May I have your attention, please?
May I have your attention, please?
Will the real Oarfishes please swim up?
We're gonna have a problem here.
It's inevitable, a photo gets posted on social media of a long ribbony fish and everyone starts shouting:
Oarfish!
That's an oarfish!
There's an earthquake coming!
It's an oarfish. They inspired the sea serpent legend!
Thanks Fukushima!
Cool oarfish.
This one weird trick helps keep oarfish out of your house forever, just click and enter your social security number and bank routing information.
OAAAAAARRRRRRRRFIIIIIIIISSSSSSSSSH!
While I absolutely love that people are so excited by the incredible oarfish (Regalecus spp.), a great many of these pictures are some other animal with a similar body shape. The ocean is much more diverse and beautiful than we often realize. Many many of the fish you see are oarfishes' cousins, so it's understandable that people would mix them up. So I thought for today we'd compare some of uncanny oarfish lookalikes; then next time you can tell who are the real oarfishes, and who's imitating.
All you other ribbonfishes are just imitating
So won't the real oarfish, please swim up?!
If we're going to figure out what isn't an oarfish, we should probably get to know what one is. Or, I guess what the three are; doing research for this article I learned that there are three species of oarfish: Oarfish (Regalecus russelii), the Giant Oarfish (Regalecus glesne), and the Streamerfish (Agrostichthys parkeri) It just goes to show that there really is always more to learn.
We're going to focus on the traits of the oarfish and giant oarfish for now because streamerfish are only found in the Southern Ocean, so they're encountered even less often than the other two. Sorry to all our Kiwi and Tasman readers who were hoping to learn more about their local oarfish. Reach out in the comments if you want a post just about streamerfish.
We've briefly mentioned oarfish before in our post about opah (aka moofish) because opah and oarfish are grouped together in the same taxonomic order. That group is called the Lampriformes (pronounced lamp-rih-for-mees) and it means "the shapes of light". The name comes from how astoundingly reflective their scales are.
Why do I suddenly feel self-conscious about how long it's been since I polished my silver?
Courtesy: David Remsen via Encyclopedia of Life
The shimmery aspect of oarfish and their cousins probably helps camouflage them in the shifting light of the mid open ocean where they usually live. They're often claimed to be a "deep sea" fish, but they're usually found between 300 and 3,300 feet down. That sounds deep to humans, but the average depth of the ocean is 12,100 feet and the max depth is three times that!
Depth aside, oarfish are pretty incredible. They have elongated, extremely narrow bodies which you'd think they'd wiggle back and forth to serpentine around the ocean, but nope. Oarfish mostly undulate their sturdy dorsal fin to hold themselves upright in the water, staring towards the surface. They only really use their tail when they need to dart away from something that bumps them. They also have long fin filaments that hang from their dorsal and pelvic fins. We have absolutely no idea what these filaments are for, though they do have light producing organs so they might attract prey or communicate to other oarfish. The filaments are so huge and dangly that a group of researchers observing larval oarfish, actually saw the babies repeatedly getting wrapped up in their fin ornaments. The little fish had to spin around to get themselves untangled, but its possible that this comes from the fact that the fish were in a tank and not the open ocean. There's some great footage of a giant oarfish in the video below, skip to about 4:30 to jump to the better shots.
Okay, so looking closely at the picture and video we can see that both species of oarfish have ribbony bodies, a squared-off almost bulldog-ish face, eyes that are somewhat small compared to their whole head, and dark blotches and streaks along their sides. You might also have noticed that the individual in the video seems to be missing the end of its tail. That fact won't necessarily help us with i.d. but it's cool to know that both oarfish species can drop part of their bodies off like a spooked lizard. In fact most adults over a certain size are seen with these stumps.
Alright, so keeping all that in mind what does the most misidentified oarfish poser look like?
Oh, yeah-- totally-- totally different...
Courtesy: Harbor Wildwatch via Facebook
Alright, I didn't say this was going to be easy, but you can do it. Take a minute to really look the fish over. Take in the overall shape, the angles of the different body parts, the patterns on its skin, the size of different body parts relative to one another. What makes this fish different from the oarfish that we've seen? Look and think for a bit, and I'll see you below.
