Did You Know?


Welcome to our Did You Know blog! Billfish and related species, like tuna and swordfish, are amazing creatures and set themselves apart from other fish. Every week, The Billfish Foundation would like to share some of the most interesting facts and stories involving these fish. What some of the things that surprised you about these magnificent animals? #didyouknow

July 25, 2017- Hunting Tool or Weapon?

Did you know that in 2010 a single blue marlin cost British Petroleum (BP) 100 million dollars in damages? The same features that make marlin one of the most desired fish to catch- their size, speed, and strength- makes them a very dangerous weapon when combined with their very strong and sharp bill. According to Bloomberg, a blue marlin punctured one of the highly protected, ultra thick main pipelines leading to BP’s Plutonio field storage barge off of the west coast of Angola, preventing 900,000 barrels of oil from being exported for sale and over 100,000 million dollars in losses. Thankfully, very little oil was leaked into the water.

The bill of a blue marlin that punctured this ultra-thick BP oil pipeline, costing BP over 100 million dollars. Photo Credit: Africa Travel Channel


Here are some more strange, gruesome, and unexpected instances where billfish (and swordfish) got wild with their bill.

A commercial fishing trip off the coast off Bermagui, Australia caught a large mako shark (below). Upon inspecting the shark and getting it ready for processing, the crew noticed that it had an object protruding from both sides of its body. It quickly became apparent that it was the bill of a large marlin that had penetrated through the shark just under the dorsal fin and broken off. The bill had started growing barnacles, signifying that the shark had been carrying the burden for quite some time. As far as scientists are aware, billfish and swordfish primarily utilize their bills to kill or stun smaller prey, not to attack larger animals. There have been a surprising amount of instances, however, like this one, that prove these fish aren’t scared to go on the offensive.

A mako shark was lucky to survive being impaled by a large marlin and had lived for quite some time with the bill in its back. Photo Credit: Narooma News Online



Some of the craziest documented attacks have been carried out by swordfish in the deep. In the first picture, a camera catches the instant a small swordfish penetrated a deep diver’s welding gear just above their oxygen tank- Click here to watch the full video. The footage clearly shows the swordfish singling out the diver, charging sword-first at speed. The second photo shows a swordfish lodged into the hull of Alvin, a deep sea Navy submarine. The Alvin is famous for voyage missions to survey hydrothermal vents, decommissioning sunken WWII bombs, and exploring the wreck of the Titanic. According to the Smithsonian, in 1967, Alvin was exploring deep sea corals in 2000 feet of water off the coast of Florida when a swordfish attacked and got stuck to its hull. The swordfish was just under 200 pounds and hit the sub so hard the majority of its head was jammed into a small gap in the sub’s exterior and was brought to the surface.

A deep sea welder is charged and his gear impaled by a swordfish, luckily the sword just missed the oxygen tank. Photo credit: Luis Nascimento

The famous U.S. Navy Submarine, the Alvin, was impaled by a swordfish in 2000 feet of water off the coast of Florida. Photo Credit: Woods Hole Oceanographic Institute

More common instances of billfish impalement are those associated fishing. There have been many instances of billfish impaling boat hulls and transoms, as well as the anglers themselves, sometimes even causing fatalities. In 2008, a young man off the coast of Panama was bringing in what looked to be a tired 600 pound black marlin when it suddenly jumped bill first into the boat. According to the Travel Channel, the marlin’s bill penetrated through the man’s mouth and lodged into his throat. Thankfully, he survived the encounter.

Billfish bone has a density and strength much closer to that of large mammals like horses than it does to most fish bone. This strength is accompanied by a dangerously sharp tip, which is why indigenous peoples around the world used bills and (swordfish) swords as daggers and spears. A 500 pound animal wielding this sort weapon is part of what makes these fish some of the most exciting fish to pursue but also some of the most dangerous. It’s important that anglers, divers, and even submarines never let their guard down around these incredible, powerful fish.

July 18, 2017- From Cat Food to Million Dollar Fish 

Did you know that the bluefin tuna sold for 1.8 million dollars in 2013 at the famous Tsukiji Fish Market in Tokyo would have probably been used for cat food prior to 1970? The tuna was sold in the traditional new year auction that is famous for attracting astonishingly high bids for bluefin. The buyer, Kiyoshi Kimura, has won the coveted tuna auction since 2011; and, although not rivalling 2013’s exorbitant price, has spent around half a million dollars on multiple other fish. Bluefin meat (maguro), more specifically the fatty meat around the belly (toro), is of the most desired meats by sushi chefs and consumers worldwide; but believe it or not, just  50 years ago bluefin meat was considered nearly worthless.

