Pelagic fish

A school of large pelagic predator fish (tuna) sizing up a school of small pelagic fish (anchovies)

Pelagic fish are fish that live and feed in the open water column, away from the bottom of the sea or a lake. They can be contrasted with demersal fish, which live on or near the bottom of the sea or a lake.

Some pelagic fishes are coastal fishes, while other pelagic fishes spend at least part of their lives in the open sea. These open sea fish are usually migratory forage fish, which feed on plankton, and the larger fish that follow and feed on the forage fish. Examples of migratory forage fish are herring, anchovies, blue whiting, mackerel, capelin and menhaden. Examples of larger pelagic fish which feed on the forage fish are billfish, tuna and oceanic sharks.

Small pelagic fish

See also: Forage fish

Small pelagic fish are usually forage fish, which are hunted by larger pelagic fish and other predators. Forage fish are plankton feeding fish that stay together in schools and tend to migrate large distances between spawning grounds and feeding grounds. They are found particularly in upwelling regions around the northeast Atlantic, off the coast of Japan,and off the west coasts of Africa and the Americas. Forage fish generally live short lives, and their stocks fluctuate markedly over the years.

Herring are found in the North Sea and the North Atlantic at depths to 200 meters. Important herring fisheries have existed in these areas for centuries. Herring of different sizes and growth rates belong to different populations, each of which have their own migration routes. When spawning, a female produces from 20,000 to 50,000 eggs. After spawning, the herrings are depleted in fat, and migrate backto feeding grounds rich in plankton.

Around Europe there are three populations of mackerel. One population migrates to the North Sea, another stays in of the Irish Sea, and the third population migrates southwards along the west coast of Scotland and Ireland. The mackerel's cruise speed is an impressive 10 kilometres per hour.

Blue whiting are found in the open ocean and above the continental slope at depths between 100 and 1000 meters. They follow vertical migrations of the zooplankton they feed on to the bottom during daytime and to the surface at night time.

Traditional fisheries for anchovies and sardines have also operated in the Pacific, the Mediterranean, and the southeast Atlantic. The world annual catch of forage fish in recent years has been around 25 million tonnes, or one quarter of the world's total catch.

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  These schooling anchovy are forage fish
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  Atlantic herring
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  Capelin
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  Menhaden

Large pelagic fish

Most large pelagic fish feed largely on the small pelagic forage fish. At times, they follow the schooling forage fish, and some species form schools themselves.

"Pelagic fish (tuna, marlin, bonito, albies, dorado, swordfish etc..) are migratory off-shore bluewater nomadic species who have no home."

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  Little tunny

Highly migratory species

See also: Straddling stock and Bonn Convention

The term highly migratory species (HMS) has its origins in Article 64 of the United Nations Convention on the Law of the Sea (UNCLOS). The Convention does not provide an operational definition of the term, but in an annex (UNCLOS Annex 1) lists the species considered highly migratory by parties to the Convention.

The list includes: tuna and tuna-like species (albacore, bluefin, bigeye tuna, skipjack, yellowfin, blackfin, little tunny, southern bluefin and bullet), pomfret, marlin, sailfish, swordfish, saury and ocean going sharks, dolphins and other cetaceans.

These are high trophic level species which undertake migrations of significant but variable distances across oceans for feeding, often on forage fish, or reproduction, and also have wide geographic distributions. Thus, these species are found both inside the 200 mile exclusive economic zones and in the high seas outside these zones. They are pelagic species, which means they mostly live in the open ocean and do not live near the sea floor, although they may spend part of their life cycle in nearshore waters.

Highly migratory species can be compared with straddling stock and transboundary stock. Straddling stock range both within an EEZ as well as in the high seas. Transboundary stock range in the EEZs of at least two countries. A stock can be both transboundary and straddling.

• Yellowfin tuna
  Yellowfin tuna
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  These Pacific White-sided Dolphins are oceanic dolphins
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  Atlantic pomfret
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  Swordfish

Oceanic sharks

• Fishing puts a third of all oceanic shark species at risk of extinction guardian.co.uk, 25 June 2009.

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  The dangerous oceanic whitetip shark
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  Silky shark
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  Tiger shark
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  White shark

See also

• Oily fish

References

• Bone Q and Moore RH (2008) Biology of Fishes, Taylor & Francis Group. ISBN 978 0 415 375627

External references

• Pelagic fish - Institute of Marine Research