Download SHARK WEEK

SHARK WEEK
http://www.youtube.com/watch?v=
UruXWui1EG8
Discovery Channel Shark Week
• http://dsc.discovery.com/sharks/shark-o-nator
• Resource site
Shark Myths
• http://www.mote.org/index.php?engine_id=&
src=search&search_id=search_new&search_t
his=shark+myth
• Resource site
• http://www.sharksworld.com/facts_about_sharks.html
#1
• Sharks prefer human blood.
• False! Most sharks don't appear to be
especially interested in the blood of mammals
as opposed to fish blood
#2
• Sharks have peanut-sized brains and are
incapable of learning.
• 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
#3
• All sharks have to swim constantly
• Misconceived! Some sharks can respire by
pumping water over their gills through
opening and closing their mouths while at rest
on the bottom.
#4
• Sharks have poor vision.
• Erroneous! Sharks' eyes, which are equipped
to distinguish colors, employ a lens up to
seven times as powerful as a human's.
#5
• Sharks are not found in freshwater.
• Forget it! 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.
#6
• Whale sharks, the largest species of shark,
are voracious predators
• Whale sharks, which are the largest fish that
have ever lived, are plankton feeders like the
great whales, thus the name.
Seaworld: sharks
• http://www.seaworld.org/infobooks/Sharks&
Rays/home.html
What are Sharks?
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Vertebrates
Cartilage skeletons
350 species
Can live for 20-30 years
Five gill openings on each side of head
Scales called “denticles” make skin feel rough
Scales do not grow larger. Shark grows more of
them. Scales cannot be used to tell the age of the
shark
Denticles of a great white shark
Cont……
• Some are solitary hunters. Others, hunt in
groups
• Found in all oceans at all depths- most
prevalent in tropical, coastal waters
• Primarily marine, but do travel up the mouths
of rivers into freshwater in some species
• Many are carnivorous, some planktonic
• Most powerful jaws on the planet
Ancient Sharks
• The most common shark fossils are teeth because
sharks, unlike most other animals, can lose many
thousands of teeth during their lives
• Shark skeletons are not made of bone- therefore,
whole skeletons are only found where the animal
was quickly covered with mud and remained
undisturbed
• Oldest shark fossil-More than 400 million years
old. 150 million years since evidence of evolution
megalodon
• http://www.youtube.com/watch?v=Spo8vkrJF
Ro
Taxonomy
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460 different species
8 orders
Hexanchiformes-six gilled and seven gilled sharks
Squaliformes- dogfish sharks
Pristiophoriformes- sawsharks
Squatiniformes- angel sharks
Heterodontiformes- bullhead sharks
Orectolobiformes- carpetsharks
Lamniformes- mackerel sharks
Carcharinoformes- hammerhead and requiem sharks
• 25 species of sharks reside in the gulf of
Mexico
Let’s get acquainted: Shark Anatomy
• Sharks typically have a fusiform body (rounded and
tapering at both ends). This body shape reduces drag
and requires a minimum of energy to swim
• No swim bladder. Tends to sink. Has oil in liver to
increase buoyancy
• 5 gill slits
• Caudal fin is well developed and powerful
• Tail is heterocercal- upper lobe is longer than the lower
lobe
• Powerful jaws with sharp teeth
fins
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Sharks have five different types of fins.
a. Paired pectoral fins lift the shark as it swims.
b. Paired pelvic fins stabilize the shark.
c. One or two dorsal fins stabilize the shark. In
some species, dorsal fins have spines.
• d. A single anal fin provides stability in species
where it is present; not all sharks have an anal
fin.
• e. The caudal fin propels the shark.
fins
Tails/Swimming
• The ability to pump water over gills (buccal
pumping) varies between shark species
• Less active sharks have an increased ability for
buccal pumping
• More active pelagic sharks use ram ventilation,
meaning they ventilate the gills by holding the
mouth open while swimming
• Some sharks are obligate ram ventilators,
meaning they have to keep constant forward
motion in order to continue respiration
Teeth
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Each type has a different shaped tooth
20,000 teeth per lifetime
Arranged in parallel rows
Studies have shown that an average nurse
shark will replace each front row tooth every
ten days to two weeks in summer when
actively feeding and every one to two months
when they are less active in the winter
• Sharks never run out of teeth. If one is lost,
another spins forward from the rows and rows
of backup teeth
Colors and Camouflage
• Countershading
• Dorsal side is darker than the ventral side
Breathing
• Most sharks swim continuously because the
opening and closing of the mouth forces water
through the mouth, over the gills, and out
through the gill slits
• When caught in fishing nets, sharks cannot swim
to force the water in and therefore “drown”
• Not all sharks need to swim for gas exchange.
