Sea
Sabres Scuba Diving club, Southern California, Fullerton
Sea Sabres
Shark Facts
All
Sharks except Makos are dclining due to over fishing
You
more likely to be hurt by a hampster than a shark.
Sharks
range from 6 inches to 45 feet
Scientific
names are useful as the Great White is known by many different names the world
over. Here's a quick breakdown of some of them and the country of origin.
Germany: Weisshai
France:
grand requin blanc
Italy:
grande squalo bianco
Spain:
tiburon blanco
Australia:
white pointer, white death
Russia:
seldevaja akula
Japan:
Hohojirozame
An
iron stomach?
Blue
sharks, popular with sport fishermen on Canada's east coast, have been found
with all kinds of odds and ends in their stomachs. Besides the expected fish,
squid and the occasional seal, they've been swimming around with rocket parts,
rubber bands, and beer cans in their bellies.
Sharks
eat periodically depending upon their metabolism and the availability of food.
For example, juvenile lemon sharks eat less than 2% of their body weight per
day. Sea Otters Eat 25% of there weight per day
Great
whites are relatively uncommon large predators that prefer cooler waters. In
some parts of their range, great whites are close to being endangered.
A
specialized osmoregulatory system enables the bull shark to cope with dramatic
changes in salinity -- from the freshwaters of some rivers to the highly saline
waters of the ocean.
Sharks'
relatively large and complex brains are comparable in size to those of
supposedly more advanced animals like mammals and birds. Sharks also can be
trained.
Sharks'
eyes, which are equipped to distinguish colors, employ a lens up to seven times
as powerful as a human's, and some shark species can detect a light that is as much
as ten times dimmer than the dimmest light the average person can see.
Some
sharks can respire by pumping water over their gills through opening and
closing their mouths while at rest on the bottom.
Although
some sharks may swim at bursts of over 20 knots (23 miles per hour), most
sharks swim very slowly at cruising speeds of less than 5 knots (5.75 miles per
hour).
Great
White Sharks grow about 10 inches per year. They can grow to mature lengths of
12 to 14 feet And will grow to 19 feet with one record length of 23 feet
New
teeth are constantly being formed in rows in a shark's jaw. Teeth are normally
replaced every eight days.
Some
species of sharks can shed as many as 30,000 teeth in their lifetime.
Whale
Sharks have approximately 300 rows of teeth, with hundreds of tiny teeth in
each row.
Dried
shark skin (shagreen) was used in the past as sandpaper. In Germany and Japan,
it was used on sword handles for a non-slip grip.
In
1937, shark liver oil was discovered to be rich in vitamin A. Sharks were
hunted for the vitamin until 1950, when a synthesizing method was developed for
vitamin A.
The
average life span of a shark is 25 years, but some can live to be 100.
The
dogfish sharks are named for their tendency to attack their prey as a pack of
wild dogs would.
Whale
Sharks grow to 45 feet long and 30,000 pounds, but average about 25 feet long
Great
White Sharks can go as long as three months without eating.
Not
all sharks have to be in continuous motion to breathe.
Bull
Sharks can tolerate a wide range of salinity and are often found in freshwater
rivers and lakes in Africa and South America.
More
people are killed each year by dogs, pigs and deer than by sharks.
The
Pygmy Shark has a maximum length of 11 inches.
Whale
Sharks arn't a whale (whales are mammals, not fish)
Sharks
have no bones. Their skeleton is made up of cartilage.
There
are more than 340 known species of sharks.
Sharks
first appeared in the fossil record over 400 million years ago.
A
significant physical trait that separates a modern shark from an ancient one is
the protrusile jaw, which gives the modern shark more biting force.
Sharks
can generate about six and a half tons per square inch of biting force.
A
shark's skin is embedded with dermal denticles, which resemble teeth.
The
Shortfin Mako is probably the fastest shark in the ocean, clocked at about 60
mph. (The marlin is the fastest fish
and can swim 65 mph.)
WHALE
SHARK isbiggest shark and biggest fish
Whale
Sharks filters plankton from the water using "gill rakers"
One
of the reasons that sharks are such successful predators is that they have such
super senses.
