Cayman Island Tiger Sharks: tagging data shows possible Caribbean migratory patterns

The Cayman News Service reported that three tiger sharks that were tagged almost a year ago in waters off the Cayman Islands have returned having roamed the wide waters of the Caribbean. The original tagging project was a joint effort between the Department of Environment (DoE), Marine Conservation International (MCI), the Guy Harvey Research Institute (GHRI) at Nova Southeastern University and the Save Our Seas Foundation.

The three sharks were tagged with satellite tags which can provide a variety of data in addition to basic positioning information. One of the three sharks spent a great deal of time cruising the coast of Jamaica; another has been in deep waters off the Cayman Islands; while the third shark spent the summer in the southwest, off Honduras and Nicaragua.

While not necessarily covering the same long "point A to point B" distances that have been reported with sharks like great white sharks and whale sharks, the data does show that the sharks can cover a considerable amount of territory and that these movements might constitute "migrations" if there is a schedule or pattern to their journeys.

Being able to verify that sharks frequent the Cayman Islands via migratory patterns might help give weight to the need to protect them - proving that they are not infrequent or fluke visitors not deserving of specific attention.

The Cayman News Service reported, "Despite their precarious situation, there is no law to protect sharks in Cayman waters but hopes for the species have been raised in the region following the ban on shark fishing by Belize, Mexico, St Maarten, Honduras and the Bahamas. Timothy Austin, Deputy Director of the DoE, welcomed the ban by neighbouring countries. 'This will give a boost to the health of the marine environment for the Caribbean,' he said."

Read about the sharks in the Cayman News Service.

Sharks on the Right Path: research indicates predators know where they're going

Researchers continue to learn more about the movement of sharks, particularly their ability to navigate along deliberate paths as opposed to random, meandering movements. Much attention has been paid in recent years to the incredible long-distance migrations that many species of shark undertake. But scientists with the Florida Museum of Natural History focused their attention on shorter distances; in essence, how and where the sharks traveled over several days or weeks as opposed to many months. What they found was that sharks at times appear to know exactly where they are going.

The Florida researchers tracked the movements of tiger, thresher, and blacktip reef sharks, and their results, recently published in the Journal of Animal Ecology, showed that the sharks would often exhibit random movements or "walks." However, there were plenty of times when the sharks, particularly the tigers, would demonstrate very directional movement behavior. The tiger sharks appeared to be the best at pursuing these directed walks, covering as much as 30 miles in a singular direction and even traveling several miles to a very specific point underwater.

Yannis Papastamatiou, co-author of the study, said, "Our research shows that, at times, tiger sharks and thresher sharks use highly directed walks to swim to specific locations. Simply put, they know where they are going.

Many people could walk to a known destination 3.7 to five miles away, but imagine doing it in deep water and at night.

As anyone who dives knows, finding your way around underwater without a compass is very difficult, but this is what we found tiger sharks could do."

As a diver, I can attest as to how difficult visual navigation can be underwater. Rock formations that appear one way as you move in a particular direction can look completely different when approached from the reverse direction or different angle. But with a full range of sensory capabilities far beyond that of man, using visual cues combined with other sensory input like temperature, currents, or even the magnetic fields of the earth could make it simply all in a day's work for a shark.

In June of last year, I wrote about similar research studying a variety of pelagic - or open-ocean - predators like swordfish, tuna, and sharks. In this study, the researchers were looking for certain mathematical patterns: Brownian walks for so-called random movements, and Levy flights for more directional straight movements. One of the researchers noted that the use of straight line movements as opposed to random may have been initiated due to the availability of food.

Lévy behavior showed up more often in waters where plankton, fish and other food was scarce. In regions with plentiful food, random motion dominated. This observation, says theoretical physicist Gandhimohan Viswanathan, fits with earlier suggestions that 'animals may use a Lévy flight motion to improve their chances of finding prey.'”

Whether motivated by food or some other impulse or whether or not supported by a keen sense of visual direction or some other ability (all questions to be answered with future research), it can be said that in a challenging environment like the ocean, sharks are being shown to demonstrate some highly intelligent movement behaviors, perhaps relying on some "cognitive maps" lodged somewhere deep within their brains.

Read about shark movements in U.K.'s Mail Online.
Read about Brownian walks and Levy flights in RTSea Blog.

Bahamas' Sharks: a moment's scarcity with disturbing implications

I returned late Thursday night from a video assignment in the Bahamas as director of photography - hence, the lack of postings over the last few days. The crew was out there to film sharks but, as it turned out, we had to look far and wide to find what we were looking for. In the "usual places" where we would expect to find numerous lemon, tiger, and Caribbean reef sharks, we were being skunked - a highly unusual experience.

The boat captain made radio calls to other boats in the area only to find that they were also experiencing the same lack of sought-after quarry. So, we were not the only ones and apparently this had being going on for several weeks. Two possible theories were being bandied about - either of which raised concerns as they illustrated the fragility of a marine ecosystem.

