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In the Jaws of Extinction

In the Jaws of Extinction

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In the Jaws of Extinction

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  1. In the Jaws of Extinction Shark Awareness and Conservation

  2. What is a Shark? • Shark is thought to have evolved from a Middle English Term, shurke (villain) • First sharks lived about 380 million years ago • Considered “primitive” because they have changed very little in that time

  3. Class: Chondrichthyes Sharks, skates, and rays Modern Advances Adaptation as predator Hydrodynamic body

  4. Anatomy of a Shark

  5. Circulation • Sharks have a 4 chambered heart like mammals • Faster moving sharks have larger hearts than slower moving sharks • Hemoglobin in blood carries oxygen • Faster moving sharks have more hemoglobin in the blood than slower sharks

  6. Respiration • Sharks, like all fish, breathe by extracting dissolved oxygen in the water • Water passes into the sharks mouth and is forced over the gills • Most sharks have five gills on each side of the head; some have up to seven.

  7. Jaws and Teeth • Jaws are only loosely attached to skull • Allows for teeth to be used more efficiently • Replaceable teeth attached to skin of jaws, not to the jaw • Can have up to 7 rows of teeth “in waiting”

  8. Bite range of a Great White can be in excess of 2.5 feet

  9. Diet • All are carnivores, but have highly varied dietary preferences • Only consume about 2% of body weight daily • Some sharks go weeks without eating

  10. Feeding Habits • All are flesh-eaters, ranging from plankton and small fish to sea lions and whales. • Do not eat every day • Undigested food may stay in stomach for several days

  11. Size, Growth and Age • Only 50% of sharks reach a size of less than one meter, and only 5% exceed 4 meters • Size Variation • 13 m (Whale Shark) to 20 cm (spiny pygmy shark) • Average life span about 20-25 years but can live to 100 • Most do not reproduce until late teens

  12. Reproductive Biology • Age at sexual maturity – 15 to 25 yrs • All sharks undergo internal fertilization • Gestation Periods – 9 to 12 months (some 15 months) • Females may retain the sperm until the next season to fertilize their eggs • Most have 1 to 2 offspring/yr • Few species can have 120+ offspring/yr

  13. Sharks reproduce more like mammals than other fishes • 70% bear live young • 55% babies develop inside female body (by placenta attachment) • Some lay eggs • Sharks’ egg called Mermaids’ s purses

  14. Giving Birth • Ovipory: 30% lay eggs • Ovoviviparous – internal incubation of eggs and live birth • Interuterine cannibalism • Viviparous – young born fully formed attached to female and nourished by placenta

  15. Viviparous

  16. Types of Eggs

  17. Shark pup emerging from egg case

  18. The Shark’s Skin • Skin protected not by scales, but by hard “skin teeth” or dermal denticles • Feels like sand paper • Important in swimming efficiency • Denticles point backward to decrease drag

  19. Nose to Tail • Sharks designed for constant, effortless swimming, though not as sustained high speeds • Color blends in with colors of the ocean • Their senses, like their teeth, are razor-sharp, and they are quick to investigate anything that could be food

  20. Tails and Fins • Propels itself through water with powerful tail fin moving side to side • Fins are non-retractable, used for balance and to prevent roll-overs • Control direction of shark and act as a braking mechanism

  21. Fin Facts • Pelvic and Pectoral fins act like wings of an aircraft for steering • Shark fins are cut off and dried to make “Shark Fin Soup” • Fins cut and live carcass thrown back into ocean – sharks die slowly by drowning • Shark finning is illegal in the U.S.

  22. Shark Finning in Asia

  23. Senses: Swimming Computers • Sharks can see, smell and hear in addition to sensing movement and electrical fields made by other animals • Uses sense of “touch” to locate food and enemies • Sharpness of senses varies from one species to another depending on lifestyle

  24. Vision • Sharks have excellent vision: especially sensitive to contrast • Sharks probably see color • Black cones on back of retina (Tametum lucidum) increases vision at night and in murky waters. • Can see better at night than cats

  25. Scent Detectors • Shark has nostrils located in front of eyes on each side of snout • Olfactory sacs in nostrils detect scent • Blacktip sharks detect one part of scent in 10 billion parts of water • Most sharks can detect a scent from over a mile away

  26. Detecting Sound • Sharks have ears located on top of head • Detect movement of water molecules • Have detected sound 4+ kilometers away • Can detect heartbeat up to 1 mile

  27. Electro-Sensitivity • Sharks are most electrically-sensitive vertebrate ever studied • Use magnetic field of earth as natural compass for migration • All organisms emit electrical signals varying in strength depending on animal

  28. Ampullae of Lorenzini • Delicate, jelly-filled canals connected to pores in the shark’s skin • Visible on the underside of shark’s snout • Can detect incredibly low voltage • Can feel heartbeat up to 1 mile away • Detects electrical stimuli from animals buried in sand or hiding in corals

  29. Lateral Line • Specialized, pressure sensitive, hair receptor cells found in grooves or canals along a central line that runs down each side of a sharks body • Movement of hairs signal the change in water pressure caused by other fish • gauge distance • useful in murky waters or complete darkness

  30. Sensing Prey • Usually pick up smell of a victim first • Tracks down bleeding prey – easy meal • Lateral line confirms position of target • Ampullae of Lorenzini picks up electrical activity of prey • Closer in, ears pick up sounds • Within striking distance, shark sees prey • Shark’s brain shuts down senses • Tastes victim by biting, then swims away • Victim moving less, moves in for the kill

  31. Behavioral Patterns • Swimming usually casual • Rarely makes any sudden moves • Noises made by humans usually scares a shark • Curiosity often draws sharks toward scuba divers

  32. Hunting • Movements of a shark become erratic during hunting • Blue sharks are fearless, attacking prey much bigger than themselves • Great whites often patrol beaches that are known homes to seals or sea lions

  33. Territorial? • Most sharks are not territorial, simply swim around the oceans • Reef sharks form a base and patrol it • Grey reef sharks may consider other sharks and people as a threat • Breeding sharks become very aggressive

  34. The Attack • Sharks usually circle their prey before attacking it • Slowly narrow the circle getting closer and closer • Nicitating membrane covers and protects eyes during the attack – rendering the shark blind during the attack • Some often bump or nudge prey to see if it is soft • Great Whites attack from below and behind, away from the head

  35. Behavioral Considerations • Very predictable, very smart and very social • Many who work with sharks maintain that they have very distinct personalities • Some sharks display a complex and subtle “body language” which may be an attempt to communicate the violation of their space

  36. Threat Warning • “Posturing” has been displayed by many sharks as a warning for attack • 1. Swims back and forth in one place • 2. May drop pectoral fins, raise nose and hunch back • 3. Turn toward you and then away • Repeats this process as a warning