Nurse sharks rest on the bottom because they
force water over their gills by opening and closing
their mouth
spiracles
• behind the eyes at the top of the head. These
openings bring oxygen-carrying water into the
gill chamber. Spiracles originate from
rudimentary first gill slits and are reduced or
absent in active, fast-swimming sharks.
Ramjet Principle
Shark Senses
• Sharks have six highly
refined senses: smell,
hearing, touch, taste, sight,
and electromagnetism
Incredible Senses
• In addition to the lateral line, sharks have a sensory organ
Organ of Lorenzini
called the
; this organ is
used to detect electrical currents when sharks are close to an
object (the movement of muscles – even those used in
respiration – emit a small electrical charge) – this allows
sharks to detect living prey even it is hidden from their view if
they can get within a few feet of the organism
• “built in compass”
Incredible Senses
• Lateral Line
• The lateral line, together with the ampullae of
Lorenzini comprise the electrosensory component of
the sharks sensory system. The lateral line allows the
shark to orient to particle movement or sound. It
consists of structures called neuromasts which are
located in canals that lie just below the surface of the
skin or the scales. Similar to the ampullae of Lorenzini
there are pores that open to the outside and
movement caused by prey can be detcted by the
neuromasts.
Shark lateral line
Incredible Senses Cont…..
• Hearing• Ears are internal, not external
• Ears: 3 semi-circular canals that resemble
those in the ears of other vertebrates
• Sharks can hear noises from over 700 feet
away
• Vibrations in the water are heard as sound
Incredible Senses
• Eyes
• Sharks have a nearly 360-degree visual field
• Some sharks have a third eyelid, called the nicitating membrane,
which protects the exposed portion of the eye during feeding or
object contact
• The great white shark does not have a nicitating membrane, and
instead rolls the eye back into its orbit to protect it during feeding
• Most sharks have a reflective layer in the back of the eye called a
tapetum lucidum which boosts the sensitivity of the eye in dim light
• A juvenile lemon shark has a lens with 7 times the optical power of
a human lens
• Humans focus by changing the shape of the lens; sharks focus by
changing the position of the lens by moving it toward or away from
the retina
Incredible Senses
• Nostrils- used only for smelling. NOT breathing
• Seawater flows over the nostrils bringing
chemical clues as to what’s nearby
• Sharks can detect tiny amounts of blood from
more than 1 mile away.
• The hungrier the shark gets, the sharper its
sense of smell. Scent makes them aggressive“feeding frenzy”
Shark Senses
• http://www.youtube.com/watch?v=h1XYa93R
z_Q
osmoregulation
• Shark Osmoregulation Facts:
• Sharks use high concentrations of body urea to help
osmoregulate
• Sharks living in salt water must balance the influx of NaCl
(salt) into the body by excretory mechanisms in the rectal
gland, kidney and gills
• Sharks living in dilute salinity or freshwater conditions must
balance the influx of water into the body by increasing
urinary water excretion and increasing salt uptake through
the gills
• 90% of the secretion of body acids/bases into the water in
order to balance internal pH is done by the gills
• http://www.youtube.com/watch?v=LxYgsyKXQ
Vg
Reproduction
• Sexually dimorphic: visible differences between males
and females
• Externally, males have claspers which are modified
pelvic fins used for sperm delivery
• Testes and ovaries are internal
• Mating is vicious. Therefore, female skin is twice as
thick as males because males will bite the females
while mating
• Sexes often segregate and only come together to mate
• Females can store sperm for a year until the eggs are
ready for fertilization
Reproduction
• Sharks have young in three different ways.
