Will the Real Oarfishes, Please Swim Up?!

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.

I'm R. glesne, yes I'm the real glesne

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.

Courtesy: USGS and OpenCage via Wikimedia Commons

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.

"There is no Dana, there is only 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)

Courtesy: NOAA via Wikimedia Commons and M.M. Khan via Fishbase

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.

Top Five Ocean Creatures You've ACTUALLY Never Heard Of

Okay internet, we've got to talk. Yes, the ocean is incredibly vast and minimally explored. There are many creatures out there that people have never heard of, and I'm really excited that you want to share the ones you just discovered with humanity. But friend, most other people have also watched Planet Earth. You can't go around publishing listicles of the animals from the deep sea episode and call it "Top 10 Ocean Creatures You've Never Heard of!" or some such thing. We've all heard of blobfish; flapjack octopuses inspired a character in Finding Nemo; and literally everyone knows about Mola mola. So for those of you who are tired of the same list getting republished on 30 different blogs with slightly different descriptions Depth and Taxa Presents our first ever listicle:

Top FiveOcean Creatures You've Actually Never Heard of!

Or: 

Top Five Ocean Creatures That Aren't Horrifying, Just Well Adapted to Their Environmental Conditions.

Seven-Arm Octopus (Haliphron atlanticus)

Courtesy: H.J.T Hoving and S.H.D. Haddock via Scientific Reports

Okay wait, wait, wait; seven-arm, octo-pus; that literally makes no sense. Why isn't it a septapus? To understand we need a refresher on our old friends, the Argonauts.

No....not....ugh...
Courtesy: Public Domain via Wikimedia Commons

If you've been following Depth and Taxa for a while you might remember our profile on the specialized octopuses called argonauts. You can check out that post (which is a personal favorite of the D&T team) here. Argonauts and their close relatives are different from more familiar octopuses because they live in open water, rather than on the bottom; and because males are waaay smaller than females. In the case of seven-arm octopuses, females are six times longer than males! The enormity of the open sea and the males' small size mean that the odds of two seven-arm octopuses running into one another are pretty low. So in order to ensure the continuation of the species males have to be sure they mate successfully on the first try. To that end, males actually tear off a specialized reproductive arm called a hectocotylus (pronounced: hek-toh-kot-uh-luss) and embed it into the body of the female. Since seven-arm males only get to use their hectocotylus once they keep it well protected inside a "thick, gelatinous" sack near their right eye. Because that arm is tucked out of sight, it looks like male seven-arm octopuses really only have seven arms.

Eulachon (Thaleichthys pacificus)

Courtesy: James Crippen via Wikimedia Commons

Yeah, it's a bait fish; but take a second to think about how many bait fish species you can name. Maybe herring, anchovy, sardine, and...... anything else? Also called forage fish; small fish like eulachon (pronounced: yoo-la-kon) are the only reason we have bigger, more charismatic animals in the ocean. Tuna, sharks, salmon, humpback whales, dolphins, seals, sea lions, pretty much anything larger than one foot wouldn't exist without forage fish like eulachon. Just because something is common, doesn't mean it's not important or interesting. In fact, forage fish are probably waaaaaay more important to the overall ecology of the ocean than many of the creatures we get really stoked about.

Eulachon in particular are really awesome. Like tiny salmon, eulachon are born in freshwater and migrate out to the ocean where they spend 2-3 years growing rich off the abundance of the open sea. And boy they get rich, eulachon have a higher body fat percentage than almost any other fish species. Eighteen to twenty percent of a eulachon's wet weight is oil! They're so greasy that if you dry a eulachon you can actually set it on fire; leading to their other common name: candlefish.

In case the plug-in doesn't work on your device:
https://www.youtube.com/watch?v=wEMQujyzHQA

The people processing the eulachon in the above video are members the Nisga'a first nation. Nisga'a territory is the watershed of the Nass river near the Alaska panhandle's southern border with British Columbia. Because eulachon come back to their home rivers to spawn in late winter when other food sources are scarce they can tide-over a family until the abundance of spring. Eulachon are so important that one of their names in Nisga'a means "savior fish". Not bad for a type of smelt.

Brachiopods (phylum Brachiopoda)

Courtesy: Peter Grobe via Flickr

"Alright wait a minute, that's literally just a clam. You can't pull one over on me. I've been to Ivar's." Well they look a lot like clams, but aside from both having two shells, brachiopods (pronounced: brak-ee-oh-pods) and clams are completely different.

Even the shells of clams and brachiopods aren't the same. The shells of a clam are oriented left and right of its body, while a brachiopod's shells are above and below. It can be a little hard to visualize without pictures so we'll use some anatomical standards to help us: Pokemon.

