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- The United States averages just 16 shark attacks each year and
slightly less than one shark-attack fatality every two years.
Meanwhile, in the coastal U.S. states alone, lightning strikes and
kills more than 41 people each year.
- Which just goes to show that sharks enjoy a reputation that is
arguably more fearsome than their bite. Read on for more surprising
shark facts compiled by National Geographic News:
- Each year there are about 50 to 70 confirmed shark attacks and 5
to 15 shark-attack fatalities around the world. The numbers have
risen over the past several decades but not because sharks are more
aggressive: Humans have simply taken to coastal waters in increasing
numbers.
- Over 375 shark species have been identified, but only about a
dozen are considered particularly dangerous. Three species are
responsible for most human attacks: great white (Carcharodon
carcharias), tiger (Galeocerdo cuvier), and bull (Carcharhinus
leucas) sharks.
- While sharks kill fewer than 20 people a year, their own numbers
suffer greatly at human hands. Between 20 and 100 million sharks die
each year due to fishing activity, according to data from the
Florida Museum of Natural History's International Shark Attack File.
The organization estimates that some shark populations have
plummeted 30 to 50 percent.
- The shortfin mako (Isurus oxyrinchus) is often recognized as the
world's speediest shark. It has been clocked at speeds of up to 20
miles an hour (32 kilometers an hour) and can probably swim even
faster than that. Makos are fast enough to catch even the fleetest
fish, such as tuna and swordfish.
- The largest shark is the whale shark (Rhincodon typus), which
can grow to 60 feet (20 meters) long. The gentle giant eats tiny
plankton.
- Among the smallest shark species is the deepwater dogfish shark
(Etmopterus perryi). A habitué of the Caribbean, the dogfish
measures a less-than-intimidating 8 inches (20 centimeters) in
length.
- Sharks are known as eating machines. But because many species
are cold-blooded, some sharks eat only about 2 percent of their body
weight each day. That's a bit less than humans typically eat.
- While scientists still have much to learn about shark migration,
researchers do know that some species get around. Blue sharks (Prionace
glauca), for example, roam the North Atlantic on journeys of 1,200
to 1,700 nautical miles (2,220 to 3,145 kilometers). After one
record-breaking blue was tagged off New York, it swam 3,740 nautical
miles (6,919 kilometers) to Brazil.
- Some sharks must swim constantly to "breathe" oxygen from water
passing through their gills. Other species can achieve this while
stationary.
- Sharks do not sleep. Rather, they experience alternating periods
of activity and rest.
Sharks are among Earth's most ancient animals. The fossil record
dates ancestors of modern sharks to as far back as 400 million years
ago. Shark species have changed relatively little during that time
span and are sometimes called living fossils.
- Sharks can replace lost teeth in as little as 24 hours and may
use thousands of teeth over the course of a lifetime. Ancient teeth
are the source of most known shark fossils. (Shark skeletons, which
are composed of cartilage, decompose quickly.)
- Sharks are diverse reproducers, and their mating has been
observed only on rare occasions. Some species are egg-laying
(oviparous), while others bear live young (viviparous). Adult sharks
do not care for their newborn pups, which are born or hatched as
smaller, juvenile versions of their parents.
- Two shark species can survive long periods in fresh water: the
bull shark and the speartooth shark (Glyphis glyphis). Both species
can engage in river journeys of epic scale. Bull sharks, for
example, have been caught 1,700 miles (2,800 kilometers) up the
Mississippi River and 2,100 miles (3,480 kilometers) up the Amazon.
Neither species, however, lives in landlocked fresh water without
ocean access.
- A major cause of shark mortality is "finning," a process in
which fishers kill sharks solely to remove their fins. Fins can sell
for U.S. $400 per kilogram (U.S. $880 per pound) or more.
- Known in China as yu chi or "fish wings," shark fins are used to
make the traditional delicacy shark-fin soup. The culturally
celebrated but controversial soup is found widely in Asia and will
even be on the menu at Hong Kong Disneyland when the park opens in
September.
- Sharks are apex predators, and as such, they affect the entire
ocean food chain from their position at the top. Because of their
dominant role, sharks have long life spans and don't reach sexual
maturity until they are 12 to 20 years old. Even then, sharks have
low reproductive rates. Such predator populations, once diminished,
have a hard time bouncing back.
- As elasmobranches, sharks have skeletons made not of bone
but of cartilage, tissue similar to that found in human noses and
ears. Cartilaginous skeletons are lighter than bone and help sharks
to remain neutrally buoyant (able to float without sinking or
rising).
- The media can have a voracious appetite for "shark bites man"
stories. The summer of 2001, for example, saw an explosion of
shark-attack hype and was even heralded on the cover of Time
magazine as the "Summer of the Shark." Yet 2001 was statistically
average: The year saw 76 shark attacks and 5 fatalities worldwide,
compared to 85 attacks and 12 fatalities in 2000.
- Thirty years ago the blockbuster Jaws brought the terror of
shark attack to movie theaters. The record-breaking film, directed
by Steven Spielberg and based on a best-selling novel by Peter
Benchley, grossed nearly 130 million dollars (U.S.) in the United
States alone. The movie arguably made sharks public enemy number
one.
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