The superhero like swimming of Manta Rays

What’s black and white and studied all over?

The post Whale Shark and Manta Ray Gif Roundup first appeared on Deep Sea News.

The largest fishes in the oceans feed on some of the sea’s smallest organisms. Several massive plankton-feeding elasmobranchs – the group of fishes that include sharks and rays – evolved adaptations to gulp huge mouthfuls of water and filter out plankton, shrimp, and small fishes. Though these tiny tidbits in themselves may not seem like a meal fit for a giant, the sheer abundance of these minuscule organisms in the sea adds up to a bounty for animals designed for sifting and straining them out of the water. What’s even more interesting is that each of the four massive filter-feeders evolved their particular diet and feeding morphology independently of one another.

Whale Sharks share a common ancestor with the docile nurse sharks, basking sharks are part of the branch of the shark family tree that has great white and mako sharks, the megamouth shark may be descended from the Odontaspidids, which includes the sandtiger sharks, and the manta rays are related to the much smaller bat rays and eagle rays. This is called convergent evolution, where natural selection steers the similar re-engineering of preexisting anatomical traits to achieve a similar solution between different groups of unrelated organisms. In the evolution of elasmobranchs over the last 45 million years, three lineages of sharks and one lineage of rays all independently evolved to filter-feed feed on plankton, swarms of tiny shrimp, and schools of small fishes as a means to successfully increase their survival.

Farther back in time, during the Cretaceous period when dinosaurs roamed the land and huge marine reptiles swam the warm, shallow continental seas around the globe, this same experiment in filter-feeding evolved much earlier, and completely independently of any of today’s huge plankton-eating sharks. In a recent paper in the Journal of Vertebrate Paleontology, Kenshu Shimada and an international team of researchers unraveled the complex and confusing identity of several species of fossil shark teeth and found them to be the earliest known example of filter feeding in sharks. Small teeth from ancient marine rocks in Colorado, Texas, and Russia showed certain characteristics seen in recent giant filter-feeding sharks. In fact, the teeth looked so much like the huge deep sea filter-feeding Megamouth shark Megachasma, that the new genus was dubbed Pseudomegachasma.

All of today’s filter-feeding sharks use highly-modified gills to strain food out of water that flows from their cavernous mouth through their gill openings. Not once do they appear use their teeth for feeding, so in these lineages of sharks, the teeth have become exceedingly reduced in size, usually barely a quarter inch in size. Unlike other instances in evolution where useless organs or appendages are eventually lost, in filter-feeding sharks the teeth didn’t go away, but they shrunk,

and strangely, increased in numbers rather than disappeared altogether, so filter-feeding sharks and rays have hundreds of itty-bitty seemingly useless teeth in their jaws. Fortunately, all sharks and rays shed their old teeth to make room for the new ones growing in, which is how such teeth from ancient sharks later become today’s fossils that guide our understanding of shark evolution.

These teeth from at least two different species make Pseudomegachasma the oldest plankton-feeding sharks yet known, and is believed to have evolved from an earlier, extinct fish-eating shark. Pseudomegachasma lived between 92-99 million years ago, first appearing in coastal waters that is now southwestern Russia, and later extending into the ancient inter-continental marine seaway that once covered an area from Texas to Colorado.  Why Pseudomegachasma went extinct, and why there seem to be no giant plankton-feeding sharks between 50 and 91 million years ago is still a mystery that only future fossil discoveries can solve.

The research team consisted of Kenshu Shimada, DePaul University; Evgeny V. Popov, Saratov State University, Russia; Mikael Siversson, Western Australia Museum, Bruce J. Welton, New Mexico Museum of Natural History, and Douglas J. Long, California Academy of Sciences and St. Mary’s College of California.

Article:
Shimada, K., E. V. Popov, M. Siversson, B. J. Welton, and D. J. Long. 2015. A new clade of putative plankton-feeding sharks from the Upper Cretaceous of Russia and the United States. Journal of Vertebrate Paleontology, Vol. 35, No. 5.

The post Before Giant Plankton-Feeding Sharks, there were Giant Plankton-Feeding Sharks. first appeared on Deep Sea News.

Off the Angolan African coast, these researchers document one whale shark and three ray carcasses at 1200 meters on the seafloor.  This is the first time any of these have been documented as deep-sea food falls and only recently have living whale sharks even been documented off Angola.

