as you know.
What is the pas?
Is that not a name?
It is the same recycling of waste.
Police, civil, modern-day shelter NSD
please step out of the way.
The idea of shark sends a chill down the spine.
They are known man eaters, designed to kill a top marine predator.
These people are deliberately entering shark infested waters.
They are prepared to risk their lives to dispel the myth that all sharks are wanton killers.
They are trying to discover what motivates the fish to attack and how aggressive some of them really are.
The great white shark, also aptly named the white death, is terrifying.
It's the world's largest predatory fish, can reach 21 feet in length and weigh up to three tons.
It holds the dubious record of having made more attacks on man than any other shark species.
Fish are its staple food, although it sometimes eats turtles, sea lions and people.
Excited by the smell of dead fish, it will attack indiscriminately out of bloodlust.
Marine biologists acknowledge that the great white is extremely dangerous.
This Australian diver lost a right leg to a great white off Melbourne.
A fellow Australian survived an attack by a great white that exposed rib cage, lungs and stomach.
But not all sharks are dangerous, and the scientists believe that by reacting appropriately, most shark attacks can be avoided.
Although the whale shark is a giant among its kind, it's harmless.
It grows to 60 feet and weighs up to 90,000 pounds.
It feeds on plankton, tiny fish and squid, which it strains from the water through sieve-like gills.
Yet the smaller, unmistakable hammerhead is an unpredictable killer.
The earliest sharks evolved 350 million years ago.
Of the 300 species alive today, there are some strange forms, remarkable adaptations to a complex environment.
The Pacific angel shark is one of the oddest.
It looks like a ray, but is a true shark.
Like many of the bottom living species, it's quite harmless, preferring to bury itself rather than attack when danger threatens.
The horn shark, too, is completely harmless, but can be a pest.
It feeds largely on mollusks and crustaceans, and sometimes damages shellfish beds.
Its teeth are specialized for crushing the hard shells of its prey.
Some sharks give birth to well-developed live young.
Others carry their eggs inside their bodies, where the embryos hatch just before they're born.
A third group lays eggs in leathery cases, often called mermaid's purses, which they attach to seaweed.
This is the spiral egg case of a horn shark.
This one shelters a swell shark embryo.
It will emerge in about five months.
Egg cases are mostly laid by bottom living sharks.
The Australian wobbegong is the weirdest of this group.
It's one of the carpet sharks and relies on camouflage to hide from enemies, as well as fool its prey.
The Port Jackson shark of Australia is another harmless shallow water species.
Not all sharks are aggressive.
The bottom feeding nurse shark is exceptionally docile.
But when it clamps onto prey, it holds on with the tenacity of a bulldog.
Death may make it let go, but even then the jaws may have to be pried open.
The leopard shark has classic menacing looks, the supposed image of a killer.
Yet it too is no threat.
It's the undershot jaws and triangular dorsal fins which tap some hidden root in the human psyche,
some dark corner where nightmares lurk.
It's these sharks, the dangerous ones, which the scientists are most interested in.
Rangiroa Island in the mid-Pacific is a center for shark research.
It's surrounded by shark-infested waters.
People have been in close contact with the sharks of Rangiroa for hundreds of years, and accidents are rare.
Six years ago, a shark almost completely tore the calf muscle from the right leg of this Polynesian spear fisherman.
Yet he continues to fish for his living, believing that the encounter was just an unlucky accident,
and that, provided the fish are treated with caution, the chances of it happening again are very slight.
Fishermen say that the sharks recognize that they're both hunting the same prey, and generally keep their distance.
The locals have been fishing here for centuries, and learned long ago how to behave when sharks are around.
This is the most dangerous moment for spear fishermen.
They know that a struggling fish will attract trouble, so they bring their catch to the surface as quickly as possible.
They can also recognize the difference between a harmless and dangerous shark from their swimming attitude and body posture.
An occasional fish has to be sacrificed to these rival predators.
It's a small price to pay for coexistence.
That the human fisherman can coexist at all is due entirely to their calm reactions and instinctive recognition of what triggers off shark attack.
By questioning skilled fishermen and following their example, the scientists believe they can help shipwreck and air disaster victims avoid shark attacks.
To back up the local knowledge and to learn as much as possible about their behavior, the team decided to enter the shark's world.
The first species they studied is active at night, an eerie time to go looking for a shark, especially one that averages eight feet in length.
The white tip reef shark is unnervingly inquisitive and persistent by nature.
Its teeth are razor sharp, although there are few records of a white tip attacking a man.
It hunts along the bottom for small fish and octopus.
On the reefs off Rangiroa, it frequents coral caves.
Divers have to be careful not to block off escape routes, which could panic a shark and even provoke an attack.
The local fishermen can recognize an aggressive shark.
These white tips are swimming in a normal and relaxed fashion, so presumably safe.
The secret to identifying a killer is not by its looks, but in the way it presents itself.
Sharks do not seem to be territorial or defend a given part of a reef, but by fitting some sharks with sonar transmitters and tracking them,
the team discovered that the fish are much more regular in their habits than previously suspected.
A transmitter is sewn into the mouth of a large fish, which the team hopes a shark will swallow.
