Blue marlin fishing: the giant nobody knows is one species or two

October 7, 2026

The FishBase page for the blue marlin contains an unusually honest sentence. FishBase follows the FAO catalogue by Nakamura (1985) and lists the Atlantic blue marlin, *Makaira nigricans*, and the Indo-Pacific one, *Makaira mazara*, as two species — mainly because the pattern of their lateral line differs. Right after that it says: many scientists consider exactly this feature not sufficient and see only one single species, living in the Atlantic, Pacific and Indian Oceans. The English Wikipedia calls the two “usually considered one species”, the German one writes that research “increasingly” recognises only one — the Japanese one, by contrast, explicitly treats them separately. For an angler in Europe, the question is less academic than it sounds: the blue marlin you will meet here is in any case the Atlantic one. The English Wikipedia names sport fishing for it in the eastern Atlantic from the Algarve to Angola, with the Azores, the Canary Islands, Cape Verde, Madeira and Ascension. This article is about the blue marlin, *Makaira nigricans* — German Blauer Marlin, French makaire bleu, Spanish aguja azul, Italian marlin azzurro, Portuguese marlim-azul, Japanese ニシクロカジキ (nishikurokajiki).

A sword, a dagger — or luck after all?

The blue marlin belongs to the family of billfishes (Istiophoridae), which also includes the sailfish and the other marlins (FishBase, the German Wikipedia). The sources start arguing as early as the genus name: according to the English and the Italian Wikipedia, *Makaira* comes from the Greek machaira, a short sword or curved dagger, and from the Latin machaera, “sword”. FishBase, by contrast, translates makaira as “happy, rich”. All agree on the species name: according to the German Wikipedia *nigricans* means “blackish, dark”, according to the English one “becoming black”. It was described by the Frenchman Bernard Germain de Lacépède in 1802 (FishBase) — according to the Russian Wikipedia only from a drawing; there is no type specimen. The Japanese Wikipedia gives 1908 as the year of the first description.

How to recognise it

The body is elongated and only slightly compressed laterally; it is deepest directly behind the head and then tapers more and more towards the rear (the German Wikipedia). The bill is long and stout and round in cross-section — this sets all billfishes apart from the swordfish, whose sword is flat and sharp-edged (the German Wikipedia). The first dorsal fin runs along most of the back; its front part rises to a point but always stays lower than the body is deep. According to the German and the English Wikipedia it is supported by 39 to 43 fin rays, the second by 6 to 7. The long, narrow pectoral fins (19 to 22 rays) can be folded flat against the body, and the first anal fin and the tail fin into grooves — which makes it streamlined (the English Wikipedia). The caudal peduncle carries two strong keels on each side. The skin is covered with thick, bony, elongated scales. One feature you hardly see on adult fish any more: the lateral line forms a chain-link-like network, clearly visible in juveniles, which later disappears beneath the skin (the German Wikipedia). This very network is why FishBase separates it from the Indo-Pacific marlin — whose lateral line, according to the Japanese Wikipedia, consists of simple loops.

The colour: blue-black above, silvery white below, and in between about 15 rows of pale, cobalt-blue stripes made of round dots or narrow bars (FishBase, the English Wikipedia). The first dorsal fin is dark blue to almost black and has no dots or spots; the other fins are brownish black, sometimes with a tinge of dark blue; the base of the anal fins shines silvery white (FishBase). Like other billfishes, it can change colour very quickly — made possible by iridophores, light-reflecting skin cells (the English Wikipedia). According to the Russian Wikipedia it usually turns bright blue when hunting; according to the German one, the contrast of the stripes depends on its mood.

Size: FishBase gives 500 cm total length as the maximum, 290 cm as the common length and 636 kg as the heaviest published weight. That is also the IGFA world record: 1,402 pounds 2 ounces, caught off Vitória in Brazil (the English Wikipedia). According to the English Wikipedia, females grow up to four times as heavy as males, which rarely weigh more than 160 kg. Anglers call fish of 1,000 pounds and more (a good 450 kg) “granders”.

