奧利亞口孵魚(Oreochromis aureus)會和本地魚類競爭食物、產卵場和生存空間，並表現出攻擊行為。他們已成為許多引入區的優勢物種。幾個引入的案例被認為會導致本土魚類大量減少，甚至影響到軟體動物。藍口孵魚偏好啃食特定的藻類，使浮游植物群落結構產生變化，嚴重影響整個生態群落。一些引入區的大部分地區已經失去了幾乎所有的原生魚類(McDonald, 1987; GSMFC, 2003; FishBase, 07; Nico, 2007)。
其他: 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).
生態系統變化: 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).
競爭: 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).
United States (USA)
競爭: 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))
競爭: 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).
競爭: 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))
降低本地生物多樣性: A dramatic reduction in native fishes coincided with the invasion of Warm Springs, Nevada by Oreochromis aureus (Nico, 2007).
Texas (United States (USA))
競爭: High densities of Oreochromis aureus in Lake Trinidad, Texas were believed to inhibit reproduction of largemouth bass (GSMFC, 2003).
競爭: Young Oreochromis aureus exhibit considerable trophic overlap with Dorosoma spp. in Texas (McDonald, 1987).
降低本地生物多樣性: The invasion of Oreochromis aureus is blamed for the decline of unionid mussels in Tradinghouse Creek and Fairfield reservoirs, Texas (Nico, 2007).