After internal fertilization, some species lay a
thick egg case that encloses the shark embryo
(seen in the photo here). Most species are
ovoviviparous, which means that the shark
hatches and develops within the female shark
and is born live. A third way (viviparous) is
similar to human development, where the
young shark grows within the female and gets
nutrients from a placental link to the mother
embryo
• 70% of the sharks living today have developed
a method to care for their brood inside the
female’s body (viviparity or ovoviviparity)
• 30% of all sharks lay eggs (oviparity)
• Gestation 6-22 months
• New borns called “pups”
Shark embryo in egg case
Shark Reproduction
• “mermaid’s purse” – egg case
• Several months-one year to hatch. Hatch faster in warmer
water
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Example: Lesser-spotted Dogfish
• A January 2013 study in the journal PLoS ONE
shows that embryonic bamboo sharks in egg
cases can react to predation signals. The
embryos in this study were exposed to electric
fields that simulate the shark's predators and,
in response, the sharks stop all gill movement
and hold still so as not to alert the predator of
their existence
Intrauterine Cannibalism in Sharks
• Adelphophagy- shark embryos eating each
other
• Two forms of within-the-womb cannibalism
are known in sharks. The most extreme form
of intrauterine cannibalism — in which the
largest and strongest embryo actually
consumes its lesser womb-mates — is termed
"embryophagy" or, more colorfully,
"adelphophagy" — literally "eating one's
brother". To date, adelphophagy is known
only in the Sandtiger.
Sandtiger shark
• The less extreme and by far more common
form of intrauterine cannibalism — in which
developing embryos feed on a steady supply
of tiny, unfertilized eggs — is termed
"oophagy" (sometimes called "oviphagy") —
meaning "egg-eating".
parthenogenesis
• Parthenogenesis, from the Greek meaning “virgin
birth” is an odd quirk of embryonic development
that allows female animals of some species to
give rise to offspring without a male genetic
contribution - usually by a doubling of the egg
genome to generate a new embryo with the
proper number of
chromosomes. Parthenogenesis is common in
insects, and among vertebrates it occurs in some
species of fish and reptiles, and strangely enough,
in turkeys.
• a white-spotted bamboo shark female gave rise
to parthenogenetic offspring that have survived
for several years. Parthenogenetic sharks are
therefore not inherently less viable - normal
sharks can be produced using only femalecontributed chromosomes.
• occurred among animals in the controlled
environment of aquaria, where the female was
isolated from males for a long period of time.
White spotted bamboo shark
Finding Nemo: Bruce “feeding frenzy”
• http://www.youtube.com/watch?v=LYmsVWm
HI78
How common are shark attacks?
• Attacks are quite rare, averaging only 25 per
year worldwide, and only ¼ of these are fatal
• More people die from wasp and bee stings
• Even pigs kill more people annually than
sharks
What is shark prey?
• It depends on the type of shark as various
species have different habits
• Shark feeding also depends on where they live
Diet evolution
• Shark diet needs to evolve based on what is
offered so they can survive. sharks easily
adapt to their habitat, therefore the number
and variety of food selection will determine
what will a shark eat in such location. Sharks
may prefer certain types of foods but when
they are scarce they will adjust their eating
habits to compensate for it.
Carnivores
• Most sharks are meat eaters and so they feed
on other fish and even other sharks. Larger
sharks aren’t afraid to go after a huge meal
such as a dolphin or a sea lion.
Jaws
jaws
• Sharks have very powerful jaws (most
powerful on the planet) and teeth so they can
rip through meat and bones without any
trouble at all.
• Since many sharks are thrashing from side to
side as they eat it may give the impression
that they are having difficulties but that isn’t
the case at all.
Attacks at Seal Island
• http://www.youtube.com/watch?v=XCWTtBLnD8
• http://www.youtube.com/watch?v=T1r3FixM
5wY
Other meals…..
• Sharks also eat crab, squid, and lobster in
areas where it is available. Due to the amount
of commercial fishing ships though gathering
such items for humans to consume though it
isn’t always a source of food that they have
available.
Small invertebrates are meals too
• Other shark species live off of small aquatic
life including mollusks and clams. These types
of sharks often live at the bottom of the ocean
where there is an abundance of such food
sources. They blend in well so they aren’t
spotted by their prey very easily. These are
often the smaller species of sharks that don’t
need a huge volume of food to live on.