Shellder has shells oriented like a brachiopod. 
Cloyster has shells oriented like a clam.

Of course we all know it's what's on the inside that counts. Once inside a brachiopod the difference from clams is pretty apparent. Fully two-thirds of a brachipod's body is taken up by a feeding structure called a lophophore (pronounced: lo-fo-for). The lophophore has spiral or u-shaped coils that are unique to each species. These structures funnel free-floating plants and animals into the brachiopod's mouth using little cellular hairs that beat back and forth.

Brachiopods have been around for a long time and at one point there were at least twelve-thousand different species! That number makes a little more sense when you remember that brachipod is a phylum, which is one of the least specific ways to group organisms. For example: humans are part of the "chordate" phylum which is everything on earth with a spinal chord. That's a bewildering number of animals. Even understanding that they're a big group, it's astonishing to realize that brachiopods were once so abundant that make up the majority of all fossils!

There are only about 450 modern species of brachiopods, but they're pretty common in cold seas around the world. Very few animals eat them, even though they have thin shells, probably because brachiopods don't pack a lot of nutritional punch once you get them open. So the next time you feel lame for being unassuming and quiet; remember that brachiopods literally took over the world for millions of years by being mundane.

Pink Ghost Shrimp (Neotrypaea californiensis)

The larger pincher is called the "master claw", which is also 
a kickass name for a metal band.
Courtesy: Ken-ichi Ueda via Flickr

Pink ghost shrimp are just one of many species of shrimps that burrow into sand and mud in the intertidal zone. Although you probably haven't seen the actual shrimp there's a decent chance you've seen one of their burrows. These shrimps' extensive burrow systems have multiple entrances that allow water to flow through when the tide is in. You can easily find the entrances because the of the mounds of darker colored sand around the hole. The material from underground is usually dark gray or black because the low oxygen conditions within the muck stain the sand. Areas with low oxygen may sound like a terrible place to live, but pink ghost shrimp can survive for six days in those conditions! And if the oxygen gets too low ghost shrimp can be seen standing at the entrance to their burrows flushing in new water using the swimmerettes on their tail.

Ghost shrimp aren't just cool because they can survive without the chemical that literally makes complex life possible; they're also a major consumer of extra nutrients that get into estuaries. So much so that ghost shrimp might actually be the key to minimizing the damage human organic waste (fertilizers and more) does on the ocean. 

Even if you're not into crustaceans there's a good reason to love ghost shrimp.

"Whale, hello there!"
Courtesy: Linda Tanner via Flickr 

Ghost shrimp are the main source of food for gray whales as they travel back and forth from Mexico to Alaska every year. The whales dive down, suck up giant chunks of mud, and filter out the shrimp with their sturdy baleen. At low tide in Puget Sound near the mouths of rivers you can actually go and stand in pits dug by gray whales foraging for ghost shrimp. Who would have thought you would have a goop dwelling shrimp to thank for your Facebook profile picture of you in San Ignacio with the baby gray whale.

Leather Limpet (Onchidella borealis)

Courtesy:  Minette Layne via Flickr

First off, leather limpets are one of those rare molluscks that are freaking adorable. Seriously they're so tiny and they have goofy little faces!

If people can think sloths are cute they can definitely love this derpy little fella
Courtesy alex_bairstow via iNaturalist

Confusingly, leather limpets are not limpets at all. True limpets have a tent or volcano like shell on their back that they can raise and lower to protect themselves. Leather limpets have no shell to speak of, just a tough coating of tissue on their back. These little dudes also don't have gills to breathe in the water, they have a lung!

 Leather limpets avoid drowning by trapping a bubble of air in an opening above their butt. The opening is kind of like your nostrils and windpipe, so they're basically holding their breath while underwater. Land slugs have a system like this too. If you've ever looked closely at a slug you'll see a hole on what you can think of as their right shoulder. Pictures here.

Instead of hiding when the tide is low and crawling about when it comes back in; leather limpets' lung allows them to do the opposite. By moving around when the tide is out, leather limpets guarantee their predators will be firmly ensconced between rocks or in the sand. In case predators like sea stars do come calling while a leather limpet is hiding at high tide they have an effective defense. The little bumps on the leather limpet's side side secrete a fluid that repels sea stars and probably crabs.