On board ship, a receiver will pick up the signals, which can be heard through a mile or more of water.
Although the white tips are interesting, it is the gray reef shark that the team most want to study.
This species is known to attack man.
The channel between the islands is a favorite haunt of the grays, so this is where the researchers set out to fit one with a transmitter.
One of the diving team goes down to make sure that only a gray takes the bait.
Although these sharks often tear chunks out of large prey, they swallow small fish whole.
The first strike fails, but stimulated by the feeding activity, more grays close in.
The divers must be on guard. Sharks are known for attacking unexpectedly when there's blood and dead fish around.
Radio tracking experiments have revealed that, like the white tips, grays follow regular daily patterns.
They often hunt in packs, but seek solitude too.
The more that's known about when they hunt and where, the greater the chances of keeping out of their way and avoiding accidents.
The transmitting shark led the team to a previously undiscovered location, where they found grays congregated in unusually large numbers.
A shark's senses are highly tuned to detect prey. Since this sometimes includes humans, it's vital to understand how they work and what they respond to.
To avoid awakening those responses is probably the best defense against shark attack.
Sharks respond instinctively to sound, particularly low frequency noises made by struggling or wounded fish, and they can detect these sounds from several hundred yards.
The team prepares to create such sounds electronically, a potentially dangerous situation.
The team and track team work close to the current inflation rate trend, each found detectively fairly close to the past two
Falls of Frunze
The
grays are curious and obviously excited.
The divers watch for the aggressive displays described by the fishermen,
which often precede an attack. They start with a series of exaggerated swimming movements.
The snout is lifted and the back arched. The pectoral fins point stiffly downwards.
This aggression is directed at another shark, but it's a warning to the diver either to stay
still or to back away slowly. A rapid retreat may trigger an attack.
Sharks also have extremely well developed senses of taste and smell and can detect dead fish from
a great distance. Their excitement is mounting. The diving team is in danger and must move to a
safe distance. A feeding frenzy can develop suddenly with white tips,
black tip reef sharks, and grays all joining in.
At times like this, even comparatively harmless species can lash out in competition with each
other and turn into potential killers.
Sharks aren't confined to tropical waters. The blue shark is common off American shores.
It's not by nature a man eater, but like all sharks is an opportunist. The blue is typical
of its kind, equipped with acute senses which make it a skilled predator.
Vision is limited underwater, but a shark's large eyes enable it to detect movement and
distinguish various fish by their outline. Their nasal pits can detect smells at less
than one part per million. Along each flank, there's a row of nerve endings and sensitive
pits called the lateral line. Using its lateral line, a shark can detect the vibrations made by
swimming fish. A strong muscular tail powers the shark through the water. The upper lobe,
which is longer than the lower, acts like a paddle to add thrust. Wing-like pectoral fins
balance and guide the body. A great deal remains to be learned about sharks, but recent research
suggests they can also perceive magnetic fields and electric impulses. The waters around Santa
Catalina and San Clemente off the Californian coast are warm, rich, and shark-infested.
The giant kelp beds support huge shoals of fish, which in turn provide food for predators,
including whales, sea lions, and sharks.
Blue shark are common here, as is the large bat ray.
Californian sea lions hunt the giant kelp beds. Their pups are occasionally killed by Mako sharks,
which also occur in these waters. Fear of sharks is a possible reason for the sea lions' agitation.
Mako's also attack people. The only safe place for researchers to study these killers is from
behind bars. Here, off the coast of California, these scientists are looking at locomotion and
the bite power of sharks. The safety cage was able to ascend and descend like an elevator by
means of compressed air. The most effective way to study sharks is to attract them with bait,
but they are unpredictable creatures. Sometimes it's difficult to do or any at all, while on
other occasions so many turn up, the team can find themselves in a very dangerous situation.
When a team as large as this is working with sharks, it's only too easy for one of them
to be surprised by an unexpected attack. So the group includes safety men, whose job is to watch
for danger. They're armed with explosive powerheads, only to be used in extreme emergency. These
primitive organisms drifting past are colonial salps, ancient and mysterious creatures, which
are like the ancestors of all animals with backbones, including sharks. Being surrounded
by big blues would be most people's idea of a nightmare, but the team regarded as a triumph.
In normal circumstances, blue sharks, even large ones, are relatively harmless,
but when they're overexcited, particularly during a feeding frenzy,
they've been known to lash out at anything that moves, even their own kind. In a situation like
this, the safety men are an essential part of the team, especially when there are known killers
about, like the hammerhead. When a Mako enters the scene, the situation changes from serious
to extremely dangerous. But this is what the researchers had hoped for, a potentially lethal
encounter. The sea lions recognize the danger. Instead of fleeing, they instinctively know to
keep the killers at a safe distance, but within sight. The research team are deliberately trying
to provoke a feeding frenzy by lowering a large basket of dead fish into the water. They want to
know what triggers one off and how best to behave in the situation. Sharks have razor
sharp, backward sloping teeth with which they seize and maintain a vice-like grip on their prey.
A victim is torn into bite-sized pieces with violent shaking, tearing and sawing movements.