Despite one of the carcasses being covered in 54 eelpouts, a considerable amount of flesh still existed on the carcasses.

[in prior studies] When presented with elasmobranch and tuna bait on a baited camera trap, scavengers clearly preferred tuna and only consumed the elasmobranch once the tuna was gone…Repeated experiments in this region using [bony] fish as bait showed a 10-fold increase in scavenging rates compared to that when elasmobranch was used.

So why in a food desert like the deep sea would fresh meat not be consumed quickly?  Apparently, elasmobranch, i.e. shark and ray, flesh is bit unpalatable and tough to chew.  The tough, sand-paper-skin may prove a formidable barrier to scavenger jaws.  The high ammonia content of elasmobranch flesh may also be, to say the least, unappetizing.  The carcasses may also smell like death and deter other scavenging elasmobranchs.

Other uncharacterized chemicals that are found in rotting elasmobranch flesh (necromones) have been proven to strongly deter shark scavenging and invoke an alarm response, even among different species of elasmobranch. If this phenomenon extends to deep-sea scavenging elasmobranchs, it can be assumed that the Portugese dogfish, Centroscymnus coelolepis, would have been deterred from scavenging the elasmobranch carcasses. This will have severely hindered utilization of the carcasses by other species, since C. coelolepis is the dominant scavenger off the Angola margin.

Yet despite the smell of death and urine, a dead elasmobranch still provides an essential snack in the deep sea.  The researchers estimate that these elasmobranchs represent 4% of the total amount food that sinks to the seafloor off Angola in the form of marine snow.

Higgs, N., Gates, A., & Jones, D. (2014). Fish Food in the Deep Sea: Revisiting the Role of Large Food-Falls PLoS ONE, 9 (5) DOI: 10.1371/journal.pone.0096016

The post Dead Elasmobranchs on the Seafloor are Not as Appetizing as One Might Assume first appeared on Deep Sea News.

The superhero like swimming of Manta Rays

What’s black and white and studied all over?

The post Whale Shark and Manta Ray Gif Roundup first appeared on Deep Sea News.

Once upon a midnight dreary, while I pondered, weak and weary,

Over many a quaint and curious volume of nautical lore —

While I nodded, nearly napping, suddenly there came a tapping,

As of someone gently rapping, rapping at my office door.

“ ’Tis some visitor,” I muttered, “asking again about ocean lore —

Only this and nothing more.”

Ah, distinctly I remember it was the gray Oregon December;

And in the distance I could hear the waves crash upon the shore.

Eagerly I wished the morrow; — vainly I had sought to borrow

From my textbooks cease of sorrow — mistake of science for ocean lore—

Of the unreal and radiant mermaiden whom I really thought a bore —

Nameless here for evermore.

As the soothing and uncertain rumbling of each aqua curtain

Thrilled me — as each tidal wave washed ashore;

So that now, to still the beating of my heart, I stood repeating

“There are amazing creatures in the waves beyond the shore —

Ones that far outshine the whisperings of ocean lore; —

They exist and nothing more.”

Presently my thrills grew stronger; hesitating then no longer,

I thought of the creatures which science has explored;

But the fact is the public’s asking, and marine science is ever tasking,

To know what creatures there lay upon the ocean floor,

That are far more fascinating than legend — than ocean lore; ——

The ones that science ought to explore.

Deep into that darkness peering, I thought of creatures then appearing,

In my head as thoughts of animals like none seen before;

The nudibranchs, echinoderms, cetaceans, each its own unique creation

Each one more fascinating than the one before.

This I pondered, as my imagination scanned the ocean floor —

Over undersea vents and near the shore.

First, Orcinus orca, the bringer of death, a beautiful fury with predator’s breath.

Whose artful visage many species do abhor

He spends his lifetime bound to kin, a social life that rivals men;

Who has his own dialect and vocabulary store —

A scourge to prey within the sea and upon the shore —

May he click and squeal forevermore.

In my mind’s eye I flung the shutter, when, within my thoughts did sputter,

Vampiroteuthis infernalis, the vampire squid with his black chromatophores;

Not the least obeisance made he; not a minute stopped or stayed he;

But, on the end of each pulsing limb, a glowing aqua photophore—

Lit up like a lighthouse hailing ships to safer shores —

He drifted into the abyssal darkness, vanishing forevermore.