Bristling like a teeny, squishy hedgehog.
Courtesy: paul_norwood via iNaturalist

So there you have it. Five ocean creatures you've probably never heard of. To be honest this list could have been thousands of animals long. The ocean makes up 99% of the habitable space on earth! It's deep, vast, and at the same time contains millions of tiny microhabitats. But there's one thing I hope you take away from this post. Look back at all the animals listed. How many of them are super rare? How many are a deep sea species that's only been seen a few times? And how many live in the waters or shore just down the road? Only one of these creatures isn't found in the intertidal zone. So what I hope everyone understands is that our planet, and even our immediate neighborhood, is incredibly rich. That you don't have to have access to high technology and millions in funding to explore and discover incredible things.

So get out there! Walk the beach. Poke around in the sand and mud. Lift rocks; peer on their undersides. And share your discoveries with us in the comments!

P.S. If you like this style of short, digestible information we do a similar segment called: "Wow Cool! of the Week" on our Facebook page every Wednesday. Check us out, and if you like what you see give us a like and a follow @depthandtaxa.
https://www.facebook.com/depthandtaxa/?ref=br_rs

References:

Cowles, David, "Onchidella borealis", Invertebrates of the Salish Sea (Online), Walla Walla University, 2007
Accessed via:
https://inverts.wallawalla.edu/Mollusca/Gastropoda/Gymnomorpha/Order_Onchidiacea/Onchidella_borealis.html

Cowles, David, "Neotrypaea californiensis", Invertebrates of the Salish Sea (Online), Walla Walla University, 2007
Accessed via:
https://inverts.wallawalla.edu/Arthropoda/Crustacea/Malacostraca/Eumalacostraca/Eucarida/Decapoda/Thalassinidea/Neotrypaea_californiensis.html

DeWitt, T H., "Response of Ghost Shrimp (Neotrypaea californiensis) Bioturbation to Organic Matter Enrichment of Estuarine Intertidal Sediments", Presented at 27th Annual Meeting of Pacific Estuarine Research Society, Port Townsend, WA, May 17-18, 2004
Accessed via: https://cfpub.epa.gov/si/si_public_record_Report.cfm?dirEntryID=81528

MacKinnon, J.B. "'Salvation Fish' That Sustained Native People Now Needs Saving", National Geographic Online, July 7th 2015
Accessed via:
https://news.nationalgeographic.com/2015/07/150707-salvation-fish-canada-first-nations-animals-conservation-world/

Pruitt, Casey & Donaghue, Cindy, "Ghost Shrimp and Gray Whale Feeding: North Puget Sound, Washington", Washington State Department of Natural Resources Report, October 28th 2016
Accessed via: https://www.dnr.wa.gov/publications/aqr_aamt_shrimp_whale_study_2015.pdf

National Marine Fisheries Service, West Coast Region, "Endangered Species Act Recovery Plan for the Southern Distinct Population Segment of Eulachon (Thaleicthys pacificus)", 2017

Accessed via:

http://www.westcoast.fisheries.noaa.gov/publications/protected_species/other/eulachon/final_eulachon_recovery_plan_09-06-2017-accessible.pdf   

Wright, J. 2014. "Brachiopoda" (On-line), Animal Diversity Web, May 21, 2018
Accessed via: http://animaldiversity.org/accounts/Brachiopoda/

Young, Richard E., "Haliphron atlanticus", Tree of Life Web Project, 2016

Accessed via: http://tolweb.org/Haliphron_atlanticus/20200

Just a FAD

Courtesy: Pedasi consultant via Wikimedia Commons

Hi there. My name is Titus. I'm a yellowfin tuna. You're probably guessing this post is going to be all about me and my family, and you're justified in thinking that. But the truth is, this is all about you.

You see your species really, really loves to eat us. Well not so much yellowfin specifically, but my cousins bluefin and skipjack tunas. Bluefin are the most expensive food fish in the world. Someone bought a relative of mine for $1.8 million in 2013! That crazy price tag means most of you have probably never eaten a bluefin. If tuna's ever crossed your lips though, you've almost definitely eaten a skipjack. Skipjack gets sold in cans that say "chunk light" on them and that's about 70% of the tuna in the US. The problem comes when you go to catch skipjack, the way you catch them means you also catch my siblings, and a bunch of other animals in the process.

Now I want to be clear; I have no moral authority to say you shouldn't eat fish. From one apex predator to another; I totally get it. Many of you have probably seen a documentary where we tear through a bait ball like it was nothing. In fact my mom was there when the BBC filmed the original Blue Planet. The difference between the way we catch our fish, and the way you catch yours comes down to effort. We really earn it, you often make it too easy. To what see I mean I'll have to show you a little bit more about where I come from.

"Follow me."

