The Antarctic Toothfish, Dissostichus mawsoni, is a large, dark-colored fish inhabiting the frigid waters of the Southern Ocean surrounding Antarctica. This species has developed extraordinary adaptations to survive in one of the planet’s harshest marine environments.
Life in the Icy Depths
The Antarctic Toothfish possesses specialized biological features that enable its survival in sub-zero waters. One adaptation is the presence of antifreeze glycoproteins in its blood and other body fluids. These proteins bind to ice crystals, preventing them from growing and solidifying the fish’s internal fluids, thus acting as a natural antifreeze.
The fish also has a high lipid content within its muscles and liver, which serves multiple purposes. These fats provide buoyancy, allowing the fish to move through various depths without a swim bladder. The lipids also assist in oxygen storage, enhancing oxygen diffusion processes within its body.
Antarctic Toothfish exhibit a slow metabolism and growth rate, common for species living in cold, deep-water environments. They can reach impressive sizes, growing over 1.7 meters in length and weighing up to 135 kilograms, making them the largest bony fish in the Southern Ocean. Their lifespans are estimated to be around 30 to 50 years, inhabiting depths from shallow coastal waters to over 2,200 meters as adults.
Apex Predator of the Southern Ocean
The Antarctic Toothfish occupies a significant position within the Southern Ocean’s marine food web, functioning as a top predator in deep-sea ecosystems. Its diet primarily consists of other fish and cephalopods, such as squid. Smaller, younger toothfish living in coastal areas often feed on Antarctic silverfish, a common prey for various Antarctic marine animals.
As they grow, their diet diversifies, with larger toothfish consuming grenadiers and other bottom-dwelling fish species. This species is considered a voracious predator. The presence of Antarctic Toothfish helps structure the populations of its prey species through predation.
Despite its predatory role, the Antarctic Toothfish also serves as a food source for several larger marine animals. Its natural predators include sperm whales, killer whales, and Weddell seals. Colossal squid may also prey on toothfish.
Global Fishery and Conservation
The Antarctic Toothfish has become a commercially valuable species, often marketed globally under the name “Chilean Sea Bass”. Commercial fishing for toothfish began in the Southern Ocean in the mid-1980s, expanding significantly by the 1990s. These fisheries primarily use bottom-set longlines at depths between 1,200 and 1,800 meters.
The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is the international body responsible for managing toothfish fisheries in the Southern Ocean. Established in 1982, CCAMLR sets annual catch limits, implements conservation measures, and reviews fishing activities to ensure sustainable exploitation and protection of the marine ecosystem. This includes strict regulations to minimize bycatch of seabirds and marine mammals.
Despite these regulations, illegal, unreported, and unregulated (IUU) fishing for toothfish posed a significant threat. CCAMLR introduced measures like the Catch Documentation Scheme in 1999 to combat IUU fishing through trade-related controls, which has led to a significant reduction in such activities. However, ongoing vigilance is necessary, as a small volume of IUU Antarctic toothfish was still reported in recent years.