Then traveling ever deeper, my feeble eyesight growing weaker,

A hydrothermal vent teeming with extremophiles upon the ocean floor,

Tubeworms, shellfish, bivalves, octopi, thrive in smoking hydrogen sulfide

Braving temperatures as hot as Celsius 464 —

Each animal more unique than the last, as if pulled from fiction’s store

Like no creatures seen above the ocean shore.

Much I marveled at this place as I ascended,

Arose swiftly from the ocean’s core;

As I left the zone that few human beings

Are very often blessed with seeing; I traveled from the ocean’s floor—

I thought of creatures bold and brighter, nearer to the ocean shore,

And dwelt in darkness nevermore.

Rising up to bluer waters, gave my imagination fodder

To seek out creatures who seemed nearer to imagination’s door

The blue dragon nudibranch, Glaucus atlanticus, surely from Poseidon’s corp,

Whose iridescent blue wings fluttered as the ocean waves rolled back and fore

A reminder that each marine invertebrate is more beautiful than the one before

Left me in awe forevermore.

Marveling at the ocean’s creatures, seeking out more faunal features,

I thought of the humble rockfish, who some might think to be a bore

Ambling through the waves unworried, ever calm and rarely hurried

A life which patience doth implore, he lives two centuries or more —

Oft ‘till the dirges of his tasty flesh make fisheries his burden bore

Long live the rockfish, nevermore.

But the sea’s treasures still piling, I found myself then smiling,

Thinking of the creatures creeping on the ocean floor;

Like the sunflower sea star, Pycnopodia helianthoides,

A beauty lethal, with 24 arms flush as the petals of a rosy fleur —

It feeds on countless prey within the rocky intertidal shore

A predator other invertebrates do oft deplore.

And where at once the tide grew stiller, I did then sight that knightly killer

The mighty shark which modern evolution did ignore.

Lithely swims with tail curled, with razor teeth flashing, whorled

Alas, the shark does claim no more the fiercest throne the ocean o’er

As the finning trade then sought him to gore

Swam the shark most proudly, nevermore.

Peering towards the vast horizon, two blue forms my eyes did spy on,

Swimming on like two Leviathons, those giants that I do adore,

The blue whale (B.musculus) and whale shark (Rhincodon typus)

Although the largest fish, and the whale, ne’er a larger creature did come before;

They feast on but the tiniest creatures that the ocean bore;

Merely these and nothing more.

Back ashore the tide was turning, and as I watched with youthful yearning

As the blue waves kept gliding, turning, and seafoam crept across the shore

Weary then my eyes did flutter, and I closed the textbook cover,

My mind reeling with creatures found in the sea and on the shore.

Each drop of saltwater a world alone to be explored.

The world which forms the ocean’s core.

How curious, thought I, then wondering, that one would spend time pondering

Imaginary creatures when there are already so many within the ocean’s store

Creatures wrought as if from fiction, but well within science’s diction.

Far more fabulous than fantasy could have ever bore;

To study them myself I swore, like many marine scientists before.

Long live our oceans, evermore.

The post An Oceanic Ode first appeared on Deep Sea News.

1st bit of evidence. Whale sharks spend a lot of time below the surface.  Derrr, I might hear you say, it’s a fish…  Except, it is a fish that spends (or so we thought) a disproportionate amount of time at the surface.  This was based on observation (obviously) and some tagging data, but as the tagging has continued we have learned that in fact they spend much more time out of sight than we thought.  We used to think they were at the surface except for occasional dives, some of which could be very deep, but now we are learning that they may stay deep for significant chunks of their lives, which puts them effectively out of detection range.  And even when they are at the surface, they make such frequent short range dives that subsurface behaviour becomes a big part of their daily pie chart of time use.  This means we need to up the estimates of population by a correction factor that accounts for the portion of time they spend out of sight.  What should that factor be?  Dunno yet, I’ll get back to you after the next conference.

