| Name | Black marlin, Atlantic blue marlin, Indo-Pacific blue marlin, white marlin, striped marlin | Diet | Carnivorous |
| Scientific name | Istiompax indica, Makaira nigricans, Kajikia albida, Kajikia audax | Weight | 45–900 kilograms (99–1,984 pounds) |
| Pronunciation | Mahr-leen | Length | 2.8–5 meters (9.2–16.4 feet) |
| Classification | Actinopterygii, Istiophoriformes, Istiophoridae | Location | Worldwide |
The Marlin
Marlins are, without a doubt, among the world’s most fascinating oceanic creatures.
Considering how large and beautifully colored they are, we shouldn’t be surprised they caught the attention of any wildlife enthusiast!
Not to mention their impressive speed and distinctive sword-like upper jaw used to slash prey!
Did you know that besides having uniquely patterned coloration, marlins can change their colors?
Are you eager to learn more details? We’ve got plenty! Grab a coffee and enjoy the ride!
Taxonomy and Classification
Marlins are part of the Istiophoridae family, and the five species are classified into three genera:
- Istiompax includes Istiompax indica, or the black marlin.
- Makaira includes Makaira nigricans, or the Atlantic blue marlin, and Makaira mazara, the Indo-Pacific blue marlin.
- Kajikia includes Kajikia albida, or the white marlin, and Kajikia audax, or the striped marlin.
We must mention that although the Atlantic blue marlin and the Indo-Pacific blue marlin are separate species, this taxonomic classification is debatable, as many scientists consider the two should be under the same species despite their different geographic distribution.
This classification makes marlins most closely related to sailfish and spearfish, as they’re part of the same family.
They’re also close relatives of the swordfish, which are also part of the Istiphoriformes order.
Further up the taxonomic tree, marlins are in the Percomorpha clade of the Actinopterygii class.
This clade consists of the most diverse teleost fish that reached their peak of diversity, size, and abundance after the Cretaceous-Paleogene boundary and continued to thrive ever since.
Physical Characteristics
Since we’re discussing five marlin species, we’ll have to mention the physical characteristics of each, as they aren’t identical.
The smallest marlins are the striped and white marlins, as they reach only 2.8–2.9 meters (9.2–9.5 feet) in length and do not weigh more than 45–200 kilograms (99–441 pounds).
Of the two, the white marlin is the smallest, as it weighs on average 45 kilograms (99 pounds).
The next in line in terms of size is the black marlin, which is 4.65 meters (15.3 feet) in length and weighs 750–900 kilograms (1,653–1,984 pounds).
The two blue marlin species are similar, reaching 5 meters (16.4 feet) in length, although the average is approximately 3.5 meters (11.5 feet).
The largest Atlantic blue marlin female registered a mass of 540–820 kilograms (1,191–1,808 pounds), although the exact weight hasn’t been officially confirmed yet.
One of the most distinguishable characteristics of marlins is their long, thin, pointed, sword-like upper jaw.
While all species have a somewhat similar appearance, they are of different colors, just as their names suggest, and feature some distinctive features.
Check out the table below to discover details that can help you distinguish one marlin from another!
| Common name | Color | Other distinctive characteristics |
| Black marlin | Dark blue on top-White-silverish on the downside-Faint blue vertical stripes on the sides-Blackish-dark blue first dorsal fin; other fins are dark brown | -Non-retractable fins-Its dorsal fin is the lowest of any billfish-Shorter bill |
| Blue marlin | Blueish-black on top-Silvery underside-15 rows of cobalt-colored stripes of dots or bands-Dark blue first dorsal fin; another fins are almost black with a hint of blue | -Longer bill-Taller dorsal fin-Long, narrow, and flexible pectoral fins |
| White marlin | Dark blue to dark brown on the upper half-Silvery-white underbelly-Bluish-black first dorsal fin, covered in black spots; the rest of the fins are brown-black-Brown spots below the dark blue line | -The dorsal fin extends along most of its dorsal part and is bigger than in other marlins-Has pectoral and pelvic fins that are rounded and wide at the tip-Has a visible lateral line |
| Striped marlin | Dark blue to black on the upper part-Silvery-white on the undersides-12-20 bluish vertical stripes on the sides consisting of small dots or narrow bands; the color changes to lavender when the fish is excited | -The slenderest bill of all marlins-Has a rather flattened body (compared to a blue marlin’s body) |
Habitat and Distribution
Black marlins live in the tropical and subtropical waters of the Indo-Pacific.
