Blue Marlins, Makaira nigricans
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Description & Behavior
Largest of the Atlantic marlins, blue marlins, Makaira nigricans (Lacepéde, 1802), aka Atlantic blue marlins, billfishes, Cuban black marlins, marlins, ocean gars, ocean guards, and squadrons, commonly reach 2.9 m with a maximum of 5 m and maximum weights between 636 - 820 kg (or 540 - 1,800 kg depending upon the source). Males, however, grow much more slowly than females and do not generally exceed 136 kg; all trophy fish are females.
The blue marlin's body is cobalt blue on top, with a silvery white belly, and their upper jaw is famously elongated like a spear. Their tails are high and crescent-shaped and their dorsal fins are pointed at the front end. Their body is covered in embedded scales which end in one or two sharp points. Their lateral line is reticulated, or interwoven like a net, but this characteristic is difficult to see in large specimens. Maturity is reached at about 80 cm in males (40 kg) and 50 cm in females (55 kg).
World Range & Habitat
A highly migratory species, blue marlins are usually found offshore in deep blue tropical or temperate waters. They are known to make regular seasonal migrations, moving toward the equator in winter and away again in summer, with some migrations spanning the entire Atlantic. Some scientists recognize Makaira nigricans and Makaira mazara as two different species based on differences in their lateral line. Many, however, lump the two together as a single species occurring in the Atlantic, Pacific and Indian oceans.
Feeding Behavior (Ecology)
Blue marlin's prey includes octopuses, squid and pelagic fishes such as blackfin tuna and frigate mackerel. They hunt during the daytime rarely gathering in schools, preferring to hunt alone. Blue marlins have been reported to use their long, sharp bills to slice or stun prey.
Very little is known about the spawning of blue marlins except that they are external fertilizers, open water egg scatterers, and they spawn in the eastern Atlantic during the summer. Their eggs are transparent and spherical and measure 1 mm in diameter.
Conservation Status & Comments
A very popular sport fish due to its challenging size and strength — they are also one of the world's fastest fishes — the blue marlin is also marketed for human consumption fresh or frozen.
Blue marlins are under intense pressure from longline fishing. In the Caribbean region alone, Japanese and Cuban fishermen annually take over a thousand tons. All vessels within 200 miles (320 km) of the U.S. coastline are required to release any billfish caught. However, the survival rate of released fish is low because of damage during capture.
Atlantic blue marlins have not (yet) been evaluated as to whether they are threatened or endangered by the International Union for Conservation of Nature (IUCN).
In 2010, Greenpeace International added the Atlantic blue marlin to its seafood red list. "The Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries."
References & Further Research
Research Makaira nigricans » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS
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