Antarctic toothfish facts for kids

Quick facts for kids Antarctic toothfish
Scientific classification

The Antarctic toothfish (Dissostichus mawsoni) is a huge fish living in the super cold waters of the Southern Ocean around Antarctica. It's also sometimes called the Antarctic cod. This fish is the biggest one you'll find in the Southern Ocean. It eats shrimp and smaller fish. Bigger animals like whales, orcas, and seals hunt it. People also catch it for food, often selling it as Chilean sea bass. It's related to the Patagonian toothfish (D. eliginoides), which lives in slightly warmer waters. Even though it's called "Antarctic cod," it's actually part of the notothen family (Nototheniidae), a group of fish common near Antarctica.

What's in a Name?

The name "toothfish" comes from the two rows of teeth in its upper jaw. These teeth make it look a bit like a shark!

The scientific name Dissostichus comes from ancient Greek words. "Dissos" means "twofold" and "stichus" means "line." This refers to the two long lateral lines on the fish. These lines help the fish sense things around it, like finding prey. The species name, mawsoni, honors Douglas Mawson. He was an Australian explorer who led an expedition to Antarctica from 1911 to 1914. During his trip, scientists collected the first sample of this fish.

The Antarctic toothfish was first officially described in 1937. An English fish expert named John Roxborough Norman gave it its name. He found the first specimen off MacRobertson Land in Antarctica.

How Big Are They?

These amazing fish can grow really big! They can be over 1.7 m (5 ft 7 in) (about 5.5 feet) long. They can also weigh up to 135 kg (around 300 pounds). That's twice as big as any other fish in the Antarctic!

Because they are so large, Antarctic toothfish are fierce hunters. They eat smaller fish, even their own young. They are the biggest fish in the middle of the Southern Ocean. This means they play a similar role to sharks in other oceans.

Most fish in Antarctica stay near the bottom. But the Antarctic toothfish can float in the middle of the water. They become "neutrally buoyant" when they are about 100–120 cm long. This means they don't need to use extra energy to stay off the seabed. So, they can hunt both on the bottom and in the open water.

What Do They Look Like?

Antarctic toothfish are usually black to olive brown. Their undersides might be a bit lighter. They often have a mottled pattern on their bodies and fins. Younger fish can blend in very well with the benthic sponges and corals on the seafloor.

They have a wide head and a long body. Their dorsal and anal fins are long. They also have big pectoral fins and a tail fin that works like a rudder. They usually move slowly. But they can burst into speed to escape predators like seals.

What Do They Eat?

Over the continental shelf, Antarctic toothfish mostly eat shrimp (Nauticaris spp.). They also eat small fish, especially the Antarctic silverfish (Pleuragramma antarcticum). Silverfish are also a main food source for Adélie and emperor penguins. Weddell seals and Antarctic minke whales also eat silverfish. This means toothfish compete with these other animals for food.

Large Antarctic toothfish are eaten by sperm whales and killer whales (Orcinus orca). Weddell seals also hunt them. They might even be eaten by colossal squid (Mesonychoteuthis hamiltoni). Toothfish living on the bottom, especially in summer, eat mainly grenadiers. They also eat other small fish and skates. They have been found as deep as 2200 meters.

Life and Family

Antarctic toothfish grow quickly when they are young. But their growth slows down as they get older. They reach about one-third of their full size by age 5. By age 10, they are about half their maximum size. Growing fast when young helps them avoid being small for too long. The oldest toothfish found so far was 48 years old!

These fish take a long time to become adults. Males mature around 13 years old, and females around 17 years old. Once mature, they might not spawn (lay eggs) every year. Scientists don't know exactly how often they spawn. Very few toothfish with mature eggs have ever been caught. This means we don't know much about how many eggs they lay.

They usually spawn sometime during winter. Large, older fish have been caught near the seamounts of the Pacific-Antarctic Ridge. This area is thought to be important for spawning. Smaller, younger toothfish tend to stay in shallower waters on the continental shelf. Older fish are found more on the continental slope. This separation by age might help younger fish avoid being eaten by older, larger ones.

How Do They Survive the Cold?

