Sharks
Sharks
- [Narrator] They glide through the water
remnants of an ancient past,
from the ocean's murky depths
to it's sun-kissed shallows,
like no other creature in the sea.
The world's biggest
living fish is a shark.
Of the estimated 34,000 species of fish,
the largest are whale sharks.
These gentle giants usually
grow to about 40 feet long
and weigh an estimated 15 tons.
Their mouths alone can
span four feet wide.
The gigantic whale shark however,
pales in comparison to the largest fish
that ever existed, the megalodon.
Dating to over 20 million years ago,
it's thought that the prehistoric shark
could of reached 80 feet long,
weighing up to around 70 tons.
Unlike whale sharks, the
megalodon was carnivorous,
and consumed any creature that fit
into it's nearly 10 foot wide mouth.
Throughout their lives
some species of shark
can shed over 30,000 teeth.
Unlike humans who are born
with a set number of teeth in their jaws,
sharks have a seemingly limitless supply.
They can grow, lose, and
replace their teeth as needed.
have multiple rows of teeth in their jaws.
The jaws of a great white shark,
the largest predatory fish in the sea,
can contain up to seven rows
that hold up to 300
teeth at any one point.
Most sharks, as they hunt their prey,
end up losing their teeth individually.
However, the cookiecutter shark loses
and replaces the teeth in
it's lower jaw all at once.
Sharks are built for speed.
The fastest known shark, the mako shark,
can reach speeds of up
to 46 miles per hour.
This speed is largely due
to their body's hydrodynamic design.
Many sharks have torpedo shaped heads
that allow them to cut through the water
Plus, shark skin is covered
with flat, v-shaped scales,
The denticles help water
flow smoothly over the skin,
and helps sharks swim quickly and quietly.
Sharks also have skeletons
made of cartilage instead of bone.
Cartilage is a much
lighter material than bone
so sharks have less weight to carry.
Sharks may lay eggs, or bear live young.
Egg laying sharks only
lay a few large eggs.
They may come in various forms,
such as sacks called mermaid
purses or corkscrews.
These eggs act as external wombs
in which shark embryos
complete their development.
However, most sharks
give birth to live young.
Called pups, the young of
most live bearing species
gestate for around one year.
Some even begin practicing
their predation skills
Before they are born, the
sand tiger shark pups compete
In fact, the strongest pup
in each of the two wombs
devours its weaker brothers and sister.
Some sharks are at risk of extinction.
Every year an estimated 100 million sharks
are killed worldwide, in large part
The sharks are caught
and their dorsal fins
are removed and sold at a hefty price,
In traditional Chinese culture,
serving and eating shark fin is a sign
Because of the high demand
and value of shark fins,
some shark populations have plummeted
by up to 70% causing a ripple effect
in ecosystems and endangering
at least 74 shark species.
However, measures are being
taken to protect sharks
with a number of countries and
jurisdictions cracking down
on unsustainable shark fishing.
In China, shark fin soup
is no longer allowed
to be served at government banquets.
A move hailed by shark conservationists.
Through continued international
conservation efforts,
the loss of sharks may be curbed,
allowing the creatures in
all their power and grace
to survive for many generations to come.