Planktonic Sharks
• Whale shark; basking shark
• gill rakers are bristlelike and are used to catch
plankton as water filters through the mouth
and over the gills.
The Perfect Predator:
Why sharks attack
• 1. attacking for food
• 2. Mistaken identity- ex. Surfboards or
people
• 3. Rogue Sharks- random where sharks
normally are not found
• 4. Defending territory
• 5. Provoked attacks
Taste Test
• Shark attack begins with a “test bite”. They will
gently wound their prey to taste flesh and blood.
The shark will shift its behavior into killing mode
if it likes the prey
• research has shown that most sharks will bite and
then let a person go as they realize it isn’t their
normal food source. Of course that will make
great damage in the person bitten, but the truth
is that sharks do not eat humans
• People who are bitten usually die from loss of
blood or from the injury caused by the bite
Sharks can’t……..??????
• Sharks can’t chew.
• Must gulp food down throat. Can swallow
small prey whole
How much do sharks eat???
• The amount of food that a shark eats each day
depends on the type of shark it is. Generally
they consume about 2% of their total body
weight. This is surprising to many people as it
would appear that these large animals should
eat much more
How often do sharks eat?
• Some Shark species will eat huge meals and then
not eat again for weeks, months, or even a year
in some cases.
• Most eat every 2-4 days
• They are able to survive on the oil that is stored
in the liver when they do eat. When that gets low
they will have the instinct to eat again.
Why don’t sharks need to eat more
often???
• The reason sharks don’t have to eat as much
as people think is because they are cold
blooded. This means their circulation is
slowed down and they burn energy at a
slower rate.
Shark attacks around the world
• Where do most shark attacks occur?
• Before the beaches of eastern AUSTRALIA
were protected with nets, Australia had the
world’s worst record for shark attacks. 300
attacks. ¼ of all the attacks recorded
• More Australians are killed as a result of
automobile accidents every MONTH than have
died in 100 years from attacks by sharks
Shark net
Shark net…..
• Protects swimmers
• Each end of the net is secured by an anchor
and its position marked by floats
• 46 South African beaches are protected by
nets
Shark “cables”
• Another way of protecting swimmers
• Cables are laid around beaches and pulses of
electric current are sent through the cables
• Current is strong enough to turn sharks away
2nd most dangerous area
• #2 SOUTH AFRICA
• Beaches of Natal
USA Sharks Attacks
• Americans have 50 times more chance of
being struck by lightening than of being
attacked by a shark.
• In the whole USA, there are fewer than 12
attacks per year
Shark repellent
• 1960’s Eugene Clark discovered a small flatfish
that would stop sharks in mid-bite
• This fish (the Moses sole) exuded a white
milky fluid over its upper surface when
threatened
• Unfortunately this material breaks down
rapidly and is easily dispersed in water
Time and Season of shark attacks
• Middle of the afternoon
• Summer season
• Depth of 5-10 feet
Shark proof material
• http://soldiersystems.net/2011/04/11/neptun
ic-technologies-protective-materials/
South America Shark Attack: Discovery
Channel
• http://dsc.discovery.com/tv-shows/sharkweek/videos/south-america-shark-attack.htm
Great White Attack
• http://dsc.discovery.com/tv-shows/sharkweek/videos/great-whites-death-strike.htm
National Geographic shark attacks
• Shark Attack! - YouTube
• SHARK ID ACTIVITY
Nova Sharks Activity Site
• http://www.pbs.org/wgbh/nova/sharks/
1. Great White Shark
• Great White Sharks are the largest predatory (aggressive) fish in the sea
• 3,000 serrated teeth
• Great White Shark meat is not recommended for human consumption
because it has very high mercury levels
• Eat blubbery animals:
• Seals, sea lions, tuna, etc.
• Great White Sharks breed late in life. They do not start breeding until
they’re at least twenty years old.
