greatly in south Florida since introduction in the 1950's, and is believed to have expanded to the Everglades National Park through Water Management District canals. Taxonomy is somewhat problematic, such that some specimens found in the United States may later be determined to be a separate species. A. ocellatus was included by the State of Florida in a health advisory warning people about eating freshwater fish contaminated with mercury in 1993. In Brazil, introductions of A. ocellatus, Pygocentrus nattereri, and Cichla cf. monoculus have been associated with the disappearance of native species from several water bodies, although the distinct contributions of A. ocellatus were not identified. Biologists have noted A. ocellatus may prey on native fish and invertebrates, compete with native sunfish for food, and possibly nesting sites, and males may be aggressive during spawning, but these potential impacts have yet to be documented. Climate match with the contiguous United State was medium, with a high match throughout Florida. Because the evidence for negative impacts of introduction is not clear and convincing, the certainty of the assessment is low and the overall risk assessment category for Astronotus ocellatus is uncertain.