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Wildlife Guide · Southern Ocean around Antarctica & Krill orders also occur in all other oceans

Krill

Order Euphausiacea — Antarctic krill Euphausia superba dominates Southern Ocean biomass

The crustacean swarm that feeds the whale — and the fishery that watches the same stock.

Least Concern — E. superba assessed; fishing pressure and climate change are active concerns
Dense pink swarm of Antarctic krill underwater in cold blue Southern Ocean water with diffuse sunlight from above

Image: AI-generated educational wildlife portrait — World Animal Rescue Network · AI visualisation, not a photograph

In brief

Krill (order Euphausiacea) are small crustaceans whose Antarctic species Euphausia superba underpins the Southern Ocean food web; the species is Least Concern but faces fishing pressure and climate-driven sea-ice loss.

By the WARN Research & Conservation TeamChecked against IUCN Red List & CITES sourcesLast updated

Krill are small, shrimp-like crustaceans of the order Euphausiacea. They are not true shrimp — different anatomy, different order — but occupy a similar ecological tier as filter-feeding mesozooplankton that convert microscopic phytoplankton into flesh large predators can use. In the Southern Ocean, Antarctic krill (Euphausia superba) forms swarms so dense they discolour the sea and are visible from space. The standing biomass is among the largest of any wild animal population on Earth. That biomass underpins the Southern Ocean food web. Baleen whales, penguins, seals, squid, fish and seabirds depend directly or indirectly on krill. Blue whales can consume tonnes of krill daily during feeding season. Adélie and chinstrap penguin breeding success tracks krill availability near colonies. Remove krill and the ecosystem does not rearrange gracefully — it collapses upward through the food chain. Commercial krill fishing operates in the same waters. Fleets harvest krill for aquaculture feed, omega-3 supplements and pet food. Catch is regulated by the Commission for the Conservation of Antarctic Marine Living Resources, but fishing overlaps spatially with predator foraging grounds, and climate change is altering sea ice — a critical nursery habitat for larval krill — faster than management frameworks adjust. Other oceans hold krill species too — North Pacific euphausiids support salmon, seabirds and whales — but none match the biomass concentration or political visibility of Antarctic E. superba. What happens in the Southern Ocean is watched as a template for ecosystem-based fisheries management worldwide. Satellite sensors can detect large krill swarms indirectly through chlorophyll and sea-surface patterns, linking ocean colour to prey availability for fisheries managers. The science is young but improving yearly as acoustic and remote tools merge.

E. superba

Antarctic krill — keystone Southern Ocean species

Swarms

Can contain millions of individuals per cubic metre

Sea ice

Critical nursery for larval krill under ice algae

CCAMLR

International body regulating Antarctic krill fishery

Figures sourced from IUCN Red List — Euphausia superba, CCAMLR .

Krill: Quick Facts

Vital statistics and key facts about the Krill
Key species Euphausia superba — Antarctic krill
Role Keystone prey in Southern Ocean
Feeding Phytoplankton and ice-algae filter feeder
Fishery regulator CCAMLR
Climate link Sea-ice loss affects larval nursery habitat
IUCN status Least Concern (E. superba)

Scientific Classification

Scientific classification of the Krill
Kingdom Animalia
Phylum Arthropoda
Class Malacostraca
Order Euphausiacea
Species Euphausia superba (Antarctic krill)
Related orders Krill occur in all oceans; Euphausiacea is cosmopolitan

Conservation Status

IUCN Status
Least Concern
Population
Hundreds of millions of tonnes biomass estimated for E. superba — figures vary by survey
Trend
Suspected decline in parts of the Southwest Atlantic; uncertain globally
Assessed
2016
CITES
Not listed

Least Concern reflects large current biomass. Sea-ice loss, localised fishing pressure and ecosystem dependence by predators justify continued precaution.

Did you know?

Antarctic krill swarms can be so dense they discolour the sea surface — and the standing biomass is large enough to feed the entire Southern Ocean whale and penguin assemblage each season.

Key Facts: Krill

  • Antarctic krill (Euphausia superba) is among the most abundant wild animal biomass on Earth.
  • Krill convert phytoplankton into food for whales, penguins, seals, fish and seabirds.
  • Larval krill depend on sea ice and ice-algae — both declining with climate warming.
  • Commercial krill fishing is regulated but overlaps with predator foraging areas.
  • Krill fishing supplies aquaculture feed and omega-3 products globally.
  • Ecosystem-based management — leaving enough krill for predators — is the conservation test.

Southern Ocean food web: krill at the centre

Antarctic krill feed on phytoplankton and ice-algae, packing energy into lipid-rich bodies that sustain cold-water predators through lean seasons. Swarms can extend for kilometres and move vertically in the water column — deep by day, surface by night — following food and avoiding visual predators. Baleen whales are the iconic krill consumers. Humpback, minke, fin and blue whales feed heavily on krill in Antarctic waters during austral summer, building fat reserves for migration and breeding. Fish such as Antarctic silverfish and icefish depend on krill; so do squid taken by albatrosses and seals. The food web is short and efficient: algae to krill to vertebrate predator, with little redundancy if krill abundance falls. Land-based predators connect through the coast. Penguin colonies require krill within commuting distance during chick-rearing. When krill is scarce — whether from oceanographic shift, sea-ice loss or local depletion — chick survival drops and colonies decline. The krill link is measurable in breeding statistics, not speculation.