Where it lives and what it eats

Distribution: according to FishBase in the Atlantic, in tropical and temperate waters between 50° North and 45° South, at 22 to 31 °C, a highly migratory fish. The German Wikipedia calls it the most tropical of all billfishes; judging by catch figures, it is more common in the western Atlantic than in the eastern Atlantic, where, according to the English Wikipedia, it occurs mainly off Africa between 25° North and 25° South. In summer its range expands into temperate latitudes, in winter it contracts towards the equator; in the west, warm currents such as the Gulf Stream determine where it is found (the English Wikipedia). According to the Finnish Wikipedia, its range extends north to the northwest coast of Spain.
Habitat: a fish of the open ocean, far from land (the English Wikipedia). It lives mostly alone, rarely in schools (FishBase). Water colour matters: in the northern Gulf of Mexico it shows a clear preference for blue water (FishBase). According to the English Wikipedia, most fish are found in water above 24 °C; they have been recorded at surface temperatures of 21.7 to 30.5 °C.
Depth: FishBase gives 0 to 1,000 metres. According to the German Wikipedia it inhabits the upper 200 metres, according to the English one it moves between the surface and about 100 metres — at night mostly near the surface, by day deeper, limited by temperature and oxygen. The French Wikipedia gives the top 40 metres as its main range.
Diet: mainly fish, plus octopus and squid; it feeds by day (FishBase), trophic level 4.5. According to the English Wikipedia, small schooling tunas such as frigate tunas (genus *Auxis*) and skipjack tuna make up a large share; but it also takes prey as large as a white marlin or yellowfin and bigeye tuna of around 100 pounds. The German Wikipedia mentions a 290 kg marlin from the Gulf of Guinea that had swallowed a 50 kg bigeye tuna.
The bill as a weapon: whether marlins hunt with their bill was long disputed, according to the English Wikipedia. A 2007 Japanese study examined 227 blue marlin and found 130 undigested prey items with stab, slash and other wounds attributed to the bill. It uses the bill to stun or injure prey and then returns to feed.
Migrations: tagged fish travelled between the Caribbean, Venezuela and the Bahamas, and from the US Virgin Islands to West Africa. A marlin tagged off Delaware was recaptured off Mauritius in the Indian Ocean — after 9,254 miles (the English Wikipedia).
Speed: here the figures diverge widely, see below. The English Wikipedia gives 72 km/h as the frequently cited top speed, but says that most of the time it swims at under 4.5 km/h.

Seven million eggs — and off Portugal to spawn

According to the English and the German Wikipedia, the blue marlin becomes sexually mature at two to four years — males at 35 to 44 kg, females at 47 to 61 kg. Spawning takes place in late summer and autumn, in the North Atlantic, according to the German Wikipedia, from July to October. A female can spawn up to four times in one season, releasing more than seven million eggs each time, each about 1 mm in size (the English Wikipedia). The larvae drift in open water and, according to the English Wikipedia, grow up to 16 mm a day; they have been found mainly off the southeastern United States, in the Caribbean and off Brazil. Of interest for Europe: according to the English Wikipedia, blue marlin migrate to the international waters off Portugal in June and July to spawn — and, according to the same source, that is exactly where they suffer particularly from overfishing. According to the English Wikipedia, males live up to 18 and females up to 27 years; based on a radiocarbon study, FishBase gives a maximum age of just under 20 years.

How it is caught — and what you should know

FishBase lists it as a game fish and as commercial; its price category is “high”. According to the English Wikipedia, the history of sport fishing for it begins in the 1920s and early 1930s in the Bahamas, when pioneers such as Van Campen Heilner and S. Kip Farrington explored the waters off Bimini and Cat Cay. Zane Grey and Ernest Hemingway fished for it off the Florida Keys, the Bahamas and Cuba and wrote a great deal about it; in Hemingway’s “The Old Man and the Sea”, the fisherman Santiago battles a blue marlin off Cuba for three days (the English Wikipedia). In the Bahamas it is the national fish and appears on the coat of arms; in Bermuda it adorns the 5-dollar note. The German Wikipedia describes the fight: a long battle with spectacular leaps out of the water.

⚠️ What follows is an inference from its biology, not a sourced statement: a fish that hunts alone in blue, warm offshore water, moves between the surface and around 100 metres by day and follows schooling tunas is searched for far offshore — where the water is above 24 °C and the small tunas are. A fish that can reach over 600 kg calls for heavy big-game tackle and an experienced crew. For European anglers, the documented grounds lie in the Atlantic: on the Algarve and around the Azores, Madeira, the Canary Islands and Cape Verde. And because, according to the English Wikipedia, the survival rate of released marlin is low — due to the injuries sustained during capture —, every minute counts when releasing: a short fight, keep the fish in the water, unhook it gently.

For the kitchen: FishBase rates it as harmless. According to the English Wikipedia, its flesh is relatively high in fat and in Japan is especially prized for sashimi; the Finnish Wikipedia describes it as light-coloured and of good quality. A note from the English Wikipedia: heavy metals accumulate in it, and in 2017 the Texas wildlife agency issued a mercury consumption advisory for all blue marlin caught off Texas.

And the stock? The IUCN lists it as “Vulnerable” (FishBase: assessed on 10 May 2021). According to the German Wikipedia, the stock is considered overfished in the Atlantic and the Indian Ocean; the world population fell by around 33 to 37% between 1987 and 2014. In 2010, Greenpeace put it on its seafood red list (the English Wikipedia). FishBase rates its resilience as “low” — stocks need 4.5 to 14 years to double —, its vulnerability to fishing as “moderate to high” (52 out of 100), and to climate change likewise (50 out of 100). According to the English Wikipedia, the greatest pressure comes from the longlines of the tuna fishery, on which it is caught as bycatch; in the US, all vessels must release billfish caught within 200 miles of the coast. Minimum sizes, bag limits and release rules are set by each country — check them locally.

