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SAVE THE SHARKS
The best place to study sharks is among them, in their natural marine habitat. Advances in diving gear and techniques, hand-held and remote camera technology, recording, tagging systems, satellite tracking, ROVs (underwater remote-operated vehicles) and other fields make studying sharks increasingly rewarding and productive.
Gradually, we can watch sharks in ever more detail and get closer to understanding what makes them tick. One of the first people to attempt serious underwater studies of sharks was the late Jacques Yves Cousteau (1910-1997). With his teams of underwater photographers, film-makers, explorers and scientists, he carried out much original research in the 1950s and 1960s. Cousteau helped to design the first scuba (self-contained underwater breathing apparatus) equipment and pioneered the use of shark cages for observation and filming.
Shark's eye view
The "crittercam" instruments are worn by wild animals for a time then retrieved. Consisting of video cameras and other information-gathering equipment, they are used on various land and ocean creatures. The "crittercam" is attached to the temporarily captured or securely held shark. When the shark is released, the camera records what it sees and where it goes. After a set time the camera strap disintegrates or unlinks, and the camera then floats to the surface, emits a radio signal and is recovered. Research around Australia, North America and South Africa is revealing the behavior of species such as great whites, tiger sharks and bull sharks.
Shark tags vary from simple plastic clip-on versions, usually attached to a fin, to sophisticated tracking devices that emit radio signals and can be detected by boats or even satellites. Some of these radio emitters are safely "force-fed" into the shark, allowing researchers to follow it for several days, until nature takes its course and the device is expelled.
In the northwest Atlantic's Cooperative Shark Tagging Program, scientists, sports anglers and commercial fishing boats work together. They do not bring their catches back but measure the shark, fit it with a numbered tag, then let it go. If it is recaught in a different place, the distance and direction it has traveled and the amount it has grown are recorded. The tags have revealed that some sharks, such as the sandbar shark, mature very late and have few offspring. The conclusion is that when a population is fished out, it will take a long time to recover.
Threats to Sharks
Estimates of the numbers of sharks killed by human activity each year vary from around 50 million to more than 100 million — that's three dead sharks every second. It compares to around 8-12 human fatalities annually in the other direction.
The threats to sharks vary hugely, as they do with many wild creatures in their natural environments. A great challenge is that we can be presented with eye-catching images of logged devastated rainforests, drained cracked wetlands and oil-polluted shorelines to raise awareness and gain momentum for conservation. But because of visual limits, we cannot encapsulate the threats to the undersea habitat into such telling images.
A great threat to most sharks is the fishing industry and overfishing in general. Some fishing deliberately targets sharks, from hammerheads to dogfish, by various means such as curtain nets, trawls and hooked lines. The sharks are caught for their flesh, liver, oil and other products. One of the most controversial practices is finning (see panel on facing page).
Another problem is bycatch, where sharks are caught incidentally while targeting other fish. Large predatory sharks naturally congregate around schools of prey fish — and these are also being sought by fishing fleets. The vast nets indiscriminately catch them all. Trapped sharks may be released, but by then they are often fatally injured.
Today's industrialized fishing fleets are so efficient that fish stocks of dozens of species are falling around the world, and some regions are almost fished out. Sharks depend on these types of fish as their food. As the fish disappear, the sharks go hungry and are less likely to grow and breed. Also, as traditionally caught food species of fish become more scarce, commercial fishing turns increasingly to sharks.
Pollution and angling
Some sharks prefer inshore waters, often around bays and estuaries. These are the places where pollution builds up, with sewage, waste and agricultural and industrial chemicals washed into the sea from rivers or inshore effluent pipes. The chemicals enter the food chains, and as smaller fish are eaten by bigger fish these chemicals become more and more concentrated in their bodies, a process known as bioamplification. Sharks are often among the top predators of their habitat and accumulate the highest levels.
Sports angling has also been a threat to the large, desirable sharks such as makos, which put up a spectacular fight when hooked.
Strategies for Conservation
Conservation campaigns picturing attractive and "cuddly" creatures, such as dolphins, pandas, baby seals, and even lion cubs, are designed to arouse public sympathy and support.
A similar campaign using the image of a fearsome shark may be less likely to succeed, but the principles are equivalent. All animals should command our respect as fellow inhabitants of our planet.
Improving the shark's image
Conservation depends heavily on education. A few species of sharks are known to attack humans, true. The same can be said of the tiger — yet there is widespread global support for tiger conservation.
Responsible education of young people at schools and colleges can obviously help, especially in nature, biology and wildlife topics. Television, books, magazines and websites can also inform about the shark's fascinating behavior and lifestyle.
Safely behind glass
Modern aquaria and sea-life centers contribute enormously to public awareness of aquatic life. Spectacular exhibits in giant tanks with walk-through tunnels allow people to stand inches away from one of the most deeply feared creatures. Most tanks feature a variety of sharks, but particularly sand tiger and sandbar sharks, which seem to take well to captivity yet look sufficiently big and frightening. Accompanying displays, commentaries and videotapes explain shark bodies and behavior.
