Tag Archives: shark

Fossil Friday: C. Megalodon, the true Jaws

Sharks are amazing animals, and they have been swimming the oceans for about 450 or 425 millions of years now. To put that into perspective, dinosaurs appeared some 230 million years ago, then largely died off. The first hominids (not actual humans, but human-like animals) date from around 4.5 million years ago. So sharks evolved some 200 million years before dinosaurs, and they’re still here — they’ve been around for 3 times as long as dinosaurs, and 100 times as long as hominids. Modern humans, who date back roughly 60,000 years, can’t even hold a candle to the sharks’ history.

And they’ve spent all that time becoming the best, most oiled killing machines you can imagine. Case in point: Carcharodon megalodon.

Famed fossil hunter Vito Bertucci with a megalodon jaw, measuring 3,4 m. (11 ft.) across and almost 2,8 m. (9 ft.) in height. It took her almost 20 years to reconstruct the jaw.

C. megalodon is an extinct species of shark that lived from the early Miocene to the end of the Pliocene, between 23 to 2.6 million years ago. And it was HUGE. While the exact length they could grow to is still a matter of debate, it’s generally agreed based on fossil records that the animal averaged around 18 meters (59 feet) in length, and most likely looked like a stocky great white shark.

A comparison between a megalodon (black) fossilized tooth and two great white shark teeth.
Image via Wikimedia.

Unfortunately, just like sharks today, megalodon was mostly built on cartilage, which usually decomposes before it has a chance to fossilize. What we did find is its jaws, however, and these are truly impressive.

Famed fossil hunter Vito Bertucci with a megalodon jaw, measuring 3,4 m. (11 ft.) across and almost 2,8 m. (9 ft.) in height. It took her almost 20 years to reconstruct the jaw.

For as long as it lived, it’s hard to imagine that C. megalodon had any natural predators — it’s the largest carnivorous fish to have ever lived, and it likely was the ultimate killer on the planet while it lived. It actively hunted whales and was so successful at it that researchers now believe its extinction is the only thing that allowed whales to grow as large as we see them today.

One thing is certain, though. I’m glad I’ll never have to come face to face with one.

Greenland Shark

Longest-living vertebrate is a 400-year-old Greenland Shark

Greenland Shark

Credit: Wikipedia Commons

A massive shark that can grow up to 20 feet long and lurks beneath the chilling waters of the sub-Arctic ocean might be the longest living vertebrate. Scientists say the Greenland shark could easily live to 400 years old, or more than twice as much as Jonathan, a Seychelles giant tortoise from the island of Saint Helena, which holds the record for the oldest terrestrial animal at 183 years of age.

A giant that lurks beneath the ocean

Julius Nielsen, a marine biologist at the University of Copenhagen, estimates the oldest of the Greenland Sharks freely swimming in the open ocean might be anywhere between 272 and 512 years old. Despite the broad range, even the lowest estimate clearly positions the shark as the most longevic vertebrate.

Though very large, rivaling the Great White in size, and known to eat animals like the polar bear, horse, moose, and reindeer these venerable sea beasts are quite non-aggressive and harmless to humans — unless you eat them. And because of its range and habitat, the Greenland shark is still a mysterious species for scientists. Of the 465 known species of sharks, only eight live in the Arctic, among them the Greenland shark which can grow to 6.5 meters (21 feet) in length and reach 900 kilos in weight. That makes it the biggest fish in the Arctic.

[ALSO SEE] World’s tiniest vertebrate

The sluggish Greenland Sharks can rarely be spotted, often choosing to live in deep waters, often as deep as 400-600 meters below the water’s surface. Which is why Nielsen and colleagues had to rely on specimens retrieved as by-catch in fishing expeditions. Fishermen don’t actively pursue the Greenland Sharks but catch them by mistake while setting their nets for more agreeable prey like cod or trout. They have a good reason, too — the Greenland Shark’s flesh is packed with toxins and eating it is considered highly poisonous.

The team managed to retrieve 28 female sharks measuring  31 in. to 16.4 ft. (81 cm to 502 cm). Typically, to determine the age of fish scientists study the growth bands in a calcified tissue located in the ear called the otolith, sort of like measuring the rings of a tree trunk to see how old it is. Since sharks don’t have this tissue, the researchers turned to a very unconventional proxy: the lenses of their eyes.