Sea ice as nursery

Krill life history ties to sea ice. Larvae feed on algae growing on the underside of ice — a food source available when open-water phytoplankton blooms are absent. Ice also provides shelter from predators. Winter sea-ice extent around Antarctica has shown long-term decline in many sectors; the ice season shortens and the algae association weakens. Adult krill can live several years and store lipids, buffering short bad seasons. Larval stages are more vulnerable — a failed ice-algae season reduces recruitment for years afterward because cohorts are missing. Climate models project continued ice loss; krill distribution may shift southward or contract to refugia where ice persists. Ocean acidification adds pressure. Krill exoskeleton formation and larval development may be affected as carbonate chemistry changes, though field evidence is still accumulating compared with the clearer ice-habitat signal.

The krill fishery

Commercial harvesting of Antarctic krill began at scale in the 1970s and is concentrated in the Southwest Atlantic sector of the Southern Ocean — the same area supporting major penguin and seal colonies. Products include krill meal for aquaculture, krill oil for human supplements and pet food ingredients. CCAMLR sets catch limits based on estimated biomass and applies a precautionary approach relative to total stock. Current catches are a fraction of the regulated limit, but spatial concentration matters: fishing in small areas near colonies can locally deplete swarms predators rely on during breeding. Ecosystem-based fisheries management — accounting for predator needs, not just sustainable yield to the fleet — is the stated goal but hard to enforce in practice. Bycatch and processing waste are lesser concerns than allocation. The political question is whether growing demand for aquaculture feed will push catches toward limits as ice habitat contracts simultaneously — a squeeze from above and below on the same population.

Managing a keystone stock

Krill conservation is fisheries management plus climate policy. No marine protected area network in the Southern Ocean is complete without considering krill distribution and predator foraging ranges. Proposals for large MPAs in the Weddell Sea and East Antarctica have stalled repeatedly in CCAMLR politics, leaving the regulatory picture fragmented. Monitoring uses acoustic surveys estimating swarm biomass, krill-dependent predator breeding success at index colonies, and satellite observation of sea-ice trends. Integrated models linking ice, krill recruitment and penguin survival are the tool for setting spatial fishing restrictions — closed zones near colonies during chick-rearing, for example. For consumers, krill oil supplements connect everyday purchases to Antarctic ecology. Supply-chain scrutiny — certification, catch location, company reporting — is one lever. The larger lever is climate mitigation: without sea ice, krill recruitment suffers regardless of fishing restraint. Antarctic krill is Least Concern on the IUCN list today; the Southern Ocean ecosystem it supports is not guaranteed that stability tomorrow.

What WARN Does

WARN publishes free, sourced species education for keystone species whose decline would cascade through ecosystems most people never see. Krill is the Southern Ocean in miniature — algae, ice, whales and fisheries all meeting in a two-centimetre crustacean.

If this guide helps you understand wildlife and the pressures it faces, a gift to WARN supports habitat protection and free public education in our partner countries.

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Krill: Frequently Asked Questions

What is krill?
Small, shrimp-like crustaceans in the order Euphausiacea. Antarctic krill (Euphausia superba) is the dominant species in Southern Ocean swarms and underpins the regional food web.

Are krill endangered?
Antarctic krill is listed Least Concern. That reflects large estimated biomass today, not absence of risk. Fishing pressure, sea-ice loss and climate change are active concerns.

What eats krill?
Baleen whales, penguins, seals, squid, fish and seabirds. Many Southern Ocean predators depend on krill directly or eat krill-eating fish.

Why is sea ice important for krill?
Larval krill feed on algae growing on the underside of sea ice and use ice for shelter. Declining ice reduces food and nursery habitat for new generations.

What do krills eat?
Krills eat CCAMLR — International body regulating Antarctic krill fishery. Krill (order Euphausiacea) are small crustaceans whose Antarctic species Euphausia superba underpins the Southern Ocean food web; the species is Least Concern but faces fishing pressure and climate-driven sea-ice loss.

Where do krills live?
Krills live in Southern Ocean around Antarctica, Krill orders also occur in all other oceans. Krill (order Euphausiacea) are small crustaceans whose Antarctic species Euphausia superba underpins the Southern Ocean food web; the species is Least Concern but faces fishing pressure and climate-driven sea-ice loss.

Are krills dangerous?
Krills are not generally dangerous to people. Krill (order Euphausiacea) are small crustaceans whose Antarctic species Euphausia superba underpins the Southern Ocean food web; the species is Least Concern but faces fishing pressure and climate-driven sea-ice loss. Give wild individuals space and do not corner or handle them.

How long do krills live?
A precise wild lifespan for krills is not firmly established in the sources cited on this guide. Krill (order Euphausiacea) are small crustaceans whose Antarctic species Euphausia superba underpins the Southern Ocean food web; the species is Least Concern but faces fishing pressure and climate-driven sea-ice loss. Where longevity figures appear in the literature they vary by region, sex and whether animals are wild or captive.

How big is a krill?
A Krill is about Swarms (Can contain millions of individuals per cubic metre). Krill (order Euphausiacea) are small crustaceans whose Antarctic species Euphausia superba underpins the Southern Ocean food web; the species is Least Concern but faces fishing pressure and climate-driven sea-ice loss. Conservation status: Least Concern (E. superba).

Sources & References

Population figures, conservation status and biological facts on this page are drawn from authoritative scientific and intergovernmental sources.

Terms used on this page

Plain-English definitions, from our wildlife and conservation glossary.

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