Black Marlin are a member of the family Istiophoridae. They possess a long, pointed bill, a retractable dorsal fin and a rigid pectoral fin, which cannot be pressed against the side of the body. Black Marlin have two keels on either side of the tail base. Their name is derived from the colouration they take on when dead. Unlike Blue (Makaira mazara) and Striped Marlin (Tetrapturus audax), Black Marlin do not usually have any blotches or stripes along the body. Juvenile Black Marlin feed on tropical pilchards and herring while adults feed on trevally, tuna-like fishes and scad. Black Marlin are not normally dangerous, but have been known to attack boats and floating objects by impaling them with their bill.
Black Marlin can grow to a maximum length of 5 m and can weigh over 700 kg. Males are smaller than females.
Black Marlin are found in tropical and subtropical waters of the Indian and Pacific Oceans. Occasionally found in waters off Australia's southern areas during the summer months. Black Marlin are a highly mobile, pelagic fish that inhabit almost any depth in the ocean, but usually prefer areas well offshore.
Black Marlin are sometimes confused with Blue Marlin, however Black Marlin have comparatively low and rounded dorsal and anal fins. The pectoral fins of Blue Marlin can be folded against the body.