Eyeing the oldest vertebrate

Credit: University of Copenhagen

Credit: University of Copenhagen

Shark lenses are formed in the uterus, which means whatever the shark mother ate made its way into the offspring. This means that by measuring the radiocarbon isotopes found in the core lens, we can determine what the environment was like before a shark was born and, hence, its age. For instance, the late 1950s saw thousands of atomic bomb tests which caused a spike in the amount of radiocarbon that eventually made its way into the sea — this is known as the ‘bomb pulse’. If a shark had high levels of Carbon-14 in its core lens, on par with bomb pulse readings, it clearly means the animal is at least 60 years old.

In our case, two of the smallest sharks had a post-bomb pulse isotopic reading making them at most 50 years or younger. The third smallest shark though had radiocarbon levels right at the onset of the bomb, making it 60 years old. The rest of the 25 sharks all had pre-bomb pulse readings suggesting they were all at least 60 years old.

By comparing these readings with known levels of radiocarbon in the ocean from various years published in a database, scientists could then estimate the age of the sharks. To make the estimates a bit better, the researchers also assumed that the larger the shark the older it was. When this was factored in, they found that the largest shark they studied, a 16-foot specimen, was about 392 years, give or take 120 years.

Not only is the Greenland shark perhaps the longest-living vertebrate, it might also be a terribly difficult one to breed. Some of the smallest sharks studied measured 31 inches, making them juveniles — at age 50 to 60 years! Since Greenland sharks are known not to reach sexual maturity until they grow to 13 ft. (400 m), this means that this shark would have to wait for around 150 years before it’s ready to become a parent. Clearly, that makes them very vulnerable to extinction. Luckily they’re poisonous and smell really, really bad — this makes them very uninteresting for humans. Maybe they’re lucky.

“Greenland sharks are among the largest carnivorous sharks on the planet, and their role as an apex predator in the Arctic ecosystem is totally overlooked. By the thousands, they accidentally end up as by-catch across the North Atlantic and I hope that our studies can help to bring a greater focus on the Greenland shark in the future,” Nielsen said.

The groundbreaking paper was published in the journal Science.

 

 

Scientists build a camera with “shark vision”

We now have shark vision: researchers have built a camera that approximates how sharks see.

Photo by David Gruber.

Underwater, the world looks mostly blue to human eyes. But the sheer diversity of marine wildlife means there’s always something extraordinary to find. For David Gruber, that something is fluorescent creatures. In 2015, he found a ‘glowing’ neon red turtle, making headlines all over the world. He’s found more than180 fish species in 2014, as well as dozens of fluorescent coral species. But he doesn’t just want to discover things, he wants to understand them – why these creatures evolved in such a unique way – so he and his colleagues built a “shark-eye” camera to simulate how fluorescent sharks appear to each other. Yes, in case you didn’t know, there are also fluorescent sharks.

Fluorescent Sharks

Don’t expect the fluorescent sharks to glow brightly. Unlike the firefly, they don’t generate their own light. They have specially adapted molecules in their skin which absorb specific wavelengths of light and emit that light in other wavelengths. As is the case with other marine fluorescent animals, they absorb blue light and transform it into green, red, or orange.

The glow is hard or impossible to notice with human eyes. At most, we could see an eerie greenish glow and that’s pretty much it. But for sharks this probably is an outstanding feature. So Gruber set out to understand how sharks see.

He started by dissecting shark eyes and learned that they are monochromats. This means that unlike humans, who construct the colors from three pigments, sharks use just one pigment. It makes a lot of sense when you think about it.

“The ocean is this huge blue filter, and it becomes more perfectly blue as you go deeper,” Gruber tells National Geographic. If there aren’t any other colors of light to see, why bother?

The study he published documents fluorescence in two species: chain catshark (Scyliorhinus rotifer) and the swell shark (Cephaloscyllium ventriosum). The swell shark is covered by small, bright green fluorescent spots over much of its body, but females have a distinctive “face mask” of glowing spots. Meanwhile, the chain catshark chain has an alternating light and dark fluorescent pattern but no spots. The pattern is stronger in females, but this time there is no face mask. These sharks are generally nocturnal and solitary creatures, but not much is known about their behavior. However, it seems plausible that fluorescence is an important feature for them, likely for finding potential mates.

“But they might also be using biofluorescence to communicate in a way we haven’t thought of,” says Gruber. “It reminds me of when researchers first tuned in to the high frequency of bat sounds, and they discovered all this hidden chatter. They had to then figure out what it meant.”

They then conducted a review of the literature, to see if other species exhibited similar features. The team found that this ability developed independently at least three times among the sharks and rays, in the distantly related families Urotrygonidae (American round stingrays), Orectolobidae (wobbegongs), and Scyliorhinidae (catsharks). Because it emerged in such distant families and in so different ways, it seems that fluorescence is quite a valuable trait and can be achieved in more than one way. Furthermore, it shows that there are likely other fluorescent sharks just waiting to be discovered.