2nd bit of evidence.  Tags and photo ID disagree on connectivity. How groups of whale sharks in different parts of the ocean are connected (or not) is an important question both biologically and for effective conservation measures.  On this matter, two different research techniques disagree somewhat, but they do it in a way that hints at a bigger population.  Satellite tags have shown plenty of evidence of connectivity between different sites in the ocean, sometimes on scales of thousands of miles.  For example, animals tagged in Mexico often show up in Belize, Honduras and the Gulf of Mexico, even Brazil.  And yet, photographic identification databases (the most important is Wildbook for Whale Sharks, formerly ECOCEAN), show surprisingly little connectivity.  Despite over a thousand individual sharks identified in Yucatan Mexico, for example, only a handful have been re-sighted in the other places I just mentioned.  How is this possible if satellite tags show frequent proof positive of connectivity between these locations?  Well, it’s probably because tagging is a “population independent” method, but photo ID is not.  That is, the results of satellite tagging depend only on the movements of the tagged animal and not on the size of the population in either place, whereas the chances of re-sighting a whale shark photographed in one place at another place depends to a large degree on how many sharks there are at the new site.   The lack of photo ID re-sightings suggests that these populations are in fact pretty big, so big that finding that familiar “face in the crowd” actually becomes statistically pretty unlikely.

3rd bit of evidence.  Where are all the ladies at?  The veritable explosion of whale shark science in recent years has been due in large part to the recognition of the phenomenon of whale shark aggregations, or constellations as I now like to call them (you chose it, dear reader).  I’ve written a ton at DSN about the one that occurs in Yucatan Mexico but there are actually at least 12 locations in the world where whale sharks gather in large numbers – always to feed – relatively close to shore.  And those are just the ones we know about.  There are constellations taking place in the Red Sea, the Persian Gulf, the Philippines, Indonesia, Australia, the Seychelles, the Maldives, Mozambique and Tanzania, to name a few, but they all have one thing in common: they are dominated by immature males.  Very consistently so, in fact; nearly all of these selachian sausage-fests show the same 3:1  male:female sex ratio, and the overwhelming majority of animals are immature.  It’s basically an elasmobranch frat party, sans the beer pong.  We know that whale sharks give birth to the genders in a 1:1 split, so you have to ask: where are all the other immature females?  For that matter, where are all the mature animals, both male and female, and where are all the little ones too, under, say, 4 meters?  When you really break it down, we are basing a sizable chunk of whale shark research on one small demographic slice of the whale shark pizza: immature  males.  That’s no way to study a species, and it certainly makes it hard to get a good handle on he global population, when the numbers you are extrapolating from represent such a small segment of the overall population.

Taken together, these bits of evidence suggest that there might be a lot more whale sharks out there than we know of.  Some genetic studies have estimated populations (in the genetic sense this means the number of mature females) between 100,000 and 250,000, which is a LOT more than what we see, especially when you add in the males and immatures of both genders.  But genetic techniques are no substitute for observational data and there we are still sadly lacking.  One one level, this actually gives me a warm inner glow.  I find it both tantalizing and fascinating to think that we are unable to account for perhaps 3/4 of the population of the world’s largest fish.  It’s like the dark matter of the marine megafauna world.  It gives me a strange sense of encouragement that they are out there somewhere, evading our best efforts and proving daily that the ocean still has her fair share of secrets.

“There are things known and there are things unknown, and in between are the doors of perception.” – Aldous Huxley

The post Where are all the ladies at? first appeared on Deep Sea News.

A year ago, I jumped off the side of a perfectly good boat. Infinite water hides the land to the west and the ocean floor below. Moments ago, the captain and Mexican marine biologist, Rafa tells me to get ready. I scramble to gather and put on my mask, fins, and snorkel. Through my fogged mask and the glaring sun I can’t see anything below the surface, but Rafa perched high on the deck above knows what to look for. He cuts the engines and we coast up to the target. Rafa shouts “Now!” I spring over the side of the boat. At first I don’t see anything except the bubbles from my water entry. The bubbles begin to clear and see nothing except blue. I swing around. Mere feet from me a mouth, as wide as I am long, quickly approaches. Following that mouth is 25 feet of whale shark. Al briefed me on whale sharks just that morning. “The esophagus of a whale shark measures only inches across.” His words are echoing in my head. I also take solace in that whale sharks prefer planktonic not human flesh.

Even if most sharks preferred man meat, most just do not measure up. Fifty percent of the sharks in the ocean are less than 3 feet in length. Seventy five percent are less than 5 feet. That is maximum length. In other words the maximum length an individual of given species has ever obtained. In the oceans, where life is tough most sharks will never reached this ideal size. It’s like saying all humans are the size of Andre the Giant. Most of us and most sharks are not giants. Of all the size classes, the greatest shark diversity occurs at less than one foot in length.

