The Somniosidae are a family of sharks in the order Squaliformes, commonly known as sleeper sharks. The common name "sleeper shark" comes from their apparent slow swimming, low activity level, and perceived non-aggressive nature.
Greenland sharks of the family Somniosidae are hunted for food in Iceland. In modern times, many Greenlandic sharks used for hákarl production are purchased from fishing ships where the sharks were trapped in the fishing nets. The shark carcass is traditionally fermented in a shallow pit, with stones placed on top of the shark, allowing poisonous internal fluids, like urea and trimethylamine oxide, to be pressed and drained out of the body. The meat is then cured for several months, rendering it safe for human consumption, if an acquired taste.
