Fish
Blue Marlin
Makaira nigricans · also called blue marlin, Atlantic blue marlin, Pacific blue marlin
The blue marlin is one of the true giants of the open ocean — a deep-blue torpedo of a fish, over four metres in the biggest females, that can outrun almost anything in the sea and slashes a spear-like bill through schools of tuna to feed.
Overview
Blue marlin roam the open tropical and warm-temperate Atlantic and Pacific, far from shore. They are built for speed — a long rounded bill, tapering body, and a dorsal fin that folds flush into a groove — and can reach 80–110 km/h in bursts. Females grow far larger than males, up to 4 m and 800 kg. They hunt tuna, mackerel, dolphinfish, and squid.
The bill as a weapon
A marlin drives into a bait ball and slashes its bill side to side, stunning several fish at once, then circles back to pick off the disabled prey.
Colour and depth
It can flash electric-blue stripes across its flanks in seconds, and tagged fish have been tracked diving past 800 m into cold, low-oxygen water.
Status
The blue marlin is Vulnerable, with Atlantic stocks assessed as overfished — mostly as bycatch on tuna longlines — though recreational anglers increasingly tag and release them.
Blue Marlin: common questions
How fast is a blue marlin?
Estimates put its burst speed in the range of 80 to 110 kilometres per hour, based on body shape, fin retraction, and tagging data, which places it among the fastest fish in the ocean alongside the sailfish and swordfish. As with those species, the highest historical figures come from indirect methods and are debated, but even conservative modern estimates make the blue marlin one of the quickest animals in the sea over a short burst, an ability it uses to close on schooling prey and to leap and run hard once hooked by anglers.
Why does the marlin have such a long bill?
The bill, technically an extension of the upper jaw, is used as an active hunting weapon rather than a simple spear. A blue marlin drives into a school of tuna, sardines, or squid and whips its bill rapidly from side to side, striking and stunning or injuring several prey fish in the pass. It then circles back and eats the disabled fish at leisure, which is a far more efficient tactic than chasing a single fast fish through open water. The bill and the marlin's speed and manoeuvrability work together, and the sharply tapered, low-drag shape of the bill also helps the fish cut through the water with minimal resistance.
How big is the biggest blue marlin ever recorded?
The largest verified blue marlin catches have weighed close to 800 kilograms and measured over 4 metres, with the females responsible for essentially all of the largest specimens, since female blue marlin routinely grow several times heavier than males of the same age. Sport-fishing record catches, including some famous ones written about by Ernest Hemingway, who fished for marlin off Cuba, have driven much of the public fascination with the species’ size and fighting power, and modern tournaments now largely practise catch-and-release tagging rather than killing large fish.
Is the blue marlin endangered?
It is listed as Vulnerable, and populations in parts of its range, particularly the Atlantic, are considered overfished. Blue marlin are not usually the deliberate target of large commercial fleets, but they are caught in very large numbers as bycatch on the longlines set for tuna and swordfish across the tropical oceans, and as a large, late-maturing, relatively slow-reproducing fish, the population cannot easily absorb that level of incidental fishing mortality. Management measures include catch limits, gear modifications intended to reduce marlin bycatch, and, among recreational anglers, a strong and growing culture of releasing marlin alive after they are caught and tagged.