Antarctic krill are the keystone prey species supporting penguins, whales, seals, and seabirds, and their welfare as a population has cascade welfare effects throughout the ecosystem.
Krill welfare questions operate at two scales: the individual experience of these crustaceans, which is uncertain but not dismissible, and the ecosystem welfare consequences of krill depletion on dependent species. Penguins that cannot find krill experience starvation and breeding failure. Blue whales that expend energy seeking depleted prey patches suffer both energetically and reproductively. The welfare stakes of maintaining krill populations are therefore enormous, extending through the entire Antarctic food web to species with clear welfare capacity.