22 Jul Sharks & Shame
Sharks & Shame
22 July 2018
As a reporter, cameraman, consultant specializing in sharks and co-author of the book/guide Sharks: “For Your Eyes Only” with his wife Monika, David Martin is part of the wonderful community of protectors of nature and whistleblowers who work tirelessly to raise people’s awareness on the necessity of protecting our ecological heritage, especially the keystone species of sharks.
What fairy, or in this case, mermaid, lighted on the cradle of the baby boy from Auvergne in 1969 to inspire him with his fascination with sharks?! From a very young age, David Martin ignored trucks and other toys, and instead collected shark teeth. His first drawings in kindergarten represented sailors,fish, fishermen, etc.
Starting at age 11, he signed up for a diving club and earned his certifications. At the age of 18, with his diving instructor certificate in hand and the blessing of his parents, he went to the Maldives and then began his beautiful love affair with sharks. He loved the Cousteau movies and so started taking diving pictures, quickly becoming one of the most famous photographers and filmmakers in this genre.
Working independently since the economic crisis in 2007, he travels the oceans, sometimes along with his two children who are aged 8 and 12, to take beautiful pictures to feed the stocks that are used to make up their documentaries, which have been seen on television, from BBC to The Discovery Channel, National Geographic, Canal Plus, and TF1.
Two incidents involving sharks have occurred in the past two years on the beaches of Phuket, and a tourist has just been bitten in Hua Hin. What do you think about this?
These are apparently bull sharks, one of the only species that approaches the beaches and mangroves and that even travels up rivers. Unlike other species of sharks that are hunters, the bull shark is a scavenger. They roam murky waters looking for carcasses, and it’s possible that it mistook the swimmer’s leg for one and bit it. But they’ve become very rare in Thailand due to intensive fishing.
Do you think that fishing is the cause behind the rarefaction of fish in general, and sharks in particular, in Thailand?
Obviously! One-hundred million sharks are fished every year (one every three seconds!), mostly to be sent to the Asian markets for shark-fin soup. This is a real threat for the reproduction of the species, and this number only accounts for industrial fishing.
Fishing is regulated in most countries, but only in territorial waters, up to 12 miles from the coast, i.e. almost nothing. On the other hand, in the Maldives, where net-fishing is prohibited, even for the locals, and you can easily find large quantities of sharks, barracudas, wrasses, groupers, etc.
Do sharks have a habitat in particular?
Not really. There are more than 400 species of sharks, the largest being 15 meters long. They can be found from the Arctic to the Antarctic, but more than 50% of them can be found in the Mediterranean because it’s a temperate sea. They enter at Gibraltar to hunt tuna. One of the largest great white sharks ever caught was in Malta in 1987; it measured more than 7 meters long! South of Sicily, where the largest tuna fisheries are found, the fishermen who clean the kilometers of nets are equipped with an underwater riffle with an exploding head.
Aren’t they usually found in the open ocean?
No, there are coastal sharks and open-water sharks; it depends on their food. Coastal sharks live mostly in the Maldives, Thailand, and in the tropics in general because there’s a lot of life in the reefs.
Can you tell us about their sensitivity to magnetic waves?
Every living being on the planet emits invisible electrical fields, like a sort of aura. Sharks are the only animals that can sense the electric fields of another animal and tell where they’re coming from. Even machines can’t do that! When you look at a close-up picture of a great white shark, you can see little dots on their snout, which are called “ampullae of Lorenzini. ” They’re microscopic holes that form the electrical field sensor.
Also, sharks have the same sensory organs as us: eyes, ears, a nose, and that story about a drop of blood attracting sharks from miles around is a myth. You really need to be only a few meters away.
When hunting, a shark locates its prey first by hearing, then by the vibrations it feels in its spine, then by sight and smell. But when it gets 25cm from its victim and opens its mouth, since its eyes are above its jaw, it can’t see anything. Also, a membrane automatically covers its pupils to protect it, so it goes completely blind! This is when the ampullae of Lorenzini take over. This is why sharks hunt at night: because other fish can’t see much and the shark has an enormous advantage, making it the best predator in the ocean for 400 million years. The orca, for example, which is a mammal, has only existed for 60 million years.
Sharks are always on the move…
All fish have bones, but the sharks are made of cartilage. The advantage of cartilage is in its exibility. Sharks can turn around, fit into holes, and are more apt to survive. Since it always needs to be swimming in order to breathe, it doesn’t have a swim bladder, which lets fish remain stable and not sink to the seafloor. If you’ve ever done trawl fishing, you must have noticed that when the fish is pulled out of the water, there’s a transparent membrane coming out of its mouth; this is the swim bladder. It comes out of the mouth because the fish is pulled up very quickly. Sharks make up for their lack of a swim bladder by having a huge liver.
