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Thekrill fishery is the commercialfishery ofkrill, smallshrimp-like marine animals that live in the oceans world-wide. The present estimate for the biomass ofAntarctic krill (Euphausia superba) is 379 million tonnes.^[1] The total global harvest of krill from all fisheries amounts to 150–200,000 tonnes annually, mainly Antarctic krill andNorth Pacific krill (E. pacifica).

Krill are rich inprotein (40% or more of dry weight) andlipids (about 20% inE. superba). Theirexoskeleton amounts to some 2% of dry weight ofchitin. They also contain traces of a wide array ofhydrolyticenzymes such asproteases,carbohydrases,nucleases andphospholipases, which are concentrated in the digestive gland in thecephalothorax of the krill.

Most krill is used asaquaculture feed and fishbait; other uses include livestock or pet foods. Only a small percentage is prepared for human consumption. Their enzymes are interesting for medical applications, an expanding sector since the early 1990s.

Krill are small animals, considered a type ofzooplankton, and hence need to be fished with fine-meshed plankton nets. Such nets pose several problems: they tend to clog fast, and they have highdrag, producing abow wave that deflects the krill to the sides.Trawling must hence be done at low speeds. Additionally, fine nets are delicate, and the first krill nets designed exploded while fishing through the krill schools. Furthermore, fine nets increase unwanted bycatch, such as fish fingerlings, which might have unforeseen side-effects on the ecosystem, even though large krill aggregations tend to be monospecific.

Another problem is bringing the krill catch on board. When the full net is hauled out of the water, the organisms compress each other, resulting in great loss of the krill's liquids. Experiments have been carried out to pump Antarctic krill, while still in water, from the cod end of the net through a large tube on board. This method had already been used by the small fishing boats in Japanese waters; it increases the capture capacity and the processing rate of krill.

External image
The krill trawler FVSaga Sea

One of the first Antarctic krill trawlers to use this technique was theFV Atlantic Navigator, registered inVanuatu and owned by theNorwegian-based companyAker ASA,^[2] which used this technique in the 2003/04 and 2004/05 fishing seasons. In these seasons, this ship alone caught 25% and 38% of the whole krill catch inCCAMLR regions.^[3] The successor ship of theAtlantic Navigator, theFV Saga Sea, can fish up to about 120,000 tonnes of krill annually,^{[Note 1]} and Aker announced plans to build more such ships -Antarctic Endurance launching early 2019.^[7][8]

Krill must be processed within one to three hours after capture due to the rapidenzymatic breakdown and the tainting of the meat by the intestines.^[9] They must be peeled because their exoskeleton containsfluorides, which are toxic in high concentrations.

Krill is a rich source ofprotein andomega-3 fatty acids which are under development in the early 21st century as human food,dietary supplements as oil capsules, livestock food, andpet food.^[10][11][12] Most krill is processed to produce fish food for use inaquariums andaquacultures. The krill is soldfreeze-dried, either whole or pulverized. Krill as a food source is known to have positive effects on some fish, such as stimulating appetite or resulting in an increased disease resistance.^{[citation needed]} Furthermore, krill containscarotenoids and is thus used sometimes as a pigmentizing agent to color the skin and meat of some fish. About 34% of the Japanese catch ofE. superba and 50% ofE. pacifica are used for fish food; the Canadian catch is used almost exclusively for this purpose.

One quarter of the Japanese catch ofE. superba is used in the form of fresh frozen krill as fishbait and half theE. pacifica catch is used aschum for sport fishing. The Japanese industry produces boiled, frozen krill and peeled tail meat. Other uses include krill pastes or processed krill as food additives, e.g. in the form ofkrill oil gel capsules. Only a small amount ofE. superba is processed for human consumption.

Medical applications of krillenzymes include products for treatingnecrotic tissue and as chemonucleolytic agents. Of the 376 krill-related patents that had been registered world-wide until 2002, 17% related to medical uses. Most of these medical patents had been registered after 1988.^[13]

Krill fishery in theSouthern Ocean targets the largest species of krill existing, theAntarctic krill (Euphausia superba), which can grow to about 6 cm (2.4 in). Although krill are found worldwide, fishing in Southern Oceans are preferred because the krill are more "catchable" and abundant in these regions. Particularly in Antarctic seas which are considered aspristine, they are considered a "clean product".^[10] Fishing began in the early 1960s, when theSoviet Union launched its first experimental operations. All throughout the decade, preparatory activities were carried out, resulting in small catches of a few tens of tonnes per year. Scientists mapped the locations of krill swarms to determine the best fishing grounds, and engineers developed and improved the equipment necessary to fish and process krill. In 1972, the Soviets set up a permanent fishery inAntarctic waters, landing 7,500 tonnes in 1973 and then expanding quickly. The Japanese began experimental krill fishing operation in the area in 1972 and started full-scale commercial operations in 1975.

Krill catch increased rapidly. In the 1980s, a few additional nations started operating in the area:Poland,Chile, andSouth Korea. Their catches amounted to a few thousand tonnes annually; the lion's share went to the Soviet Union, followed by Japan. A peak in krill harvest was reached in 1982 with a total production of over 528,000 tonnes, of which the Soviet Union produced 93%. In the following two years, production declined. It is unclear whether this was due to the discovery offluorides in the krill's exoskeleton or to marketing problems. The trade recovered quickly, though, and reached more than 400,000 tonnes again in 1987.

