The Atlantic blue marlin (Makaira nigricans) is a species of marlin endemic to the Atlantic Ocean. The blue marlin (hereafter, marlin) feeds on a wide variety of organisms near the surface. By using its bill, it can stun, injure, or kill while knifing through a school of prey and then return later at its leisure to eat. Marlin is a popular game fish and has commercial value because its meat has a relatively high fat content.
This pelagic and migratory species occurs in tropical and warm temperate oceanic waters. In the Atlantic Ocean it is found from 45°N to 35°S, and in the Pacific Ocean from 48°N to 48°S. It is less abundant in the eastern portions of both oceans. In the Indian Ocean it occurs around Ceylon, Mauritius, and off the east coast of Africa. In the northern Gulf of Mexico its movements seem to be associated with the so called Loop Current, an extension of the Caribbean Current. 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.
The biggest females are more than four times as heavy as the biggest males. Males rarely exceed 160 kilograms (350 lb) in weight, and females commonly weigh over 540 kilograms (1,200 lb). The longest females can reach a length of more than 4 metres (13 ft) with the bill, from eye to tip, constituting about 20% of the total body length.
This marlin has two dorsal fins and two anal fins. The fins are supported by bony spines known as rays. Its first dorsal fin has 39 to 43 rays from front to back. Its second dorsal fin has 6 to 7 rays. Its first anal fin, which is similar in shape and size to the second dorsal fin, has 13 to 16 rays, and the second anal fin has 6 to 7 rays. The pectoral fins, which have 19 to 22 rays, are long and narrow and can be drawn in to the sides of the body. The pelvic fins are shorter than the pectorals, have a poorly developed membrane, and are depressible into ventral grooves. Its first anal fin, along with its pectoral and caudal fins, can be folded into grooves. This streamlines the fish and thereby reduces drag.
The body is blue-black on top with a silvery white underside. It has about fifteen rows of pale, cobalt-colored stripes, each of which has round dots and/or thin bars, located on both sides of the fish. The first dorsal fin membrane is dark blue or almost black and has no dots or marks. Other fins are normally brownish-black, sometimes with a hint of dark blue. The bases of the first and second anal fins have a hint of silvery white. Marlin can rapidly change color and usually appear bright blue when hunting. The coloration results from pigment-containing iridophores and light-reflecting cells. The body is covered with thick, bony, elongated scales that have one, two, or three posterior points, with one being the most common form.
The bill is long and stout. Both the jaws and the palatines (the roof of the mouth) are covered with small, file-like teeth. The lateral line system is a group of neuromasts rooted in lateral line canals that can sense weak water motions and large changes in pressure. It has the appearance of a net. It is obvious in immature specimens but unclear in adults, becoming progressively embedded in the skin. The anus is just in front of the origin of the first anal fin.
They are known to feed on squid and pelagic fishes, including blackfin tuna and frigate mackerel. 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.
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