Atlantic bluefin tuna (Thunnus thynnus) in a fattening pen, feeding on dead sardine. The blufin tuna is prized as food, and commercial aquaculture operations help to regulate the supply for the market. The wild population of Atlantic bluefin tuna has crashed by as much as 90% in the last 40 years, due to overfishing and unsustainable aquaculture relying on wild-caught stocks captured before breeding age. Some efforts have been made to rear the fish in a sustainable way. The bluefin tuna remains classified as an 'Endangered species' by the IUCN. Filmed off the coast of Barbate, Andalusia, Spain.