Euphausiacea

Krill (Euphausiids) (: krill) are small and exclusively marine crustaceans of the order Euphausiacea, found in all of the world's oceans. The name "krill" comes from the Norwegian word '', 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, to a lesser extent, zooplankton, and are also the main source of food for many larger animals. In the Southern Ocean, one species, the Antarctic krill, makes up an estimated biomass of around 379 million tonnes (418 million tons), making it among the species with the largest total biomass. Over half of this biomass is eaten by whales, seals, penguins, seabirds, squid, and fish each year. Most krill species display large daily vertical migrations, providing food for predators near the surface at night and in deeper waters during the day.