Courtesy: Elias Levy via Flickr

My relatives and I live a pelagic (pronounced pel-aj-ick) lifestyle. That means that we're always swimming closer to the surface than to the bottom. Don't get me wrong though; we've been seen diving over 2,000m down. It's just that we live in the big part of the ocean, the part that makes your stomach drop when you look down and there's nothing but blue fading to black over the miles beneath your feet.

It still doesn't do it justice, but for scale, those aircraft carriers are 1,000 feet long.
Courtesy: US Pacific Fleet via Flickr

It takes some really special adaptations to find food in this great azure emptiness. There's little phytoplankton to feed the ecosystem out here so prey are spread very far apart. That means we have to cross hundreds of miles of what's essentially desert to have opportunities to hunt. And we're not talking about pretty, cactus rich desert like the American Southwest here. The open ocean is more like the Dune Sea on Tatooine from Star Wars.

Even the way we're born is designed to help us get by in the vastness. My mom, carrying about 2 million of the eggs that would become me and my siblings, swam from the open Atlantic into the Gulf of Guinea off the West coast of Africa. Why there? Upwelling and river runoff. Nutrients from the bottom of the ocean and far inland travel into the surface waters of the Gulf and fertilize massive blooms of planktonic algae. Those plant-like plankton feed animal plankton, which are pretty much Gerber baby food for larval tuna.

Way cuter than that weird larval human on the jar
Courtesy: K. Dale via NOAA

I hatched from my floating egg into this rich soup of life where I fed on all kinds of tiny and delicious animals. Seriously, you guys haven't lived til you've tried copepods. Anyway, chowing down on these energetically rich little buggers meant that it only took about a month for me to develop the muscles I needed for adulthood. High stamina "red muscle" in my sides allows me to continuously swim for hundreds of miles with no breaks. In fact, I can't actually breathe if I'm not always swimming so taking a break would be a terrible idea. Those stoic red muscles are the tissue that you eat as poke, or sashimi, or in sushi rolls, or seared, or on salads. You really like to eat our red muscle is my point. And like I said before, I totally understand wanting to eat delicious fish. That's basically my entire diet.

So my parents set us up in a great feeding ground and we grew quickly, but the ocean is a fickle place. Pretty soon the plankton blooms started to die back and the anchovies, herring, and other small fish my relatives and I were eating began to disappear. Luckily one part of the ocean's end of the bloom is another's beginning and I felt something deep inside me stir. This instinct drove me to join up with other tunas and pushed us all out into the formless wilds of the open sea.

And here's where we start to get to the larger point. I didn't school up with just yellowfin tuna. I joined with albacore, skipjack, bigeye, you name it. As long as we were about the same size none of us cared if we were the same species or not. My school doesn't even care if we're all fish; sometimes we work with dolphins. We even hang out with whale sharks every fall in the Gulf of Mexico, those dudes are super chill. While this embracing of diversity is awesome it poses a problem when you scoop up our whole school in nets. If you're fishing for skipjack, which are a stable fishery, but you use a big net you almost always catch a bunch of the rest of us. There are fewer of us yellowfin, and waaaay fewer bluefin than some of the other species. You could theoretically sort through and pick out the species you're not targeting, but remember we don't last long if we're not continually swimming, and to be honest we all look a lot alike when we're young.

Case in point: Both these pictures are labelled as yellowfin on Flickr. 
The two on the left are skipjacks.
Courtesy: Stephanie Rogers and NOAA via Flickr


To make it worse, people catching tuna often use something called a FAD to lure us in. FAD stands for Fish Aggregating Device. That's a fancy sounding name, but it could be literally anything anchored to the bottom that provides something to hide on, under, or around. Old plywood, clumps of rope and sail, seaweed and branches, literal trash; all are shockingly useful to us pelagic creatures.

 For animals that spend their lives travelling, floating debris is like a cute diner you stop at to pee and buy a slice of pie while on a road trip. Small fish are drawn to the piles because they think it will give them somewhere to hide from predators. Larger fish are attracted to the piles because we aren't dumb. There's literally nowhere else for you to hide anchovy! Anyway this is normal and good when it's natural debris, but when humans place the material on purpose....

Once every fish from miles around has come to your FAD you can efficiently dent the population with a single net haul.

Truthfully, I can't really get mad at you for such cleverness. Humans have used the adaptations they were given to survive challenging environments the same way we have. But the difference is that you have a choice. Your species is so smart that most of you have access to more calories than any of us in the ocean could dream of. So if you want to make sure me and my cousins don't disappear there are a couple things you can do.

