THE ANIMAL FILES

North Pacific krill

Euphausia pacifica

A tiny Pacific animal makes a daily vertical journey.

North Pacific krill form swarms that feed fish, whales and birds. Adults often occupy deeper water by day and move near the surface at night. Their movements change where predators can encounter this important crustacean.[2]

Follow the evidence ↓
North Pacific krill
Image: CBG Photography Group, Centre for Biodiversity Genomics · Commons · CC BY 3.0
Up and down
Adults undertake strong vertical migration.[2]
A northern ocean range
The range crosses the North Pacific.[3][2]
A concentrated meal
Swarms supply food to larger animals.[2]

Up and down

Adults commonly occupy deeper water by day and move near the surface at night. Occasional daytime surface swarms have also been observed off Japan and California.[2]

A northern ocean range

Records extend from waters near Japan across northern Pacific systems to the California Current. Fisheries and Oceans Canada identifies the species as a major component of British Columbia krill biomass, while noting that several krill species coexist there.[3][2]

A concentrated meal

Dense swarms attract fish, whales and birds. The importance lies in food-web connections, not the size of an individual krill. Aggregation concentrates many small animals into a patch that a predator can exploit.[2]

A COMMON MIX-UP

Is all Pacific krill one species?

No. British Columbia waters contain multiple krill species, including Euphausia pacifica.[3]

TRY A LITTLE REASONING

Why could depth affect whether a predator encounters a swarm?

Reveal the explanation

The krill change vertical position through the day, so food patches are not fixed at one depth.[2]

Sources & editorial notes

Original explanations, checked against the sources below. The image has its own credit and licence above.

  1. NCBI Taxonomy — Euphausia pacifica
  2. Naturalis — Euphausiids of the World Ocean: Euphausia pacifica
  3. Fisheries and Oceans Canada — Euphausiids, Pacific Region

Last fact check:

One discovery leads to another

Antarctic krillA tiny feeding basket can work beneath the ice.Euphausia superba ↗Giant tiger prawnA striped prawn whose address changes as it grows.Penaeus monodon ↗European lobsterTwo claws, two different kinds of work.Homarus gammarus ↗