Krill fishery

Antarctic krill(Euphausia superba)

Thekrill fisheryis the commercialfisheryofkrill,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.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). Theirexoskeletonamounts to some 2% of dry weight ofchitin.They also contain traces of a wide array ofhydrolyticenzymessuch asproteases,carbohydrases,nucleasesandphospholipases,which are concentrated in the digestive gland in thecephalothoraxof the krill.

Most krill is used asaquaculturefeed 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.

Technology

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 wavethat deflects the krill to the sides.Trawlingmust 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 inVanuatuand owned by theNorwegian-based companyAker ASA,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 inCCAMLRregions.The successor ship of theAtlantic Navigator,theFV Saga Sea,can fish up to about 120,000 tonnes of krill annually,and Aker announced plans to build more such ships -Antarctic Endurancelaunching early 2019.

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

Products

Deep frozen plates ofAntarctic krillfor use as animal feed and raw material for cooking

Krill oilcapsules

Krill is a rich source ofproteinandomega-3 fatty acidswhich are under development in the early 21st century as human food,dietary supplementsas oil capsules, livestock food, andpet food.Most krill is processed to produce fish food for use inaquariumsandaquacultures.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.Furthermore, krill containscarotenoidsand is thus used sometimes as a pigmentizing agent to color the skin and meat of some fish. About 34% of the Japanese catch ofE. superbaand 50% ofE. pacificaare used for fish food; the Canadian catch is used almost exclusively for this purpose.

One quarter of the Japanese catch ofE. superbais used in the form of fresh frozen krill as fishbaitand half theE. pacificacatch is used aschumfor 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 oilgel capsules. Only a small amount ofE. superbais processed for human consumption.

Medical applications of krillenzymesinclude products for treatingnecrotic tissueand 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.

Antarctic krill

Catch ofEuphausia superbain theSouthern Oceanfrom 1974 until 2003 (FAOdata)

Krill fishery in theSouthern Oceantargets 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".Fishing began in the early 1960s, when theSoviet Unionlaunched 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 inAntarcticwaters, 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 offluoridesin 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,RussiaandUkraine,took over the operations. Russian operations and catches dwindled, and were abandoned altogether in 1993. Since then,Japanis one of the top producers, but facing stiff competition by other countries. Since 2000, the smallSouth KoreanAntarctic krill fishery has also expanded considerably. AU.S.company entered the market in 2001. TheNorwegiancompanyAker ASAentered the business in 2003 with a ship registered inVanuatu.

Annual catch ofE. superbaby the major fishing nations (in 1000 tons). Data from the FAO.A dash means "no catch"; a zero indicates a small catch < 500 t.

Country	80	81	82	83	84	85	86	87	88	89	90	91	92	93	94	95	96	97	98	99	00	01	02	03	04	05	06	07	08	09
Japan	36	28	35	43	47	40	60	78	73	79	69	69	78	57	61	63	59	60	67	66	81	67	51	60	34	23	33	24	38	21
South Korea	-	-	1	2	3	-	-	2	2	2	4	1	1	-	-	-	-	-	3	0	7	8	14	20	25	27	43	33	38	43
Norway	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	9	40	63	44
Poland	0	-	0	0	-	0	2	3	5	8	3	10	15	7	8	13	22	14	20	20	20	14	16	9	9	4	5	7	8	8
Ukraine	-	-	-	-	-	-	-	-	-	-	-	-	55	-	13	59	10	-	-	7	-	14	32	18	12	22	15	-	8	0
USSR/Russia	441	420	492	186	69	228	333	344	310	258	326	249	103	2	-	-	-	-	-	-	-	-	-	-	-	-	-	-	0	10
U.S.	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	2	12	10	9	2	-	-	-	-
Vanuatu	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	29	48	-	-	-	-
Total	476	448	528	231	119	267	394	426	389	347	402	329	251	65	81	135	91	75	90	91	107	104	125	117	118	129	106	104	156	125

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.

The annual catch ofEuphausia superbasince 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.Plans to take up to 746,000 tonnes a year were disclosed at the 2007 meeting of CCAMLR.

Fishing for Antarctic krill was commonly done from large stern trawlers usingmidwater trawlsbefore the purpose built krill trawlers likeAntarctic Endurancewere 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.

Around Japan

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 shelfclose to the coast and at most 200 m (660 ft) deep.E. nanareaches only 1.2 cm, andT. inermiscan grow to 3 cm (1.2 in).

E. pacificawas 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%.

Experimental fisheries

Small-scale fisheries for krill also exist in other areas. InCanada,fishing forE. pacificatakes place in theStrait of GeorgiaoffBritish 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. inermisin theGulf of St. Lawrenceand on theScotian Shelfhave 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 & Fosterconsider 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.

See also

• List of harvested aquatic animals by weight

References

General reference

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.ISBN92-5-104012-5.

Further reading

• Inigo Everson, ed. (2000).Krill: Biology, Ecology and Fisheries.Fish and Aquatic Resources Series. Vol. 6. Oxford:Blackwell Science.ISBN0-632-05565-0.
• 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.ISBN978-1-62703-215-5.
• 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.S2CID84158071.
• 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.

External links

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