The shark show
Shark shows truly bring education alive. At the reef, the sharks learn by simple association and habituation that the noise of the boat engine and the splash of people means food. Tourists marvel and take photographs as guards feed the sharks. Such demonstrations can certainly help to change the shark's image, but they depend on a thorough understanding of shark behavior, and there are potential problems. The general wildlife of the reef is disrupted and more sharks may be attracted to the area, which is often near a popular beach resort. It has been suggested that local sharks could even lose their own natural fear of us and come to associate humans with food.
National and international efforts
National governments, regional organizations and international authorities can be persuaded to look after the welfare of marine life and develop strategies for conservation. There is huge potential for fishing quotas and restrictions, which would not only help save sharks but also safeguard almost exhausted stocks of fished-out commercial species. However, many cultural differences remain, such as the popularity of shark's fin soup in certain regions.
|Chapter 1||Shark Success||8|
|Chapter 2||Ecology and Biology||30|
|Chapter 3||Sense and Supersense||62|
|Chapter 4||Design for Living||88|
|Chapter 5||Design for Killing||114|
|Chapter 6||More Sharks--or Fewer?||136|
|Chapter 7||Shark Talk||156|
Sharks have been living for over 400 million years. They came through the five great mass extinctions, and competed favorably with the rapidly evolving bony fishes, and today they are among the top predators in the sea.
During all that time, sharks have been honed to evolutionary perfection, with a body that yacht and submarine designers can only envy and with wide-ranging sensory systems that military technologists would die for.
The archetypal shark is a sleek, torpedo-shaped hunter with a tall, triangular dorsal fin and powerful scythe-shaped tail, but this is only one of many types of shark. There are gigantic filter feeders resembling whales, sluggish and flabby deep sea sharks, flattened bottom-dwelling angel sharks, reef sharks with wedge-shape heads for pushing into cracks and crevices, carpet-like wobbegongs that are camouflaged as coral, parasitic cookie-cutters with sucker-like mouths and enormous teeth, eel-like sharks with frilly gill slits, and epaulette sharks that can walk on their fins like salamanders.
They live in all parts of the sea, from the desert-like surface waters to the inky depths of the deep sea, and from the tropics to colder waters. There are sharks inhabiting coral reefs, mangroves, rocky shores, estuaries, and one species — the bull shark — that can live in freshwater hundreds of miles from the sea. Another — the Greenland sleeper shark — can survive even under the Arctic ice.
Throughout human history, however, all sharks have been tarred with the same brush, and have gained an evil reputation. Much of it was based on myth and folk tales, but some was due to the tendency of a few sharks to attack, kill and sometimes devour people. But this negative view is changing. There has been a revolution and now sharks have friends.
As shark biology and behavior become gradually clearer, people realize they can share the water with sharks ... as long as it is on the shark's terms. We now know sharks have a personal space that we must not invade or they will treat us like any other intruder and attack. They have a body language that we are beginning to interpret, and a new understanding of why they behave in the way that they do. They are not solitary killers looking for the next human victim, but many are social animals abiding by the rules of their own shark society.
New Status for Sharks
Understanding sharks in this way has changed attitudes. Shark scientists now dare work with sharks outside shark cages, even with potentially dangerous sharks, such as great white, tiger and bull sharks, which were once feared as insatiable man-eaters. Groups of tourists can attend specially arranged shark banquets on the sea floor. Fear has been replaced with respect. People want to swim with sharks, and some even hug them.
But people cannot turn sharks into pets. They are wild animals, and highly efficient predators. In certain circumstances they can be very dangerous, and the press is quick to react when an attack occurs on a person. The world's newspapers still consider sharks as front-page news, and a spate of shark attacks in US waters during 2001 began to tarnish the shark's new image. But those who are beginning to understand sharks realize that many of these attacks are not due to the shark's behavior but to our own. We place ourselves in places where sharks expect to find food, and attacks are often cases of mistaken identity. Sharks are not interested in people as food. There are no rogue sharks with a taste for human blood, just sharks living in their own environment going about their daily lives as top ocean predators.
Posted June 10, 2009
I rented this book from the city library, and I was satisfied with the information it contains. It has basically everything you need to know about sharks. Also includes many photos of different species of sharks and illustrations of their body systems. Great for anyone!
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I was shocked at how many errors, grammatical and otherwise, I found in this book when it claims to be an encyclopedia. It appears as though the editors of the book knew nothing about sharks and as such did not catch the errors in fact and image inherent in this book. As an amateur shark expert, I am upset by the amount of speculation presented in this book as fact, and many of the images are mislabeled. I can clearly tell that the picture the book claims is a tiger shark is actually a blue shark in multiple occurrences. Also, many of the images are obviously either digitally created or enhanced or fake sharks, which is just plain unprofessional. While I have to admit that this book would not lead the reader to believe things about sharks that are wholly untrue or damaging to the relationship between human and shark, I am appalled at the amount of inaccurate or misleading information presented that anyone who knows anything about sharks would be very quick to doubt. I highly recommend avoiding this book and instead purchasing a different, more credible and complete shark book.
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Posted February 6, 2010
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