The Killer Whale or Orca (Orcinus orca), or less commonly, Blackfish, is the largest species of the dolphin family, though they are commonly mistaken as a species of whale. They are called killer whales often because they sometimes hunt whales for food. They are found in all the world’s oceans, from the frigid Arctic and Antarctic regions to warm, tropical seas. Some killer whale populations feed mostly on fish while others hunt sharks, marine mammals, including sea lions, seals, walruses and even large whales and Great white sharks. The killer whale’s large size and strength make it among the fastest marine mammals, often reaching speeds in excess of 35 kn (65 km/h).