A flesh sample being taken from a bluefin tuna at the Tsukiji Fish Market in Tokyo on the first Saturday of 2013 – It would eventually be sold for 1.8 million dollars

According to the Smithsonian, during the 40’s, 50’s and 60’s, when tuna sportfishing was becoming exceedingly popular, bluefin were sought out by anglers due to their massive size –  measuring larger than 14 ft and weighing more than 1500 pounds. During that period, however, tuna were perceived to have little to no food value for the human consumer. They were often weighed, pictured, and then dumped back into the ocean or ground up for cat and dog food. The drastic turnaround from pet food to million dollar sushi meat began in the 1970’s when a palate shift occurred in Japan. Rather than favoring only light, white meat fish, an increase in beef consumption around the same time shifted Japanese palates toward the dark, rich meat of the bluefin. Once the appreciation for bluefin as a raw delicacy spread to the U.S. and Europe, the bluefin became one of the most sought after fish in the world.

An Atlantic bluefin tuna feeds in the cold waters off of the coast of Canada

Commercial fisherman utilizing large, encircling purse seine nets began targeting the giant schools of North Atlantic bluefin to sell to Japan. Intense overfishing has led to a severe depletion of bluefin stocks worldwide, where populations of the three bluefin species are less than 10 percent of their levels prior to the 1970’s. Although currently considered endangered, a high demand still exists.


A bluefin tuna tagged by Captain Eric Stewart near Cape Cod, Massachusetts migrated 5,000 miles before being re-captured off of the island of Malta in the Mediterranean Sea

On the bright side, over the last 20 years, there have been some strong conservation efforts worldwide trying to halt overfishing. The United States has been a standout leader in conservation efforts, establishing rigid regulations and low catch quotas for both commercial and recreational bluefin fisherman. However, conservation has proven difficult due to the bluefin being a highly migratory fish, often making multiple trans-Atlantic trips in its lifetime. In order to help synchronize efforts, much research is needed in order to understand where these fish migrate, breed, and feed. TBF is proud to collaborate with the Large Pelagics Research Center in their quest to gather this vital data through large scale tagging operations. Hopefully efforts such as this can help in preserving these incredible fish for years to come.

July 11, 2017 – Billfish Eye Heaters

Did you know that billfish, although cold blooded, can heat up their eyes to help them see better? Billfish and tuna are considered some of the ocean’s most athletic apex predators- and they have to be. Picking off small, agile baitfish from a dynamic school in the open ocean requires extreme speed, precision, and agility. Recent science has revealed one of physiological adaptations that gives these fish a major advantage over their prey- an internal eye and brain heating system.

The ability to heat their eyes allows billfish and tuna to react to visual cues much faster than their prey

Fish are ectotherms (cold blooded), meaning that their body heat is heavily dependent on the ambient water temperature. But billfish, swordfish, tuna, and most sharks possess the unique ability of heating their eye muscles and certain parts of their brain. According to a 2005 study, these fish have muscles tucked behind their eyes and adjacent to ocular nerves that vibrate to create heat. By heating their eyes 10-15 degrees celsius above the ambient water temperature, these fish significantly enhance their ability to detect and respond to motion. The same 2005 study found that fish with these heating muscles can pick up and react to visual cues up to ten times faster than fish whose eyes are the same temperature as the surrounding water. This physiological trait is especially important in swordfish, since the temperature in their deepwater habitat can reach near freezing.

The opah, also known as the moonfish, is the only true “warm blooded” fish

The opah is the only truly “warm-blooded” fish. According to National Geographic, opah generate their heat from metabolic activity, just like most other fish. But rather than losing heat to the colder ambient water, they conserve it and circulate the heat throughout their entire body, warming their muscles, heart, and brain.

June 29, 2017 – Billfish Breathing

Did you know that the cone shaped mouth on billfish is designed to do more than just maximize the fish’s hydrodynamic profile? Their large, smooth cone shaped mouths funnel massive amounts of water over their gills as they swim. Billfish and tuna-like species are ram-ventilators, meaning that they breathe by swimming with their mouth open, forcing water through their gills. In contrast, fish like groupers take in water by creating a vacuum in their mouths to “suck” it in, a method called buccal pumping. This allows them to breathe while stationary, which is why you may often find them motionlessly hiding out under a rock outcropping waiting for unaware prey.

Cone shaped mouths help billfish funnel massive amounts of water through their gills

The fact that billfish can only breathe while swimming means that they must constantly be moving at a decent pace to ensure that they receive enough water to their gills. This is why it’s crucial to keep them moving forwards in the water when reviving them. No movement… no oxygen!