The Patagonian toothfish lives in the waters of the Antarctic. One of the largest fishes found in this area, it is usually a grayish-brown color with a torpedo-shaped body and an unusually long but depressed head. It has a large mouth well-equipped with teeth and an underslung jaw.
It has two dorsal fins, the first much smaller than the second, which stretch from about the middle of the body almost to the tail. The fish has two lateral lines, with the lower beginning below the middle of the longer dorsal fin. This lateral line has 64 tubular scales, while the upper lateral line has about 95. Scales cover the fish, except for two areas on the top of its head.
The Patagonian toothfish can grow as large as 7 feet long, though 2.3 feet is more common. Some adults weigh as much as 220 pounds. It lives between 230 and 4,921 feet deep, and it eats other fish as well as squid and other cephalopods. In turn, it is prey for large cephalopods such as giant squid. It spawns in waters as deep as 3,281 feet, and ocean current sweep its eggs and larvae around. When the larvae are about a year old, they descend to an area just above the seabed.
Commercial fishermen call the fish the Chilean seabass, even though it is a type of cod icefish.