• OCRAS have been known to kill Great White Sharks
• http://www.youtube.com/watch?v=d-1xU0VfJ-g
• http://www.youtube.com/watch?v=qRaJ9p4CWwU
Great White Shark
Great White Shark Video
• http://www.youtube.com/watch?v=d1xU0VfJ-g
• http://www.youtube.com/watch?v=aoPZCIGKpQ
Killer Sharks vs Killer Whales
• http://www.youtube.com/watch?v=6zOrUT0s
mV8
1. Octonauts: Great White Shark
• http://www.youtube.com/watch?v=Upvc0fZd
NIE
2. Tiger Shark
• named for the dark, vertical stripes found mainly
on juveniles. As these sharks mature, the lines
begin to fade and almost disappear
• One of nature’s most successful predators
• One of the world’s most common sharks
• “garbage can of the sea”
• A tiger shark that was caught off South Africa was
found to contain the front half of a crocodile, the
hind leg of a sheep, three gulls, and two cans of
peas
2. Tiger Shark
• They are second only to great whites in
attacking people. But because they have a
near completely undiscerning palate, they are
not likely to swim away after biting a human,
as great whites frequently do.
• Used for shark fin soup
Tiger Shark
3. Hammerhead Shark
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Solitary
Night hunters
School during the day
Hammerheads are aggressive hunters, feeding on
smaller fish, octopuses, squid, and crustaceans. They
do not actively seek out human prey, but are very
defensive and will attack when provoked.
Likes to eat sting rays
Uses head like a shovel to dig up the ray
Immune to the venom of the rays’ tail barb
http://www.youtube.com/watch?v=s6Djl_inVQE
3. Hammerhead
Hammerhead Video
• http://www.youtube.com/watch?v=hgCKBTv0
3vc
4. Nurse Shark
• Nurse sharks prefer to dwell near the sea floor in
the warm, shallow waters of the western Atlantic
and eastern Pacific oceans
• Nurse sharks are slow-moving bottom-dwellers
and are, for the most part, harmless to humans
• Feed mostly on bottom invertebrates- lobster and
sea urchin
• They use their strong jaws to crush and eat
shellfish and even coral, but prefer to dine on
fish, shrimp, and squid
4. Nurse Shark
5. Whale Sharks
• More Whale Shark Facts:
• Whale sharks can grow to be more than 14
meters (~45 feet) long!
• Whale sharks can be found in tropical and warmtemperate oceans.
• Whale sharks do have teeth--in fact, they have
more than 300 rows of them in either jaw, but
they are only 1/12-of-an-inch long.
• The pattern of stripes and dots are unique for
each shark- like a fingerprint
5. Fish and whale sharks
• Remoras and the Pilot fish
• “Suckerfish”
Why do the fish follow the shark?
• The small fish follow the shark because it
protects them from the larger fish that would
otherwise eat them
Remora
• Both of these fish form a symbiotic relationship
with the shark. The Remora is a Commensalism
relationship where the Remora gains basically all
of the benefits such as protection from other
predators and free transport as the Remora
attaches itself directly to the shark by means of a
sucker on the top of it's head. The shark gains no
real benefit from this relationship as they tend
not to feed on ectoparasites on the shark etc, but
neither is the shark directly harmed, as the
Remora's sucker does not cut into the flesh or
damage the skin to any noticeable extent
Remora
Pilot Fish
• The Pilot fish on the other hand, shares a Mutualism relationship
where the benefits are to both the Pilot fish and the shark. Pilot fish
do not attach themselves to the shark but instead swim in an
almost perfect harmony and favour such species as the Oceanic
Whitetip Shark. They again gain a great source of protection from
other predators and also a regular food supply from left over scraps
from the sharks meals, but also more importantly feed on the
ectoparasites on the sharks skin. It is this last part that makes this
relationship mutualist, as the sharks can enjoy a virtually
ectoparasite free life. Small juvenile Pilot fish also serve as good
dentists, and will happily swim into the obliging shark's open mouth
to clean food particles from between the teeth with virtually no
fear of becoming a meal themselves.
