Overview
Japanese longliners report that the blue marlin is the largest of the istiophorid fishes. It apparently grows larger in the Pacific. All giant marlins are females, and male blue marlin rarely exceed 300 lb (136 kg). The pectoral fins of blue marlin are never completely rigid, even after death, and can be folded completely flat against the sides except in the largest specimens. The dorsal fin is high and pointed anteriorly (rather than rounded) and its greatest height is less than the greatest body depth. The anal fin is relatively large and it too is pointed. Juveniles may not share all the characteristics listed above, but the peculiar lateral line system is usually visible in small specimens. In adults it is rarely visible unless the scales or skin are removed. The vent is just in front of the anal fin, as it is in all billfish except the spearfish. The back is cobalt blue and the flanks and belly are silvery white. There may be light blue or lavender vertical stripes on the sides, but these usually fade away soon after death, and they are never as obvious as those of the striped marlin. There are no spots on the fins.
Taxonomy
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Actinopterygii
- Order
- Perciformes
- Family
- Istiophoridae
- Genus
- Makaira
- Species
- mazara
Habitat
Pacific blue marlin primarily inhabit open pelagic waters of the tropical and subtropical oceans, including the Pacific, Indian, and Atlantic, often in areas with surface temperatures above 20°C. They prefer deep blue waters far from shore but can be found near underwater structures, currents, or upwellings that concentrate prey. Their highly migratory nature leads them to follow warm ocean currents and seasonal food sources.
Diet
They are known to feed on squid and pelagic fishes, including blackfin tuna and frigate mackerel.
Behavior
Seasonal concentrations occur in the southwest Atlantic (5°-30°S) from January to April; in the northwest Atlantic (10°-35°N) from June to October; in the western and central North Pacific (2°-24°N) from May to October; in the equatorial Pacific (10°N-10°S) in April and November; and in the Indian Ocean (0°-13°S) from April to October.
Fishing
A powerful, aggressive fighter, they run hard and long, sound deep, and leap high into the air in a seemingly inexhaustible display of strength. Fishing methods include trolling large whole baits such as bonito, dolphin, mullet, mackerel, bonefish, ballyhoo, flying fish and squid as well as various types of artificial lures and sometimes strip baits.
Conservation Status
Listed as Vulnerable by IUCN.