Jamaican waters contain considerable resources of fresh and saltwater fish. The chief varieties of saltwater fish are kingfish, jack, mackerel, whiting, bonito, and tuna. Fish that occasionally enter freshwater and estuarine environments include snook, jewfish, mangrove snapper, and mullets. Fish that spend the majority of their lives in Jamaica's fresh waters include many species of livebearers, killifish, freshwater gobies, the mountain mullet, and the American eel. Tilapia have been introduced from Africa for aquaculture, and are very common. Also visible in the waters surrounding Jamaica are dolphins, parrotfish, and the endangered manatee.