Pelagic fish can be categorized as coastal and oceanic fish, based on the depth of the water they inhabit. Coastal pelagic fish inhabit sunlit waters up to about 655 feet deep, typically above the continental shelf. Examples of species include forage fish such as anchovies, sardines, shad, and menhaden and the predatory fish that feed on them. Oceanic pelagic fish typically inhabit waters below the continental shelf. Examples include larger fish such as swordfish, tuna, mackerel, and even sharks.
There is no distinct boundary from coastal to ocean waters so some oceanic fish become partial residents of coastal waters, often during different stages of their lifecycle. However, true oceanic species spend their entire life in the open ocean.
Pelagic fish get their name from the area that they inhabit called the pelagic zone. The pelagic zone is the largest habitat on earth with a volume of 330 million cubic miles. Different species of pelagic fish are found throughout this zone. Numbers and distributions vary regionally and vertically, depending on availability of light, nutrients, dissolved oxygen, temperature, salinity, and pressure.