Eating lower on the food chain is a great choice. Be like me and eat mackerel! Mackerel have nice, soft white meat like albacore, with none of that fishy taste that scares a lot of people off. Also if you're going to eat tuna make sure it comes from someone who's committed to ensuring we stick around on this planet. Since canned represents the vast majority of the tuna you eat, it's especially important to consider the health of our stocks when you're buying it. Thankfully some nice humans have produced this chart:

Courtesy: Greenpeace via Greenpeace.org

It's awesome! Open Nature, American Tuna, Whole Foods and Ocean Naturals all employ fishing boats that don't use FADs. They also catch us with individual hooks and lines so that it's nearly impossible to catch the entire school! I chase down prey at 30 miles per hour or more so I can understand the thrill of the hunt that comes with bringing a fish in on a single line too. Just know that if it's ever me you catch; I'm gonna fight hard. We're all just trying to live as best we can.

Editor's Note: The text of this post was dictated to a tuna researcher by Titus from his autumn home in the Gulf of Mexico and emailed to the Depth and Taxa team. It would be absurd to think that a fish could type. However tuna do in fact have a broad knowledge of human culture particularly: Star Wars, memes, and Star Wars memes.

References:

Allain et al., "Interaction Between Coastal and Oceanic Ecosystems of Western and Central Pacific Ocean through Predator-Prey Relationship Studies", PLOS One, Vol 7 Issue 5, May 2012 

Via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0036701

Arocha et al., "Update on the Spawning of Yellowfin Tuna, Thunnus albacares, in the Western Central Atlantic", Collective Volume of Scientific Papers, 52(1): 167-176, 2001

Via: https://www.iccat.int/Documents/CVSP/CV052_2001/no_1/CV052010167.pdf

Gonzales-Andres et al., "Abundance and Distribution Patterns of Thunnus albacares in Isla de Coco National Park Through Predictive Habitat Suitability Models", PLOS One, December 14th 2016

Via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0168212

Scutt Phillips et al., "Revisiting the Vulnerability of Juvenile Bigeye (Thunnus obesus) and Yellowfin (T. albacares) Tuna Caught by Purse-seine Fisheries While Associating with Surface Waters and Floating Objects", PLOS One, June 29th 2017

Via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0179045 

Mom! They're Copying Me!

The old saying goes: "Don't pretend to be something you're not." It's great advice for humans trying to navigate the complexities of identity and our place in society.

I'm lookin' at you, High School Me!

However, if you're a small creature that's constantly at risk of being eaten, pretending to be something else might not be so bad. 

There's familiar examples of passive camouflage everywhere in the ocean. Sea Dragons look like loose, floating kelp; stonefish lie as unmoving as their namesakes on the bottom; grunt sculpins are nearly indistinguishable from a barnacle when they're still. There are even animals that actively camouflage to look like their environment. The many species of decorator crabs attach seaweed, sponges, hydroids, and any other flappy materials to their shell to blend in with their surroundings.

Microscopic hooks cover the crab's shell to facilitate camouflage

Courtesy: Ruth Hartnup via Flickr, and

Monique Salazar and W. Randy Brooks via Journal of Marine Science

But sometimes blending into the background isn't enough. Sometimes, you've got to do more than look the part. Sometimes you have to live your role to complete the illusion. Enter the cephalopods.

Octopus, squid, cuttlefish, and nautilus are all cephalopods (pronounced: sef-a-lo-pod). Cephs are probably the most intelligent and adaptable invertebrates in the world. A closer look at their anatomy can help us understand why. Cephalopods don't have claws or spines; they're not very fast; they have a sharp beak, but they have to get close to use it; and except for nautiluses cephs don't have a hard shell to protect their squishy, protein-rich bodies. So what do you do when you lack anatomical defenses? You get smart.

The most famous of this class to have the smarts to watch another animal and copy its behavior is the appropriately named mimic octopus (Thaumoctopus mimicus).

<in a nasally mocking voice> "watch another animal and copy its

behavior is the appropriately named mimic octopus"

Courtesy: Rickard Zerpe via Flickr

Dude, don't copy me that's ridiculous.

"Don't copy me that's ridiculous."

Courtesy: Avi Alpert via Flickr

<The following was typed very fast so the mimic octopus couldn't possibly copy it quick enough, and we can all actually learn something>

Mimic octopuses are found on sandy bottoms in the waters around Indonesia, the Philippines, and Papua New Guinea. These sandy and silty bottom habitats have few rocks, little animal growth, and minimal algae to hide among. While mimic octos can change their colors to match the background just as well as their cousins; movement tends to break the illusion. Other octopus species take advantage of rocky reefs or coral crevasses to slink along unnoticed while in motion, but mimics don't have that luxury. They also typically have to swim farther and more often than octopuses in other habitats because their prey isn't concentrated in a small area. A swimming octopus is very distinct, so mimics exactly copy the swimming behavior of flounder to conceal their true nature. They bend all their arms around and cluster them together so their eyes are sticking up in front of a big flat disk. As their arms trail, the ends flap just like the fins of a flatfish. The octopuses even stop and start moving with the same frequency as flounders all while hugging the contours of the rippled bottom.

