How Giant Oarfish Work

Now that's a noggin. A NOAA biologist measures the head of a giant oarfish that washed up in Southern California in October 2013.
Image courtesy NOAA

Ah, Regalecus glesne -- king of the herrings! Mistaken for sea monsters by centuries of sailors. Feared in legend and myth. What regal creature would have such a majestic history? R. glesne is what we call the giant oarfish, and it mostly resembles a colossal snake with a startlingly ugly mug. Stately this king is not.

To be fair, we haven't seen giant oarfish in their prime in the past few years. In October 2013 alone, two specimens washed up separately on the California coast, dead and bloated. They made the news in part because of their enormous size: Giant oarfish have been known to grow up to 36 feet (11 meters) and weigh 600 pounds (272 kilograms) [source: Bester] Unconfirmed reports have claimed a length of 56 feet (17 meters) [source: Howard]. The ones that washed up were mere trifles at 14 and 18 feet (4 and 5 meters), but with their bulging eyes and the red rays sprouting off their dorsal fin, you can see how "monster" might spring to mind. (And why Palauans refer to it as a "rooster fish.")


There are a few things to know about oarfish in general before we dive in to the nitty-gritty of our giant friend. One is that there are actually two different genuses of oarfish: Regalecus and Agrostichthys. Agrostichthys grows much smaller than Regalecus, and even the smaller Russelli species of Regalecus are reported to grow about 16 feet (5 meters) [source: Yamamoto]. But we're sticking mainly to our giant friends, since they're the most likely to haunt your dreams.

Speaking of dreams and other shadowy omens, we'll also discuss a long-held Japanese legend that says oarfish washing ashore portends an earthquake. Should we be running to the hills after the multiple beachings in October 2013? Surprisingly, a couple of theories give the legend credence.

Ready to get to know R. glesne? Read on.


Physical Traits of Giant Oarfish

R. glesne gets vertical in waters nears the Bahamas. This photo is rare because giant oarfish aren't usually photographed alive.
Jonathan Bird/Photolibrary/Getty Images

Undoubtedly, the giant oarfish's physical credits are what make it most interesting to us, at the offset. But it's important to dive a little deeper into the physicality of this fish, because it's not just a pretty face. If you looked at the shiny, silvery body of Regalecus glesne you might assume that they have scales, much like a trout or most other "bony fish." (Giant oarfish are the biggest of the bony fish, which have bone -- as opposed to cartilage -- skeletons.) But R. glesne actually has soft skin covered with guanine, the crystals that add a lovely pearlescent sheen. So in reality, giant oarfish skin is fairly delicate and easily damaged when these animals aren't in their high-pressure, deep-sea surroundings. Also referred to as "ribbonfish," giant oarfish are flat too, more like an eel than a snake [source: National Marine Fisheries].

The dorsal fin also provides a bit of visual va-va-voom to R. glesne. (Remember that the dorsal fin is located where we think of as the spine or "back" of the fish.) On the dorsal are thin, red or coral-colored fins that stretch from end to end, including a sprightly crest of red over its head. The giant oarfish also has pelvic fins that fan out at the ends, resembling -- aha! -- oars [source: Burton]. Interestingly, these fins and rays are apparently easily broken off and often aren't intact on giant oarfish that have washed up; it's still not known if they signify the sex of the giant oarfish, or are for any other purpose [source: Whittaker].


The sheer size of this bony fish could preclude many predators from harassing it, although no one is quite sure who those predators are, aside from the usual shark suspects. They must have some though because a lot of giant oarfish that have been studied seem to have previous wounds on their lower half or have lost part of their tail. That's not as problematic as it might sound. While the oarfish has an extremely long body, most of its organs are crowded into its front-most quarter. That could mean that if a shark or some other predator attacks the fish away from its organs, it has some protection from fatal wounds [source: Burton].

One other cool thing: While we imagine our serpentinelike friends slithering gracefully through the water like snakes, we know that the fish spends at least some time in a face-to-the-surface vertical position. A solitary sort, it can quickly swim up or down in that position, maintaining that verticality. That ability would help to hide it from predators that look for lateral shadows. The flattened, upright body of the oarfish would be hard to spot from either above or below if it was just a narrow, shadowy line in the water as the rays on the dorsal fin undulate [source: Whittaker].


Habitat of the Giant Oarfish

Giant oarfish mostly live in depths of 600 to 3,000 feet (183 to 914 meters). However, it's believed that they probably make their way up to a much higher ocean depth at times [source: Whittaker]. Mostly, these big ones spend a good deal of their time in the ocean's twilight zone: depths with very little sunlight, lots of pressure and the first flickerings of the bioluminescent animals of the sea.

At this point, you already know that giant oarfish are, um, gigantic. Not only would you think nobody wants to mess with it, but you'd be surprised if the the fish had much trouble finding food. Not too many creatures could keep its sharp teeth at bay, right?


Well, not so much. Turns out that the fierce-looking giant oarfish doesn't have any teeth. In fact, our fearsome king of the herrings has little interest in wresting huge prey or chowing down on fish friends. Or you. While old-time sailors scared themselves silly by confusing oarfish with the terrifying sea monsters of myth, they were actually observing a gigantic fish that eats a steady diet of plankton. (They also might throw down little crustaceans and a small squid or two, for good measure.) The bottom line? If you happen to spot a giant oarfish while you're lazily swimming in the ocean, do not fear he or she will take a bite of you. Do, however, fear that you're probably swimming really, really far out -- not to mention deeper than is safe -- and you're probably wrestling with deeper issues, anyway.

