Krill are small, shrimp-like crustaceans of the order Euphausiacea that swarm in the open ocean in colossal numbers — the Antarctic species Euphausia superba alone is among the most abundant animals on Earth. Harvested mainly for omega-3-rich oil and a salty, deeply savoury paste, they are also eaten directly in parts of Asia and are the keystone food of whales, seals, penguins and seabirds.