When you open up a shark, the liver is three times the size of its stomach! It breathes through the mouth, bringing water in, and letting it out through the gill slits. While fish only have one, sharks have several. Only one family, the sleeper shark, will rest at the bottom and breathe by opening and closing its mouth.
Also remember that sharks and rays are in the same family, just like the poodle and the Doberman are both dogs!
How do sharks reproduce?
Reproduction takes place in three forms: oviparous, viviparous, and ovoviviparous.
Mammals make their babies directly, birds lay eggs, and fish lay thousands of eggs because eggs that are left on the bottom are at the mercy of predators, so they need to make lots of them so that a few will survive.
Sharks are the only fish that reproduce like mammals; they’re viviparous. They make babies like mammals, but since they’re not mammals (“mammal” refers to the mammary glands), there’s no maternal assistance. Baby sharks are born from their mother’s belly completely independent, unlike mammal babies, which have to be helped and fed by their mother for months. So, the baby shark is immediately autonomous and has more chances of survival.
The other difference with fish is their method of fertilization. In fish, eggs are fertilized externally: the male releases sperm and the female releases eggs, and they’re mixed together in the water, which is why there’s a tremendous loss of fertilized eggs. However, male sharks deposit sperm directly into the female’s body, so there’s zero loss! The male has two penises, but this isn’t for threesomes!
Under their bellies, male sharks have pelvic fins and claspers, or penises, and females have a slit or vagina. In adult males, the claspers extend past the fins, otherwise, penetration would be impossible. The male first has to grasp the female. Since it doesn’t have hands, it will hold on with the pectoral fins and its mouth, which is why you often find females with scars. Once he holds on, they will rest on the bottom, and depending on which side the female lands, either the right or left penis will penetrate.
Once, in the Maldives, I watched a fertilization take place. The female had two males, one on each side, but only one managed to get the job done!
What are some other special features in sharks?
As we’ve seen, sharks don’t have bones, but rather cartilage, so its teeth are embedded in the cartilage and fall out often. They regrow every two weeks, all the way to the end of its life.
Another particularity in sharks is their gestation. For some time now, I’ve been studying sand tiger sharks in South Africa. They’re ovoviviparous, meaning that they have eggs with a shell that hatch inside the mother’s body. The babies feed inside the womb, on the eggshell, and… on its weaker siblings; they’re cannibals! This makes it so that only the genetically strongest ones will make it out.
During the 9 months of gestation, the future mother will spend the last 3 months near the coast, in 12 meters of water, and she’ll stop feeding in order to give all its energy to the embryos. During this period where she doesn’t feed, algae grow on her teeth, the composition of which we’re studying right now.
Why do you think it’s important to protect them since apparently, they’re the best equipped to reproduce and perpetuate the species?
Sharks reproduce with five or six babies once or twice every two years, unlike other fish that make hundreds of thousands of offspring every year. But nature didn’t account for people fishing sharks more quickly than they can reproduce!
In the North Sea, 97% of the great whites have disappeared! However, we need them in the food chain. The food chain for fish goes from the smallest animals, krill, to the largest ones, the sharks. A 2-meter shark eats a large fish about every four days, so if they disappear, the link beneath them in the chain will overmultiply and decimate the link below it, and so on.
The whole balance will be off ! Then, for example, there will be too many sea snails, which will destroy all the seaweed that coral depends on, etc. The entire ecosystem will be affected.
One example: in North Carolina, there’s a fishing industry that the entire region depends on: scallops, which are preyed on by rays. The ray’s predator is the shark, but since 97% of sharks have disappeared from the North Atlantic, for the past ten years, the rays have multiplied and completely decimated the scallop population, and the industry has collapsed! The general public isn’t aware of this phenomenon.
What can we do as individuals to reverse the trend?
Millions of sharks are killed every year for one reason: to provide the Chinese with shark fins for soup! We need to tell the Chinese to stop eating shark fin soup, which is, by the way, only full of mercury and cartilage. This occurs through education. We need to pass the message.
Talk about it to change the negative image that sharks have, show young children swimming with sharks, for example. Reach public opinion. The most effective thing to do would be to go to all the schools in China to show Chinese children that the traditions their parents have put into place need to be abandoned because, with 2 billion people, this is a deadly situation!
As for me, whenever I go diving with Chinese visitors in the Maldives, for example, the message gets passed more and more. The proof of this is that up until last year, China Airlines used to serve shark fin soup to first-class passengers, but they have stopped this year after petitions from divers! We can spread the message as a scientific warning, like: the mercury found in shark meat makes you impotent!
Won’t nature just adapt? There have been lots of animals that have gone extinct over the centuries.
Of course, nature will adapt. What won’t adapt are people. The day when there’s no more coral, which is there to make plankton, oxygen, etc., the consequences will be dramatic for humankind’s survival. In short, ecology isn’t about protecting nature, it’s about protecting people.