Never seen a John Dory? You have to catch it sideways on, says Paul Naylor
Stuff of legends The John Dory is a strange, mournful-looking fish. Its name is said to be derived from the Latin for doorkeeper, janitore, but its Latin name, Zeus faber, means 'blacksmith of the gods'. The species seems surrounded by legends, the best-known being that the dark blotches on each flank are St Peter's fingerprints, left when he took a coin from the fish's mouth to pay his tax.
Round round, get around The John Dory can be seen all around Britain but the South-west probably represents the northern extent of its breeding range. Distribution is virtually worldwide in temperate and tropical waters. British divers surrounded by the sort of fish found in New Zealand, for example, get quite a surprise when they suddenly see the comparatively familiar John Dory.
Shooting its mouth off The jaws of the John Dory have a special bone construction which makes them highly protrusible. Once close to its unsuspecting victim, usually small fish such as sand-eels, herring and pilchard, the mouth shoots out to engulf it. In the shallow water where encounters with divers occur, it is often seen hunting two-spot gobies that hover in patches of seaweed.
Call it Kate Moss The body of a John Dory is shaped like a flat oval plate on edge. It is so thin that it virtually disappears when viewed head- or tail-on. It uses this characteristic to good effect both when approaching unsuspecting prey and avoiding predators. A John Dory can be difficult to photograph, as it continually turns its back on watching divers.
Big John The John Dory is a fast-growing fish and can reach more than 60cm in length (females are largest), though most individuals seen by divers are youngsters of around 20 to 30cm. The British rod-caught record fish was hefty, weighing almost 5kg.
Angle poise While not a rapid mover, this species shows great manoeuvrability when stalking its prey, swimming while tilted at all sorts of angles and even upside-down. At the same time, stripes on its flanks can alternately recede and intensify which, coupled with the thin outline, makes its approach even harder to spot.