Oreochromis aureus competes with native fishes for food, spawning area, and space, and exhibits aggressive behavior. They have become the dominant species in many of their introduced ranges. Several introductions have correlated with and are believed to cause reductions in abundance of native fishes and even molluscs. Blue tilapia structure phytoplankton communities by their feeding preference of specific algae, having significant effects on the entire community ecology. Some reports maintain certain introduced areas have lost most and nearly all native fishes (McDonald, 1987; GSMFC, 2003; FishBase, 2007; Nico, 2007).
Location Specific Impacts:
Competition: Introduced tilapias, including Oreochromis aureus compete for breeding and/or feeding resources directly with Hypsophrys nicaraguensis, Parachromis dovii and some forms of Amphilophus citrinellus (McCrary et al. 2007).
Ecosystem change: The introduction of Oreochromis aureus to Lake Nicaragua is likely to have effects on the planktonic community and primary productivity of the lake (McKaye et al. 1995).
Other: Oreochromis aureus is believed to displace native cichlids such as Cichlasoma nicaraguense, Cichlasoma longimanus, Cichlasoma rostratum and Cichlasoma citrinelluml in Lake Nicaragua since their populations have been dramaitcally reduced following the introduction of O. aureus and catches are inversely associated (McKaye et al. 1995; McCrary et al. 2007).
United States (USA)
Competition: Oreochromis aureus is known to have competed with Micropterus salmoides salmoides for spawning space thereby affecting their population size (FishBase, 2007).
Florida (USA) (United States (USA))
Competition: The invasion of Oreochromis aureus to the Taylor Slough portion the Everglades National Park has caused a major management problem for the National Park Service (Nico, 2007).
Competition: Young Oreochromis aureus exhibit considerable trophic overlap with Dorosoma spp. in early life stages indicating exploitative competition in Florida, which may explain decline in Dorosoma spp. shad abundance (McDonald, 1987; Zale & Gregory, 1990).
Nevada (United States (USA))
Reduction in native biodiversity: A dramatic reduction in native fishes coincided with the invasion of Warm Springs, Nevada by Oreochromis aureus (Nico, 2007).
Texas (United States (USA))
Competition: High densities of Oreochromis aureus in Lake Trinidad, Texas were believed to inhibit reproduction of largemouth bass (GSMFC, 2003).
Competition: Young Oreochromis aureus exhibit considerable trophic overlap with Dorosoma spp. in Texas (McDonald, 1987).
Reduction in native biodiversity: The invasion of Oreochromis aureus is blamed for the decline of unionid mussels in Tradinghouse Creek and Fairfield reservoirs, Texas (Nico, 2007).