Ultimately, they used what they learned about this feature to create a camera with “shark vision”.  It’s “a very high-resolution movie camera,” Gruber says, fitted with filters that simulate what a shark would see. The results are what you can see above.

Now the real question is, if a shark sees something like this, what does it mean for it? What information can it draw based on these fluorescent patterns? Does the extra light serve some specific purpose? Is it simply to find other members of its species? These are all questions researchers hope to answer in the future.

But not everyone is convinced. Nathan Hart, a biologist at Macquarie University in New South Wales, Australia, who studies shark vision, believes fluorescence has little importance. He told the Atlantic:

“It makes perfect sense if you think about life in the blue ocean,” Gruber says. “Why wouldn’t they come up with a way to make their world richer in texture?”

But being able to see as humans see is a great achievement in itself. It helps us understand these magnificent predators which have been around for hundreds of millions of years – and which we’re quickly driving to extinction.

“This work forces us to take a step out of the human perspective and start imagining the world through a shark’s perspective,” says Gruber. “Hopefully it will also inspire us to protect them better,” he says, noting that an estimated 100 million sharks are killed by people each year.

Human limbs might have evolved from shark gills

A controversial idea has just received some significant backing, as a group of Cambridge researchers found evidence supporting human limbs evolving from shark gills.

Credit: J. Andrew Gillis

In 1878, German anatomist Karl Gegenbaur proposed an evolutionary link between the gills of cartilaginous fish (such as skates and sharks) and the limbs of vertebrates. The idea was popular for a short bit, but was then generally discarded due to the lack of supporting evidence in the fossil record. However, support may come in the form of a genetic study – specifically, something called the Sonic hedgehog gene.

“Chondrichthyans (sharks, skates, rays and holocephalans) possess paired appendages that project laterally from their gill arches, known as branchial rays. This led Carl Gegenbaur to propose that paired fins (and hence tetrapod limbs) originally evolved via transformation of gill arches,” the study writes.

The Sonic hedgehog gene makes sure all your limbs are in the right place and have the right size. It dictates how the limbs will grow, maintaining the right direction for the skeleton growth. In cartilaginous fish, the gills are protected by flaps of skin supported by arches of cartilage. Interestingly, the purpose of the Sonic hedgehog gene plays the same role for the fish, directing the growth of gills and cartilage. This could indicate that the gene’s function remained unchanged across millions of years of evolution. Writing in this week’s edition of the journal Development, MBL scientist Andrew Gillis and his colleagues support this idea:

“Gegenbaur looked at the way that these branchial rays connect to the gill arches and noticed that it looks very similar to the way that the fin and limb skeleton articulates with the shoulder. The branchial rays extend like a series of fingers down the side of a shark gill arch,” said Andrew Gillis, who led the research, in a statement. “The fact that the Sonic hedgehog gene performs the same two functions in the development of gill arches and branchial rays in skate embryos as it does in the development of limbs in mammal embryos may help explain how Gegenbaur arrived at his controversial theory on the origin of fins and limbs.”

In order to show that the gene works in the same way, they inhibited it at several stages of skate’s development. They found that when inhibited early in development, branchial rays grew on the wrong side of the cartilage arch. When inhibited later in development, the branchial rays grew on the correct side, but were fewer in number.

“Taken to the extreme, these experiments could be interpreted as evidence that limbs share a genetic programme with gill arches because fins and limbs evolved by transformation of a gill arch in an ancestral vertebrate, as proposed by Gegenbaur,” Gillis said.

“However, it could also be that these structures evolved separately, but re-used the same pre-existing genetic programme. Without fossil evidence this remains a bit of a mystery — there is a gap in the fossil record between species with no fins and then suddenly species with paired fins — so we can’t really be sure yet how paired appendages evolved.”

Of course, this is still a hotly debated claim. It doesn’t seem likely for this gene to develop separately, but the fossil evidence is still missing. Additional research is needed to fully compare the functions of the gene, but even if this is further confirmed, I doubt the theory will be widely accepted without fossil evidence. Unfortunately, this type of evidence can be difficult or impossible to find, so this will likely remain an open question for year to come. But the premise is there, and the prospect is certainly interesting.

Journal Reference: A shared role for sonic hedgehog signalling in patterning chondrichthyan gill arch appendages and tetrapod limbs

Fossil Friday: Helicoprion

Helicoprion bessonovi fossil, housed at The Idaho Museum of Natural History’s Earth Science collection.
Image via imnh

Helicoprion is an extinct genus of shark-like, cartilaginous fish that lived from the early Permian (~290 m.y. ago) all through to the massive Permian-Triassic extinction episode (roughly 250 m.y. ago.)

Their most distinctive characteristic, the lower jaw, baffled scientists for over a hundred years. This “tooth-whorl” structure was the only bony tissue to be found in the animal’s body, and the only part of it that fossilizes under normal conditions — so for all this time, paleontologists didn’t have enough context to describe it beyond “round…thingy. With teeth!”

In 2011 IMNH researchers performed a CT scan on an exceptionally well preserved specimen that contained the elusive jaws. The research eventually led to the first accurate reconstruction of the shark as well as placing in its proper position on the great tree of life.

The CAT scans also allowed a partial reconstruction of the rest of the animal, estimated to have been 3-4 meters (9.8 to 13.1 feet) long, but some potentially grew to almost 7.5 meters (24.6 feet) long. As their jaws aren’t resilient enough to break shells, Helicoprion most likely dined on soft prey, such as mollusks.

sharks_infographic

How many friends would a shark have on facebook?

Sharks have a reputation of solitary predators. They’re not the life of the party, so to say; one new research casts doubt on this assumption, though. The findings suggest that sharks, or at least Sand Tiger sharks, have a complex social structure not all that different in some instances from highly social mammals like dolphins, chimps or even humans.

Sand Tiger sharks often get mistaken for great whites. They are in fact harmless and never attack humans. Photo: Danielle Haulsee.

Sand Tiger sharks often get mistaken for great whites. They are in fact harmless and never attack humans. Photo: Danielle Haulsee.

Tracking sharks is very difficult. Most studies follow sharks kept in pens or in a lab environment but the researchers at University of Delaware in Lewes used acoustic tags to track the movements of over 300 individual Sand Tiger sharks. The tracking was made in the wild and took a whole year.

For this reason, not a lot is known about how sharks behave in the wild. Every year Sand Tiger sharks undertake long migrations. This means they always appear seasonally – normally within a specific time period of several weeks – at the same places. In the summer, Sand Tigers congregate together in the shallow waters of the Delaware Bay. For the rest of the year, though, it’s all a black box for biologists.

The initial readings from only two sharks show that each individual encountered nearly 200 other sand tigers throughout the year, as well as several individuals from other shark species. In some instances, the same sharks were encountered multiple times throughout the year. Interestingly, the sharks congregate in groups but only in some locations and for a limited time. This is what the scientists called fission-fusion social behavior.

sharks_infographic

The researchers found it odd that encounters were lacking during early spring and winter. It’s thought that during these times, it’s better if the sharks venture solo or in very small groups because food stocks are limited.

“If you’re living with a group, there could be some kind of protection or information sharing that comes with being in that group,” said Danielle Haulsee, a PhD candidate in oceanography at the University of Delaware in Lewes. “But if there’s a lot of competition for food resources or mating resources, then it’s not beneficial anymore to be in a group, and you might swim away from your group and go off on your own.”

Over the last decades, Sand Tiger populations have seen a drastic decline. Though they looks pretty threatening, Sand Tigers are harmless. Alas, many are killed or chased away because they look dangerous. With their study, Haulsee and colleagues hope to fill in a lot of blanks. For instance, we don’t know yet if Sand Tigers congregate in groups based on family or other characteristics like sex or size. This information might prove invaluable for conservation efforts.

The initial findings will be shared at the 2016 Ocean Sciences Meeting.

The prickly shark, Echinorhinus cookei, is a large predatory shark with a pan-Pacific distribution. Prickly sharks are amazing looking and have a traditional shark body type although they are a bit thicker around the middle than many other species. Photo: Wikipedia

Some deep-water sharks can float up, contrary to conventional wisdom

Researchers at University of Hawaii, Manoa in collaboration with a team from the University of Tokyo were surprised to find not one, but two species of deep-water sharks that have positive buoyancy. Most sharks have a negative buoyancy, meaning if they stop swimming they’ll sink to the bottom, and some researchers have posited that there may be some species with neutral buoyancy. Finding sharks that defy this conventional wisdom is definitely an important discovery. Now the researchers are trying to find out how the positive buoyancy is attained and whether other shark species have this ability.

