Pelagic Fish Definition

There are nearly 25,000 species of fish in the world living in a huge variety of environments, which means there are many ways to classify them. Some live in saltwater alone, some live in freshwater alone, some spend some time in saltwater and freshwater. There are fish that cling to rocks or hang out near coral reefs and fish that lie on the bottom of lakes and rivers. Then there are the fish that live and hunt in the open water, not on the bottom or near a reef. These fish are called pelagic, after the Greek word for "open sea."

  1. Not Pelagic

    • Sting rays are nonpelagic species belonging to a group of fish known as demersal.

      A common nonpelagic species is the hagfish which lives on the bottom of the ocean and survives on consuming dead and dying creatures that have fallen to the bottom. A typical reef dweller is the bright orange garibaldi. Species that live and feed on the bottom are called demersal and those that live near reefs are called reef fish. Demersal fish are further classified as benthic, like halibut, which live on the sea floor and benthopelagic which live in the water just above the floor.

    Saltwater Species

    • Familiar marine pelagic fishes are tuna, salmon, many sharks, swordfish and sailfish. There are many smaller pelagic schooling species too: anchovies, menhaden and herring for example. Pelagic fish can be both predator and prey and many, like menhaden and whale sharks, are filter feeders. So the category defies efforts to pin it down.

    Big Fish, Little Fish

    • Pelagic fish tend to be fast swimming and adapted to a variable diet.

      Size doesn't matter when it comes to whether a fish is pelagic or not. At more than a ton, the oceanic sunfish is both the largest fish with a skeleton and a pelagic fish as is the tiny sardine. What distinguishes them is where they make their home and look for food. Pelagic species do tend to be fast swimming and adapted to a variable diet since they have to get around in the open water where food can be scarce.

    Freshwater

    • Trout are an important freshwater pelagic species.

      Three fish families account for the largest number of pelagic freshwater species including the salmon, trout, grayling, whitefish and smelt. These are not surprisingly important sport and food fish and states go to great lengths to protect pelagic fisheries. However, agricultural pollution, loss of habitat and overfishing have endangered many pelagic species in both fresh and saltwater.There is considerable concern over the decline of pelagic fisheries in both fresh and saltwater.

    Cod Is Dead

    • The crash of the demersal cod has affected how governments react to pelagic species' declines.

      While it is not a pelagic but a demersal species, the cod remains one of the starkest examples of how humans can overuse a marine resource, and its history has had a profound effect on how states react to declines in pelagic fisheries. The amount of Atlantic cod off Nova Scotia has declined by 96 percent since 1850, according to a census of marine life by Andrew Rosenberg and others. The economies of the Maritimes and New England were devastated. In California, a freshwater pelagic species, smelt, is now facing a similar though less far-reaching crisis point, partly because of nitrogen runoff from waste treatment plants.