epic tiger shark diving expeditions
diving with caribbean reef sharks

Shark Diving Tourism in Malaysia – Publication

Shark-diving tourism as a financing mechanism for shark conservation strategies in Malaysia

As seen in many other instances, this new publication serves to identify the monetary value of sharks to a local community through tourism.  Studies like these were instrumental in many locations, including the Bahamas, being declared as shark sanctuaries.  Here’s the information on the recent publication looking at shark diving tourism in Malaysia.

ABSTRACT

This study estimated the economic value of the shark-diving industry in Semporna, the most popular diving destination of Malaysia, by surveying the expenditures of diving tourists and dive operators through the region. A willingness-to-pay survey was also used to estimate the potential of the industry as a financing mechanism for enforcement and management of a hypothetical shark sanctuary. The study showed that in 2012, shark-diving tourism provided direct revenues in excess of USD 9.8 million to the Semporna district. These economic benefits had a flow-on effect, generating more than USD 2 million in direct taxes to the government and USD 1.4 million in salaries to the community. A contingent valuation analysis indicated that implementation of a fee paid by divers could generate over USD 2 million for management and enforcement of a shark sanctuary each year. These findings suggest that shark diving is an important contributor to the economy of the Semporna region that could be used as a mechanism to assist financial resourcing for management and conservation strategies.

Shark Diving Tourism

If you would like to read more information on this particular study, click on the link here!

Let us know your thoughts in the comments below.  Have you ever been diving in a shark sanctuary?

diving with caribbean reef sharks

Read about Bahamas Shark Tourism Survey

shark senses vision

Shark Vision: Do Sharks have Good Eyesight?

Here’s the next segment on our Shark Senses Series.  If you missed the first article, click here.  Shark vision has always seemed to be a bit of a mystery. We often hear about the mistaken identity argument related to shark-human interactions and that leads many to believe that sharks have poor eyesight. We also constantly hear about sharks amazing sense of smell, and it’s often thought that some other senses are sacrificed as a result. Is this true? Do sharks have poor vision?

A research group in Australia has been studying shark vision for years. In fact, they may be the worlds experts on vertebrate vision and have studied the eyes of literally hundreds of different species of elasmobranch (sharks, rays, skates and sawfish). Here, we’ll try to summarize their findings and explain what that means in practical terms.

Sharks lack color vision. That’s right. Sharks lack the necessary cells that process color vision and can only see in Black and White. This seems to be the case for all sharks as none of the tested animals possessed the necessary photoreceptor cells to see in color.So what’s all that talk about Yum Yum Yellow? We’ll get back to that. On a side note, rays are able to see in color.

Visual Acuity. Sharks are thought to be able to see very focused images. The fact that shark vision is monochromatic does not mean they lack visual acuity. In the human eye, we have muscles that control the shape of our lens and focuses light signals on the retina. By contrast, the lens in a sharks eye does not change shape. Rather, they have muscles that move the lens forward or backward to focus light. In both cases, the effect is the same and the retina receives a focused image. Sharks have great visual acuity and they absolutely rely on that vision for many of their behaviors. Obviously, water conditions will play a major effect on their ability to see and from what distance. In ideal conditions (the kind we get while shark diving in the Bahamas), sharks can see clearly from 10-15 meters or more.  This means while their vision is good, it’s not the first sense that keys them into their prey and becomes more important as they get closer.

Light Sensitivity. The ability to see in low light conditions varies greatly between the shark species studied. Essentially, there are 2 types of photoreceptor cells located in the retina. The cones are active in bright light conditions and the rods are active in low light scenarios. Each species will have a different proportion of these cells. Not surprisingly, deep water sharks have large eyes with a much higher proportion of low light photoreceptor cells (rods) compared to cones. Shallow water sharks have cells in the opposite proportion. In addition, sharks possess a structure called the Tapetum lucidum. This is the reflective part of the eye that lies behind the retina and causes the shining eye you may have seen in a cat or a deer in headlights. This will actually reflect the light one more time back through the retina thereby making it available to the retina a second time and increasing low light vision.

