The expensive Chilean sea bass is actually a deep-sea Antarctic fish called a toothfish.

Nature · Published 30 September 2026 Swipe more like this →

In short: Marketed as Chilean sea bass to entice diners, this creature is a long-lived predator from the frigid Southern Ocean. Its high price reflects the difficulty of reaching its remote, deep-water habitat. While it thrives in icy conditions, its biology is surprisingly specialized, featuring a skeleton that prioritizes buoyancy over swimming speed.

The Patagonian toothfish, scientifically known as Dissostichus eleginoides, is a large notothenioid fish native to the Southern Ocean and the southern shelves of South America. It is a long-lived species, capable of surviving for over 50 years. These fish are highly adapted to their extreme, cold environment, possessing weakly mineralized skeletons and high muscle fat content. These traits provide neutral buoyancy, though they limit the fish's overall swimming capacity to a generally slow, labriform motion, with bursts of speed reserved for emergencies.

The life cycle of the toothfish involves a significant ontogenetic migration. Spawning occurs in deep water, approximately 1,000 meters below the surface, during the austral winter. The resulting larvae are pelagic, but by the time they reach one year of age and roughly 100 millimeters in length, they shift to a demersal habitat. Juveniles reside in relatively shallow waters of less than 300 meters, where they act as active piscivorous predators. As they mature, typically between 6 and 7 years of age, they begin a gradual descent into deeper, darker waters, where their diet shifts to include more scavenging.

The commercial history of the species is relatively recent. Initially caught only as incidental by-catch in shallow trawl fisheries, the development of deep-water longlining techniques in the late 20th century allowed for rapid expansion. This led to a peak in reported landings of over 40,000 tonnes in 1995. This rapid growth brought significant challenges, including illegal, unreported, and unregulated fishing, as well as accidental bird by-catch. Today, the fishery is largely managed under the ecosystem-based approach of the Commission for the Conservation of Antarctic Marine Living Resources, which treats the Southern Ocean as an integrated system to ensure sustainable harvesting levels.

The name Chilean sea bass was a marketing invention created in 1977 by a wholesaler named Lee Lantz to make the fish more appealing to American consumers. The U.S. Food and Drug Administration officially recognized this as an alternative market name in 1994. While the fish is a member of the diverse teleost group—which includes most of the world's commercial fish species—its specific adaptation to the Southern Ocean's cold, remote depths makes it a unique and valuable resource.

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