We don't know why, but sometimes the mimic octopus will keep its distinct pattern while moving like a flounder and sometimes it will change to the fish's usual coloration.

Courtesy: Klaus Stiefel and Bernard Dupont via Flickr

The internet is full of reputed stories of mimic octos copying other species as well. While reports of mimic octopuses mimicking lionfish, sea snakes, and stingrays are out there we should remember that octopuses evolved entirely without our perceptions in mind. This means that what may clearly look like a lionfish to us, may look nothing like it to a grouper hungry for a bite of octopus arm. However, it may be that the mimics' strategy is just to look like "not an octopus", and whatever other creatures they see, they try and copy.

Amazingly mimic octopuses aren't the only species of octopuses to mimic other creatures. Living in the same waters as mimics the excitingly named "blandopus", which has which hasn't been formally described yet, also copies flounder. And if you Atlantic Ocean folks have been feeling left out, don't worry. The Caribbean has a copy-cat octo as well. Atlantic longarm octopuses (Macrotritopus defilippi) live in a very similar habitat to mimics and blandopus, and also engage in flat fish plagiarism.

Some species just have no regard for copyright law.

Courtesy: Wayne via Flickr 

Clearly impersonating another animal is an effective way to avoid becoming someone's lunch. But can cephalopods use mimicry to catch their own prey?

Just off the coast of southern Brazil; in the southern summers of 1999, 2000, and 2001 a pair of scientists used lights shined from a boat to attract zooplankton. Light attractants like this are an important tool in many fisheries, particularly those for squid. Rodrigo Silvestre Martins and Jose Angel Alvarez Perez wanted to study how a community of predators and prey develop under these lights. Who's eating whom, how are they going about catching one another, and what could that mean for fisheries conservation? The researchers found that a column of animals, gradually increasing in size, formed under the lights. The smallest zooplankton were near the surface, and as you descended  progressively larger predators lurked, waiting for a chance to strike at the prey above them.

Lurking in the shadows is pretty typical behavior for any predator, but one squid species' actions caught Martins and Perez by surprise. Atlantic brief squid (Lolliguncula brevis) are an estuary specialized squid that eat small schooling fish like anchovy and sardines. During Perez and Martins' study they watched brief squid regularly mimic the shape, color patterns, and swimming behavior of anchovies in order to get inside their schools without being noticed before striking.

Brief squid isn't a cool enough name for these masters of infiltration.
I propose we call them "subterfuge squid" from now on.
Courtesy: NOAA Photo Library via Flickr 

Now, squid aren't the only cephalopods to pantomime another animal in order to get close to prey. We've found one species of cuttlefish engages in a similar behavior to creep up on reef fish.

Pharaoh cuttlefish (Sepia pharaonis) are a widespread, small cuttlefish found throughout the warm waters of the Indian and Western Pacific Oceans. In 2011 a team of Japanese researchers noticed their cuttles doing something weird when they were placed in a large open tank for an experiment. The cuttlefish pushed together their upper pair of arms and colored them like eyes on the end of stalks. Then they set their other arms at odd, jointed angles and started twitching them, seemingly at random. Lastly they colored their mantle a shade lighter than all of their arms. The whole illusion came together to look exactly like a hermit crab.

In case the video widget doesn't work, click here to watch the pharaoh cuttles in action; it's astonishing. The research team thought maybe the cuttlefish were mimicking to protect themselves from potential predators when exposed in a large barren tank; kind of like mimic octopuses pretending to be other animals when they're moving in the open. But the scientists were curious if faking crabbiness (definitely the scientific term) could also help the cuttles catch prey like brief squid pretending to be anchovies.

So in 2013 they collected more pharaoh cuttlefish and put them in a tank with small tropical damselfish. The cuttles that pretended to be crabs got closer to the schools and caught twice as many fish as those that hunted while acting like cuttlefish! So yeah, I'd say that's an effective hunting strategy.

As we begin to look closer at cephalopods we're starting to understand just how diverse and seemingly intelligent their behavior is. Mimicries like these are just a sample of the ways octopus and their cousins use their adaptable camouflage. So maybe pretending to be something you're not isn't always bad. Maybe we shouldn't deal in absolutes all the time and recognize that there's advantages and disadvantages to lots of behaviors and life styles. There's a lot to be learned still about cephalopods, but there's also a lot to be learned from them.