Six contradictions, left open

One species or two? FishBase: two (*M. nigricans* in the Atlantic, *M. mazara* in the Indo-Pacific), but it concedes that many scientists see only one. The English Wikipedia: usually one; genetic data point to the same species, while another study found a “striking” separation in the genome. The German one: increasingly one. The Japanese one: deliberately two — and it reports that the FAO already lumps both together under one name in its catch statistics.
Mediterranean — yes or no? FishBase names only the Atlantic, the English Wikipedia calls it endemic to the Atlantic, the Russian one writes “only in the Atlantic”. Yet the Norwegian and the Turkish Wikipedia include *Makaira nigricans* in their lists of Mediterranean fish species. The Norwegian list even names, right before it, another large marlin, *Makaira indica*, said to have entered through the Suez Canal.
How heavy? FishBase: 636 kg, equal to the IGFA record. The English Wikipedia: 818 kg as the heaviest published weight, 540 to 820 kg for large females depending on the source. The Hebrew one: up to 829 kg. The Dutch one: over 900 kg. The French one: up to 600 kg. The German one still gives 581.51 kg as the heaviest IGFA-confirmed weight and mentions anglers’ reports of 680 kg.
How fast? The English Wikipedia: top speed 72 km/h, mostly under 4.5 km/h. The Italian one: top speed 81 km/h, sustained top speed around 36 km/h. The Dutch one: 90 km/h — the fastest animal in the water. The French one: around 8.3 metres per second, i.e. about 30 km/h.
When sexually mature, how old? FishBase: males at around 80 cm, females at 50 cm — and larger females. The French Wikipedia: females at 2 years at 178 to 221 cm. The English one: by weight, 35 to 44 kg and 47 to 61 kg. On age: FishBase just under 20 years, the French one 20, the English, Russian and Finnish ones 18 years for males and 27 for females.
Threatened or not? FishBase and the English, German, Russian and Japanese Wikipedia: classified by the IUCN as vulnerable. The Dutch Wikipedia writes that the IUCN lists it as “not threatened”.

Five names that lead to the wrong fish

“Black marlin”, “marlin negro”. For the blue marlin, the GBIF name list also gives “Black marlin” and “Cuban black marlin” in English, and “Marlin negro” in Spanish. The actual black marlin, however, is a different fish, *Istiompax indica* — and for it GBIF lists exactly the same names, black marlin and marlin negro.
Black means blue, white means black. In Japanese, the blue marlin is a “black” fish: クロカジキ (kurokajiki), literally “black marlin”; the Atlantic one is called ニシクロカジキ. The English black marlin, on the other hand, is called シロカジキ (shirokajiki) in Japanese according to GBIF — “white marlin”. And クロカジキ on its own means, in the Japanese Wikipedia, the Indo-Pacific blue marlin, *M. mazara*; GBIF lists the name for both.
“Picudo blanco”. For the blue marlin, GBIF also lists “Picudo blanco” and “Merlin rayado” in Spanish — that is, “white billfish” and “striped marlin”. But the white marlin is called aguja blanca or marlin blanco in Spanish, and “striped marlin” is a species of its own in English. The only safe Spanish name is aguja azul.
“Espadarte”. The Portuguese Wikipedia also calls it espadarte-azul, and GBIF adds “Espadarte-sombra”. But in Portuguese an espadarte is the swordfish (GBIF). And GBIF lists “Peixe agulha” in Portuguese for both fish.
Peito, castero, ocean gar. On Madeira it is called Peito according to the Japanese Wikipedia and GBIF, on Cuba Castero or Aguja de caste according to the Japanese Wikipedia. Old English names, according to the English Wikipedia, are ocean gar and ocean guard. And in English? GBIF lists Atlantic blue marlin and Blue marlin; in German it is Blauer Marlin or Atlantischer Blauer Marlin, and the Indo-Pacific relative Pazifischer Blauer Marlin. The only marlin that spends its whole life in the Mediterranean, the Mediterranean spearfish, is covered by a separate group in this series, as is the swordfish.

That leaves the question every article in this series starts with: when. Depth, prey and hunting style are covered above, and they are fixed. What changes every day is everything else — and that is exactly where it is decided whether a day on the water is worth it. That is what StrikeAhead calculates: it takes the conditions on your water and tells you when the trip is worth it. And because you can’t read the blue water off an Atlantic island from day one, StrikeAhead Pathfinder tells you who to go out with: curated guides and skippers, personally vetted before listing — licence and insurance —, with verified catches instead of promo photos, no paid ranking and, for you as an angler, no booking fee.

Fish the right moment →