A premier member of the Istiophoridae family of billfish, the blue marlin is one of the foremost big-game species worldwide. It has exceptional size and strength and is a powerful, aggressive fighter. It runs hard and long, sounds deep, and leaps high into the air in a seemingly inexhaustible display of strength.
Intensively pursued commercially in many parts of its range, it is overexploited. The ﬂesh is pale and ﬁrm and makes excellent table fare, especially when smoked. In the Orient it is often served as sashimi or in ﬁsh sausages. Blue marlin are seldom eaten in North America, and the vast majority caught by anglers are released after capture, and many of those released are tagged.
IdentificationThe pectoral fins of blue marlin are never rigid, even after death, and can be folded completely ﬂat against the sides. The dorsal fin is high and pointed (rather than rounded) anteriorly, and its greatest height is less than its greatest body depth. The anal fin is relatively large and also pointed. Juveniles might not share all of these characteristics, but the peculiar lateral line system is usually visible in small specimens. In adults it is rarely visible unless the scales or the skin are removed.
The lateral line of a Pacific blue marlin is a series of large loops, like a chain, along the ﬂanks. The lateral line of all Atlantic blue marlin is a reticulated network that is more complex than the simple loops of Pacific specimens. The vent is just in front of the anal fin, as it is in all billﬁsh except the spearﬁsh, and the upper jaw is elongated in the form of a spear.
The back is cobalt blue and the ﬂanks and the 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. Small blue marlin are similar to white marlin, but the blue has a more pointed dorsal fin at the anterior end and more pointed tips on the pectoral and the anal ﬁns, and it lacks dorsal fin spots.
Size/AgeThe blue marlin is the largest marlin existing in the Atlantic Ocean. Elsewhere, it is capable of growing to sizes that equal or exceed those of the black marlin. Japanese longline reports indicate that the blue marlin is the largest-growing member of the Istiophoridae family.
It apparently grows larger on average in the Paciﬁc Ocean, where decades ago one commercially caught specimen reportedly weighed 2,200 pounds, and an angler-caught specimen (which did not qualify for world-record status) weighed 1,800 pounds. The all-tackle world record for Atlantic blues is a 1,402-pounder caught in 1992 at Vitoria, Brazil; the all-tackle world record for Paciﬁc blues is a 1,376-pounder caught in 1982 at Kona, Hawaii.
The giants are all females, as male blue marlin rarely exceed 300 pounds. Most blue marlin encountered by anglers range between 150 and 400 pounds. Blue marlin are believed to live for more than 15 years, although ﬁsh exceeding 10 years of age are uncommon.
Life history/BehaviorThe life history of the blue marlin is poorly known. The full extent of its oceanic wanderings, as well as its open-sea spawning activities, are unknown. These ﬁsh are found in the warm blue water of offshore environs, usually over considerable depths and where there are underwater structures (for example, canyons, dropoffs, ridges, seamounts) and currents that attract copious supplies of baitﬁsh. They are usually solitary.
Food and feeding behaviorBlue marlin feed on squid and pelagic ﬁsh, including assorted tuna and mackerel, as well as on dolphin. They feed on almost anything they can catch, in fact, and they feed according to availability, rather than selectivity. Because they require large quantities of food, they are scarce when and where prey is limited.
Other NamesAtlantic blue marlin, Paciﬁc blue marlin, Cuban black marlin; French: espadon, makaire bleu; Japanese: makajiki, nishikuro; Portuguese: agulhao preto; Spanish: abanco, aguja azul, castero, marlín azul.
Distribution/HabitatThis pelagic, migratory species occurs in tropical and warm temperate oceanic waters. In the Atlantic Ocean, it is found from 45° north to 35° south latitude and in the Paciﬁc Ocean from 48° north to 48° south latitude. It is less abundant in the eastern portions of both oceans. In the northern Gulf of Mexico, its movements seem to be associated with the socalled Loop Current, an extension of the Caribbean Current.
Seasonal concentrations occur in the southwest Atlantic (5° to 30° south latitude) from January through April, in the northwest Atlantic (10° to 35° north latitude) from June through October, and in the western and central North Paciﬁc (2° to 24° north latitude) from May through October.