Escolar (Lepidocybium flavobrunneum), often sold as "white tuna," "butterfish" or "super white tuna," is a large deep-water snake mackerel prized for its exceptionally rich, buttery white flesh. The same oiliness that makes it so silky, however, comes from indigestible wax esters that can cause an unpleasant digestive upset if too much is eaten.