References:

Hanlon, Roger T., Watson, Anya C., & Barbosa, Alexander, "A 'Mimic Octopus' in the Atlantic: Flatfish Mimicry and Camouflage by Macrotritopus defilippi", Biological Bulletin, 218: 15-24, Feb. 2010.
Accessed via: http://www.journals.uchicago.edu/doi/10.1086/BBLv218n1p15

Hanlon, Roger T., Conroy, Lou-Anne, & Forsythe, John W., "Mimicry and Foraging Behaviour(sic) of Two Tropical Sand-flat Octopuses of North Sulawesi, Indonesia", Biological Journal of the Linnean Society, Jan. 2008.
Accessed via: https://academic.oup.com/biolinnean/article/93/1/23/2701347

Martins, Rodrigo Silvestre & Perez, Jose Angel Alvarez, "Cephalopods and Fish Attracted by Night Lights in Coastal Shallow-waters, off Southern Brazil, with the Description of Squid and Fish Behavior", Revista de Etologia, Vol. 8 No. 1 Pg. 27-34, 2006.

Accessed via http://pepsic.bvsalud.org/pdf/reto/v8n1/v8n1a03.pdf

Okamoto et Al., "Unique Arm-flapping Behavior of the Pharaoh Cuttlefish, Sepia pharaonis: putative Mimicry of a Hermit Crab", Japan Ethological Society and Springer Japan, May 2017.

Accessed via: https://link.springer.com/article/10.1007/s10164-017-0519-7

Basking Case

What follows is a cautionary tale. A story about acting out in frustration; of letting passions get the better of our collective judgement. A yarn of life, economy, adventure, and...tourists.

Folks living in major coastal towns around the world know the story. As the days lengthen the sun's rays warm the air and the scent of dry grass drifts in the breeze. Locals finally get on the water as the rains and long dark of winter are left behind. But that's when they come: massive, constantly in the way, slowly moving in impassable groups, gorging themselves on an all you can eat buffet. 

Courtesy: Devin Braun via Flickr 

I am, of course, talking about basking sharks (Cetorhinus maximus). 

-"Hey, Kool-Aid"

-"Oh Yeah!" 

Courtesy: jidanchaomian via Flickr

Basking sharks and cruise ship travelers may not seem to have much in common at first, but diving in (Ha! Ocean puns) to their life history reveals some surprising commonalities.

Baskers are the second largest fish species in the world, growing to average lengths of 15-20 feet, but they can get as long as 30. Because they're so big; a single flick of a basking shark's tail moves a lot of water and thus their streamlined bodies are propelled smoothly along with very little effort. This energy efficient movement allows basking sharks to travel great distances through temperate seas. One shark was tagged in late June of 2007 between Ireland and the UK, and had traveled all the way across the Atlantic to south of Greenland by early August. Like other related sharks that make long treks, basking sharks are cruising in search of food. But these massive fish aren't hunting for seals or other large prey; they're cruising along, mouths agape, straining plankton from the water. The filters on their gills are so good at collecting particles, yet remaining unclogged, that they're even inspiring engineers designing industrial and commercial water and air filters.

Basking sharks migrate seasonally across the ocean, and daily up and down in the water column following their favorite food: calanid copepods (pronounced: ko-peh-pods).

Copepods are rich in fats despite their constant failed attempts
at stealing the Krabby Patty secret formula.
Courtesy: DFO via WOrld Register of Marine Species

During the winter these planktonic crustaceans tend to hang out deeper in the water and farther out to sea, so baskers do the same. During the summer, copepod populations explode near shore as lengthening days cause massive blooms of phytoplankton for the copepods to graze on. Basking sharks head shoreward just ahead of this explosion of life to catch the bloom right as it begins and optimize their own feeding. Like most other zooplankton, copepods also participate in the planet's largest migration. During the day they descend to avoid active predators at the surface, and at night they come up to the phytoplankton rich layer that formed while the sun was high. Typically basking sharks do the same daily vertical migration, but occasionally tons of copepod predators called arrow worms will show up at the surface at night. This unexpected pulse of predators drives the majority of the copepods, and consequently the basking sharks, deep when we'd expect them to be shallow.  So not only do basking sharks show up in the inland waters of the far north and south like cruise ships and their passengers, but they also predictably attend to the abundance of the buffet at the times of day it's most well stocked.

