What's it all about? Shark<\/p>\n
Ivy Susanti, The Jakarta Post, Jakarta<\/p>\n
Sharks are fish without bones, so they are grouped together
\nwith rays, skates and ratfish in the cartilaginous fish
\n(Elasmobranchii) subclass. They live in waters all over the
\nworld, in every ocean and even in some rivers and lakes. There
\nare about 368 different species of sharks, which are divided into
\n30 families.<\/p>\n
A shark's skeleton is made of cartilage, a tough fibrous
\nsubstance that is softer than bone. Unlike bony fish, sharks do
\nnot have a swim bladder.<\/p>\n
The oceanic whitetip shark (Carcharhinus longimanus), which
\nmeasures up to 3.9m, is regarded as a dangerous species.<\/p>\n
Size and shape<\/p>\n
Sharks range widely in size -- some species are as small as a
\nperson's hand while others are larger than a bus. Full-grown
\nsharks range in length from 18-centimeters (Spined Pygmy shark)
\nup to 15m (Whale shark). Most sharks are intermediate in size and
\nhave human-like dimensions, ranging from 1.5 to 2.1m in length.<\/p>\n
The largest living shark -- also dubbed the biggest fish -- is
\nthe whale shark (Rhincodon or Rhiniodon typus). Next largest is
\nthe basking shark (Cetorhinus maximus), which is about 12.3m
\nlong. Both are filter feeders and sieve enormous amounts of
\nplankton through their gills as they swim.<\/p>\n
Sharks have a variety of body shapes but most of them have
\nstreamlined, torpedo-shaped bodies that glide easily through the
\nwater. Bottom-dwelling species like the angel shark have
\nflattened bodies that allow them to hide in the sand on the ocean
\nbed. Some sharks have an elongated body shape (cookiecutter
\nsharks and wobbegongs). Sawsharks have elongated snouts, thresher
\nsharks have large elongated upper tail fins which are used to
\nstun prey, and the hammerheads have extraordinarily wide heads.
\nThe goblin shark has a large, pointed protuberance on its head
\nbut its purpose is still unknown. (see anatomy chart).<\/p>\n
Teeth<\/p>\n
Sharks may have as many as 3,000 teeth at any one time. Most
\nsharks do not chew their food but gulp it down whole in large
\npieces. The teeth are arranged in rows. When one is damaged or
\nlost, it is soon replaced by another. Most sharks have about five
\nrows of teeth with the front set the largest and the one that
\ndoes most of the work.<\/p>\n
Habitat<\/p>\n
Pelagic sharks live in the open ocean and include the great
\nwhite shark and the basking shark. Benthic sharks are those that
\nlive on the ocean floor, and count among their number the zebra
\nhorn shark, the wobbegongs and the angelshark.<\/p>\n
The other species live in relatively warm waters (hammerheads,
\nbull sharks and tiger sharks). The thresher, mako, basking and
\nblue shark live in temperate waters. Others, like the dogfish,
\nGreenland and goblin live in cold waters.<\/p>\n
Sharks can migrate distances exceeding 1,600 km. The blue
\nshark (Prionace glauca) can migrate some 2,000 to 3,000km in its
\nseasonal journey from the U.S. state of New York to Brazil.<\/p>\n
How to avoid shark attack<\/p>\n
If you want to reduce the risk of becoming a victim of shark
\nattack, bear in mind the following rules from senior biologist in
\nichthyology (the study of fish) at the Florida Museum of Natural
\nHistory, University of Florida, George Burgess, in his book The
\nKids' How to Do (Almost) Everything Guide:<\/p>\n
1. Always swim in a group. Sharks most often attack lone
\nindividuals.
\n 2. Don't wander too far from shore. By doing so, you isolate
\nyourself and place you away from assistance.
\n 3. Avoid the water at night, dawn or dusk. Many sharks are most
\nactive at these times and are better able to find you than you
\nare to see them.
\n 4. Don't enter the water if bleeding. Sharks can smell and taste
\nblood, and trace it back to its source.
\n 5. Don't wear shiny jewelry. The reflected light looks like
\nshining fish scales.
\n 6. Don't go into waters containing sewage. Sewage attracts bait
\nfish which in turn attract sharks.
\n 7. Avoid waters being fished and those with lots of bait fish.
\nDiving seabirds are good indicators of such activities.
\n 8. Don't enter the water if sharks are present. Leave immediately
\nif sharks are seen.
\n 9. Avoid an uneven tan and brightly colored clothing. Sharks see
\ncontrast particularly well, so use extra caution when waters are
\ncloudy.
\n 10. Don't splash a lot. Also, keep pets out of the water. Erratic
\nmovements can attract sharks.
\n 11. Use care near sandbars or steep drop-offs. These are favorite
\nhangouts for sharks.
\n 12. Don't relax just because porpoises are nearby. Sightings of
\nporpoises do not indicate the absence of sharks. Both often eat
\nthe same foods.
\n 13. Don't try to touch a shark if you see one!
\n 14. If attacked by a shark, the general rule is \"Do whatever it
\ntakes to get away!\" Some people have successfully chosen to be
\naggressive, others passive. Some yelled underwater, others blew
\nbubbles. Burgess says he would go down fighting.<\/p>\n
Types of Shark Attack<\/p>\n
Burgess, also the Director of the International Shark Attack
\nFile, says that sharks occasionally attack humans, but not for
\nfood. They sometimes grab people by mistake or in a bid to
\nprotect their territory.<\/p>\n
He says there are two kinds of shark attack: provoked and
\nunprovoked. The yearly average of unprovoked shark attacks on
\nhumans is 75, resulting in about 10 deaths. But these worldwide
\nnumbers are considered small given the millions of humans that
\nenter the water.<\/p>\n
* Provoked attacks happen when you touch sharks. They often
\ninvolve unhooking sharks or removing them from fishing nets.
\nHowever, there have been a number of incidents involving divers
\nwho were attacked after grabbing or feeding sharks while
\nunderwater.<\/p>\n
* Unprovoked attacks happen when sharks make the first contact.
\nThey can take three forms:<\/p>\n
Hit and run attacks that take place near beaches where sharks try
\nto survive by capturing fish. In pounding surf, strong currents
\nand murky water, a shark may mistake the movements of humans,
\nusually at the surface, for those of their normal food, fish. The
\nshark makes one grab, lets go, and immediately leaves the area.
\nLegs or feet are often bitten; injuries are usually minor and
\ndeaths rarely occur.<\/p>\n
Sneak attacks take place in deeper waters. The victim doesn't see
\nthe shark before the attack. The result can be serious injury or
\ndeath, especially if the shark continues attacking.<\/p>\n
Bump and bite attacks happen when the shark circles and actually
\nbumps the victim with its head or body before biting. As in the
\nsneak attack, the shark may attack repeatedly and cause serious
\ninjury or death.<\/p>\n
Sources: www.sharkattacks.com, www.enchantedlearning.com,
\nwww.greatwhite.org, www.megmawl.com, The Florida Museum of
\nNatural History.<\/p>",
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