Just like fresh fruit and vegetables, fresh fish too are seasonal. St Pierre are currently in season here in Tunisia. This fish can easily be identified by the dark spot on its flank and the long spines along its dorsal fin.
John Dory, also known as St Pierre or Peter's Fish, refers to fish of the genus Zeus, especially Zeus faber, of widespread distribution. It is an edible benthic coastal marine fish with a laterally compressed olive-yellow body which has a large dark spot, and long spines on the dorsal fin. The dark spot is used to flash an 'evil eye' if danger approaches the John Dory. Its large eyes at the front of the head provide it with bifocal vision and depth perception, which are important for predators. The John Dory’s eye spot on the side of its body also confuses prey, which are scooped up in its big mouth.
Various explanations are given of the origin of the name. It may be an arbitrary or jocular variation of dory (itself from the French dorée, gilded), or perhaps an allusion to John Dory, the hero of an old ballad. Others suggest that "John" derives from the French jaune, yellow. The novel An Antarctic Mystery by Jules Verne gives another account, which has some popularity but is probably fanciful: "The legendary etymology of this piscatorial designation is Janitore, the 'door-keeper,' in allusion to St. Peter, who brought a fish said to be of that species, to Jesus at his command." (St. Peter is said to be keeper of the gates of Heaven, hence "door-keeper".) Considering that the other known names for the John Dory are the "St. Pierre", or "Peter's Fish", as referenced above, this seems the most likely etymological origin and may also explain why dories were often referred to as Peter Boats (Saint Peter being the patron saint of fishermen). A related legend says that the dark spot on the fish's flank is St. Peter's thumbprint.
John Dory are coastal fish, found on the coasts of Africa, South East Asia, New Zealand, Australia, the coasts of Japan, and on the coasts of Europe. They live near the seabed, living in depths from 5 metres (15 ft) to 360 metres (1200 ft). They are normally solitary.