In the Presence of Sharks



 

One of the more common worries that new scuba divers often mention goes something like this: “What about sharks? Should I be nervous?” The answer is “Yes, you should be very nervous.” But not for the reasons you might think. I often tell new diving students about the first shark I ever saw underwater. It happened around twilight on a cool Caribbean evening as a diving buddy and I splashed into the water just off a small isolated key in the British Virgin Islands. We chose this spot because it was known for having lots of sharks that can be seen feeding. The hours just before and just after sunrise and sunset are the prime feeding times for many species of sharks. Their eyesight is maximized for this brief transitional period, during which they can see even better than cats. Just as I have been asked many times since, I hit the water wondering, Am I on the menu? Would panic set in at the sight of this vicious predator? What was I getting myself into?

And then I saw one—a blacktip reef shark! Barely, at first, but then slowly its sleek powerful shape came into view. I couldn't believe my eyes—I was transfixed by this majestic creature; yet, it took no notice of me. Quietly, and with graceful coordination, its large tail fin swung back and forth as it scanned the seafloor for signs of life. Within an instant it was underneath me, not 20 feet between us. The gray shading of its back blended almost perfectly against the rocky substrate dimly lit by the dying light of the evening sun. I was mesmerized as it silently ambled away from me. And then the fear set in, but it wasn’t panic, rather I was terribly worried that it was swimming away from me.

My reaction was somewhat of a surprise—I chased after it, leaving any rational thoughts or worries behind me, hoping to spend just a few more seconds alongside this ancient wonder. How could something so beautiful have been so demonized by the society above? It seemed to me that this was certainly a creature to respect, but not to fear. Time and again, I would see many future students repeat this exact scenario. Their preconceived notions and fears about “killer sharks” were torn to pieces by the enchanting, nonchalant nature of these aloof passersby. 

So, why then do I tell my students to worry about sharks? Because, on average, 100,000 to 200,000 sharks are killed each day. In the time it takes you to read this article, 1100 sharks will be slaughtered—and that’s only if you read it quickly. With little to no regulation on shark fisheries worldwide, scientists have recorded a 90% decline in shark populations in the last 60 years. Sharks represent the largest group of threatened species on the International Union for Conservation of Nature (IUCN) Red List of endangered species. Of the 64 species of major sharks studied by the IUCN, 30% are threatened with extinction and over 150 shark species are classified as endangered or threatened. Yet, of the 360 species of sharks found worldwide, only three have gained protection from international trade: the basking, great white, and whale shark.

This is a major problem for sharks, the ocean environment, and people! Although sharks have gained notoriety because they are an aggressive apex predator at the top of the food chain, their role in the environment is anything but sinister. They help to regulate and maintain the balance in marine ecosystems by controlling population dynamics, spatial distribution, community structure, and species diversity. A great example of how important sharks are to a healthy ecosystem is right here in the Hawaiian Islands. Studies have shown that in the relatively isolated waters around the Northwest Hawaiian Islands the amount of overall biodiversity is directly correlated with a greater abundance of apex predators such as sharks. Whereas, around the main Hawaiian Islands, the biodiversity of fish lower down on the food chain is greatly reduced due to a lack of these apex predators.

Unfortunately, the situation around the main Hawaiian Islands is commonplace around the globe. Removing these keystone species from the environment in the millions upon millions over the past 100 years has effected the ocean environment. How badly this will affect people is a global game of Russian roulette, and we are already a few clicks deep into the game. The ocean regulates life on earth from the amount of air we breathe to the temperatures we can survive in, and it does so while providing the majority of the food people consume for protein. Sharks are the masters and, in many ways, the gatekeepers of the marine ecosystems that help regulate the oceans. They existed for millions of years before even the dinosaurs, all the while providing their invaluable services maintaining a healthy ocean.

It has been proven both in aquatic and terrestrial ecosystems that if the top predators are removed, the consequences both economically and ecologically can be enormous. Without sharks, the smaller mesopredators they control begin to increase in population. A great example of the problems this creates is the loss of the century-old bay scallop fisheries caused by the explosion of cownose ray populations whose natural predators, sharks, have been eliminated by people. Every level on the food chain exerts control over all the levels below. The increased ray population decimated the scallops below them on the food chain. Sharks, being at the top, have the greatest influence in regulating ocean ecosystems. The complex and interconnected balance in an ecosystem begins to transform and possibly break down without that top-down control. The effects cascade down the food chain. This balance is what allows ecosystems, such as the oceans, to provide natural services, which support the comfortable habitation of many other species, including people.           

Yet, we seem willing to gamble our resources and interfere with evolution for commercial purposes. The main reason why most sharks are killed is to supply an enormous demand for shark fin soup, a traditional Asian delicacy. The primary ingredient for the dish comes from the shark’s fins, which leads the majority of fishing vessels to hack off the shark’s fins at sea and throw the finless creature back into the ocean alive, but incapacitated. It is a gruesome, sober sight. A finned shark can only wail back and forth uncontrollably as its deformed body slowly sinks. This once great predator reduced to a horrific fate, a slow, but certain death.

The thing is, shark fin soup has been proven to have little health or medicinal benefits. Ironically, it would be much healthier for humanity as a whole to have sharks in the ocean, rather than served up in soup. Although it is an important custom and understandably a significant cultural practice in many Asian communities, we must learn from the lessons of the cultures, which have come and gone before us, or we are doomed to repeat their mistakes. To preserve our much-needed natural resources, many countries have now begun banning the consumption of shark-related products and the finning of sharks.      

