sailfish, common name for a marine game and food fish belonging to the family Istiophoridae and related to the swordfish and the marlin. It is named for its high, wide dorsal fin, colored deep blue with black spots. Like the marlin it has a pikelike upper jaw and small scales embedded in its skin. The average length is 6 ft (180 cm), though it may reach 10 ft (305 cm). The Atlantic sailfish, Istiophorus americanus, found north to Cape Cod in summer, averages 60 lb (27 kg) in weight, while the Pacific sailfish, I. orientalis, grows to 100 lb (45 kg). Sailfish are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Perciformes, family Istiophoridae.