The John Dory, also widely known as Saint Peter's Fish or the Kupfish, is one of the most recognisable and distinctive fish in the regional seas. It belongs to the order of Zeiformes and is distinguished by its extremely high and compressed body that resembles a plate. The body is almost circular and is covered with microscopic scales, while its mouth is huge and can extend strongly forward using a protrusible jaw.

The most famous feature is a large, round, black spot in the centre of each side, surrounded by a yellow ring. According to legend, this spot represents the fingerprint of Saint Peter, which explains its alternative names in many cultures. Another interpretation suggests that this spot serves as a false eye to confuse predators or prey.

This is a benthopelagic and solitary species. It lives near the bottom, although it often hovers a few metres above it. It prefers muddy and sandy seabeds but often approaches rocky areas. The depth at which it is encountered usually ranges from 10 to 400 metres, though it is more commonly found between 50 and 150 metres.

The John Dory is a medium-sized fish. The usual length of capture is 30 to 40 centimetres. It can, however, reach a maximum length of 60 to 70 centimetres, or even 90 centimetres in rare cases, and a weight of up to 8 kilograms, although it is usually 1 to 2 kilograms due to its thin body.

The animal is a skilful ambush-and-approach predator. It is not a fast swimmer, but it uses its almost-invisible pectoral fins to approach its prey slowly and silently. Due to its compact body, it is almost invisible when viewed head-on. Once it reaches firing range, it shoots out its huge mouth, creating a vacuum that sucks in the prey. It feeds mainly on schooling fish such as sardines, bogues, and picarels as well as cephalopods.

Reproduction of the John Dory takes place in the spring. In the Mediterranean, this period extends primarily from March to May. The eggs are pelagic and float in the water. The fish reach sexual maturity approximately in the fourth year of their lives when they are around 30 to 35 centimetres long.

It is not targeted in large quantities, but it is a valuable bycatch for bottom trawlers and static nets. It is also caught occasionally on deep handlines. It has very high commercial value and is considered one of the most select gourmet fish. The meat is white and firm, without small bones, and has a delicate, sweet flavour that resembles seafood such as crab or lobster. It is an ideal choice for filleting in a pan, in the oven, or steamed.

The International Union for Conservation of Nature has not fully assessed the species in the region, but it is generally not considered to be at immediate risk. Scientific studies have shown that the John Dory has a relatively long lifespan of 12 to 14 years and that females grow faster and live longer than males. Furthermore, research on the Black Sea has confirmed its presence and shown its wide distribution.