The term billfish is applie to a number of different large, predatory fish characterised by their large size (swordfish can be over 4 metres long) and their long sword-like bill. Billfish include the sailfish and marlin, which make up the family Istiophoridae, and the swordfish, sole member of the family Xiphiidae. They are important apex predators feeding on a wide variety of smaller fish and cephalopods. While billfish are most common in tropical and subtropical waters, swordfish in particular are sometimes found in temperate waters as well.