A frenzied blue lashes out at one of its own kind. Once a shark has got hold of prey,
almost nothing will make it let go. This makes rescuing human victims difficult,
especially when sharks can support their own weight by their teeth. When the water becomes
clouded with fragments of tissue and blood, the sharks appear like vultures on a kill,
blues so far, but suddenly there's a stranger in their midst, a mako. Compared with a blue,
it has more evenly sized upper and lower lobes of the tail and shorter jaws. It also has a
double row of particularly vicious teeth. Any victim hooked by this mouthful has little chance
of escape. While filming the frenzy, one of the divers got raked across the head by a shark.
Luckily, only his wetsuit hood was damaged. To kill a shark was the last thing the team wanted.
They maintain that recent fiction and feature films have resulted in divers killing far too
many sharks on site or for so-called sport. Nevertheless, during the filming,
the safety men were responsible for the team.
This was the one occasion when they judged that a mako was about to attack.
There's no bullet. A blank charge kills the shark.
A number of sharks bear large wounds, which were almost certainly inflicted by their own
kind during feeding frenzies.
No one has ever tried hand-feeding blue sharks before. In calmer circumstances,
the team found the blues sensitive and even friendly.
Grabbing a shark by its fins makes it irritable or even causes it to panic.
It's not a recommended way to handle a shark. A safer method of dealing with an over-inquisitive
shark is to seize it by the tip of its nose, so keeping its mouth at arm's length.
The team advocates banging and attacking shark on its sensitive nose only as a final resort.
The fish could lash out in response to pain and confusion.
Even though the scientists were feeding and handling potentially dangerous sharks,
the only casualty was a lightly grazed wrist.
The next series of experiments was designed to determine the means by which blue and mako
sharks detect prey. The team hoped to discover more facts which would help survivors of shipwrecks
and air disasters. They wanted to test the relative strengths of the three main feeding stimuli.
The aroma of dead fish rapidly attracts some big makos.
Large blues too home in on the scent.
Beyond the fish bait is a container holding an underwater speaker emitting low frequency
sounds which imitate a struggling fish. The waving white object is a visual attractor,
a dummy squid. Squid are a particular shark delicacy. The question was which of the three
known shark attractors would achieve the most response. The electronic fish begins its simulated
struggles. At the first attempt, a number of sharks arrived and milled around indiscriminately.
Too much fish oil accidentally released into the water probably overwhelmed their acute
senses. The experiment was retried in another area with less fish bait.
A single blue approaches the sonar device then heads for the fish baited lure attracted
by the oily smell. It's obviously interested. But unable to get at the food, it goes off
to inspect the other attractors.
It circles the visual signal for a while. But returns to the audio imitation of a struggling
fish and actually mouths the transmitter. Before the team can come to any conclusions,
the tests will have to be carried out at length and on many different species. But this blue
shark appears to find the sound of a wounded fish most attractive while it practically
ignored the visual enticement of the beckoning squid. The implications are that visual stimuli
are much less important than once thought. It's sound and smell which sharks home in
on. If this proves to be true, then anyone stranded out at sea should try to stop any
bleeding and remain calm and still.
Another study group are looking at locomotion and the bite power of a shark's jaws.
The scientists want to take close-up photos of the shark's open mouth at the moment it
bites. It's dangerous work, so the researchers operate mainly from inside the cage. To get
close-up photos, the bait is attached just outside the cage.
This bait fish has been implanted with a bite gauge. The gauge consists of a metal rod surrounded
by ball bearings. The amount by which the rod is dented by the ball bearings gives
a measure in pounds per square inch of the force exerted.
The sharks are curious but nervous. It's typical of sharks when unsure of themselves that they
circle the prey, getting closer and closer as their confidence builds, another piece
of behavior that all divers would do well to remember. Eventually, when the circle gets
small enough and they've lost their fear, they usually move in for the kill.
When a shark makes an attack, it closes its eyelids, presumably to protect its eyes when
it shakes the bait. This big blue has taken an ordinary fish bait,
but the nearer one has got a bite gauge. The tube can be seen nearly out of the fish as
the shark shakes the bait.
In fact, this small blue was more intent on shaking than biting and eventually shook
the gauge right out of the fish. The gauge is retrieved in order to load it inside another
bait. The hungry sharks, impatient for food, storm
the cage.
With that said, I'll be back.
Again, it was
the man killers, the big Makos, which most interested the team. When they at last turned
up, the bite gauge was waiting for them. At the trailing edge of this Makos' dorsal and
pectoral fins, there are streamer-like parasites. The fish are discouraged until both cameras
are set.
At last, both cameramen are ready to film, but now the Mako is reluctant.
At the first attempt, the shark simply cuts the rope.
Finally, a perfect grab. These Mako bites were later analyzed. The tips of the shark's
teeth were found to have exerted a pressure of 8,000 pounds per square inch. That's enough
to sever a human arm.
We now know that sharks are not unpredictable killers. Fewer than a hundred shark attacks
on people occur annually, and less than half of these are fatal. In comparison, six times
as many people a year die from bee stings in the United States alone. Sharks are dangerous,
but they're also magnificent and awe-inspiring creatures, whose menace must be kept in perspective,