In Practical Terms. Sharks have monochromatic vision. Sharks have good visual acuity. Sharks have vision suited to the environment they live in. Given their sharp focus and black and white view of the world, do we need to worry about the color of our dive gear? In short, Yes! Sharks do tend to be interested in high contrast areas. It’s the reason we don’t like very bright accent colors on dive gear as that may peak their interest. It’s also the reason we require divers to wear gloves for our shark dives. A pale fleshy hand sticking out of a black wetsuit sleeve may be a recipe for trouble.

If you’d like to learn more about shark vision, take a look at Vision in elasmobranchs and their relatives: 21st century advances.

Shark Vision

shark vision

Images used are by Jean-Lou Justine licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

shark senses ampullae of lorenzeni

Shark Senses – How Do Sharks Hunt Their Prey?

Perfectly evolved over 500 million years and surviving 5 mass extinction events, sharks are true super predators. So how do they do it? What’s senses come in to play as sharks hone in on their prey? Here’s a quick look at each of the shark senses, and how each help make them successful predators.

Shark Senses – Long Range

Hearing. A long range and highly developed sense, the auditory system of sharks can also give important information about potential prey. This will often occur well before the animal is in visual range. They are especially tuned in to low frequency sounds, the kind made by a wounded or struggling fish, and are able to detect them often from distances greater than a kilometer away!

The Sense of Smell. It’s true, sharks have a great sense of smell. You may have heard some of those interesting little factoids such as sharks being able to smell a drop of blood in an olympic sized swimming pool. Well, it’s not far off from the truth. Sharks sense of smell (olfaction) is remarkably effective and fine tuned to pick up the amino acids in proteins, such as blood. Studies have shown sharks to be able to detect 1 part per 20 million parts water! This is likely one of the first senses that clues sharks in to potential prey items at a distance.

Shark Senses – Mid Range

Vision. Contrary to some myths out there, sharks actually have good eyesight, as far as fish are concerned. They lack color vision and only see in black and white, but still possess the visual sensory equipment to produce focused images. Water conditions play a big role and low light or murky water will have a big impact on their visual acuity. Take a look at our blog focused on Shark Vision for more details.

The Lateral Line – Mechanosense. Sharks have evolved another sense that is quite foreign to humans. The lateral line system is a series of canals located throughout the sharks body with openings to the skin. It allows for water to enter and is very sensitive to picking up water movements. Because of this, sharks are able to tune in to the vibrations caused by wounded or struggling fish, again helping them to hone in on potential prey.

shark lateral line

Shark Lateral Line System – illustration by Chris Huh

Shark Senses – Close Range

Ampullae of Lorenzini – Electrosense. Another sense unfamiliar to us is electrosense, the shark’s ability to detect the weak electrical field given off by all living things. This highly tuned sense is thanks to countless small pores located throughout the sharks skin, mostly concentrated around the snout, and called the ampullae of Lorenzini. These gel filled pores help amplify these weak electrical signals allowing sharks to detect prey even if it’s completely hidden, such as in the sand. It’s effective at close range, typically within 1 meter or less.

shark senses ampullae of lorenzeni

Shark Electroreception – illustration by Chris Huh

Touch. Obviously a close range sense, sharks will often bump potential prey items before taking a bite to get a better sense of what they’re dealing with. Lacking hands, it’s common for sharks to investigate items in the water column by hitting with their snout or even “feeling” with their mouths. This is the reason for the often described bump and bite scenario, and also a reason that we let divers know they cannot let sharks bump into them, as it’s often followed by a test bite.

Taste. Like us, sharks have taste buds in their mouths, making it the final sense involved in determining if a shark has found it’s next meal, or made a mistake. We have no idea what tastes good to a shark, but given the frequency that shark-human interactions only end in a single bite, and our terrestrial nature, it seems we are certainly not on the top of the shark menu.

 

tiger shark bahamas diving

Tiger Shark – Longest tagged tiger still reporting

Now transmitting for more that 1,240 days, “Andy” is the longest reporting tiger shark ever tagged.  Back in 2014, researchers from Nova Southeastern University’s Guy Harvey Research Institute (GHRI) tagged the male tiger shark off the island of Bermuda.  Over the past three years, the shark has logged more than 37,500 miles with the last ping picked up on December 28, 2017.