The smallest shark is the dwarf lanternshark (Etmopterus perryi) is a rare animal from the deep waters of Columbia and Venezuela. The largest known individual, ever, reached only 8.3 inches. Not feet. Inches. This is just barely longer than a pencil.  What is lacks in size it makes up for in flashiness. Like its name suggests, the dwarf laternshark can generate light through an array of photophores that line its body.

Another close contender for the smallest shark is the enigmatic Campeche catshark (Parmaturus campechiensis). The species is only known from one individual held now in the Smithsonian. In other words, we have only seen one…once. Like the dwarf lanternshark, the species is known only from deep waters. The one individual measured just 6.3 inches. That’s only big for a phone.  Notably the individual was a juvenile and adults, if ever caught, may measure longer.

Another contender, and often wrongly assumed to be the smallest shark, is the spined pygmy shark (Squaliolus laticaudus). It is a giant among small sharks at whopping 11 inches. Like the other small sharks here it lives in deep water, lurking about typically at 1,600 feet.  However, it is by no means rare or geographically limited being found across the Atlantic, Pacific, and Indian Oceans.

Given the size of most sharks, of far greater concern is how many can fit into our mouths.

The post Megalodon…phhh…most sharks are Microlodons. first appeared on Deep Sea News.

My colleague Rafael de la Parra is the executive director of Ch’ooj Ajauil (Mayan for “Blue Realm”), a long time research partner of Georgia Aquarium and an excellent naturalist; he knows more about whale sharks in this area than anyone, and he’s a dab hand with marine mammals and other pelagic (in the water column, i.e. not on the bottom) species as well.  We headed out on Rafa’s boat, Grampus, for a day of whale shark photo identification in the waters east of Isla Contoy, an insular national park about 20 miles north-north-east of Cancun.  The wind and waves were against us and I didn’t have high hopes; indeed, the Harbor Master only opened the harbor for small boat activity at the last minute.  It was a predictably long and sloppy ride to the area of interest, but along the way I was encouraged to see some turtles (las tortugas), a curious group of spotted dolphins (delfin) and an abundance of flying fish (pez volador).  Eventually we reached a small flotilla of ecotourism boats, which gather as predictably around whale sharks as the frigate birds do above schools of baitfish.

Despite the conditions it turned out to be a truly magical day!  The whale sharks, perhaps 70-100 of them, were clustered especially tightly and it was not unusual to put your mask under the water and be able to see three or four simultaneously.  In fact, it makes it hard to get good photo ID images, because they are just coming too thick and fast, which I guess is a good problem to have on any day!

The ecotour boats gradually petered away until we were left alone to snorkel with the animals in the vast expanse of the offshore waters of the warm clear Caribbean.  I love it when it’s like that, because without distractions for us or the animals, behaviours are more normal and your eyes gradually open to all the other things that are going on around you.  And that’s when you realise that this patch of ocean, seemingly empty except for, you know, 100 whale sharks (!), is in fact replete with life.

Most obvious among the whale sharks were a number of manta rays.  These graceful pelagic animals are filter feeders just like the whale sharks so it’s no surprise that they often show up together.  I was lucky enough to experience several encounters with the same ray over the course of the day: a male missing one of his cephalic lobes, which are normally used for steering (like canards on aircraft) and to direct food into their capacious mouths.  Each time he found a dense patch of food (in this case almost certainly tuna eggs), he would barrel roll over and over, seemingly oblivious to his new dance partner floating enraptured above.

In between whale sharks, which are almost exclusively feeding at the very surface, it pays to look down deeper, perhaps 40-50ft.  Down there can be seen other graceful residents of the pelagic zone.  Mustard-coloured cownosed rays form large schools, gliding so slowly that they appear to hang suspended in the water.  Swifter are the mobulas or devil rays, which look like miniature manta rays and fly in formations of black white and grey against the cobalt blue of the deeper water.

Fish are there too.  I was buzzed by half a dozen small mahi mahi, which passed by so quickly that I barely had time to snap a picture as they passed.  Other fish hitch their wagon to the bigger animals; every whale shark is accompanied by a plethora of remoras, big and small, hitching a ride on the fins, riding alongside, or even swimming in and out of the mouth and gills.  Rainbow runner and small schools of sardines draft along behind or below their giant spotty compadres.