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What'd you come up with? Did you notice there are only a few dark blotches and they're all close to the dorsal fin? This fish also has a more pointy-oval shape than the continuous width of the oarfish. It's also clearly a large adult that isn't missing a chunk of its tail. While not perfect for i.d. this trait that's common in the life history of oarfish can give us a hint that we shouldn't jump to our first assumption when we see this fish. The two traits that stand out most to me are the shape of the face, and the size of the eye. Let's zoom in and get a closer look.
Courtesy: Harbor Wildwtach via Facebook
The eye in particular jumps out; it's absolutely massive! The whole thing take up probably a third of the fish's face. On the jaw front, you can see that the angle is much different from that of the oarfishes'. This fish looks like they're doing a duckface selfie, while the oarfish have more a Statler and Waldorf thing going on.
This fish is the King-of-the-Salmon (Trachipterus altivelis) and they're a great example of the ribbonfish family. Ribbonfish is the largest group in the Lampriformes with ten different species represented. Readers from the around the North Atlantic might have heard of Dealfish before, and those are closely related to the king-of-the-salmon. I love king-of-salmon for two reasons; one: they're my home waters' local ribbonfish, and two: their name has an interesting origin.
Along the Strait of Juan de Fuca and the outer coast of the lands now known as Washington State the Makah Tribe have lived since time immemorial. The Makah rely on salmon, whales and other ocean creatures for their life and health, and so they have strong ties to the species that dwell in their waters. They noticed that when the salmon would return to their home streams in the fall, Trachipeterus altivelis would often be found near the shore or at the surface. The belief followed that these fish are leaders showing salmon the way home. Europeans had already been calling oarfish and dealfish king-of the-herring and so they adopted the Makah's understanding into their name for this new (to the Europeans) fish.
Look, I'm not saying one is better than the other, just that I know which one I would prefer to be named after.
Reports of King-of-the-Salmon in the shallows or on beaches have increased in recent years. This has made some folks nervous that there's something wrong with their habitat. While that's possible, Washington State's population has about doubled since 1970 so it's equally likely that there are just more people walking the beaches and paddleboarding. We'll need to collect more information to know if one of these factors is more significant than the other.
Okay how are we doing? Ready for another i.d. attempt? There are two other groups within the ribbonfish family and they actually get easier to tell apart from oarfish. First up is Zu.
Courtesy: NOAA via Wikimedia Commons
See not too bad right? This Scalloped Ribbonfish (Zu cristatus) has the same shimmeriness and elongated red dorsal fin as the others, but it's definitely distinct. The eye is very large, but it's higher on the head than on the oarfish or the king-of-the-salmon. The mouth shape is a little misleading because it's relaxed out, but you can see that it doesn't quite match the other shapes. But the most obvious trait is how much the tail tapers compared to the other fishes we've seen. This gives us a good view of just how much of oarfish realtives' bodies are tail. That little notch on the underside shows where the body cavity ends, and the tail starts. In this fish the tail is about half the length, in oarfish it's about three-quarters! It's a little hard to see in this picture, but at the end of the tail there's also a distinct fin that we haven't seen in the other species so far. I couldn't get permission to use it in time for posting, but there's an even better picture of a scalloped ribbonfish here.
Alright, feeling confident? Ready for another go? Let's look at the Desmodema.
The Polka Dot Ribbonfish (Desmodema polystictum) and the Whiptail Ribbonfish (Desmodema lorum)
Oh wow, way different, right? These two have bodies that are much wider vertically and more compressed lengthwise than anything we've seen so far. I guess that's why their genus Desmodema means "fat band". There's also just how narrow their tails are, and the polka dot ribbonfish barely has a tail at all. Eagle-eyed readers might also have noticed that these two species have very circular pupils compared to the scalloped ribbonfish's and the king-of-salmon's almost rectangular ones.
Nice work! There's only two more families to go! I bet by now you can spot one of these fake Slim Shimmeries from a mile off. Let's see if you can notice the difference in this Tapertail (radiicephalus elongatus)!
