Transcript Sharks Powerpoint

Species
• There are over 360 species of sharks!
• They can range in size from small enough to fit
in your hand to up to 46 feet!!
• Smallest Shark is the Pygmy Shark
• Largest Shark is the Whale Shark
– Filter feeder, feeds on plankton
Skeleton
• Sharks are cartilaginous fish
• Skeleton made of cartilage which is
lighter and more flexible than bones
Respiration
• Sharks have uncovered gills used for respiration
• Extract oxygen as water passes over the gills
• Most species of shark
can pump water over
their gills for when
they are not moving
using the spiracle
• A small percentage of
sharks need to stay in
constant motion to
respire
Teeth
• Sharks teeth are NOT attached to their
jaws
• Teeth range from needlelike to large flat
teeth
• Teeth are grown and replaced often
• Sharks have multiple rows of teeth
• Sharks can have about 25,000 to 30,000 teeth
in one lifetime
• Some replace teeth every
8-10 days, others every few
months
Life Span
• Lifespan varies by species
• Most live about 20 – 30 years
• The spiny dogfish can live up to 100 years
• It is thought that the whale shark can live
over 100 years as well
Sense of Smell
• Incredible sense of
smell
• They can detect
amounts of blood as
small as 1 ppm. (part
per million)
• Rely on sense of
smell to locate prey
Locating Prey
Lateral lines
Sense organ used to
detect motion or
vibrations in the
water
Electro-receptors
Allow sharks to
sense minute
electricity caused
by muscles and
nerves in prey
Vision
• Sharks have eyelids but do not blink
• Water surrounding eye cleans it
• Sharks have a membrane over eye that protects
when being attacked or during predation
• Great White Sharks roll eyes back when
attacking
Do Sharks Sleep??
• Scientists unsure!!
• Possible they sleep
in a similar manner
to Dolphins
– Half the brain
sleeps at a time
Shark Attacks
• 2000 - 79 attacks, 11 fatalities
• 2005 - 61 attacks, 4 fatalities
• 2006 - 62 attacks, 4 fatalities
• Majority occur in the United States
• More people die from lightning strikes each
year
Sharks Involved
• Three types of sharks have
been involved in a
significant amount of attacks
– Great White
– Tiger Shark
– Bull Shark
Great White Shark
• Great Whites are generally about 13-16 ft
and weigh 1500 - 2450 lbs
• Found in waters between 54 and 75
degrees F
• Countershading
– White underside and gray dorsal side
– Difficult to see when looking at
horizontally
– When seen from above, gray blends in with
the water
– When seen from below, white blends in
with surface of water
Typical Prey
• Sting rays, tuna, smaller sharks, dolphins,
seals, sea lions
• Shark attacks most often occur in the
morning, within 2 hours after sunrise
• Hard to see a shark close to the bottom
• Attack from below at fast speeds
Tiger Sharks
• Average 11 feet and 850 - 2000 lbs
• Commonly found around islands in the central
Pacific
• Dark spots and stripes are prominent in young
sharks and fade as the shark matures
Hunting Habits
• Teeth can bite through
bone and turtle shells
• Known to circle its
prey and even study it
by prodding it with its
snout
• Tiger sharks devour
their entire prey when
attacking
Hawaii
• Tiger sharks have become a problem in
Hawaii
• Hunted to help control attacks, but no
decrease occurred
• Considered sacred by native Hawaiians
Bull Shark
• Dwell in shallow water,
possibly posing highest
threat to humans
• Can tolerate freshwater
• Males: 6.8 ft, about 200 lbs
• Females: 11.5 ft, about
700 lbs
Hunting Habits
• Bump and Bite Technique
• Shark circles prey often bumping them
before the actual attack.
• They are extremely territorial and will
attack other animals that enter their
territory.
Why attack?
• Mistaken Identity:
– Shark mistakes a person in the water as a
seal when looking from below the waters
surface
• Curiosity
• Sharks typically bite once and then swim away
• Explanations:
– Humans do not taste like their typical prey
– Return to the prey after it exhausts itself
Dolphin Protection
• Sharks will not attack
when dolphins are
around
• Scientists unsure why
this phenomenon
occurs
Avoiding an Attack
• Avoid water during darkness or twilight hours
• Do not enter water if bleeding from an open
wound
• Do not wear shiny jewelry – resembles fish
scales
• Avoid areas near commercial fishing
• Avoid murky waters
• Do not splash a lot
Fending off an attack
• Hit back in sensitive areas such as the eyes
and gills
• Shows shark you are not defenseless
Hammerhead Shark
• Habitat: Shallow tropical and warm temperature
waters
• Diet: Stingrays, Other small sharks, fish, crustaceans
• Size: 12 - 20 ft.
• Attacks: 18 (0 fatal)
• Hammerheads have small mouths and seem to
do a lot of bottom-hunting. (Stingrays!)
• Their wide-set eyes give them a better visual
range than most other sharks.
• They are also known to form
schools during the day,
sometimes in groups of over
100.