Pilot Fish
5. Whale Shark
Whale shark video
• http://www.youtube.com/watch?v=hgCKBTv0
3vc
• http://www.youtube.com/watch?v=uQrBwN3
9LJI
• http://www.youtube.com/watch?v=_B8qiqeD
rI0
Basking Shark
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Gill slits encircle its enormous mouth
Very slow swimmers
Only one species exists
Social animals. Live in groups up to 100
Can filter 2,500 tons of water every hour
Basking Shark
Basking shark video
• http://www.youtube.com/watch?v=UbeXqgTC
7g8
6. Bull Shark
• Can live in freshwater
• Solitary
• many experts consider bull sharks to be the
most dangerous sharks in the world
6. Bull Shark
7. Reef Shark
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There are 5 types of Reef Sharks:
Blacktip Reef Sharks
Gray Reef Sharks
Caribbean Reef Sharks
Whitetip Reef Sharks
Silvertip Reef Shark
8. Lemon Shark
• This shark is yellow in color which is where the
name derives from.
• Lemon sharks are mainly found along the
Southeastern coast in the United States. The
Gulf of Mexico is also a prime location for
them
• feed on various types of fish that are found in
the waters. Mainly they stick to small prey
that aren’t able to put up much of a fight.
• http://www.youtube.com/watch?v=f6UNSij65
BA
• http://www.youtube.com/watch?v=LfQgRCg1
bNA
• http://www.youtube.com/watch?v=l6JgnBq88s
“sea dogs”
• Pygmy shark, piked dogfish, prickly dogfish,
velvet belly shark
• Can life up to 5,000ft deep
• “lantern sharks” because they produce a slimy
mucus that glows in the dark
“cow sharks”
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Sharpnose sevengill shark
Bluntnose sixgill shark
Crocodile shark
Cookiecutter shark
Leopard shark
Tope shark
Atlantic weasel shark
“weird and wonderful” sharks
• Angel shark
• Filled shark
• Bramble shark- covered with sharp spines and
a foul smelling mucus covers the shark’s body
• Goblin Shark- odd shaped head and unusually
long beak like snout. Teeth at the front of
their mouths look like fangs
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SawsharkAren’t aggressive
Saw can grow to be 3 ft
Barbels on saw poke around for prey hiding on
the seafloor
carpetsharks
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Epaulette shark
Brownbanded bambooshark
Tasselled wobbegong
Nurse shark
Zebra shark
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Blacktip reef shark
Whitetip shark
Spinner shark
Blue shark
Silky shark
Lemon shark
Sandtiger shark
• “Ragged tooth shark”
• “Gray nurse shark”
• They can stay afloat while not moving. They
come to the surface and gulp in air. They keep
some of it in their stomachs and either release
it as gas. They can control the amount of air n
their bellies and hover in the water where
they want
White tip shark
Thresher shark
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Most famous for its tail
Upper lobe of caudal fin is very large
Hunt in groups
Can jump out of the water like dolphins.
Called breaching
• Have enormous black eyes
Mako Shark
• Fastest swimmer
• speed up to 20 mph
• Can leap 20 ft out of the water as well
Cookie cutter shark
• Small, deep water sharks that attack larger
fishes and dolphins and cut out chunks of
flesh with their razor sharp teeth and sucking
lips
• Even the rubber sonar domes of nuclear
submarines have not escaped their bites
• http://www.youtube.com/watch?v=U3M7wW
pX9qI octonauts
“How do you save a shark you know
nothing about” TED talk
• http://www.ted.com/talks/simon_berrow_ho
w_do_you_save_a_shark_you_know_nothing
_about.html
Why Sharks need our help: discovery
channel
• http://dsc.discovery.com/tv-shows/sharkweek/videos/why-sharks-need-our-help.htm
Sharks and humans
• http://www.sharksworld.com/sharks_and_humans.html
Sharks and Humans
• What is a shark’s biggest threat??
• humans because of hunting, pollution, global
warming, and taking over their natural habitat
• “Sharks have no place else to go but in the
water. Humans have the choice though of
where they are going to be. Therefore it really
isn’t fair at all to blame sharks when humans
end up in their territory.”
Using Sharks
• For thousands of years, sharks have provided
people with a valuable source of food
• Ex. Chinese cooking shark fin soup
Shark fin soup
• Sharks fins are currently one of the most
valuable and sought after marine products in
the world
Using sharks: Shark oil
• The livers of sharks are rich in oil and this oil
has been used for many purposes. In some
isolated communities where other resources
were not available, it has been used as a fuel
for heating and lighting
Shark oil….cont….
