Blue Marlin | Oceana
Home / Blue Marlin

Marine Life Encyclopedia

Ocean Fishes

Blue Marlin

Makaira nigricans

Distribution

Worldwide in tropical to temperate latitudes

ECOSYSTEM/HABITAT

Open ocean (pelagic)

FEEDING HABITS

Aggressive predator

TAXONOMY

Order Xiphiiformes (swordfish and billfishes), Family Istiophoridae (billfishes)

This species is known for its long bill that grows from the front of its head. Blue marlin use this bill to stun their prey by slashing their heads in a side-to-side motion, knocking potential prey unconscious, and making it easier to catch. The blue marlin’s bill differs from the swordfish’s and the sailfish‘s by being round and pointed, rather than flat and blunt. Like many open ocean bony fishes, blue marlin start out as extremely tiny larvae, no more than a few millimeters long and weighing only a few hundredths of a gram. Soon after hatching, they already have a visible bill. Blue marlin grow rapidly, and in the course of their lives they may increase their body weight by at least one million times.

Because blue marlin undergo such an amazing transformation in size (from being nearly microscopic to being one of the largest open ocean predators), they eat a wide variety of prey, throughout their lifetimes. At a young age, they eat tiny zooplankton, and their prey increases in size as they do. As adults, they eat fairly large bony fishes and squids. Similarly, blue marlin are eaten by a wide variety of predators. When they are newly hatched, they are eaten by other fishes that specialize on eating plankton. The size of their predators increases as they grow, and adult blue marlin are not eaten by anything other than large open ocean shark species.

The blue marlin is a highly migratory species, with individuals migrating across entire ocean basins and even between oceans. One individual, for example, was tagged off the east coast of the United States (western Atlantic Ocean) and recaptured in the Indian Ocean. Like many migratory species, the females are larger than males. In fact, adult female blue marlin are as much as four times the size of the largest males. All of the largest individuals are female.  blue marlin reproduce through external (rather than internal) fertilization, where the female releases her eggs into the water column while the male releases his sperm. Once the sperm find the eggs, fertilization occurs.  While spawning, a single female may release several million eggs, increasing the likelihood that some will be fertilized and that at least one hatched larva will grow to reach adulthood. Though almost all fishes are cold blooded, blue marlin and the other billfishes have a specialized blood vessel structure – called a countercurrent exchanger – that allows them to warm their brains and eyes. This adaptation provides them with a major advantage when hunting, by allowing them to think more quickly and see more clearly.

The blue marlin is a targeted fishery species in only a limited number of areas but is captured as accidental bycatch in fisheries targeting other species throughout its range. In some areas, this accidental capture is threatening blue marlin populations, and scientists consider the species vulnerable to extinction. Generally speaking, blue marlin populations are decreasing in numbers. Though it is not targeted commercially throughout much of its range, the blue marlin is one of the most highly sought after big game fishes in the world. Sport fishing enthusiasts spend tens of thousands of dollars to catch large blue marlin, and they are typically released alive (though recent data suggests that released individuals may frequently die after the fact).  If numbers continue to decline, this highly valuable sport fishery may be in danger of collapse.

Taxonomy note: Several times throughout the history of studying marine fishes, researchers have divided the blue marlin into multiple species, but recent genetic studies leads scientists to believe that all blue marlin around the world are the same species.

Engage Youth with Sailors for the Sea

Oceana joined forces with Sailors for the Sea, an ocean conservation organization dedicated to educating and engaging the world’s boating community. Sailors for the Sea developed the KELP (Kids Environmental Lesson Plans) program to create the next generation of ocean stewards. Click here or below to download hands-on marine science activities for kids.

Kids Environmental Lesson Plans

Additional Resources:

IUCN Red List

NOAA Fisheries

Get Involved

Donate Today

SUPPORT OUR WORK TO PROTECT THE OCEANS BY GIVING TODAY

With the support of more than 1 million activists like you, we have already protected nearly 4 million square miles of ocean.

Donate Now

TAKE ACTION NOW

Support policy change for the oceans

Decision-makers need to hear from ocean lovers like you. Make your voice heard!

Sign Now

VISIT OUR ADOPTION CENTER

SYMBOLICALLY ADOPT AN ANIMAL TODAY

Visit our online store to see all the ocean animals you can symbolically adopt, either for yourself or as a gift for someone else.

Shop Today

DOWNLOAD OCEAN ACTIVITIES

HELP KIDS DISCOVER OUR BLUE PLANET

Our free KELP (Kids Environmental Lesson Plans) empower children to learn about and protect our oceans!

Learn More

FEATURED CAMPAIGN

Save the Oceans, Feed the World

We are restoring the world’s wild fish populations to serve as a sustainable source of protein for people.

Learn More

More CAMPAIGNs

Protect Habitat

Bycatch

Plastics

View All

CONTACT

Oceana International Headquarters
1025 Connecticut Avenue, Suite 200
Washington, DC 20036 USA

General Inquiries
+1(202)-833-3900
info@oceana.org

Donation Inquiries
+1(202)-996-7174
wavemaker@oceana.org

Press Inquiries
+1(202)-833-3900
press@oceana.org

OCEANA'S EFFICIENCY

BECOME A WAVEMAKER

Sign up today to get weekly updates and action alerts from Oceana.

SHOW YOUR SUPPORT WITH A DONATION

We have already protected nearly 4 million square miles of ocean and innumerable sea life - but there is still more to be done.

Donate Now

QUICK LINKS: