Tuesday, November 27, 2018

Shark Diver and Great White Shark research.

Shark Diver has been running trips with Great White Sharks at Guadalupe Island since 2000. Our owner, Martin Graf, encountered these sharks while SCUBA and freediving there for about 10 years prior to the first shark dive. Mostly while spearfishing, he, along with many  other divers, started to encounter more and more great white sharks, which led us to explore the possibility of specific shark diving there. Little did we know that we discovered arguably the best place in the world to observe these awesome creatures. Typically crystal clear waters, with male and female sharks of all sizes in abundance, Guadalupe Island has become the premier place to dive with Great White Sharks.


A couple of years after we started shark diving, the Marine Conservation Science Institute, MCSI, began putting together a photo ID database, to keep track of all the sharks sighted at Guadalupe Island. Our ability to identify the individual sharks is what really got me hooked on shark diving. After a few expeditions, I started to get a little bored with watching the sharks seemingly doing the same thing over and over. Luckily for me, just before I decided to stop going there, something amazing happened. A shark, later named "Shredder" swam really close to the cage and made eye contact with me. I realized that he was as much interested in us, the divers, as we were in him. He made eye contact with each individual as he swam along our cage. Realizing that he was checking me out instantly fascinated me. Knowing that they look at us as individuals made me realize that they are all individually different as well. For a lack of a better word, they all have different "personalities".  Thanks to the Photo ID database, we have the ability to keep track of all the different individuals we encounter at Guadalupe. We use the transition from the white belly to the grey top, which is like a fingerprint, along with mutilations and individual characteristics to identify the sharks. So now, after diving with the Great White Shark for 18 years, I'm more excited than ever to go back. I don't care if it is the last dive of the last trip, I'm always eager to go into the water. Who is back? Who is new? What are they up to now? I can't wait to go back.


Of course maintaining a database involves some expenses. It is time consuming work to look through literally thousands of pictures and videos, to determine who all the sharks that were sighted are. Initially the research was funded through grants, but after about 2012, those funds ran out. When Nicole Lucas from MCSI told me that the research was no longer funded, we decided that we had to do something to keep financing that important database. Shark Diver specializes in identifying each individual shark and giving our guest all the information about them. What year did we first see it, what has this shark done in the past, is it a brand new individual that we have never seen before? These are the things we like to share with our guests and that would of course be impossible without an updated and maintained database. The need to maintain this database is why we came up with the concept of our "Science Expeditions". Our expeditions are designed to raise funds for MCSI and specifically for the maintaining of the database. Shark Diver donates a spot on the expeditions hosted by Nicole to MCSI, and our divers on all of our trips get a copy of that photo ID database. On the expeditions where Nicole Lucas acts as the host, she shares the results of her research with our divers. Not only do you support the ongoing research by joining us on our expeditions, but you'll learn how to identify the individual sharks you see. How cool will it be when you watch shark week the next time and you can say "This is the shark that swam right by me!"? All of our expeditions are either hosted by Nicole or by our owner Martin Graf, who has been diving with these sharks since before there was shark diving at Guadalupe Island. He probably has more hours observing these sharks than anyone at the Island.


Shark Diver is committed to not only give you an experience of a lifetime, but to also foster a personal connection to the sharks you encounter, all while supporting conservation. Shark Diver also started the Shark Free Marinas, which has since been taken over by the Humane Society.

 Let's go shark diving!

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.

Thursday, October 25, 2018

Deformed shark at Guadalupe Island

During our last expedition to Guadalupe Island we encountered "Slash Fin", a shark that has been seen previously and is in our database. She is a very active shark, swimming around normally and exhibiting all the typical white shark behaviors.

There is however something very different about this shark. Aside from a big lump on her side, she only has 3 visible gill plates on her left side. When looked at from the top, the left side of her head is pretty straight, while the right side curves out around her gills. It doesn't look like she is getting much water through her left side gills either and she seems to be breathing mainly through her right side gills.

Check out the video below. Aside from a nice bite injury she has, there are only 3 visible gill plates.

When you look closely, you can see that she has 5 gill slits, but 2 of her gills are completely covered by another gill plate. The bite on her gills has nothing to do with this oddity, since she has looked this way since we first met her and the injury is new.

Aside from her gills, she also has a deformed dorsal fin, with the trailing edge looking all ragged. It could be due to an injury, but I don't see an obvious signs of a trauma there.

On her right side, just behind and below her dorsal fin, she has a growth that is sticking out at least 6 inches. Is it a tumor, or is something embedded in her body?

Watch the video below and check out that growth for yourself.

Slash fin is a subadult female and about 13' in lenght. Despite her deformities, she doesn't exhibit any signs of distress and seems to be doing well.

The longer I dive with these sharks, the more I'm amazed by the new things we discover and learn about them. Are her deformities genetic? Is it a birth defect? Or....? I don't know, I'm just reporting my observations. Any scientists out there want to take a look at this?

Come join us on one of our expeditions to Guadalupe Island and meet our sharks face to face.

Let's go shark diving!

Martin Graf
CEO Shark Diver

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.

Thursday, October 11, 2018

Meet our Great White Shark "Luca Arnone"


"Luca Arnone" listed as #163, is one of our recent additions to the photo ID database at Guadalupe Island. We first met him in 2013 and he has been coming back every year since.

2 years ago "Luca" looked a bit rough. He was partially wrapped in a thick rope, which fortunately was being removed by Dr. Mauricio Hoyos, the local researcher at Guadalupe Island. The cut caused by the rope was not too deep and since white sharks have an amazing ability to heal, it did not cause him any permanent harm. When he swam by my a couple of weeks ago, his injury was barely noticeable, with just a faint black mark remaining.

"Luca" is a fairly small shark, probably just shy of 12', but he doesn't seem to mind the bigger sharks and is a frequent visitor to our cages. 

Luca was named by one of our diver, who named 2 different sharks, one after his son, Luca and the other after his daughter Milana. Naming a shark is one way you can support the ongoing research at Guadalupe Island. The Marine Science Conservation Institute, "MCSI" who maintains the photo ID has various levels of sponsorship available, including naming a shark.

Another way you can support "MCSI" is by coming on one of our "science" trips. A portion of these expeditions goes to fund the research and Nicole Lucas-Nasby, the researcher maintaining that database is coming along as the host. She is sharing the results of her research with you and if we encounter a new shark, you'll also have an opportunity to name that shark. How cool would it be, if you see a shark that you named on "Sharkweek"?

If you want to find our for yourself what it's like to come face to face with a great white shark and maybe name one of these sharks, come join us on one of our expeditions. We do have some spaces open and would love to introduce you to our sharks.

Call 619.887.4275, email crew@sharkdiver.com or visit www.sharkdiver.com for more information.

Let's go shark diving!

Martin Graf
CEO Shark Diver

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.

Sunday, October 7, 2018

Awesome new conservation effort in Fiji!

When we dive with Bull Sharks in Fiji, we always go with Beqa Adventure Divers "BAD", because "BAD" is awesome. "Dashark", who's behind their operation is the guy who was the driving force that got the Shark Reef Marine Reserve designated as a national marine park.

Fortunately for the environment, "Dashark" can't leave well enough alone, he's always looking for the next opportunity to improve things. After also being involved with the establishing of "Mangroves for Fiji", he is now involved with "My Fijishark".


Instead of me telling you what it is all about, here is all the info directly from his blog http://fijisharkdiving.blogspot.com/

We were contacted by the UNDP several months ago. The backdrop were the UN's Sustainable Development Goals in general and SDG 14 = Life Below Water in particular. 
They told us that they wanted to explore alternative solutions and financing mechanisms by partnering with the private sector as opposed to embarking on the usual NGO route, and that we had come to their attention due to our long track record in conservation and ecotourism.

We gladly agreed to a meeting.
Ever since the historic Fiji-led Ocean Conference (and here), we knew that something big was brewing and have been exploring avenues to lend a helping hand if and when Government would pull the trigger and start with the implementation. At stake are not only Fiji's Shark and Ray commitment but among several others, this specific pledge for delivering improved coastal fisheries management. 

Like I said yesterday, the SoPac is running out of fish, and Fiji is certainly no exception. 
Case in point, as Kerstin has been repeating her ground-breaking interviews, it has become sadly apparent that the situation has since deteriorated considerably whereby as the price of seafood keeps increasing,  overfishing and poaching especially here in Viti Levu have become ubiquitous. In essence, we are witnessing what has already happened elsewhere, i.e. that more and more previously artisanal subsistence fishermen have morphed into small-scale commercial fishermen, with locally devastating consequences - and like already stated, we surely cannot hope to succeed in conserving Shark populations if we continue to obliterate their prey and destroy their environment!

Possible solutions?
Look no further than this old post advocating community involvement and ecotourism, etc, etc - but of course the controversy about who really owns Fiji's traditional fishing grounds, or quoliqoli is far from being resolved and Government resources remain scarce.

Sorry it is so long, and for the many links - but as always in the real world it is complicated!

Back to My Fiji Shark.
We did meet several times and after some lengthy brainstorming, we resolved to focus on two principal projects
  • Assisting Government in implementing and enforcing any upcoming Shark and Ray management and conservation measures. This would involve launching a nifty and innovative campaign and likely cost approx. FJD 20,000.00 in its first year, after which the fines collected would hopefully cover the costs.
  • Developing and funding 3 community-based 5-year pilot projects that would trial some simple yet hopefully effective coastal fisheries management measures, this in view of hopefully upscaling them to national level if successful. This would cost approx. FJD 30,000.00 per year and most certainly require some co-funding by other quarters.
  • Any surplus could then be set aside and used for our long-term goal of establishing a more permanent Shark research presence in Fiji, this possibly including a proper field station but also research internships etc. But that's another story altogether.
And the funding?
Very much in line with the new trend towards mobilizing the private sector to assist in Ocean Finance (read this!), we resolved to create My Fiji Shark as the vehicle for collecting those funds. Natasha and our marine scientists will run and manage the adoption program, whereas the UNDP and the Sustainable Tourism department of the SPTO will be acting both as facilitators and marketing entities but also ensure the required transparency and accountability =  you can obviously rest assured that this is certainly not aimed at enriching BAD or its staff and directors!
As to why you should adopt.
Needless to say that on top of having very specific and measurable aims, this program is unique insofar as you are not adopting some theoretical animal but real individuals with totally distinct personalities who we intimately know and love and you, too, may have already personally met!

Anyway, the universe of potential adopters is limitless.
In fact, so far, adopters range from parents wanting to give a very special gift to their children to people interested in marine conservation to our clients and volunteers all the way to people who simply find it a cool thing to do - and we're also talking to our first corporate contact, so fingers crossed!

So there you have it - sure hope you like it.

Thank you very much!

I would definitely encourage you to adopt a shark. They are doing awesome work and have a direct impact on saving the sharks. Aside from helping the sharks, check out the really cool benefits YOU get by adopting a shark. Depending on the level of support, you actually get to dive with these awesome animals.

I have personally adopted "Blunt". She is one of the sharks that always comes really close to say hello and inspect my camera. ;-)


Martin Graf
CEO Shark Diver

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.

Wednesday, September 26, 2018

Unusual shark behavior at Guadalupe Island

The 2018 season at Guadalupe Island has been phenomenal so far. Thanks to Nicole Lucas from the Marine Conservation Science Institute, we have a way to identify and keep a record of all the sharks seen at Guadalupe Island. This is how we know that on our last expedition we encountered a record breaking 47 different individuals, including a whopping 16 sharks that have not been previously identified. This shattered our previous record of 34 individuals seen on a single trip.

Here is a list of all the sharks we encountered.

It's not just the number of sharks we encountered that was unusual. It was also the behavior of a couple of the new sharks. One individual, now officially named "Tryss", or crazy Tryss as I like to call her, displayed a very unusual behavior. She came to the cages multiple times, without any bait attracting her to them, sticking her nose into it,  bumping the boat and squeezing through gaps. She did all that in slow motion, never freaking out  like other sharks when they touch the cage, keeping her eyes open and totally aware of her surroundings.

Check out the pictures and videos of her.

"Tryss" coming between the cages and the boat.

"Tryss" sticking her nose into the cage.

Checking out the boat.

Sticking her nose into the cage.

Hello there!

Hey, anyone up there?

See ya guys!

In 18 years of diving with these amazing animals, I have never witnessed a shark behave like this. It just goes to show you that they will never stop to surprise you. That's why I love my job and am completely fascinates by these awesome creatures.

Shark Diver proudly supports the Marine Conservation Science Institute through our MCSI hosted expeditions.  Joining us on one of these expeditions is  a great way to learn about our sharks and support the research. Maybe you'll even get to name a shark, like the ones who just named "Tryss" on our last trip.

Let's go shark diving!

www.sharkdiver.com, crew@sharkdiver.com, 619.887.4275

Martin Graf
CEO Shark Diver

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.

Thursday, April 5, 2018

Bull Shark with Cancer?

There are a lot of misconceptions when people talk about sharks. One of them is the myth that they don't get tumors or cancer. We previously talked about sharks with cancer, here and here, but while those 2 blogs were about a Great White Shark, we also have a Bull Shark in Fiji with a tumor growing out of her mouth. Her name is "Ms Jaws".

DaShark from Beqa Adventure Divers thinks it all started when he first saw her swimming around with a fishing popper stuck to her jaw.

                                     Video ©DaShark Beqa Adventure divers, source

Her jaw got progressively worse. This photo shows the progression of her lesion from 2011-2013.
Photos by Sam Cahir, predapix

When I met "Ms Jaws" for the first time in 2014, her jaw already looked like this.

The next time I saw her was in 2016 and she looked a lot worse. Her jaw was hanging down and it looked like it would be impossible for her to feed successfully.

Aside from her badly broken jaw and tumor, she did seem to be OK though. She didn't look skinny or showed any obvious signs of malnutrition. I have to admit that I was worried about her and didn't have high hopes of her surviving much longer.

                                          video ©Martin Graf www.sharkdiver.com

Now we have some good news! DaShark just reported that "Contrary to my dire prediction, Mrs. Jaws is alive and kicking - and judging from her girth and body shape, she is very capable of feeding herself which is real good news indeed!"

He also posted a video of her swimming around on facebook here and you can read his blog here.

If you are interested in more information on this particular shark's tumor, read this paper by Juerg Brunschwiler from the ETH University in Zuerich.

I really hope that she will continue to do well. She is a remarkable animal.

Of course, if you really want to know how she is doing, join us in May on our expedition to Fiji, where you can look for her on our Bull Shark dives. We have a couple of openings left. Call us at 619.887.4275 or email crew@sharkdiver.com for more information.

Let's go shark diving!

Martin Graf
CEO Shark Diver

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.

Sunday, February 18, 2018

Is Shark finning the only threat to Sharks?

We all know that shark finning is a huge problem and a threat to global shark populations, but is it the only threat? Is the demand for shark meat an equal threat?

There is a new publication by Project AWARE® that addresses this issue.

It is not only the fins that makes sharks the target of the fishing industry. The demand for their meat is also a factor. From the Project AWARE® article:

"The appetite for shark fin soup has played a major role in shark overfishing and is often positioned as the main threat to sharks today. Recent data on international trade in shark fins and meat analyzed in the report however, reveals a global, interdependent market for a variety of shark products across scores of countries, including several in South America and Europe, whose demand for shark meat places them among the world's top shark consumers."

They have an interactive infographic that shows the different issues. The infographic can be found by clicking on the picture below.


From their article: "With so many shark species and products in trade, it can be difficult to get your head around what is really happening,” says Dr. Shelley Clarke, co-author of the FAO shark trade report and renowned shark fisheries scientist. “Understanding sources and trends is a critical step toward making sure the trade is sustainable and traceable, and the underlying fisheries are properly managed.”

 The infographic reveals the significant growth in markets for shark and ray meat, as well as the countries and inadequately restricted fisheries associated with this largely under-the-radar trade.
“The shark fin trade is at long last receiving worldwide attention from the media, conservationists, and law-makers, but we must urgently broaden our horizons to also consider other threats to sharks and closely related rays,” said Sonja Fordham, President of Shark Advocates International, a project of The Ocean Foundation. “We hope that Project AWARE’s initiative will shine light on these emerging issues and channel public concern toward workable solutions before it’s too late.”
The interactive infographic and related information can be found here: www.projectaware.org/globalsharktrade

Here is a provocative thought. Could the demand for shark meat actually be a good thing? You might think that's a ridiculous thing. How could demand for shark meat actually be good for the shark population? Could it be possible that a growing market for shark meat might increase the price of shark meat and thus give an incentive to the fishermen to keep the entire shark, instead of finning it and throwing the body back into the ocean? Since there is only so much space on a fishing vessel, this could actually mean that a vessel is killing fewer sharks to fill it's holds, than if they fill it with fins only.

This might be wishful thinking, but if shark meat would become as priced as say blue fin tuna, a lot of fishermen might actually catch fewer sharks for the same profit.

What Project AWARE®'s paper documents is the fact that shark conservation involves a lot more than just shark finning!

What are your thoughts? I would love to hear your thoughts.

Martin Graf,
CEO Shark Diver

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.

Thursday, December 7, 2017

Why do sharks attack?


Why do sharks attack?

Recently there was another shark attack on a spear fisherman in California and a fatal shark bite at Cocos Island in Costa Rica.  Inevitably when someone gets bitten by a shark, there is speculation about why it happened. “Mistaken identity” is a popular explanation, and of course the people arguing “it’s their home” and the “fill in the blank” kills more people than sharks every year are always ready to chime in.

There are statistics on shark bites, like the “international shark attack files” by the Florida Museum of Natural History, and we have a pretty good idea of how many people actually get bitten by sharks each year. Most of those statistics only collect data on what happened and are recording the circumstances of the attack. Since in very few cases was the shark actually seen before it bit the victim, most of the information we have is only about what the victims were doing before they got bit. When we discount the provoked attacks, like someone pulling a nurse shark by the tail, a fisherman getting bit by a shark he hooked, or like in the case of the Manhattan Beach incident, a fishermen hooking a shark and pulling it through a group of swimmers, very little is known about what the sharks were doing prior to biting the victim.

Obviously I don’t know what those sharks were doing or thinking either, nor do I know what lead them to bite. I wasn’t there and don’t have any firsthand knowledge. What I do have is some first hand knowledge of how some of the shark species implicated in attacks on humans behave and how that behavior might determine why they attack.

I have been diving with and observing Great White Sharks for over 17 years at Guadalupe Island and been around Bull-, Tiger- and Hammerhead Sharks for more than 6. What I found is that there are a lot of misconceptions about how these animals behave. Probably the biggest mistake is that people think “A shark is a shark”, pretty much assuming they all behave the same way.

There are well over 400 species of sharks, with most of them absolutely harmless to humans. Think about it this way. We have the top 10 deadliest sharks list. With an average of fewer than 10 fatal shark bites worldwide each year, that means that if a species is listed as #10, it stands to reason that that species is responsible for fewer deaths than #1, it may in fact only be responsible for a death every 30-40 years. Most of the species responsible for deadly bites on humans are the Great White, Tiger and the Bull Shark.

So let’s take a look at a couple of those species.

Great White Shark

The Great White Shark is probably the most feared animal in the world. Movies like “Jaws” and the way the media reports any encounter with them have instilled fear into most people who contemplate going into the Ocean. The thinking that one drop of blood in the water will cause a huge frenzy and pretty much any shark within 10 miles will come and attack you is very common.

The reality looks a lot different. Did you know that Great White Sharks don’t “frenzy”. In 17 years of observing them, I have never seen a bunch of Great Whites buzzing around a food source or a prey animal. When we put tuna heads in the water, or back when we used chum to attract sharks, we sometimes have to wait for hours for a shark to approach the cages. We could see them swimming below, but even though there was fish blood and Tuna in the water, they would not come up. When multiple sharks are around a food source, they typically measure each other up in order to decide who gets first crack at the food, instead of a free for all frenzy.

If that measuring doesn’t settle it, the bigger shark tends to bite the smaller one to assert it’s dominance. It is only after the pecking order is established, that they go after the food. They give each other space, with the smaller ones only going for the food after the bigger shark is a safe distance away.

Another common belief is that Great White Sharks will attack just about anything, even if they don’t know what it is. My observations have actually shown that Great White Sharks are not only very cautious, but seem to be almost timid. For example, a couple of years ago, a beach towel fell overboard and 3 sharks came to investigate it. 2 of them jerked away and took off, like something was chasing them, while the 3rd shark kept approaching it, jerking away repeatedly, until I lost sight of both the towel and the shark. I don’t know if the shark eventually bit the towel to figure out what it was, but it clearly kept checking it out repeatedly, being very cautious in it’s approach. We have actually observed the same timidness in some sharks when they approached a Tuna head. They clearly smelled the tuna, but when it was pulled slightly when they approached, a lot of them jerked away and would not attempt to bite the tuna until the made several passes to inspect it.

Screaming Mimi, a subadult female Great White Shark swam by my go pro that I had on a 20ft. pole 3 times, coming really close and checking it out, before biting it on the 4th pass. Again, she didn't just attack, she first checked out the go pro a few times, before she decided to take a bite at it.

Another interesting observation we made is that Great Whites attack a sea lion differently than a seal. If they are not biting their head off, the bite a seal in the butt, because seals swim with their  rear fins, while they bite sea lions in the pectoral fins, which is the way they swim. So if Great Whites know the difference between a seal and a sea lion, I think it’s unlikely they would mistake a surfer for a turtle or a sea lion.

There is a general belief that if you are bleeding, a shark can smell your blood from miles away and will come and bite you. Did you know that the Great White Sharks can differentiate between the blood from different species of fish? There is a distinct difference in how they react when they smell tuna blood, vs. yellow tail blood. So if they can tell the difference between the blood from different fish, it stands to reason that they can tell the difference between human blood and the blood of a seal or fish. Instead of increasing the chance of an attack, I actually think that if you are bleeding you might be even safer. Since your blood is giving the shark a way to know what you are, it actually might prevent an investigatory bite.

So why do White Sharks attack? There are of course different reasons. In the case of the spear fishermen who got bit in California, I believe that the shark wanted the fish and is was not actually going for the diver. When we were spear fishing at Guadalupe Island, we always put the fish on our float and didn’t attach it to our body, so that if a shark wanted the fish, it would not come for us. With surfers and swimmers, since I don’t believe in the mistaken identity, I think that most bites were actually an investigation. After they checked out the victim for a while, they took a bite, trying to figure out what it is.

However, I don’t want to take away the possibility that some of the bites are actual predatory attacks. Bites on humans by Great White Sharks are extremely rare, and the number of actual predatory attacks even rarer. While Great Whites are not mindless killers, out to get us, they are apex predators and definitely not harmless pets. There is no need to fear these animals, but we have to respect them for what they are.

Bull Sharks

We all heard that Bull Sharks are the most aggressive, because they have more testosterone than any other shark. While the testosterone part may be true, it has nothing to do with them supposedly being aggressive. People mistake aggression with hunger. When a Bull Shark is hungry, it has to eat. Unless it finds some animal that is already dead, that means it has to hunt and kill something. That’s not aggression, that’s just simply feeding. Aggression is fighting for territory, dominance etc. and that is actually something that is strangely absent from my observations. In an environment, where up to 70 bull sharks were competing for food, I’ve seen multiple sharks go for a tuna head, without any of them biting the others to get to the food. It was very rare to see a Bull Shark with a bite mark on them, something that definitely can’t be said about White Sharks.

Something I found out in Fiji really surprised me. DaShark, told me that the Bull Sharks that are taking tuna heads offered by hand from a feeder, are not the same as the ones who go for the tuna heads dropped from a trash can. He even told me that sharks that take a tuna head from one particular feeder would not take it from a different feeder. I would have thought that as soon as the sharks smell and see the tuna, they would go for it and not be picky.

Bull Sharks don’t naturally hunt for prey that is human sized, but they do hunt in brackish water, where the visibility can be quite bad. That is also the place where a lot of humans are in the ocean. So I think it's not the "fact" that they are aggressive and attack anything, but rather their proximity to humans that makes it more likely that they are implicated in an attack. When chasing fish, Bull Sharks are not stalking. They pretty much have to attack at full speed in order to get the fish. When they are hunting, specially around humans, it’s easily possible that a foot flashes in the middle of some fish and the shark bites it by mistake. Also while more common than bites by Great Whites, Bull Shark bites tend to be less severe.

So what does all this mean for anyone going into the ocean? First and foremost, think about the rarity of a shark bite. There are far greater dangers in the oceans than sharks. Currents, waves and heat strokes have killed more people in the ocean than sharks. You are also more likely to get hurt on the way to the Ocean, than by a shark in it. There are however some common sense things you can do though to reduce the extremely small chance of getting bit even further.

1. If you see a potentially dangerous shark, get out of the water while keeping your eyes on it. Since they are stalkers, they are unlikely to attack when they first notice you and since they like to ambush their prey, they are less likely to attack if they know that you see them.

2. Don’t swim at dusk and dawn, when sharks tend to be more active.

3. Avoid shiny jewelry, sharks hunting in shallow water might mistake that for a fish.

4. Don’t go spearfishing or surfing in an area known to have big predatory sharks. In some areas that depends on the time of year.

Again, to put everything into perspective. In California, some of the most famous surf spots are in an area that seasonally has adult White Sharks. The busiest time for surfing is before and after work, dusk and dawn, the time sharks are most likely to hunt. The surfers are on the surface of the water, the most dangerous place in the water, because these sharks tend to attack from below, yet with all that, in 100 years from 1900 to 2000, there were only about a dozen fatal shark attacks. That's about one every 9 years and those happened all over California, not just the area where White Sharks aggregate.

Bull Sharks can not only swim in salt water, but can go from salt to brackish and even fresh water. That fact means that they tend to be in waters that are also frequented by humans, which naturally increases the chances of that species being implicated in an attack. With the ever growing number of people going into the water, we would expect the frequency of bites to go up every year, something that actually hasn't happened.

When it comes to our fear of shark, I keep thinking of a quote by President Roosevelt that says: "the only thing we have to fear is...fear itself".

Go out and enjoy the Ocean. And if you want to observe these awesome animals yourself, let's go shark diving!

Martin Graf
CEO Shark Diver

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at crew@sharkdiver.com.

Sunday, November 26, 2017

Great White Mystery?

In 17 years of diving with the Great White Sharks at Guadalupe Island, we have learned a lot about these awesome creatures. From not knowing where they are heading when they leave the Island, to thinking they are heading to an area offshore to mate, to finding out that we were wrong on that and realizing that they are actually mating at Guadalupe, we have come a long way.

What never ceases to amaze me is the fact that we keep learning new things and that things we thought we knew were actually wrong. Observing them over time has given us some insights into their behavior and how the relate to each other and how their personality changes as they grow. The most important thing I have learned is that just when you definitively think you know something about them, you find out that it may not always be true.

First I have to make a disclaimer. I'm not a marine biologist, so most of what I know about their biology and migration I learned from my friends who are biologists and study these sharks. What I know about their behavior comes from literally thousands of hours spent observing them, both in the water and from above.

The latest theory that has come into question is how the shape of their teeth changes as they growand the reason for that.

Georgina French, a PhD student at the University of Sussex, published a new study that deals with that theory.

From her paper: Up until now, scientists have accepted that white sharks start out their lives with cuspidate (pointy) teeth, which are thought to be adapted for gripping onto slippery fish. When the sharks hit roughly 3m in length, they’re then thought to develop much broader teeth, which are believed to be adapted for catching and eating marine mammals like seals and dolphins. This shift in diet and tooth shape with age/size is referred to an ontogenetic shift.
©Georgina French
Her new discovery seems to be that there is a distinct difference between male and females, something I have never heard before.

She writes: Previous studies of white shark teeth have always lumped males and females in together, despite the fact that they are quite different in other aspects of their biology and ecology. I decided to explore their tooth shape/shark length relationships separately. When I combined all of the data from the photographs, the literature and the KZN jaws, I found startling differences between the sexes.  While males seem to follow the accepted pattern of broadening teeth when they get to about 3m long, females didn’t. Instead, a female of any size could have either broad, pointed or intermediately shaped teeth. Females also didn’t change the angle of their upper third teeth, while males did.

©Georgina French
As with any new discovery, there are instantly a bunch of new questions. In this case, first and foremost, 

What does this mean?

 Broadly speaking, the results indicate that either males and females are feeding on different things as they grow up, or that the tooth shape change isn’t related to diet.
When sharks mate, males hold onto the females using their teeth. It’s possible that the broadening of the teeth and the change in tooth angle found in males could be an adaptation for mating, rather than for handling different prey. Alternatively, females with broad, pointy and intermediate teeth may be specializing on different types of prey i.e. they are polymorphic. I also found significant variation in the size at which males developed their broad teeth, which combined with other evidence indicates that some individuals mature a lot more quickly than others. Polymorphism and differing rates of maturity among individuals can have pretty big ecological consequences, and these factors need to be taken into account in future studies and white shark management.

This is what I love about working and diving with Great White Sharks. Every question that gets answered opens up a lot more questions. I wonder to what new insights about Great White Sharks this new discovery leads to. Maybe we should call these sharks Great White Mysteries instead.

Let's go shark diving and discover new and exciting things about these awesome animals!

Martin Graf
CEO Shark Diver 

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.

Saturday, October 28, 2017

What's eating the brains of sharks and rays in California?

Between February and July, there have been a lot of incidents, where dying or dead sharks and rays have washed up on beaches in San Francisco bay. What is causing them to die?

According to an article in National Geographic, CDFW senior fish pathologist Mark Okihiro, Joseph Derisi, an expert on the genetics of infectious diseases at the University of California, San Francisco and Hanna Retallack, an MD-PhD graduate student have found the answer.

Their headline reads : "Mysterious Brain-Eating Shark Killer Identified, Though Questions Remain"
It looks like the culprit is "a well-known fish-killing parasite called Miamiensis avidus."

The article further states: This appears to be the first case, Retallack said, of Miamiensis avidus infecting wild sharks. It’s noteworthy, she added, because sharks are evolutionarily quite different from the bony fish that have previously been known to suffer infections. 

Read the entire article here

Martin Graf
CEO Shark Diver

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.

Friday, October 27, 2017

What causes sharks to have crooked spines?

Earthtouchnews has an article describing a bull shark with a crooked spine. That shark was found by the shark lab in Bimini. They named him "Quasimido" and are speculating on what caused that deformity.

The Bimini Shark Lab team secures "Quasimodo" for workup (a short checkup that includes taking various measurements of the animal). Image: Chelle Blais/Bimini Biological Field Station
Sarah Keartes writes: "Dr. Natalie D. Mylniczenko, a veterinarian who has spent time with the Shark Lab beforepresented several possible explanations for the bull shark's strange skeleton. It's possible that a deep abscess, granuloma, or slow-growing cancer is to blame – but Quasimodo's overall state seems to suggest otherwise. If disease were at the root of the deformity, we would expect to see at least some abnormal behaviour. The more likely culprit, according to Mylniczenko, is either a congenital or traumatic incident. In either case, this would have occurred when the shark was very young, and over time, his body would have compensated and healed in a skewed position."

Read the full story here: https://www.earthtouchnews.com/oceans/sharks/meet-quasimodo-the-bull-shark-with-a-very-crooked-spine/
Image: Chelle Blais/Bimini Biological Field Station

This Bull Shark is not the only shark with a deformed spine. At Guadalupe Island, we have our own Great White Shark with the same deformation. When we first met her a couple of years ago, I nicknamed her "Kinky" because of the very distinct kink in her tail. I have no idea what caused that kink, since she doesn't have any obvious scars or signs of injury. She was named "Screaming Mimi" by someone through the "Sponsor a shark" program of the Marine Conservation Science Institute. That sponsor program, is one of the ways they raise funds for the Photo ID database at Guadalupe Island.
"Screaming Mimi"

Just like the "Quasimodo" in Bimini who was seen swimming around a couple of weeks after the people from the Shark Lab examined it, "Screaming Mimi" also seems to be doing well and has been very active around our cages at Guadalupe Island.

If you want to meet "Screaming Mimi", or any of our other sharks at Guadalupe, contact us at 619.887.4275, crew@sharkdiver.com or www.sharkdiver.com

Let's go shark diving!

Martin Graf
CEO Shark Diver
About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.