Two-thirds
of a shark's brain is dedicated to its keenest sense -- smell.
Some
sharks have eyes similar to a cat. A mirror-like layer in their eyes allows
them to see better in the water. This allows the shark to hunt in clear seas or
murky water.
To
top it off, sharks have a few unusual senses. For instance, they are able to
feel vibrations in the water using a line of canals that go from its head to
its tail. Called a "lateral line", these canals are filled with water
and contain sensory cells with hairs growing out of them. These hairs move when
the water vibrates and alerts the shark to potential prey.
Sharks
also have a sensory organ called the "ampullae of Lorenzini" which
they use to "feel" the electrical field coming from its prey.
Baby
sharks are called pups. Just like there are many types of sharks, there are
also different ways that sharks come into this world. There are three ways that
sharks are born:
Shark
eggs are layed (like birds)
Some
shark eggs hatch inside the mother and then are born
pups
sharks grow inside the mother (like humans)
Sharks
can have from 1 to 100 babies at a time, depending on the type of shark. The
ones with pups that grow inside the mother have fewer babies at a time than
sharks that lay eggs outside the body.
Sharks
do not care for their babies after they are born, but they do search for a safe
place where they can lay their eggs or give birth.
DANGEROUS
REDATORS
Think
sharks are dangerous? The most dangerous sharks are the Great White shark, the
Tiger shark, the Hammerhead shark, the Mako shark and the Bull shark. On
average, there are only about 100 shark attacks each year and only 10 of those
result in a human death.
You
should check it out from their perspective though! People kill thousands of
sharks in a year for sport and for food. Shark skins are used to make products like
any other leather would be. Up until the 1950's, shark livers were used as a
vitamin A supplement. Shark fin soup and shark steaks are both eaten in many
countries (Mako, seen in the top photo, is the most popular in the United
States).
So
who's the dangerous predator?
GENTLE
GIANTS
Not
all sharks are fierce carnivores. Some are quite harmless. Oddly enough, the
most harmless sharks tend to be the largest! The basking shark, the whale shark
and the megamouth sharks all fit this description.
These
huge sharks eat plankton, a tiny shrimp-like creature found in the ocean. To do
this, they swim forward with their mouths wide open. "Gill rakers" at
the back of their throat strain the tiny food from the water.
CARNIVORES
Almost
all sharks are "carnivores" or meat eaters. They live on a diet of
fish and sea mammals (like dolphins and seals) and even such prey as turtles
and seagulls.
Sharks
even eat other sharks. For example, a tiger shark might eat a bull shark, a
bull shark might eat a blacktip shark and a blacktip shark might eat a dogfish
shark!
The
teeth of the carnivores are sharp and pointy. Their skeleton is made of
cartilage instead of bone, which allows greater flexibility.
Their
skin is made of denticles instead of ordinary fish scales. The denticles are
constructed like hard, sharp teeth and help to protect the shark from injury.
Sharks
have the most powerful jaws on the planet. Unlike most animals' jaws, both the
sharks' upper and lower jaws move.
A
shark bites with it's lower jaw first and then it's upper. It tosses it's head
back and forth to tear loose a piece of meat which it swallows whole.
Each type of shark has a different shaped
tooth depending on their diet (the shark in the photo is a great white -- you
can tell he's a carnivore just by looking at those sharp, pointy teeth!).
A
shark may grow and use over 20,000 teeth in its lifetime!
Sharks
never run out of teeth. If one is lost, another spins forward from the rows and
rows of backup teeth.
In some
form, sharks have been around for about 400 million years.
Even
before dinosaurs roamed the earth, sharks hunted through the oceans! They're such good survivors that they've had
little need to evolve in the last 150 million years
Normally,
sharks eat alone. But sometimes one feeding shark attracts others. They swim up
as quickly as possible and all begin to try to get a piece of the prey. They
bite wildly at anything that gets in their way -- even each other.
Oddly
enough, the great white shark rarely partakes in feeding frenzie
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Posted August 22, 2003