Floating sharks

The prickly shark, Echinorhinus cookei, is a large predatory shark with a pan-Pacific distribution. Prickly sharks are amazing looking and have a traditional shark body type although they are a bit thicker around the middle than many other species. Photo: Wikipedia

The prickly shark, Echinorhinus cookei, is a large predatory shark with a pan-Pacific distribution. Prickly sharks are amazing looking and have a traditional shark body type although they are a bit thicker around the middle than many other species. Photo: Wikipedia

Sharks’  cartilaginous skeletons are less dense than bones, and most employ an oil-filled liver to increase buoyancy. Despite this, sharks can’t float and have to start swimming at some point to avoid sinking to the bottom of the ocean. Some scientists have considered that maybe some species are neutral buoyant based on observations of some species which live in austere environments (low oxygen, few food resources). You can imagine how remarkable it was for the Hawaiian researchers to discover that the  sixgill and prickly sharks have slightly positive buoyancy which helps them slowly rise to the surface without any effort.

The team strapped cameras, lights and sensors to the several specimens from each species. Each 30 seconds, a strobe would turn on and light the shark’s surroundings, while a camera instantly took a picture. Meanwhile, sensors recorded the temperature and depth of the water. To record when the shark began to swim and measure the effort that went into the process, an accelerometer was also added. After a predefined time, the whole pack detached from the shark and rose to the surface from which it was collected by the researchers.

The researchers were so surprised by the results that they had to recheck their equipment and start fresh with a new set of experiments. But the results stayed consistent: the sixgill and prickly sharks can float. . “It was not at all what we expected to find,” said study co-author Carl Meyer, an assistant researcher at the University of Hawaii at Manoa’s Hawaii Institute of Marine Biology. “Conventional wisdom suggests sharks are generally negatively buoyant — they’ll sink if they stop swimming.”

“When I first downloaded the camera, I thought it had failed because all I saw were thousands of completely black frames. Suddenly a string of images appeared with a brightly-lit, alien-looking reef and strange deep-sea invertebrates. I was elated and realized that the black frames resulted from the shark swimming around too high in the water column for the camera strobe to illuminate the seabed.”

Data from the accelerometer clearly showed that when sharks swam, the muscles and tail worked harder at any given speed when the individuals were going up. “When they were going uphill, they could glide for minutes at a time without beating their tails,” Meyer added.

It’s not clear how this trait appeared, however. Deep-water sharks spend their day time at lower depths (~600 meters), and start swimming towards the surface from sunset to a higher depth (~300 meters). The buoyancy could be a physiological trait which allows the sharks to explore the cold, deep habitats. It may also be result of some evolutionary mechanism that allows the sharks to sneak up on prey or conserve energy. There’s still much to learn, that’s for sure.

“Finding positive buoyancy in [deep-sea] sharks is demonstrative that we have a lot to learn about deep-sea animals and how they survive,” Meyer said.

Findings were documented in the journal PLOS ONE.

Sharks act like Math Geniuses

At least in one aspect, sharks behave as world class mathematicians – although the cause may be sensibleness more than cleverness.

Image via Flickr.

The behavior associated to both mathematicians and sharks is called the Lévy flight. A Lévy flight is a random walk in which the step-lengths have a probability distribution that is heavy-tailed. In other words, it’s a seemingly complex form of random walk comprising clusters of short step lengths with longer movements between them.

“Lévy flights, named after the French mathematician Paul Lévy, arose in a purely mathematical context in the first half of the last century,” Andy Reynolds of Rothamsted Research told Discovery News. “Sharks and other marine predators use Lévy flight to locate their prey. “

Indeed, sharks aren’t the only marine predators to exhibit this kind of behavior. But why do they do it – and how? That’s what Reynolds set out to answer, and he does have one theory:

“[The technique] can be advantageous when searching for randomly distributed resources because they reduce ‘over sampling’ without the need for cognitive maps and sophisticated navigational abilities.”

That may or may not be true, but it still doesn’t provide any hints as to why they do this. The only theory they came up with was that they follow queues from their environment, such as turbulent waters for example.

“This seemed reasonable,” he said, “because turbulent flows are very complex — the whirls within whirls within whirls like the ones Leonardo da Vinci drew — and within which could be lurking the necessary clues.”

Using mathematical simulations of what is known as “turbulent theory,” they managed to show a really surprising thing: Levy flight movements arise naturally when marine predators encounter patches of relatively strong turbulence.

They ran computer simulations using information observed on sharks, and the results seem to confirm the theory.

“There is no need for sharks to have evolved sophisticated neurological and physiological processes for the execution of the Lévy flights, which are the lead to optimal foraging, ” he said. “Lévy flights will come for free if they just turn away from patches of strong turbulence.”

However, the exact biological mechanism is much more complex than can be currently simulated in models. But the cause may actually be pretty simple: maybe sharks don’t want to be pushed around by turbulence, and this is why they started doing Lévy flights.