Hunting for sharks:
One of the dive operators that regularly works the area off the Bahamas related a rumor that a tiger shark, possibly a pregnant female, was taken by a fisherman the week before. Had the sharks, in response, moved away from their usual haunts, perhaps deeper or farther out to sea? Possibly - although the theory demands a multi-species reaction to a singular event that may not be that plausible. But it's a tantalizing idea: what would be the response by schooling predators like lemon and tiger sharks to life-threatening events? No matter how much bait or chum was used, at sites where we would normally have so many sharks on hand, you could almost walk across the water on their backs, there were virtually none.

Rising temperatures:
The other theory, which we were experiencing first hand, was an increase in water temperature. We found the temperature in be in the mid-80's from the surface (which is to be expected this time of year) to as deep as 60 feet before it abruptly dropped about ten degrees. Could this abnormal wider range of warmer water have pushed the sharks to deeper and more comfortable depths? Several of the locations where one would typically be surrounded by sharks are in the 20-foot depth range - and we had no luck at those sites. Ultimately, on the last day of shooting, we came upon a small but suitable number of Caribbean reef sharks at 80 feet. My B-camera operator, Scott Cassell, commented to me that he also noticed a lot more algae growing on the reefs in the shallower, warmer depths, versus the more colorful sponges and corals.

In the end, the production crew was able to get the footage it needed, but it was challenging to say the least. And disturbing to think about the implications to a balanced and healthy marine ecosystem when normal conditions are disrupted. In the end, either of these two mitigating factors - fishing or water temperature - which impacted the number of sharks we encountered could be mere anomalies. But it did provide a disturbing indication as to the impact of shark fishing and climate change.

In a couple of weeks, all we experienced could be forgotten and the frequency and range of the Bahamas' sharks could return to normal. But it was sobering to think what the future may hold in store.

Tiger Shark in Long Beach, CA: Aquarium of the Pacific has a new predator

While many aquariums across the country have healthy co-working relationships when it comes to animal care, exchanging animals, or simply keeping up with what's new, there is a bit of competitive rivalry that fuels their desire to distinguish one institution from another. The Aquarium of the Pacific in Long Beach, CA, where I had offered my services as a dive team leader for over 8 years, has had several milestones to distinguish itself: first successful breeding of Leafy Seadragons, successful surgery and rehabilitation on a Sawfish's broken saw, a Bull Shark on public display, and many more.

They are adding one more to that list, with one of the few Tiger Sharks to be on display in North America. Now, I had known for a while that the Aquarium had a tiger shark in holding, but was sworn to secrecy by my friend, Steve Blair, assistant curator and featured in my documentary, Island of the Great White Shark. New animals at the Aquarium go through an obligatory quarantine period and a ground-breaking specimen like a tiger shark would get special attention to insure that it is feeding and behaving normally.

As a recent article in the Los Angeles Times pointed out, getting the animal to that predictable state can be challenging. And then acclimating the animal with the rest of the animals in the exhibit - in this case, the Aquarium's Shark Lagoon exhibit where there are sand tigers, black tip reef, white tip, sand bar, nurse, and zebra sharks, not to mention large rays and a sawfish - can require a careful step by step process.

Even though a tiger shark would represent a major "big cheese" in the exhibit, there is equal if not greater concern regarding the established animals picking on or harassing their new neighbor. Once the pecking order is established then tables might turn and it becomes necessary to watch that larger or more dominant sharks, no matter how new, may begin to assert themselves.

The tiger shark is an absolutely gorgeous animal, particularly with younger specimens where the "tiger stripes" are so prominent. I have had the opportunity to see these animals in the wild and they are indeed a wonderful example of oceanic beauty and grace. Let's wish the Aquarium of the Pacific well and hope that having this particular animal on display - one considered to be a member of the four most dangerous sharks - will provide an opportunity for visitors to see and better appreciate a critically important ocean predator.

Read Los Angeles Times article. Visit Aquarium of the Pacific web site.

Sharks and the Media: another casualty

Several months back, an unfortunate incident took place where several free-divers spearfishing and filming in the Gulf of Mexico were approached by a large tiger shark whose moves were perceived as aggressive and so began a long and tortuous (for the shark) adventure to kill the offending animal. The incident is now getting wide media attention on morning talk/news shows and several online news sources - once again perpetuating the evil shark mythos.

My colleague, Patric Douglas, CEO of Sharkdivers.com, posted a comprehensive op-ed on his blog. Dead on, no need for me to say more.

Shark Kill - The "Sin of Media"

Friday, March 13, 2009

Last month we blogged about an Outside Magazine article called Ready, Aim, Sushi. The story was about a group of professional spearos caught in a "life and death" moment with a large tiger shark.

Shark Perceptions

At the time we wanted to know more and called Ryan McInnis who shot much of the video of this tragic event. Ryan was upset about this, in his world the killing of a tiger had never happened and according to him it was unavoidable.

In fact none of these free divers had ever encountered a tiger at this site.

