Tropical to temperate latitudes of eastern Atlantic, Indian, and western Pacific oceans
Deep reefs and soft bottoms
Order Zeiformes (dories and relatives), Family Zeidae (dories)
The John Dory is an interesting looking fish that lives throughout the tropical and temperate latitudes of the world oceans, except in the Americas (i.e., except in the eastern Pacific and western Atlantic oceans). There are several theories about the origination of the common name but little evidence about its actual meaning. The discus-shaped body is broad when viewed from the side but very thin when viewed head on, giving the John Dory the ability to confuse predators by “changing size” quickly, simply by turning to the side. The dark spot on its side is also meant to provide confusion.
The John Dory is an active predator and eats a variety of schooling fishes and invertebrates. It lives in a wide depth range, from 15 feet (5 m) to 1200 feet (360 m) and usually stays near the seafloor, over both soft and hard bottoms. John Dories are medium-sized predators in the systems in which they live. They reach lengths of approximately two feet (65 cm) and weights of a few pounds. Larger bony fishes and sharks are known to feed on John Dories.
This species is typically somewhat solitary but comes together in groups to reproduce. It spawns by a behavior known as substrate scattering, where females scatter their eggs, haphazardly, on the seafloor, and males release their sperm in the same location to fertilize them externally. Individuals of this species do not construct nests and do not provide any care of the eggs. Unlike the eggs of species that reproduce via broadcast spawning, the eggs of the John Dory and other substrate scattering fishes do not float. Only after the eggs hatch do the larvae swim up into the water column to live a planktonic lifestyle.
The John Dory is generally considered an excellent food fish and is targeted by commercial fisheries in some areas. Its conservation status is not currently known, but it is not fished as heavily as some closely related species. However, this species is targeted by bottom trawling, a method known to be highly destructive to benthic habitats. It is therefore important to carefully manage the fishing activities for the John Dory, in order to ensure that this species’ habitat is not irreversibly damaged.