If you are lucky enough to see a shark underwater, do so with an experienced guide and a healthy respect for these amazing creatures. Always keep an open mind and remember a few statistics. There is a 1 in 264 million chance of getting killed by the shark swimming past you. You have a higher chance of winning an Oscar or becoming a Nobel laureate. Food for thought: for those who have ever been brave enough to approach a vending machine, well, I congratulate your bravery as tipped over vending machine accidents kill four times as many people than sharks! Conversely, the likelihood of that same shark getting killed by you is about 1 in 85. In 2010, according to the International Shark Attack File (ISAF), for every human killed by a shark, humans killed twelve million sharks.

Of course, sharks can be dangerous, but if you respect their boundaries and understand the reasons people do get attacked by sharks, you are highly unlikely to be a shark attack victim. Most importantly, not all sharks are alike. There are only a handful of shark species responsible for the majority of attacks. Most of these are often cases of mistaken identity, such as a surfer who looks like a seal from below, or spear-fishermen who are trailing wounded fish. Learn about the various species and you can easily avoid the places they are found. Murky waters, river mouths, and the open ocean are all places where dangerous sharks can be found, but are also easily avoidable. Remember sharks feed at sunset and sundown, don’t swim alone away from the beach during these hours. Follow standard water safety techniques such as swimming in groups, hire a guide in unfamiliar waters, and stay away from harbors, high boat traffic areas, or fishing spots to avoid both people and shark hazards. Most importantly, get educated so that you can safely enjoy sharks and even have an unforgettable positive encounter with one.      

The implications of killing so many sharks are profound and largely unknown. We have no way to quantify the exact consequences of these actions as the large scale and interconnected dynamics of the ocean ecosystems are too complicated for any person or computer to accurately predict. But if I told you before your next flight that I removed a bunch of random parts from the jet's engines, would you still get on it? I certainly hope not. Similarly, we need to ensure the conservation of these precious creatures, and it starts by getting to know the real facts about their true nature, ecological importance, and relationship with people. Try diving or snorkeling with a respected local company and it’s likely that it will be you chasing the sharks, not the other way around.

Whether I am leading a group to a hidden coral cavern where baby whitetip reef sharks like to hide or staring in amazement as a mighty tiger swims by for a look, one of the most exciting and rewarding experiences underwater is spending a few precious moments in the presence of sharks.

 

Common Sharks of Hawai'i:

Blacktip Reef Shark (Hawaiian: Mano Pa'ele)

Scientific: Carcharhinus melanopterus
Length: Up to 6-ft, but generally under 5-ft. Can be seen close to the coastline and the reef edge.
Body: Main dorsal fin has large black tip with cream band underneath. Black tips on all other fins and a very large black tip on lower tail fin.
Food: Eats reef fish and invertebrates.
Disposition: These pose little danger to humans. They are very inquisitive toward divers and swimmers, but lose interest quickly.
IUCN Red List Status: Near Threatened

Gray Reef Shark (Hawaiian: 'Aumakua)

Scientific: Carcharhinus amblyrhynchos
Length: Up to 8-ft. Most grays are under 6-ft in Hawai'i and are among the most common species.
Body: Distinguished by a black border on the very edge of their tails and lower fins and no black on their dorsal fins. Gray upper body with a white underbelly and long slender shape.
Food: Feeds on bony fishes, squid, and shrimp.
Disposition: Grays are both curious and shy. They are inquisitive toward divers, but posture (agnostic display) and flee if startled. They pose little threat to humans unless provoked.
IUCN Red List Status: Near Threatened

Sandbar Shark

Scientific: Carcharhinus plumbeus
Length: Up to 8-ft. Most in Hawaiÿi are 4-6 feet or less and seem to prefer slightly deeper waters off shorelines, harbors, and bays.
Body: Gray or light tan with a high dorsal fin and sloping forehead.
Food: Eats reef fishes, octopuses, squid, crustaceans, and mollusks.
Disposition: This is a curious shark that will investigate but quickly leave an area if no food is present. It is not aggressive to humans and prefers areas away from the reef.
IUCN Red List Status: Vulnerable

Scalloped Hammerhead Shark (Hawaiian: Mano Kihikihi)

Scientific: Sphyrna lewini
Length: 12-13 feet but averages 5-7 feet. Common in shallow waters during the spring and summer.
Body: Characteristic hammer-like head with four shallow lobes, hence “scalloped” on the front margin of its head.
Food: Reef fishes, sharks, rays, cephalopods and crustaceans.
Disposition: These sharks are very shy and tend to avoid people, but can be aggressive if not left alone.
IUCN Red List Status: Endangered

Tiger Shark (Hawaiian: Niuhi)

Scientific: Galeocerdo cuvier
Length: Up to 18-ft. Most tigers in near shore waters of Hawai'i are juveniles around 6-8 feet in length.
Body: Distinct spotted pattern in juveniles and vertical stripes in adults. Broad round snout and wedge-shaped head.
Food: Often called the “garbage can of the sea,” tigers prefer injured or dying prey plus just about any marine creature they are able to scavenge such as sea turtles. Humans are not on their menu, but they have been known to eat license plates and discarded chicken coops.
Disposition: This can be an aggressive shark. Of the 360 species of sharks, it is one of the four species which are responsible for most mistaken identify attacks on people. Most commonly, they avoid people.
IUCN Red List Status: Near Threatened

Whitetip Reef Shark (Hawaiian: Mano Lalakea)

Scientific: Triaenodon obesus
Length: Up to 7-ft. Most in Hawai'i are 5-ft or less and are the most commonly seen shark species.
Body: Distinct white tipped dorsal and caudal (tail) fins. Gray slender body with a flat head and short snout.
Food: Eats reef fishes, octopuses and crustaceans.
Disposition: One of the few sharks that can lie motionless and continue to breathe. Very docile and poses no more danger to humans than the family dog.
IUCN Red List Status: Near Threatened

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