By Harold McGee
The “cod icefish” family is a group of large, sedentary plankton-eaters that live in the cold deep waters off Antarctica. The best known of them is the fatty “Chilean sea bass,” an inaccurate but more palatable commercial name for the Patagonian tooth-fish (Dissostichus eleginoides), which can reach 150 lb/70 kg. Its fat is located in a layer under the skin, in the chambered bones, and dispersed among the muscle fibers: toothfish flesh can be nearly 15% fat. It wasn’t until the mid-1980s that cooks came to know and appreciate this lusciously rich, large-flaked fish, which is unusually tolerant of overcooking. Like the orange roughy and other deepwater creatures, the toothfish is slow to reproduce, and there are already signs that its numbers have been dangerously depleted by overfishing.