“This amazing, nearly three and a half year track is revealing clear repeated patterns in the shark’s migrations between summer and winter,” reported Dr. Mahmood Shivji.   In the following video, you’ll see the entire track made since he was first tagged. Looks like Andy hasn’t made any stop offs at Tiger Beach, but has gotten close!

According to a paper published in the most recent ICES Journal of Marine Science by Shivji and his colleagues, tiger shark migrations are heavily influenced by a shark’s physical characteristics (i.e. size, age) and environmental variations (i.e. water temperature, prey availability). This study reveals not only the environmental factors driving these massive migrations by tiger sharks but also highlights how the different age groups behave. This information could prompt fisheries managers to reevaluate how best to protect this near-threatened species.

bahamas tiger beach shark diving

 

tiger shark fishing

Texas fisherman reels in enormous shark 10 years after it’s tagged

tiger shark caught

A Texas fisherman recently reeled in a massive 11-foot tiger shark with an attached research tag, leading to what may be the biggest coincidence in shark-catching history.

hooked tiger shark fishing

Although we could do without the beached/hooked shark images, there’s certainly interesting information learned from this catch. Turns out, this shark was tagged 10 years to the day prior to this catch. It measured only 32 inches at the time, was tagged, and released from a location only 40 miles from this catch. The fisherman took his photos, recorded the tag number, and discussed the information with the scientist later. Everyone was excited to learn the details and the amazing coincidence.

Tiger sharks are quite hardy animals, unlike some other species. Certain sharks, like the great hammerhead, have very high mortality rates after a long fight on a fishing line and being dragged out of the water. By contrast, this tiger shark should manage well after the release.

Source: Texas fisherman reels in enormous shark, finds unbelievable coincidence – Houston Chronicle

shark meat and fin toxins

Shark Fins & Meat Contain High Levels of Neurotoxins

shark meat fins neurotoxins

In a new study, University of Miami (UM) scientists found high concentrations of toxins linked to neurodegenerative diseases in the fins and muscles of 10 species of sharks. The research team suggests that restricting consumption of sharks can have positive health benefits for consumers and for shark conservation, since several of the sharks analyzed in the study are threatened with extinction due to overfishing.

The species sampled for this study were the:

  • Blacknose shark (Carharhinus acronotus)
  • Blacktip shark (Carcharhinus limbatus)
  • Bonnethead shark (Sphyrna tiburo)
  • Bull shark (Carcharhinus leucas)
  • Great Hammerhead shark (Sphyrna mokarran)
  • Lemon shark (Negaprion brevirostris)
  • Nurse shark (Ginglymostoma cirraum)
  • Atlantic Sharpnose shark (Rhizoprionodon terraenovae)
  • Smooth Hammerhead shark (Sphyrna zygaena)
  • Tiger shark (Galeocerdo cuvier)

The two toxins analyzed were Mercury and β-N-methylamino-L-alanine (BMAA) which have been linked in recent studies to both Alzheimer’s disease and ALS.

Find the full article and link to the scientific publication here: Study Finds Shark Fins & Meat Contain High Levels of Neurotoxins Linked to Alzheimer’s Disease | The Rosenstiel School of Marine and Atmospheric Science at the University of Miami

greenland shark

400-year-old Greenland shark ‘longest-living vertebrate’

Amazing new research was just published this month (August 2016) in Science titled Eye lens radiocarbon reveals centuries of longevity in the Greenland shark (Somniosus microcephalus).  

