Description:

Dorsal spines: 0; Dorsal rays: 45-50; Anal spines: 0; Anal rays: 19-23.

Body elongate, not very compressed. Upper jaw extended into long bill, extremely stout and round in cross section. Nape strongly elevated. Both jaws and roof of mouth with 
small, file-like teeth. Lateral line a network of interconnecting canals. Two dorsal fins. Height of anterior lobe of first dorsal fin less than greatest body depth. Second 
dorsal fin slightly posterior to second anal fin. Two anal fins. Pectoral fins long and narrow. Pelvic fins shorter than the pectorals and depressible into deep ventral 
grooves. Caudal peduncle fairly compressed (laterally) and slightly depressed (dorsoventrally), with strong double keels on each side and a shallow notch on both the dorsal 
and ventral surfaces.
 
Colour. Body blue-black dorsally shading to silvery white ventrally. About 15 bars of pale, cobalt-coloured round dots and/or narrow bars on the flanks. First dorsal fin 
blackish or dark blue, other fins blackish brown, sometimes tinged with dark blue; bases of first and second anal fins tinged with silvery white.

Maturity: Lm unknown. Range: 50 - ? cm for females and 80 - ? cm for males. Females grow larger. Max Length: 500cm TL. Typically to 290cm TL.

Pelagic-oceanic species (depth 0-100 m, usually 0-40 m) not usually encountered close to land unless in the vicinity of a steep drop-off from the shelf. Feeds during the day 
mostly upon squids, tuna-like fishes, crustaceans, and cephalopods. Usually found as scattered individuals, rarely in small schools of up to 10.

This species is not protected or subject to fishery regulations. It is targeted and caught in the semi-industrial longline fishery, it is a rare catch in the artisanal fishery.

Formerly considered as 2 species, one in the Atlantic (M. nigricans) and the other Indo-pacific (M. mazara). Now considered a single species with M. mazara a synonym of M. nigricans. 
 

Collette, B. et al. (2011). Makaira nigricans. The IUCN Red List 2011: http://dx.doi.org/10.2305/IUCN.UK.2011-2.RLTS.T170314A6743776.en. (15/08/19).
Froese, R. & D. Pauly. (Eds.) (2019). FishBase. https://www.fishbase.se/summary/Makaira-nigricans (15/08/19).

Nevill, J.E.G. (2019). Makaira nigricans, Blue marlin. Seychelles Seatizens. www.seatizens.sc. https://seatizens.sc/species/makaira-nigricans-lacepede-1802/ (edited 08/07/22).