Krill are a type of shrimp-like marine invertebrate animal. These small crustaceans are important organisms of the zooplankton, particularly as food for baleen whales, manta rays, whale sharks, crabeater seals, and other seals, and a few seabird species that feed almost exclusively on them. Another name is euphausiids, after their taxonomic order Euphausiacea. The name krill comes from the Norwegian word krill meaning "young fry of fish," which is also often attributed to other species of fish.
Krill are an important element of the food chain. Antarctic krill feed directly on phytoplankton, converting the primary production energy into a form suitable for consumption by larger animals that cannot feed directly on the minuscule algae. Many animals feed on krill, ranging from smaller animals like fish or penguins to larger ones like seals and even baleen whales.
Krill occur in all oceans of the world. They are considered keystone species near the bottom of the food chain because they feed on phytoplankton and to a lesser extent zooplankton, converting these into a form suitable for many larger animals for whom krill makes up the largest part of their diet. In the Southern Ocean, one species, the Antarctic krill, Euphausia superba, makes up an estimated biomass of over 500 million tons, roughly twice that of humans. Most krill species display large daily vertical migrations, thus providing food for predators near the surface at night and in deeper waters during the day.
Commercial fishing of krill is done in the Southern Ocean and in the waters around Japan. The total global harvest amounts to 150,000–200,000 metric tonnes annually, most of this from the Scotia Sea. Most of the krill catch is used for aquaculture and aquarium feeds, as bait in sport fishing, or in the pharmaceutical industry. In Japan and Russia, krill is also used for human consumption and is known as okiami (オキアミ) in Japan.
Krill has been harvested as a food source for humans (okiami) and domesticated animals since the 19th century, in Japan maybe even earlier. Large-scale fishing developed only in the late 1960s and early 1970s, and now occurs only in Antarctic waters and in the seas around Japan. Historically, the largest krill fishery nations were Japan and the Soviet Union, or, after the latter's dissolution, Russia and Ukraine. A peak in krill harvest had been reached in 1983 with more than 528,000 metric tons (520,000 LT; 582,000 ST) in the Southern Ocean alone (of which the Soviet Union produced 93%). In 1993, two events led to a drastic decline in krill production: first, Russia abandoned its operations, and second, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) defined maximum catch quotas for a sustainable exploitation of Antarctic krill. The annual catch in Antarctic waters seems to have stabilised around 100,000 metric tons (98,000 LT; 110,000 ST) of krill, which is roughly one fiftieth of the CCAMLR catch quota.The main limiting factor is probably the high cost associated with Antarctic operations, although there are some political and legal issues as well. The fishery around Japan appears to have saturated at some 70,000 metric tons (69,000 LT; 77,000 ST).
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Krill"