Courtesy: James Maclaine via Twitter
Hm, a little less to go on with this dude. But the name is accurate, the tail really does taper more gradually than we've seen so far. Also if you look very closely, this one doesn't have any pelvic fins hanging down like all the others have. We know very, very little about these fish except that they eat lanternfish, they're smaller than most of their relatives, and they can shoot out brown fluid from a sack like a frightened squid. Convergent evolution is the coolest.
Aaand with that, it's time for our final family, the crestfish!
Courtesy: NMFS via Fishbase
This specific individual is the Unicorn Crestfish (Eumeichthys fiski) and the difference with the other fish we've seen so far is pretty distinct. In fact it's right in the name. These fish have large crests on their forehead that the decorative spines from their dorsal fin stick up from.
So there you have it! A handy guide to most of the fish you might see on the internet that aren't oarfish. I hope you enjoyed comparing and contrasting all these different species. Although I want to recognize that you might have gotten to the end of this post and been like: "They still all look pretty similar to me. Why are we using such tiny differences in traits to call these different species?" That is an extremely valid question. It's true that we use seemingly tiny details to decide what one thing is and another isn't. Often those details are also wrong because things that look alike can be unrelated (puffins and penguins) and things that look different can be very closely related (sand dollars and sea urchins). Only the genetic code of various species can tell us for sure if they're related or not, and we just haven't gotten around to sequencing everything yet. Even then, how many differences genes make for a different species? Five, a hundred, twenty thousand, any that code for significantly different morphology? But then what's significant? As a friend of mine phrases it: "Systems of classification are arbitrary." We can use classification to help us understand the world and make decisions about how we manage it, but in the end, everything in nature is a spectrum.
I take a lot of solace in the idea that nothing and no one in the universe fits into one box, and I hope you will too.
P.S. If you'd like to learn more about how confusing speciation and classification can be check out our post on sculpins from guest author Brian Harmon.
References:
Froese, Rainer & Capuli, Estelita Emily, "Regalecus glesne (Ascanius, 1772) King of herrings", Fishbase. Accessed via: https://www.fishbase.in/summary/regalecus-glesne.html
Froese, Rainer & Garilao, Cristina V., "Eumeichtyhs fiski (Gunther, 1890) Unicorn Crestfish", Fishbase. Accessed via: http://www.fishbase.org/summary/Eumecichthys-fiski.html.
Froese, Rainer & Ortanez, Auda Kareen, "Desmodema poystictum (Ogillby, 1898) Polka-dot ribbonfish", Fishbase. Accessed via: https://www.fishbase.in/summary/3263
Garilao, Cristina & Capuli, Estelita Emily, "Regalecus russelii (Cuvier, 1816) Oarfifish [sic]", Fishbase. Accessed via: https://www.fishbase.se/summary/25038
National Ocean Service, "How Deep is the Ocean?", Ocean Facts. Accessed via: https://oceanservice.noaa.gov/facts/oceandepth.html#:~:text=That's%201.7%20miles%20down!,U.S.%20territorial%20island%20of%20Guam.
Oka, Shin-ichiro, Nakamura, Masaru, Nozu, Ryo & Miyamoto, Kei, "First observation of larval oarfish, Regalecus russelii, from fertilized eggs through hatching, following artificial insemination in captivity", Zoological Letters, 6, 4 (2020). Accessed via: https://zoologicalletters.biomedcentral.com/articles/10.1186/s40851-020-00156-6#Fig1
Papasissi, Chritine & Kesner-Reyes, Kathleen, "Zu cristatus (Bonelli 1819) Scalloped ribbonfish, Fishbase. Accessed via: http://www.fishbase.org/summary/Zu-cristatus.html
Pietsch, Theodore Wells & Orr, James Wilder, "Trachipterus altivelus Kner 1859 King-of-the-Salmon", Fishes of the Salish Sea : Puget Sound and the Straits of Georgia and Juan de Fuca, volume 2 pg. 371-372, University of Washington Press, 2019.
Torres, Armi G. & Kesner-Reyes, Kathleen, "Radiicephlaus elongatus Osorio, 1917, Tapertail", Fishbase. Accessed via: http://www.fishbase.org/summary/Radiicephalus-elongatus.html.