“It is sensible to avoid being pushed around by turbulence, ” Reynolds said. “Being pushed around causes damage and disorientation. Better to simply turn away when the going is tough.”

Shark Week Lied to Scientists to Get Them to Appear in “Documentaries”

An accurate depiction of what Shark Week is all about these days.

I’ve given up on watching TV years ago – the occasional documentary or football game (guilty) once in a blue moon will do for me. But recently, there are fewer and fewer quality documentaries being shown on TV; not to say that there aren’t any awesome ones being made – there’s excellent documentaries coming out every year, but TV channels like Discovery or History seem to have dropped the bar in the past few years. Now, Discovery Channels’ “Shark Week” is a great example of that low quality. But why are reputable scientists allowing themselves to feature in this pseudoscience mumbo-jumbo disaster? The answer is simple, and unethical: Shark Week producers have been lying to them, just like how they’ve been lying to their audience.

Jonathan Davis now works for the Texas Parks and Wildlife Department, but a while ago he was studying the bull sharks in the Gulf of Mexico for his Masters research. It was then that he was approached by a Shark Week film crew.

“They were interested in the sharks in Louisiana, and I was the person doing the research there,” Davis says.

Naturally, he accepted, wanting to share his research with the world. But he soon started suspecting something was a bit fishy. Producers offered him no information about what their project was:

“I asked a few of the crew members, including the producer, what the show was going to be about. I never got a straight answer and the producer seemed to avoid the question. I was just told it would be combined with some other filming to make one show about Louisiana shark research.”

He was shocked when he found out what his interview and research was being used for. In 2013, a Shark Week special called Voodoo Shark, which was about a mythical monster shark called “Rooken” that lived in the Bayous of Louisiana. His answers, from unrelated questions were edited in such a way that it seems that he believes in the monster, and is actually looking for it. That’s right, Shark Week lied and edited unrelated answers to manipulate and mislead the viewers. Davis explains how this trickery was carefully planned and done:

“Throughout the interview I was fed certain words to rephrase my sentences in ways that the producer thought would spark more interest. Some words or phrases they asked me to say were beyond anything I would say on my own and I refused. However, they were clever in their questioning by getting me to respond to a vague question with a response that could be used as an answer to a completely different question. The prime example that was used on the show was towards the very beginning of Voodoo Sharks. The voice-over introduced my researchers and I as we were riding in a boat out looking for sharks on the edge of the Lake. They said, “They believe that if there is a monster shark entering Lake Pontchartrain it is likely sticking to this area…” and then it pans to a clip from my interview where they asked me, “Do you think there are large Bull Sharks in these bayous and swamps around Lake Pontchartrain?” so my response was to THAT question. They used my response to one question to make it sound like I believed in this monster shark ‘Rooken’ that they had just laid the groundwork for being real as a preface for the whole show.”

This isn’t a singulary case – Shark Week did the same thing this year, in 2014. Kristine Stump, a Postdoctoral Research Associate at Shedd Aquarium, will be featured in the 2014 Shark Week documentary Monster Hammerhead. Here’s the description for the documentary:

“Monster Hammerhead explores a legendary hammerhead shark that has been patrolling Florida’s shores for the past 60 years. Now, a team of scientists and anglers look to explore the mystery and find out if the legend could be real.”

Hammerhead are amazing creatures, it’s sad that media seems to be more interested in misrepresenting and antagonizing them.

So, let’s take it from the start – great hammerhead sharks have been documented to live 44 years at most. While it’s not impossible for them to live beyond that, for a “legendary shark” to “patrol Florida’s shores” for 60 years… that seems more than unlikely. But this is not even the worst thing – Stump was lied by the production crew, who told her the documentary was about something else.

“The basic premise was a camera crew was dropping in on real scientists doing actual hammerhead research,” Stump said. “We’d talk about the research goals and the challenges we face in trying to achieve those goals. Monster Hammerhead does not match the description of what we filmed.”

Now, scientists suggest taking these documentaries with a huge grain of salt – or don’t look at them altogether. But they believe there can still be some good coming from Shark Week.

 “While we can’t control the editing, we can control what we say on-camera,” she said. “By being involved, I could have the opportunity to be a voice of real science amid an otherwise sensationalist line-up. If we want to make a difference in Shark Week, then be the difference.”

Or, if you don’t want to make a difference and risk being misquoted, simply avoid the show:

“Had I known they would combine it with those ridiculous fishermen to make a show about a mythical shark I would have had some serious second thoughts about participating,” Davis said.

