page_title: Krill
section_title: Swarming
hierarchical_section_title: Krill / Life history and behavior / Swarming
caption_attribution_description: English: Many krill. Photo taken in the Gulf of the Farallones.
context_page_description: Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian word krill, meaning "small fry of fish", which is also often attributed to species of fish.
  Krill are considered an important trophic level connection – near the bottom of the food chain. They feed on phytoplankton and zooplankton, yet also are the main source of food for many larger animals. In the Southern Ocean, one species, the Antarctic krill, Euphausia superba, makes up an estimated biomass of around 379,000,000 tonnes, making it among the species with the largest total biomass. Over half of this biomass is eaten by whales, seals, penguins, squid, and fish each year. Most krill species display large diel vertical migrations, thus providing food for predators near the surface at night and in deeper waters during the day.
  Krill are fished commercially in the Southern Ocean and in the waters around Japan. The total global harvest amounts to 150,000–200,000 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.
context_section_description: Most krill are swarming animals; the sizes and densities of such swarms vary by species and region. For Euphausia superba, swarms reach 10,000 to 60,000 individuals per cubic meter. Swarming is a defensive mechanism, confusing smaller predators that would like to pick out individuals. In 2012, Gandomi and Alavi presented what appears to be a successful stochastic algorithm for modelling the behaviour of krill swarms. The algorithm is based on three main factors: " (i) movement induced by the presence of other individuals (ii) foraging activity, and (iii) random diffusion."
caption: A krill swarm
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