Also known as King Mackerel, a true Kingfish is the species Scomberomorus cavalla.
Various other fish such as King Carangue, Yellowtail Amberjack and Pompano are sometimes mistaken for Kingfish but, although related, are a Jack or Trevally.
Once identified though, Kingfish is a great fish!
It has rich, oily, firm flesh, which can take a bit more abuse than Tuna, and like Mackerel, works better with sharp flavours.