Tilapia (/tɨˈlɑːpiə/ ti-LA-pee-ə) is the common name for nearly a
hundred species of cichlid fish from the tilapiine cichlid tribe. Tilapia are mainly freshwater fish inhabiting shallow streams, ponds, rivers and lakes and less commonly found living in brackish water. Historically, they have been of major importance in artisan fishing in Africa and the Levant and are of increasing importance in aquaculture and aquaponics. Tilapia can become problematic invasive species in new warm-water habitats, whether deliberately or accidentally introduced, but generally not in temperate climates due to their inability to survive in cooler waters below about 21 °C (70 °F).
Kind of like getting 'scrod' or 'schrod' in Boston. It's the white fish of the day, typically the most available 'white fish catch of the day'. Scrod = Cod and Schrod = Haddock.
I do not wish to begin a semantic battle, however to say Talapia is not a fish because the name is common for nearly a hundred species of Ciclid would be the same as telling his “Urchin” they could not go fishing for catfish because there is not real fish called a catfish.