The Antarctic toothfish lives in water that is below freezing point. This is south of latitude 60°S. Like most other Antarctic notothenioids, it makes special "antifreeze glycoproteins." These proteins stop ice crystals from forming in their bodies. This is why they can live and thrive in the super cold waters around Antarctica. Their close relative, the Patagonian toothfish, doesn't have this antifreeze.

The Antarctic toothfish's huge appetite also helps it cope with the cold. They are mainly caught in the Ross Sea during the Antarctic summer. But they have also been seen in other cold coastal waters around Antarctica.

Fishing for Toothfish

People have been fishing for Antarctic toothfish since 1997. This fishery is managed by the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR). Most toothfish are caught in the Ross Sea.

Fishing for toothfish in the Ross Sea is a debated topic. Some people worry because we don't have enough information. We don't know the exact original number of fish, how many eggs they lay, or how many young fish survive. Also, some researchers believe the main fishing areas are where all the toothfish pass through.

The fishing season usually ends by late February. For the rest of the year, thick sea ice covers the area. This naturally stops fishing. Fishing for toothfish often involves longline fishing on the bottom. Sometimes, other fish are caught by accident. This is called "bycatch." CCAMLR sets limits on how much bycatch is allowed each year.

CCAMLR has rules to make sure fishing is sustainable. They aim for the number of adult fish to be at least 50% of what it was before fishing started. They also want to make sure the population doesn't drop below 20% of its original size. Currently, the number of adult Antarctic toothfish in the Ross Sea is estimated to be around 75% of its original level. This is well above the target.

Scientists continue to study the toothfish and its ecosystem. They want to understand its life cycle and how it interacts with other animals. This helps them manage the fishery in a way that protects the whole ecosystem. For example, they monitor young toothfish to predict changes in the population.

Protecting the Environment

CCAMLR has strict rules to protect the environment and reduce bycatch in Antarctic toothfish fisheries. These rules include:

• Monitoring fishing boats if they catch too many seabirds.
• Using "streamer lines" to keep birds away from baited hooks when lines are set.
• Adding weights to lines so they sink fast, preventing seabirds from reaching the bait.
• Using devices to stop birds from getting to hooks when lines are pulled in.
• Limiting when fish waste (offal) can be dumped overboard. This stops birds from being attracted to the boats. South of 60°S, no offal can be dumped at all.
• Banning the dumping of oil, plastic, garbage, food waste, and other harmful materials from fishing vessels.
• Banning plastic packaging bands on fishing vessels.

These measures have greatly reduced accidental deaths of seabirds from fishing. In 2011–12, no seabirds or marine mammals died from toothfish fishing. Only two seabirds have been killed in the Ross Sea fishery since 1996/97.

Following the Rules

CCAMLR has rules to make sure everyone follows the fishing regulations. These include:

• Inspecting fishing boats at sea.
• Requiring boats to have licenses.
• Inspecting fishing boats at ports.
• Tracking fishing boats' positions using satellite systems.
• A special system to track toothfish from when they are caught until they are sold. This helps prevent illegal fishing.
• Requiring two scientific observers on each licensed boat. One must be from a different country than the boat's flag.

Is It Sustainable?

In 2010, the Marine Stewardship Council (MSC) said the Ross Sea Antarctic toothfish fishery was sustainable. This means it's well-managed. However, some conservation groups disagreed. They felt there wasn't enough information to be sure it was sustainable. Also, not all fishing boats in the area were certified by MSC.

Some people worry that the high price of toothfish encourages illegal fishing. It also leads to mislabeling, where other fish are sold as toothfish. A study in 2011 found that some MSC-labeled toothfish were not from the certified stock. Some weren't even toothfish at all! However, MSC did its own study and found no evidence of mislabeling.

Because of past problems, some seafood guides, like Seafood Watch, used to tell people to "avoid" Chilean sea bass (both toothfish species). But in 2013, after reviewing new scientific information, Seafood Watch changed its rating for the Ross Sea Antarctic toothfish fishery to a "good alternative."

Greenpeace International added the Antarctic toothfish to its "red list" of seafood to avoid in 2010. This is different from the MSC's high rating for the fishery.

Images for kids

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  A close-up of an Antarctic toothfish.