Sometimes they wander through temperate waters and are occasionally spotted in the Atlantic, although they do not breed there.
Black marlins prefer swimming close to the shore and rarely dive deeper than 30 meters (98.4 feet).
Atlantic blue marlins live in the tropical waters of the Atlantic, just as their name suggests.
These fish do not go deeper than 100 meters (328 feet) because they cannot withstand the oxygen levels and temperatures of deeper waters.
In fact, during the night, they’re almost always near the surface.
The largest Atlantic blue marlin populations gather in waters warmer than 25 degrees Celsius (77 degrees Fahrenheit).
The Indo-Pacific blue marlin lives in the Pacific and Indian Oceans, preferring their tropical and subtropical waters.
Unlike other marlins, they do not typically come close to islands or coral reefs.
White marlins live in the Atlantic, from Nova Scotia to Argentina, and can also be spotted in the Caribbean Sea, the Mediterranean Sea, and the Gulf of Mexico.
Unlike their relatives, white marlins can stay in waters deeper than 100 meters (328 feet) but they are often spotted near the water’s surface.
Striped marlins live in tropical and subtropical Pacific and Indian waters, although they’re sometimes seen in temperate waters.
They remain in waters of 20–25 degrees Celsius (68–77 degrees Fahrenheit) and spend most of their time close to the water’s surface.
Behavior and Social Structure
Most marlins stay above the thermocline, a layer of transitioning temperatures between the warmer and the cool waters.
Of all marlin species, the white marlin prefers the deepest levels, whereas the others are most often seen close to the surface.
Despite this, most marlins remain hidden in deeper waters during the day and surface at night, some coming close to islands and coral reefs, except for the Indo-Pacific blue marlins, which seem to not like shores.
Some marlin populations are known to be migratory, but there aren’t enough studies to confirm their migratory patterns or seasonality.
For example, studies on Atlantic blue marlin migratory patterns have shown that many individuals move between the Caribbean and Venezuela, whereas others remain in the same place for a longer period.
Therefore, scientists couldn’t confirm a well-outlined migratory seasonality.
It has been observed, though, that many populations travel north or south during the summer and return closer to the Equator during the winter.
The white marlin stands out among other marlins in terms of migration, as it’s often spotted in seawater.
They’re known to have established their spawning grounds in the Gulf of Mexico, southwest Bermuda, Mona Passage, and northwest Grand Bahama Island.
Marlins are solitary creatures.
They swim and hunt alone, except for the spawning season when they occasionally form small schools.
Black marlins are renowned for being among the world’s fastest fish, although this is probably exaggerated as the numbers have no scientific backup.
For example, some reports show that black marlins can reach speeds of 132 km/h (82 mph), although the maximum confirmed burst speed is 36 km/h (22.4 mph).
Marlins are considered obligate ram ventilators.
This means that they can breathe only while swimming.
They open their mouths, and as they swim forward, the water passes through them and across the gills.
Now you’re probably wondering how they do not get tired, right?
It has been suggested that ram ventilators can rest in currents, where the oxygenated water flows passively over their gills while they stand still.
However, this is only a theory and hasn’t been confirmed for marlins specifically.
Diet and Feeding
Marlin larvae feed on zooplankton, fish eggs, and other larvae. As they mature, marlins switch to a different diet that includes various fish. Here’s a list of prey marlins are known to hunt:
- Tuna
- Mackerel
- Flying fish
- Squid
- Crustaceans
- Octopus
- Frigate mackerel
- Skipjack tuna
- Snake mackerel
- Yellowfin
- Bigeye tuna
- Filefish
- Snipefish
- Mahi-mahi
- Sardines
Obviously, the type of prey highly depends on the size of the marlin.