Basking sharks' feeding and travel habits aren't the only ways they jive with tourists. As their name implies, basking sharks often hang out in the sun not doing much. Since the sharks already have a pretty bitchin', deep-brown tan they must not be longing to soak up rays. Nope, it's that layer of copepods again. Because there's so much food at the surface, basking sharks don't have to move fast or far during the spring and summer blooms. The sharks are found in aggregations hundreds strong just lolling at the surface with their mouths open like they've fallen asleep sunbathing.

Okay I know there's a shark in this picture somewhere but...
Courtesy: candiche and Noodles and Beef via Flickr

These high concentrations of slow moving basking sharks occur in only a few places in the world. It's likely that these big shivers (the name for a group of sharks) show up in places like southern Chile, but we only know for sure that they happen in the Irish Sea, outside the Bay of Fundy, and historically in the Northwest Straits of the Salish Sea.

Just in case you're not from one of those places or didn't pay attention in geography

Now, you might have noticed that I said "historically" in the Salish Sea. In the past, basking sharks came to the region in droves every year to bathe in the Pacific Northwest sun and chow on the rich abundance of copepods in those waters. But like any pulse of summer tourists visiting a port; they were slow, in the way, and causing problems for traffic.

I'm lookin' at you; Pike Place!
Courtesy: Michael Munch via Flickr

As happens with anyone who deals with influxes of tourists too often; salmon fisher folk in British Columbia largely hated this yearly migration. The sharks were so numerous and slow that they frequently became entangled in salmon gill-nets. Basking sharks also have the same skin-teeth that other sharks possess, so when they thrashed to free themselves they often destroyed more of the net than just where they were caught.

Since much of the BC economy relied on salmon fishing at the time, basking sharks were listed as "Destructive Pests" by Canada's fisheries department in 1949. Six years later the department began an eradication program that, coupled with a commercial fishery for their skin and oil, did exactly as intended. Basking sharks were functionally extinct in the Salish Sea by the late 60s.

The Comox Post with its shark-slicing bow blade
was the pride of the program.
Courtesy: Popular Mechanics via Google Books

However attitudes towards basking sharks (and to a lesser degree cruise tourists) are changing. People better understand the role baskers play in the marine ecosystem as the massive end of a petite food chain. Ironically basking sharks now bring tourists to the Irish Sea and surrounding waters every year to watch their incredible shivers. Having basking sharks and cruise tourists around can greatly enhance the economies of northern port towns in the summer. And Lord knows we can use that extra cash for good beer and faux daylight to get us through the dreary mists of maritime winters.

There's also hope for the Salish Sea's population of basking sharks. They've been granted the protections that being listed as "endangered" under Canada's Species At Risk Act affords them since 2010. Baskers are also occasionally showing up in unexpected parts of the Salish Sea. In 2014 a basking shark gave a family out fishing a unique encounter when it basked about their boat for 15 minutes off of Edmonds, just 16 miles north of Seattle. No word on if the shark was planning to visit Pike Place.

" Excuse me, can you tell me how to get to the gum wall?"
Courtesy: Grace Coale via Q13 Fox

References:

Gore et al., "Transatlantic Migration and Deep Mid-ocean Diving by Basking Shark", Biology Letters: Marine Biology, Vol. 4 pg. 395-398, 2008.

Accessed via: http://rsbl.royalsocietypublishing.org/content/4/4/395

Lorch, Matt, "Close Encounter with Rare 25-foot Basking Shark in Puget Sound: "I didn't really feel scared, just excited", Q13 Fox News, Aug. 13th 2014

Accessed via: http://q13fox.com/2014/08/13/close-encounter-with-rare-25-foot-basking-shark-in-puget-sound-i-didnt-really-feel-scared-just-excited/

Pynn, Larry, "Rare B.C. Photograph of Endangered Basking Shark Shines Light on Change in Federal Attitudes", Vancouver Sun, Nov. 11th, 2013.

Accessed via: 

http://www.vancouversun.com/technology/Rare+photograph+endangered+basking+shark+shines+light+change+federal+attitudes/9152553/story.html

Sanderson et al., "Fish Mouths as Engineering Structures for Cross-step Vortical Filtration", Nature Communications, Vol. 7, Article #11092, 2016.

Accessed via: https://www.nature.com/articles/ncomms11092

Siders et al., "Seasonal Variation in the Spatial Distribution of Basking Sharks (Cetorhinus maximus) in the Lower Bay of Fundy, Canada", PLoS ONE, Vol 8 Issue 12, 2013.

Accessed via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0082074

Sims et al., "Habitat-specific Normal and Reverse Diel Vertical Migrationin the Plankton-feeding Basking Shark", Journal of Animal Ecology, Vol. 74 pg. 755-761, 2005.

Accessed via: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2656.2005.00971.x/full