Blue Marlin

Blue Marlin, Makaira nigricans

The Blue Marlin, Makaira nigricans, whose common Spanish name is marlin azul, is the second largest fish within the Billfish or Istiophoridae Family, known collectively as picudos in Mexico. Some members of the scientific community believe that the fish found in the Pacific is a separate species, the Pacific Blue Marlin, Makaira mazara, however I have treated them as one and the same. Globally, there is only one species in the genus Makaira, this species which is found in Mexican waters of both the Atlantic and the Pacific.

The Blue Marlins have long robust cylindrically-shaped slightly compressed bodies. They are dark blue dorsally and silver ventrally with 15 vertical rows of blue spots on their sides visible against a background of silvery white with a bluish tint. The base of their anal fin has a tinge of silvery white, their first dorsal fin is uniform blue-black, and their other fins are very dark with a tinge of blue. Their head has a long stout upper bill with a rounded cross section and relatively small eyes. Their mouth is equipped with small rasp-like teeth on both jaws. They do not have gill rakers. They have two anal fins, the first with 13 to 16 rays and the second with 6 or 7 rays, which are very similar in size and shape to the second dorsal fin. They have two dorsal fins; the first being high, but never higher than the body depth, with a long base, a steep posterior slope, and 39 to 43 rays; the second located slightly behind the much smaller second anal fin and with 6 or 7 rays. Their caudal fin is deeply forked. Their pectoral fins are long, narrow, and fold against the body. Their pelvic fins are slender and shorter than the pectoral fins. There are two keels on the side of their tail base. Their lateral line forms a large net-like pattern of hexagons covering the sides. Their body is covered with thick elongated bony scales.

The Blue Marlins are an epipelagic and oceanic blue-water species usually found in surface waters above the thermocline over very deep waters away from land masses; they are seldom found in shallow waters. They have been located at depths up to 3,000 feet via satellite tagging. They are the most tropical of the billfish and are only found in waters with temperatures between 24oC (75oF) and 31oC (88oF). They are a seasonal migratory species traveling in schools toward the equator in winter months and will move to avoid colder and off colored waters. Smaller fish travel in schools of up to ten individuals; larger fish are solitary. Males and females are indistinguishable by external features. All trophy catches are females, as females are significantly larger than males; males do not exceed 300 pounds. They can reach 4.3 meters (14 feet) in length and 910 kg (2,000 pounds) in weight. The World Record caught in Brazilian waters in 1992 is 636 kg (1,402 pounds). They feed during the daylight hours consuming primarily near-surface pelagic fish such as dorados, mackerels, tuna, and squid. They compete for the same food as other billfish, dorados, jacks, large sharks, swordfish, large tuna, and wahoo. They are believed to use their bill to stun prey. This species is also known for driving its bill into animate and inanimate objects, a behavior usually resulting in bill breakage and leaving the distal segment embedded. Some recover from this bill loss as there are records of apparently healthy fish missing rostra. Generally only one rostral fragment is found in each object, but multiple stabbings of whales and boats have also been reported. They are preyed upon by the White Shark, Carcharodon carcharias and the Shortfin Mako, Isurus oxyrinchus. Reproduction is via pelagic eggs with each female releasing approximately one million eggs that take approximately one week to hatch. Juveniles are fast growing and seldom seen by humans. The lifespan is 27 years for females and 18 years for males.

In Mexican waters the Blue Marlin are found in waters of the Atlantic and the Pacific with the exception that they are absent from shallow coastal areas in the Atlantic and from the the central and northern Sea of Cortez.

The Blue Marlin is most likely confused with the Black Marlin, Istiompax indica (no bars on sides; deeper body) and the Striped Marlin, Kajikia audax (dorsal fin deeper than body depth).

The Blue Marlins are a prized big game species and one of the true “BIG FISH” from the ocean. Scientifically they have not been studied quite as extensively as the other marlins. They are coveted by sports fishermen and trophy hunters, primarily due to their phenomenal acrobatic aerial displays when hooked, their size and strong stamina. They are caught by recreational anglers by trolled surface baits during early morning hours and also provide an important economic benefit to several developing countries. Commercially they are pursued by longlining, with a recent focus on going deeper to catch more fish, artisanal fleets, and purse seines, with global annual catches reaching 2,000 to 5,000 tons. The majority are caught as a by-catch of commercial longlines targeting swordfish and tuna who use as many as 2,000 hooks in one string. The quality of the flesh is considered “good” and they are marketed fresh and frozen and utilized primarily for sashimi and sausages with a large market in Japan. From a conservation perspective, their global population is not well documented, however, they are currently considered Vulnerable, with declines in their global populations estimated to be occurring at a rate of about 5% per year. Globally, they are poorly managed with a very limited and declining number of conservation measures in place. However, they are protected in Mexico, where they cannot be taken commercially in a 50-mile coastal zone area.

 A word of caution: these fish are ginormous wild animals and their spears are very dangerous!

Blue Marlin, Makaira nigricans. Fish caught from coastal waters off Puerto Los Cabos, Baja California Sur, July 2006. Weight:  321 kg (706 pounds).  Catch courtesy of Kevin Murphy. Photo courtesy of Eric Brictson, Gordo Banks Pangas, La Playita, Baja California Sur.

Blue Marlin, Makaira nigricans. Underwater photograph taken in coastal waters off Ixtapa, Guerrero, August 2015. Weight: 136 kg (300 pounds). Photograph courtesy of John Wier, Stillwater, OK.