White marlins, for example, are the smallest and will go for small prey, whereas the Atlantic blue marlin can eat prey as large as a white marlin!
Marlins have their distinctive long, pointed bills, right? So they must be using them to kill prey.
The truth is, scientists don’t yet know whether this is entirely true.
White marlin stomach contents showed that the prey did not exhibit any slashing wounds, so it has been suggested that they take prey by speed rather than by injuring it.
On the other hand, studies on blue marlin stomach contents showed that prey had slashing and spearing injuries.
Reproduction and Life Cycle
Marlins reproduce through external fertilization.
This means that females and males release the eggs and sperm into the water, upon which fertilization occurs.
The number of eggs varies depending on the species.
Atlantic blue marlins, for example, lay seven million eggs during one spawn and spawn four times a season.
White marlins, on the other hand, rarely lay more than half a million eggs, whereas striped marlins are known to release 120 million eggs over a spawning season, which are laid in batches every few days.
Additionally, striped marlins have between 4 and 41 spawning events over a spawning season!
Black marlins usually lay 40 million eggs.
The spawning period depends on the species, too, as follows:
- The precise spawning season of black marlins hasn’t been confirmed, but they’re known to breed in water temperatures of 27–28 degrees Celsius (81–82 degrees Fahrenheit).
- Atlantic blue marlins breed in late summer and fall.
- Indo-Pacific blue marlins and striped marlins spawn in the summer.
- While marlins spawn in the early summer.
The marlin larval appearance remains poorly known, as the larvae are difficult to identify, although some sources mention that they probably lack the long bill and have unusually large eyes.
It has been suggested that Atlantic blue marlin larvae add 16 millimeters (0.63 inches) daily and reach sexual maturity once they weigh 35–61 kilograms (77–134.5 pounds), depending on whether they’re males or females.
Females typically need to be larger to become sexually mature.
This is valid for white marlins as well – females can start reproducing when they’re 1.89 meters (6.2 feet) long, while males must have a length of 1.53 meters (5 feet) to become sexually mature. Either way, white marlins grow rapidly.
Male striped marlins can start reproducing once they grow to 1.4 meters (4.6 feet), while females must be at least 1.8 meters (5.9 feet) long.
Here’s the maximum lifespan of all species, although remember that it’s affected by numerous factors and they rarely reach old age:
- Black marlins: 12 years for females; 5 years for males
- Atlantic blue marlins: 27 years for females; 18 years for males
- Indo-Pacific blue marlins: 20 years for females; 10 years for males
- White marlins: 25 years for females; 15 years for males
- Striped marlins: 20 years for females; 8–10 years for males
Ecological Role and Interactions
Marlins play a significant role in keeping their habitat healthy and fully functional. Some sources mention that they are keystone predators in their ecosystems.
Naturally, blue and black marlins, which are the largest, have fewer predators than the smaller species.
Killer whales, shortfin mako sharks, and great white sharks sometimes hunt marlins.
Conservation Status and Threats
The only marlin species listed as Vulnerable on the IUCN Red List is the Atlantic blue marlin.
The others have been assessed as Least Concern, and only some specific populations are Endangered.
Nonetheless, this doesn’t mean that they face no threats.
Although marlins have few natural predators, humans regularly fish marlins for their meat.
Additionally, they’re often caught as bycatch in longline fisheries.
For example, over 1,000 tons of Atlantic blue marlins are caught yearly in longlining in the Caribbean region.
Besides this, although some regions require the release of any caught marlins, they rarely survive the damage.
Luckily, many conservation acts are in motion to save the marlin population, and fishery management organizations are constantly trying to educate people about the ecological importance of billfish.