Which does bring us to where you could technically catch up with a giant oarfish in the wild. While we used to think they were pretty rare, we're now seeing them caught more often in nets and the like, as well as hearing reports of them washing up on beaches. The actual range of the giant oarfish is pretty wide. They're known to be in the Atlantic (and the Mediterranean Sea), as well as the Indian Ocean. They're also in the eastern Pacific, from southern California down to Chile.


Giant Oarfish in the News ... and in Myth

Scientists dissect a giant oarfish in the necropsy suite of NOAA's Southwest Fisheries Science Center. It's easy to make out the animal's crest in the foreground of this photo.
Image courtesy NOAA

As you can imagine, fish that resemble 600-pound sea serpents have a bit of backstory (true and untrue) surrounding them. For instance, it's pretty rare for a giant oarfish to wash up, although it might not seem so with all the attendant cell phone photos and social media coverage. Even the two October 2013 California discoveries probably weren't coincidence: The same heavy storm likely caused a surge that caught both of the oarfish and carried them to turbulent waters. These big creatures aren't terribly adept swimmers, so they probably took a beating. Once they're closer to shore, it's easier for them to wind up on the beach [source: Schaefer].

But some claim that giant oarfish have a much more mysterious motivation for beaching. There's a Japanese legend that oarfish can predict earthquakes, and there are several (anecdotal) instances wherein beached oarfish coincide with seismic activity [source: Connor]. There are a few theories about how this would work. For instance, perhaps a release of carbon monoxide gas before an earthquake causes a mass exodus from deeper parts of the sea. On a similar note, hydrogen peroxide could be produced if deep-sea rocks have built up enough pressure to release a massive amount of ions in the water before a quake. Sea animals would have to surface more or move to shore, as we see the oarfish doing [source: Connor]. Of course, neither of these theories have ever been proven (or even studied), and scientists point out that it wouldn't just be oarfish that would feel these effects [source: BBC Radio].


But there's an even bigger issue with this myth -- it's not even about the giant oarfish [source: Yamamoto]. Nope, this legend has to do with the slightly smaller slender oarfish (Regalecus russelii), which the Japanese call ryuguno tsukai, or "Messenger from the Sea God's Palace." (Which puts the designation 'oarfish' to shame.) But don't relax too much -- is it a coincidence these smaller oarfish were washing up on Japan's shore a mere year before the big 2011 earthquake [source: Yamamoto]? Well, probably.

Lots More Information

Author's Note: How Giant Oarfish Work

As someone who lives on the coast, I consider myself fairly jaded about sea creatures washing up to shore. Mola? Yawn. Squid? Just another day. But there's something about the giant oarfish -- perhaps its unreasonably large size, tempered by its nearly troutlike face -- that really must give one pause. I think I'd like my monsters to stay in the sea, thank you.

Related Articles

  • BBC Radio. "Oceanographer debunks oarfish earthquake myth." BBC. Oct. 23, 2013. (Nov. 5, 2013)
  • Bester, Cathleen. "Oarfish." Florida Museum of Natural History. (Nov. 5, 2013)
  • Burton, Maurice and Burton, Robert. "International Wildlife Encyclopedia." Marshall Cavendish. 2002.
  • Carstens, John. "Seals find serpent of the Sea." All Hands Magazine. April 1997. (Nov. 5, 2013)
  • Connor, Steve. "Oarfish mystery." The Independent. Oct. 22, 2013. (Nov. 5, 2013)
  • Froese, Rainer and Reyes, Rodolfo B. "Regalecus glesne." (Nov. 5, 2013)
  • Garilao, Cristina V. and Froese, Rainer. "Regalecus russelii." (Nov. 5, 2013)
  • Goldman, Russell. "Monster oarfish beachings raise earthquake questions." ABC News. Oct. 22, 2013. (Nov. 5, 2013)
  • Howard, Brian Clark. "5 surprising facts about the oarfish that has been washing up on beaches." National Geographic. Oct. 22, 2013. (Nov. 5, 2013)
  • Knight, J.D. "Oarfish." Sea and Sky. (Nov. 5, 2013)
  • Mazza, Sandy. "Scientists eager to unlock mysteries of deep-sea oarfish." The Torrance Daily Breeze. Oct. 22, 2013. (Nov. 5, 2013)
  • National Marine Fisheries. "Giant Oarfish." National Oceanic and Atmostpheric Administration. (Nov. 6, 2013)
  • Schaefer, Samantha. "Deaths of two giant oarfish may be linked, scientists say." Los Angeles Times. Oct. 21, 2013. (Nov. 5, 2013),0,995333.story#axzz2jh2Kx6f7
  • Whittaker, D.E. "Recent examinations of the oarfish, regalecus glesne, from the North Sea." Yorkshire Coast Sealife, Fisheries and Maritime Archive and Museum. 2013. (Nov. 5, 2013)
  • Yamamoto, Daiki. "Sea serpents' arrival puzzling, or portentous?" The Japan Times. March 6, 2010. (Nov. 5, 2013)