I even picked up my own hangers on: a pair of baby jacks that acted as pilot fish, riding the bow wave in front of my mask as I kicked hard to keep up with the sharks and rays, and getting in the way of my photographic efforts!

On the ride back to port (now thankfully with a gentler, following sea), I chatted with the others in our group about the feelings you get from these sorts of experiences and we concluded that you can’t really know unless you see it for yourself.  The two biggest things for me are first, the sense that the seemingly empty ocean really isn’t, that even in the absence of bottom features or structure of any kind, the pelagic zone is alive with diversity large and small, and second that this is a truly alien world here on earth.  We can intrude from the edges, for a brief period, and admire the grace and adaptive successes of the animals that live here, but this is not our world, not really, except in so far as we are stewards of the sea.  That feeling of having a window into another world must be a glimmer of how astronauts felt the first time they set foot on the moon.  It’s comforting to know that there are still amazing biological phenomena to see here on earth, in the oceans, if we just take the time, make an effort and peel back a corner of the curtain to peek into the fantastic world of the pelagic zone.

The post TGIF – Magical Quintana Roo first appeared on Deep Sea News.

Do you know anyone who lives near Seadrift TX, east of Corpus Christi/West of Houston?  I have a satellite tag that came ashore in Espiritu Santo Bay, inside Matagorda Is. and I’d love to get it back.  It was on a female whale shark called Lucy, who was tagged near Isla Contoy, Mexico.  The tag came off in the Flower Garden Banks offshore from Texas and gradually drifted inshore.  I’m pretty sure its on the beach now.

Last ping was 28.333N 96.598W, or the green arrow in this map.

It’s likely lying on the beach of that tiny spit of land, which is called Long Island.  There’s a boat ramp close by at the end of Lane Rd. that comes off Adams St (Rt. 185), which connects Seadrift to Pt. O’Connor.  Any help much appreciated, please share with your Texas friends and colleagues.  People can contact me through this website.

And THANKS!

The post DSN community, I need your help first appeared on Deep Sea News.

Why should I give a flying flip about how big they get?

Let’s just say it’s about more than bragging rights. Precise, accurate, and quantified measurements matter at both a philosophical and pragmatic level.  Saying something is approximately “this big” while holding your arms out to indicate your full arm span just won’t cut it.  This is science not a fishing story recounted over brews with the buds.  And just like knowing whether you’re meeting your buds at 8 a.m. or 8 p.m. determines how you pace those brews, knowing the size limits of an organism makes a huge difference as well.

Given their size, both the whale shark and giant squid are surprisingly elusive.  These behemoths lead predominantly solitary lives in the open, and often deep, oceans far from human sight.  Finding a specimen to measure is like finding the proverbial needle in a haystack.  So, why pursue it, right? Because this seemingly impossible task offers a huge payoff, duh.

From accurate measurements of size we can infer much about an organism. In some aspects this is basic physics.  The mass of an object dictates friction, acceleration, force, and so on. The metabolism of an organism, telling us how much oxygen and carbon an animal consumes, is a function of size as well.  Indeed, we have precise mathematical equations, based on studies of closely related species, that can tell what the metabolism of such giants would be.  Knowing whether a whale shark is 10 tons, 15 tons, or 20 tons lets us know whether a whale shark uses 868, or 1176, or 1,460 light bulbs worth of energy every day.  It doesn’t stop with metabolism either.  In spite of errors and exceptions, heart rate, speed, growth, lifespan, population size, lifetime reproductive output, and many more things can all be estimated from body size.  This provides a substantial advantage when trying to understand organisms we know virtually nothing about.

Changes in size over time can also tell us when a species, including our whale shark and squid, is in trouble. Researchers working on Nigaloo Reef off Australia found that the average length of whale sharks decreased by nearly two meters in the last decade. The most likely culprit is overfishing pressure the whale sharks encounter during other parts of their migration.

So, How big do Whale Sharks get?

Beer Google version:  If you search around the internet you will find varying answers.  This Whale Shark FAQ places the upper estimate of length at 21.4 meters (70.21 feet).  A YouTube video claims that a filmed individual is 18.29 meters (60 feet).  The conservation organization Oceana suggests the upper size is 20 meters (65.6 feet).  Compare that to what you find in the scientific literature. Martin in 2007, “1 of only 10 sharks that routinely attain lengths of more than four metres [13.12 feet],” and Coleman ten years prior,  “Most specimens reported in the literature are between 4 and 10 m [32.8 feet].” 