Some of the video supports Ryans claim that this animal was ready to attack - from his perception. A large tiger coming in danger close, frantic voices can be heard in the distance. To others in our industry who have had 100's of hours with tigers this video shows nothing more than a curious animal.

For a spearo who has never encountered a tiger having an animal this large come within six inches, head on, might be considered a prelude to an attack, justifying a kill.

That fact of "justified kill" remains debatable depending on your perception of sharks. As this story has blown up in the media those with many hours of experience with tigers are calling foul, or worse. Those with many hours of experience are in the absolute minority as well, and come to the table with a full understanding of these animals under a range of conditions that few in the general populace understand.

The Sin of Media

What I think is more to the point in this discussion is not what happened, or even why it happened, it is the "Sin of media". This absolutely sad story about a split second perception of a large predatory sharks "intentions" was well documented by the spearos. In fact one might argue too well documented. As these spearos recount, the final death of this animal took two hours, after six shafts were put into the shark, it was dragged behind the vessel, and finally was put to rest with a dive knife to the brain. Horrific.

In my opinion, where this group goes completely wrong, nine months after the event, is to appear on major news channels to recount their stories. In effect being used by a biased anti-shark media to regurgitate a man vs shark 70's story that pushes the perception of sharks back into the stone age. The "Sin of media". There's really no point for being on television with this story but for the two minutes of fame it generates.

This story has been picked up by the British tabloids and has migrated to the US where these spearos are on the morning talk shows and CNN. The "Sin of media" is taking a negative shark event and allowing it or promoting it to a wider audience, where sharks are once again seen in the worst light.

Did these guys stage the whole thing? They might have. In my conversation with Ryan he was verbally upset and even broke down on the phone. If they staged the event - why wait nine months to get major media attention?

I keep coming back to the "Sin of media". These guys documented an unusual event in great depth. They killed a tiger they felt was going to attack. All of that is horrific enough. The real sin is showing this to the world with the perception that tigers in close proximity are "going to attack".

Shark Diving Industry

Industry members are outraged as we suggested they would be last month. We know the worlds perception of sharks is ultimately negative, and these stories serve to cement that perception into the zeitgeist. As an industry we can help change this, media is not a one way street. We need more pro-shark 2 minutes PSA's on You Tube and elsewhere. We need more pro-shark dive media everywhere. We need effective counters to media stories like this when they break, from credible sources.

If we want to see change to the perception of sharks, we have to make that change. Getting in front of the major media with our own pro-shark stories would be a good first start.

Shark-Free Marinas Initiative, Bahamas

I'm pleased and honored to assist SharkDivers.com with this new program they just recently devised to help promote the conservation of sharks. It's one way to encourage commerce to get on board and make a difference, realizing the long-term benefits for Bahamian tourism.

Shark-Free Marinas Initiative

In the spring of 2008, Shark Diver was alerted to a female Tiger shark that was taken off Freeport, Bahamas. The animal was caught by a sport fisherman and displayed at a local marina where it was cut open to reveal several half-dead pups inside, some of which were dropped into the marina and struggled to survive for a few days.

We have decided to act. The Government of the Bahamas allows sport fishing for sharks and we fully support sustainable catch-and-release fisheries. However, the taking of gravid female sharks for a one-time photo op and a set of jaws is a senseless waste of a valuable resource.

The Shark-Free Marinas Initiative is a way to work with existing resort marinas in the Bahamas that cater to sport fishing vessels, seeking their cooperation in asking them not to allow sharks to be taken and displayed at their marinas. This initiative, in turn, encourages the use of catch-and-release programs and promotes sustainable fisheries.

Each marina and resort that supports this initiative will receive both, a metal sign and logo we have created to post in their marina office and the following information for posting on their marina websites:

(Name of resort and marina) supports the Shark-Free Marinas Initiative in the Bahamas region. The Bahamas is home to many shark species and the healthy reef systems that support these sharks. We feel the one-time harvesting of sharks for photo images or souvenir jaws is not in the best interests of the Bahamian people or Bahamian tourism.

Worldwide, sharks are being decimated for fins and jaws at a completely unsustainable rate. An estimated 60 million sharks per year are taken in this manner. By asking vessels not to arrive at our facilities with sharks, we hope to encourage responsible sport fishing, thereby ensuring a lasting and healthy population of sharks in Bahamian waters for future generations and contributing to the overall health of the Caribbean.

Please practice catch-and-release with all sharks and enjoy our facilities.

Welcome to the Bahamas.

SharkDivers' Note: This initiative is not only limited to the Bahamas and the several marinas who have expressed an interest in joining it (press release to follow). As a concept we will allow and help promote any organization or group to use this logo to enact their own regional Shark-Free Marinas. In places like Florida and the East coast this could conceivably help redirect shark kills and weigh ins. It offers the opportunity for marinas to claim the "Green Card" while at the same time redirecting fishermen into sustainable fisheries. Special thanks to Richard Theiss RTSea Productions.

One blog, one website, one person at a time.