ABSTRACT

The Greenland shark (Somniosus microcephalus), an iconic species of the Arctic Seas, grows slowly and reaches >500 centimeters (cm) in total length, suggesting a life span well beyond those of other vertebrates. Radiocarbon dating of eye lens nuclei from 28 female Greenland sharks (81 to 502 cm in total length) revealed a life span of at least 272 years. Only the smallest sharks (220 cm or less) showed signs of the radiocarbon bomb pulse, a time marker of the early 1960s. The age ranges of prebomb sharks (reported as midpoint and extent of the 95.4% probability range) revealed the age at sexual maturity to be at least 156 ± 22 years, and the largest animal (502 cm) to be 392 ± 120 years old. Our results show that the Greenland shark is the longest-lived vertebrate known, and they raise concerns about species conservation.

greenland shark publication

August Issue Science

The team believes the animals only reach sexual maturity when they are 4m-long. And with this new, very lengthy age-range, it suggests this does not occur until the animals are about 150 years old.

Source: 400-year-old Greenland shark ‘longest-living vertebrate’ – BBC News

Read about an epic megamouth encounter.

oceanic whitetips shark research group

Oceanic Whitetip Shark tagging at Cat Island

The folks over at the Cape Eleuthera Institute have just wrapped up their 2016 Oceanic Whitetip Shark tagging program. This concludes their sixth year of the program which has now caught and tagged nearly 60 individual whitetips in the waters surrounding Cat Island.

The goals of the study are to:

  • Determine generalized movements and determine high-use areas of sharks in relation to the Bahamas shark sanctuary.
  • Examine diving behavior through high resolution temperature and depth data.
  • Investigate potential hormone markers to identify reproductive cycles.
  • Examine prey-preference potential seasonal diet switches through tracing relative concentrations of Carbon and Nitrogen isotopes.
  • Gather baseline genetics data which will be incorporated into fin-trade management, and will detect fins from Oceanic whitetips found in the Western Atlantic.

Investigating these large knowledge gaps are intrinsic to the contemporary management of oceanic whitetip shark populations, and will provide novel insights into the biology and ecology of a severely threatened apex predator.

Read more about there work here: Shark Research and Conservation Program facilitates another successful year of Oceanic Whitetip (Carcharhinus longimanus) tagging at Cat Island | CEI Blog

tiger shark at tiger beach bahamas

Don’t bite the hand that feeds

The team and UM published an article in March 2012 called Don’t bite the hand that feeds: assessing ecological impacts of provisioning ecotourism on an apex marine predator.

The article represents a strong scientific look at the the potential impacts of “shark provisioning” for the shark diving tourism industry on the natural behavior and migration patterns of the sharks involved. Here’s the article’s summary:

    1. There has been considerable debate over the past decade with respect to wildlife provisioning, especially resultant behavioural changes that may impact the ecological function of an apex predator. The controversy is exemplified by the shark diving industry, where major criticisms based on inference, anecdote and opinion stem from concerns of potential behaviourally mediated ecosystem effects because of ecotourism provisioning (aka‘chumming’ or feeding).
    1. There is a general lack of empirical evidence to refute or support associated claims. The few studies that have investigated the behavioural impacts of shark provisioning ecotourism have generated conflicting conclusions, where the confidence in such results may suffer from a narrow spatial and temporal focus given the highly mobile nature of these predators. There is need for studies that examine the potential behavioural consequences of provisioning over ecologically relevant spatial and temporal scales.
    1. To advance this debate, we conducted the first satellite telemetry study and movement analysis to explicitly examine the long-range migrations and habitat utilization of tiger sharks (Galeocerdo cuvier) originating in the Bahamas and Florida, two areas that differ significantly with regards to the presence/absence of provisioning ecotourism.
    1. Satellite telemetry data rejected the behaviourally mediated effects of provisioning ecotourism at large spatial and temporal scales. In contrast, to the restricted activity space and movement that were hypothesized, geolocation data evidenced previously unknown long-distance migrations and habitat use for both tiger shark populations closely associated with areas of high biological productivity in the Gulf Stream and subtropical western Atlantic Ocean. We speculate that these areas are likely critically important for G. cuvier feeding forays and parturition.
  1. We concluded that, in the light of potential conservation and public awareness benefits of ecotourism provisioning, this practice should not be dismissed out of hand by managers. Given the pressing need for improved understanding of the functional ecology of apex predators relative to human disturbance, empirical studies of different species sensitivities to disturbance should be used to guide best-practice ecotourism policies that maximize conservation goals.

Read the full research article here.

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