Meanwhile, it seems clear that Shark Week is one of the worst sources of information regarding sharks. Shame on you, Discovery! Go sit in a corner and think about what you’ve done!

national_geographic

Sharks may confuse kitesurfers with birds and attack them

national_geographic

Photo: National Geographic

A new study investigated the circumstances under which a  15-year-old kitesurfing male died after a tiger shark attacked him in the South Pacific. Their analysis suggests that attack took place mostly likely because the kitesurfer’s motion was confused by the shark with a bird overtaking the water. In light of other similar shark attack cases, the researchers advise any kitesurfing in waters known to harbor sharks should be made with extreme care.

[NOW READ] What’s the chance of being attacked by a shark?

The researchers studied the remains of the teenager who was attacked on  May 21, 2011 while  kitesurfing with a group of five in waters off the city of Koumac on the northwest coast of New Caledonia. The young man’s friends report the victim was attacked two times, after the teenager initially lost his board, but continued to hold his kite, pulling him across the water’s surface. The first attack pulled most of the tissue from his left leg, and judging from the location of the attack and tooth bite impressions, the scientists concluded the teenager was killed by 10-foot-long tiger shark.

“[…] when a kitesurfer does lose his board and is pulled by his sail (kite) along the surface, such as in the present case, with relatively high speed and intermittent touching down on the surface, it could represent a strong feeding stimulus for a shark.”

Learning by doing

Unlike marine mammals, sharks learn to navigate their surroundings and survive by experimenting. No shark youngling is thought beforehand what is good to eat and what isn’t, so often times a shark’s life involves a series of trial and errors. Tiger sharks and certain other sharks are known to feast on birds, as well as sea snakes, fish, turtles, marine mammals and more. Typically, if a shark is old enough, he will stick with what he knows and won’t attack humans. When on a surf board or kite, humans look like turtles or birds, respectively.

 “Sharks, as a main difference with marine mammals that learn from their older conspecifics, have to learn by themselves…So (attacking a human) might be a mistake at the beginning and then (later become) a more ‘normal process’ for a given shark to prey on a human being,” said Eric Clua, a marine biologist and veterinary surgeon based in French Polynesia.

The authors conclude that people venturing for fun in treacherous waters should do so knowing full well the dangers they expose themselves too. The sharks aren’t to blame; the responsibility is all on them.

“The sea is not a zoo where you go to see dangerous animals without any chance of being wounded,” Clua said. “If you go to sea, you must accept the rules and risks, like an alpinist accepts the risk of falling from the mountain. Why should we cut the mountain if he falls and dies?”

The findings were reported in the Journal of Forensic and Legal Medicine.

 

Historic day for shark protection

We’ve been telling you on and on – millions and millions of sharks are perishing each year, mostly due to shark finning – people fish sharks, cut off their fins, them let them go, only to suffer a slow, painful, humiliating death, unable to move at the bottom of the ocean. Shark fin soup is a delicacy everywhere from Indonesia to mid US, and the situation sharks are in right now is pretty dire to say the least. But there is hope after all.

shark finning

Three types of critically endangered but commercially valuable shark have been given added protection at the Cites meeting in Bangkok. The body regulates trade in flora and fauna – they pretty much say what’s legal and illegal in terms of what plants and animals you can sell. Shark supporters in the group have been trying to adopt this measure since 1994, but even after 19 years, it’s better late than never.

“They’ve come to realise, particularly for those with hammerhead stocks, the tourist value of these species and the long term future that will be protected by a Cites listing,” said Dr Colman O’Criodain from WWF International.

The thing is that the accord doesn’t ban shark trade, but it regulates it. Basically, both countries importing and exporting sharks must have a license to do this, and there’s a limit to how much you can trade. This will definitely be abused and corrupted, but this is the first measure of this type ever voted, which is still a historic move.

“It is really significant for Cites to come of age like this,” Dr Susan Lieberman explained. “To say we can deal with these species, we can manage the international trade and lets not be afraid of marine species.”

Another significant measure is funding poorer countries who cannot regulate shark fishing themselves – funding which will probably come from the European Union.

“If there’s a need for it the funding will be available,” Feargal O’Coigligh told the meeting.

Shark embryos stay still to avoid predators

Sharks are the ultimate predators, comfortably sitting at the very top of the food chain; but even they have their enemies (the biggest one being us, of course), especially when they’re small – nobody fears a small shark. But even in their defenseless period, sharks have managed to find a way to adapt.

Australian researchers found that the embryos know when a predator is coming by detecting its electric field, despite being confined in the small case. Sharks use jelly-filled pores on their heads called electroreceptors to recognise other animals, and especially other predators.