With the demise of the Soviet Union, two of its successor nations,Russia andUkraine, took over the operations. Russian operations and catches dwindled, and were abandoned altogether in 1993. Since then,Japan is one of the top producers, but facing stiff competition by other countries. Since 2000, the smallSouth Korean Antarctic krill fishery has also expanded considerably. AU.S. company entered the market in 2001. TheNorwegian companyAker ASA entered the business in 2003 with a ship registered inVanuatu.

In 1982, theConvention on the Conservation of Antarctic Marine Living Resources (CCAMLR) came into force, as part of theAntarctic Treaty System. The CCAMLR was originally signed by fifteen states; as of 2004 it had 24 members. Its purpose is to regulate the fishery in the Southern Ocean to ensure a long-term sustainable development and to preventoverfishing. In 1993, the CCAMLR set forth catch quotas for krill, which amount to nearly five million tonnes per year.^[15]

The annual catch ofEuphausia superba since the mid-1990s is about 100–120,000 tonnes annually, i.e., about one fiftieth of the CCAMLR catch quota. Still, the CCAMLR is criticized for having defined its catch limits too generously, as there are no precise estimates of the total biomass of Antarctic krill available and there have been reports indicating that it is declining since the 1990s.^[16] Plans to take up to 746,000 tonnes a year were disclosed at the 2007 meeting of CCAMLR.^[17][18]

Fishing for Antarctic krill was commonly done from large stern trawlers usingmidwater trawls before the purpose built krill trawlers likeAntarctic Endurance were planned and put into use. For scientific purposes, vertical trawls using, for example, a bongo net, are also employed.

In 2018 it was announced that almost every krill fishing company operating in Antarctica will abandon operations in huge areas around the Antarctic Peninsula from 2020, including “buffer zones” around breeding colonies of penguins.^[19]

The krill fishery in Japanese waters primarily targets theNorth Pacific krill (Euphausia pacifica), which reaches a size of about 2 centimetres (0.79 in). The annual catch is of the order of 60–70,000 tonnes. Minor fisheries forEuphausia nana (a few thousand tonnes) andThysannoessa inermis (a few hundred tonnes annually) also exist. The fishing ground are all above thecontinental shelf close to the coast and at most 200 m (660 ft) deep.E. nana reaches only 1.2 cm, andT. inermis can grow to 3 cm (1.2 in).

E. pacifica was fished as early as the 19th century. Fishing is done with small boats. The traditional technique uses bow-mounted trawls, augmented by fish pumps since the 1980s. A bow-mounted trawl can exploit only surface swarms of krill up to a depth of about eight metres. In the 1970s, the krill fishery expanded drastically and began to use also one- or two-boatseines, which can catch swarms as deep as 150 m (490 ft). A peak in the krill production was reached in 1992 with over 100,000 tonnes. The following year, catch regulations were enforced, and since then the annual catch has been reduced by about 30%.

Small-scale fisheries for krill also exist in other areas. InCanada, fishing forE. pacifica takes place in theStrait of Georgia offBritish Columbia; there is a government-imposed catch limit of 500 tonnes per year. Fisheries targeting theNorthern krill (Meganyctiphanes norvegica), a medium-sized krill reaching body lengths of more than 4 cm (1.6 in), as well asTysanoessa raschii (2 cm) andT. inermis in theGulf of St. Lawrence and on theScotian Shelf have been proposed, but didn't get beyond early experimental stages. They are limited to harvesting a few hundred tonnes of krill per year, and Nicol & Foster^[13] consider it unlikely that any new large-scale harvesting operations in these areas will be started due to the opposition from local fishing industries and conservation groups.

• List of harvested aquatic animals by weight

The main reference for this article is a report from 1997:

• Steven Nicol & Yoshinari Endo (1997).Krill Fisheries of the World. FAO Fisheries Technical Paper. Vol. 367. Rome:Food and Agriculture Organization.ISBN 92-5-104012-5.

• Inigo Everson, ed. (2000).Krill: Biology, Ecology and Fisheries. Fish and Aquatic Resources Series. Vol. 6. Oxford:Blackwell Science.ISBN 0-632-05565-0.
• Hill, Simeon (2013)."Prospects for a Sustainable Increase in the Availability of Long Chain Omega 3s: Lessons from the Antarctic Krill Fishery"(PDF).Omega-6/3 Fatty Acids. New York: Springer Business + Media. pp. 267–299.doi:10.1007/978-1-62703-215-5_14.ISBN 978-1-62703-215-5.
• Steven Nicol & Yoshinari Endo (1999)."Krill fisheries: Development, management and ecosystem implications"(PDF).Aquatic Living Resources.12 (2):105–120.doi:10.1016/S0990-7440(99)80020-5.S2CID 84158071.^{[permanent dead link]}
• Stephen Nicol, Jacqueline Foster & So Kawaguchi (2012). "The fishery for Antarctic krill – recent developments".Fish and Fisheries.13 (in press):30–40.doi:10.1111/j.1467-2979.2011.00406.x.

• An active network of internationalnon-governmental organizations dedicated to the protection of Antarctic krill is theAntarctic Krill Conservation Project, started by theAntarctic and Southern Ocean Coalition and other entitites.

• Krill
• Fishing industry

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