English: Model of an Atlantic wolffish (Anarhichas lupus) at the Sant Hall of Oceans at the Smithsonian Museum of Natural History in Washington, D.C.

The wolffish is generally about 5 feet (1.5 m) long and weighs about 40 pounds (18 kg). It has an eel-like body and swims slowly. It has six fang-like teeth, and three rows of crushing teeth. Even its throat has teeth in it! They like cold water, and generally live in nooks or caves or rock clusters on the ocean floor 250 to 400 feet (76 to 120 m) down. Their blood contains a natural antifreeze. They eat mollusks, clams, oysters, crabs, hermit crabs, starfish, sea urchins and green crabs. Their favorite food is sea urchins and green crabs, and if the wolffish is overfished then the population of these other animals explodes!

Unlike most other fish, the female wolffish's eggs are fertilized while still inside her body. Then she lays them on the sand for the male wolffish to guard. The eggs are among the largest of any fish species. Once the fry hatch, the male will stay with them until they are big enough to fend for themselves. Wolffish become sexually mature at six years of age, and generally live about 20 years.

Wolffish are under investigation in the U.S. for endangered species status. Bottom trawlers have killed off so many of them that scientists believe the North American population is close to dying off.