That's a great fish on fly, Leonard. It's an adolescent giant grouper, also known as the Queensland groper (as some grouper are referred to Down Under), Epinephelus lanceolatus. This species is the largest reef-dwelling bony fish, and has been reliably recorded to 9 feet long and nearly 900 pounds. Indeed, they grow big enough to attack divers and are one of the few bony fishes confirmed to initiate fatal attacks on humans. Giant grouper range widely throughout the Indo-Pacific region from the Red Sea to Japan, Australia and the Hawaiian Islands. The juvenile giant grouper that frequent tropical and subtropical estuaries are pretty fish with distinctive black-and-yellow blotchy flanks. Growth is fast, and they begin to mature in four to five years at between 3 and 4 feet long, as females and later changing into males. During maturation, most giant grouper leave estuaries and move offshore, where the yellow blotches on their flanks give way to a more uniform drab green/gray. Once offshore, adults frequent underwater caves, wrecks, and ledges in rocky and coral reefs. The adults eventually lose the yellowish tinge on fins and tail altogether once they exceed 150 pounds or so. Giant grouper merit their name: The all-tackle world record weighed 395 pounds, 11 ounces, from Tanzania in 2004. Their diet consists mainly of crustaceans (whole mud crabs or crayfish), small sea turtles, and fish. Giant grouper appear on threatened species lists and are now very rare in the wild throughout Asia, largely because of their popularity in the live reef-fish trade, where they fetch extremely high prices ($50 to $80 per pound) thanks to being considered a "lucky fish."