• Because shark oil contains large amounts of
Vitamin A, which is important for human sight,
scientists are investigating the possibility of
using shark’s liver oil for human consumption
• A chemical called squalene, which is present
in the liver, has several commercial uses:
leather, cosmetics, skin creams, medicines and
drugs
Using sharks: Shark skin
• Because sharks are covered with DENTICLES, it
was only recently that their skins were widely
used as a source of leather
• Stronger than cattle hide
• Denticles can be removed to produce smooth
leather. Touch leather, “baroso” contains
denticles
Using sharks: medicine
• The liver oils of some sharks, especially the
deep sea dogfishes, are thought to contain
ingredients that can lower blood cholesterol
and help prevent blood clotting
• Used to treat heart disease
Saving Sharks:Conservation
• The population numbers in many species of sharks are
declining due to harvesting sharks for meat, oil, skin, fins,
leather (shagreen), and for sandpaper (skin)
• Some believe that shark cartilage is a “joint nutrient” that
may help in the treatment of arthritis
Why are shark populations depleting?
• most sharks have slow rates of growth, mature
late and give birth to a small numbers of welldeveloped young after a long gestation period.
• For example, Basking sharks take at least 15 years
to mature, have a gestation period of 2-3 years
and produce only 4-6 pups.
• Sharks life history strategy is typical of top
predators with few natural enemies; therefore
their populations usually decline rapidly when
threatened. Hence, if given the opportunity to
recover they would do so very slowly, if at all.
Threats:
• #1: Commercial and incidental overfishing
• Today, the increasing average wealth of
people (especially in East Asia) together with
well-developed fishing methods have led to a
vast over-exploitation of many shark
populations.
• an estimated 50% of all sharks are caught
unintentionally or as 'by-catch' in other
fisheries
• #2: Habitat degradation
• Besides geographically defined, habitat also
has physical (such as temperature), chemical
(such as salinity) and biotic (such as prey
availability) aspects
• “habitat destruction “
The importance of shark conservation
• We have no idea what the environmental impact of
removing a very large number of sharks from the
ocean ecosystems would lead to. Most sharks are top
predators and scientists believe it is likely that sharks
play a 'keystone' role in marine ecosystems. Predatory
sharks assist in their prey's evolution by culling
genetically defective and diseased animals and keeping
their populations in check. Removal of this control due
to extinction is liable to have a detrimental effect on
marine ecosystems. Sharks are distributed worldwide
and the consequences of their decline will also be
widespread.
Important economic resource
• Although sharks contribute to economic
growth through directed fisheries and trading
of by-products, live sharks can also be
economically valuable. Shark predation on
weaker and diseased fish creates a stable,
healthy and quality supply of fisheries. Besides
that, shark populations in their natural
habitats are used as the main attraction in
sustainable trades such as ecotourism
Medical research
• There are several aspects of shark physiology
that can be used to further our knowledge in
medicine such as the ability of shark wounds
to heal within 24 hours without treatment,
the rapid healing and functioning of lacerated
shark corneas whereas blindness ensues in
other species, and resistance of sharks
towards cancer tumours
Intrinsic scientific value
• Shark exhibits many unique and puzzling life history traits
and behaviours. For example, there are species of
predatory sharks that can detect blood in very low
concentrations (Lemon shark). Some species of sharks can
osmoregulate their body fluids in both freshwater and
marine environments (Bull shark and Ganges shark). Other
behaviour such as navigation is thought to be influenced by
magnetic and electric fields, lunar movements, chemical
stimuli and geographical topography. Besides that, unique
forms of nourishment include interuterine cannibalism in
reproduction (Sandtiger shark). Scientists have also yet to
understand fully other physiology and behaviour such as
attack, mating, schooling and use of nursery grounds.
Shark conservation societies
• http://www.bite-back.com/
• Pewsharks.com
Top 10 shark conservation projects
• http://dsc.discovery.com/tv-shows/sharkweek/lists/top-10-shark-conservationprojects.htm
Sharks and global warming
• http://www.sharksworld.com/sharks_and_global_warming.html
Dogfish Dissection