“Embryonic sharks are able to recognise dangerous stimuli and react with an innate avoidance response,” explained Ryan Kempster, a shark biologist and member of the research team.

The embryos (of some sharks) are encased in a leathery egg shell, developing independently from their mothers, something which renders them vulnerable to several species. When the embryo starts to grow, the egg starts to open, marking the moment when outside predators can detect the embryos movement. Scientists were expecting to find some sort of adaptation to this problem, but they were surprised to see just how efficient the method really is.

shark embryo

“Despite being confined to a very small space within an egg case where they are vulnerable to predators, embryonic sharks are able to recognise dangerous stimuli and react with an innate avoidance response,” says Kempster. “Knowledge of such behaviours may help us to develop effective shark repellents.”

The study was conducted on bamboo sharks, a species that grows up to 1.2m in length, most often found in the western Pacific or in the Australia-New Guinea region. The thing is, this kind of study could be very useful for humans in developing shark repellants, and also for saving sharks from being killed as by-catch in fishing nets.

Via University of Western Australia

Hope delayed from sharks in the Atlantic

Sharks are in a dire position right now, with their numbers decreasing by the millions each year. However, conservationists failed to win new protections for threatened sharks in the Atlantic Ocean at the annual meeting of a major international fisheries commission; they still have hope for following years though, because for the first time, the International Commission for the Conservation of Atlantic Tunas has agreed to make some changes in regulations, including shark management.

“This is unprecedented,” says Elizabeth Wilson of the Pew Environment Group, an environmental advocacy organization based in Washington, D.C.

Hang in there!

I’m not sure though if this is truly that much of a good news, or if this is just throwing a bone which environmentalists are just chowing down. ICCAT, which was established in 1966, manages some 30 species, including swordfish, marlin, and other tunalike species; they are not directly responsible for sharks, but an incredible number of sharks are actually caught in tuna nets.

At the meeting where this was decided, seven proposals were actually brought to the table, but only one passed – urging members to comply with measures already on the books.

“It sets the stage for real shark management in the Atlantic,” says Wilson, who expects the process will take a couple of years.

Americans are eating endangered shark soup

Would you eat shark fin soup? Please, tell me that the answer is ‘NO!’. Nearly a third of all shark species are endangered, due to wreckless killing – mostly for soup. Proceed at will, but the article contains some gruesome pictures.

The champions’s tragedy

Freshly cut shark fin.

Sharks are on top of the food chain – they have been for 400 million years, 100 million years since before dinosaurs even appeared on land. They are the most adapted, the most agile, probably the deadliest creatures in the world. Yet their numbers are dramatically declining because people want to eat shark fin soup, considered a delicacy in several parts of the world, America included, it seems.

Most of the times, the fate they suffer is absolutely dramatic: the sharks are captured, their fins are cut off, and then they are released back into the water, only to suffer an excruciating death, unable to move, exiled at the bottom of the sea. Each year, humans kill over 100 million sharks worldwide, including the tens of millions killed only for their fins.

Also, not only are sharks remarkable creatures, but they are also vital to the health of the oceans: as top predators, or ‘apex’ predators, they feed on animals below them in the food chain, helping maintain a balance in oceanic ecosystems, ultimately protecting coral reefs and seagrass beds. Without a sufficient number of sharks, here’s how things will most likely go: animals typically eaten by sharks will grow uncontrolled, and their food supply (which includes coral reefs, algae, other fish, etc) will drop massively, ultimately up to the point of no return, at which the balance of the ecosystem is broken permanently, with cascading uncalculable effects.

Americans eat shark fin soup

A team of researchers from the Pew Environment Group and Stony Brook University in New York set out to collect and genetically test samples of shark fin soup across the United States. They gathered 51 samples from restaurants in 14 different cities. A sample contained scalloped hammerhead, which is endangered, while many contained fin of vulnerable and near-threatened species, including bull, smooth hammerhead, school, spiny dogfish and copper sharks. Interestingly enough, some samples didn’t contain shark DNA at all.

This is the first major shark soup testing ever made, and the results highlight some crucial aspects. First of all, people are consuming sharks, but they don’t really know what they’re eating. Is it a commonly found species, and endangered one, an almost endangered one, or what?

This – this is what you are eating. Bon apetit…

Second of all, the study clearly shows shark fishing has to be stopped as much as possible. As many as 73 million sharks are killed for fins yearly, and the trend shows no signs of slowing down. What’s interesting is that several people involved in the study are shark attack survivors, some of which have lost limbs, but are now shark advocates, because they understand the global importance of these magnificent creatures.

Via Discovery