The Sober Truth:  According Coleman in 1997 the largest scientifically, i.e. accurately, measured whale shark was 12 meters (39.37 feet).  Newer work on the Nigaloo Reef whale sharks also reports the maximum size at 12 meters.  During my work with Al Dove on the estimating sizes of whale sharks at the Afeura (with lasers!), we found the maximum length to be 10 meters (32.8 feet).  And although we’ve only measured just a few individuals so far, the length is far cry from the 20 meters so often reported.  UPDATE: Simon Pierce commented below that it may be that one of the reasons we tend to measure smaller sharks in aggregations in coastal zones is that they are predominantly juveniles. He also notes that a “20 meter specimen was reported in the scientific literature from the Taiwan fishery in the 1990s and an 18.8 m specimen was reported from the Indian fishery (summarised by Rowat & Brooks 2012, JFB).”

What about the other big ‘un, the giant squid. How big do they get?

Beer Google Version:  Getting a handle on how large another colossus of the ocean, the giant squid, can grow is equally vexing.  In this video the reporter claims Giant Squids can reach 50 feet (15.24 meters).  Marinebio.org claims that Giant Squids can reach 18 meters (~60 feet).  Indeed the idea of a 60 foot Giant Squid appears to be part of the lore of the media (CBS, National Geographic, Discovery, Santa Cruz Sentinel to name just a few of many).

The Sober Truth:  Does the 60-foot giant squid actually exist?  No.  As Steve O’Shea, giant squid expert, published at TOMNO,

“the largest specimen known washed ashore on a New Zealand beach, Lyall Bay (Wellington) in the winter of 1887. It was a female and “in all ways smaller than any of the hitherto-described New Zealand species”, according to Kirk (1887), the gentleman who described this very specimen. Apparently it measured 55 feet 2 inches in total length (16.8m), but this simply cannot be correct, and this length almost certainly is a product of imagination or lengthening (stretching like rubber bands) of the very slight tentacular arms, as it mantle was only 71 inches long (1.8m). We know that it was not measured with a conventional tape, but was paced, as Kirk says so in his publication. A comparable-sized female (ML 1.8m) measured post mortem and relaxed (by modern standards) today would have a total length of ~32 feet (9.8m)…Of more than 130 Architeuthis specimens that the authors have examined, none has attained total length [exceeding] of 13m (42 feet). “

For my own work, I have compiled every known scientific measurement of a giant squid (these don’t include Steve’s unpublished data).  Below is a plot of how many individuals of different sizes are known to date.  The three largest washed ashore in Spain in 2003 are 36.4, 39.1, and 39.4 feet long (11.1, 11.97, and 11.99 meters).  However, as Steve mentions most giant squids rarely reach this size. Most are between 10 and 30 feet almost half of the super giant squid purported at 60 feet.

Why do we make a “big fish” out of everything?

Frankly, humans are crap at eyeballing size. We suffer from what is called size constancy.  Psychologist Irene Sperandio explains it like this:

Humans also have the tendency to tell distorted stories either for simplicity or just plain good entertainment value. In one study, participants labeled 61% of their retellings as distorted (containing exaggerations, omissions, minimizations, or additions) and 42% of their retellings as completely inaccurate (pdf is here and gives a great overview of this area of research).  The accuracy and recall of details gets even worse if we are telling a story for entertainment as opposed to accuracy. Of course, accuracy can be altered by who the audience is and how attentive they are and by the accounts of other eyewitnesses.

Humans also seem to focus on extremes.  Stephen Jay Gould acknowledged this tendency when he slammed the idea of Cope’s Rule (that size of animals increases through the fossil record and through time).

“Our strong and biased predilection for focusing on extremes (and misconstruing their trends as surrogates for a totality), rather than documenting full ranges of variation, generates all manner of deep and stubborn errors…We should remember Little Buttercup’s admonition to Captain Corcoran in H.M.S Pinafore, that ‘things are seldom what they seem,’ while we must shun the allure of bigness, for ‘bulls are but inflated frogs’.”

In short (pun intended), size does matter.  And, whale sharks and giant squids are large enough without humans helping them along.

The post Whale Sharks and Giant Squids: Big or Bu!!$hit? first appeared on Deep Sea News.