Unique Adaptations and Survival Strategies
By far the most renowned adaptation of marlins is their color-changing ability.
Blue marlins, for example, can rapidly change their stripe colors to a purplish shade.
Fishermen noticed them changing their body colors when attacking bait, so this might be prompted by a feeling of excitement.
It is believed they can do so thanks to their iridescent, light-reflecting skin cells.
Striped marlins are also known to turn their stripes into a distinguishable lavender when excited.
Besides their unique color-changing ability, nature has gifted marlins with a body form that allows fast swimming, a pointed upper jaw that ensures quick prey catch, and the ability to release millions of eggs during a spawning season to ensure their population’s survival.
Furthermore, they can swim for long periods without getting tired, which, equipped with their fast speed, makes for an excellent means to escape predators!
Cultural Significance and Human Interactions
Besides being highly prized for their meat, marlins have gained the public’s interest after Ernest Hemingway wrote and published his famous novel, The Old Man and the Sea.
It tells the story of an aged fisherman who spends 84 days in the water without catching anything until he ventures out to the sea and hooks a huge marlin.
Needless to say, The Old Man and the Sea is now among the most renowned books and is undoubtedly a must-read for its literary beauty and unique portrayal of marlins.
It is believed that Hemingway himself caught several marlins in the Gulf Stream.
Marlins are now regularly caught by big-game fishermen.
In fact, the art of catching marlins led to the rise of a multimillion-dollar industry.
However, fishermen are generally advised to release marlins after catching them, but the laws and restrictions vary between locations.
The biggest marlin-related event is the White Marlin Open, which takes place in Ocean City, Maryland, and gathers anglers from all around the world.
Sometimes there’s even a million-dollar prize!
Future Prospects and Research
Nowadays, most conservation efforts are oriented toward maintaining the marlin populations steady.
This implies reinforcing how important marlins are for the ecosystem, educating people on their lifestyle and behavior, and establishing protection and management laws, such as the catch-and-release rule for tournaments and recreational fishing.
Conclusion
With their breathtaking size and coloration, distinctive sword-like bills, and unique adaptations, marlins are now among the world’s most fascinating fish species!
They live in oceanic waters and are skilled predators that play a crucial ecological role in their ecosystems.
Although solitary, marlins can sometimes gather where prey is abundant or cooperate with other species to forage more efficiently.
Unfortunately, some marlin populations are significantly affected by bycatch, artisanal, and sport fisheries.
In some regions, their numbers are steadily decreasing, so conservation efforts must be continuously reinforced.
FAQs
Is marlin a swordfish?
Marlins are not swordfish, as the latter form the Xiphiidae family.
However, marlins and swordfish are closely related.
Sources:
- https://en.wikipedia.org/wiki/Marlin
- https://en.wikipedia.org/wiki/Black_marlin
- https://fishbase.mnhn.fr/summary/Istiompax-indica.html
- https://en.wikipedia.org/wiki/Atlantic_blue_marlin
- https://en.wikipedia.org/wiki/Indo-Pacific_blue_marlin
- https://en.wikipedia.org/wiki/White_marlin
- https://en.wikipedia.org/wiki/Striped_marlin
- https://www.afma.gov.au/species/striped-marlin
- https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/kajikia-albida/
- https://www.mass.gov/info-details/learn-about-atlantic-blue-marlin
- https://www.deq.nc.gov/about/divisions/marine-fisheries/public-information-and-education/species-profiles/white-marlin
- https://www.marinebio.org/species/black-marlins/istiompax-indica/
- https://www.biologicaldiversity.org/species/fish/Atlantic_white_marlin/natural_history.html
- https://dnr.maryland.gov/fisheries/Pages/fish-facts.aspx?fishname=White+Marlin
- https://link.springer.com/chapter/10.1007/978-94-011-6558-7_3
- https://karger.com/bbe/article/94/1-4/37/452/Evidence-for-Sleep-in-Sharks-and-Rays-Behavioural
- https://www.iucnredlist.org/species/170314/46936155
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