Published on January 15, 2008
Sharks: Sharks Characteristics & Physiology Characteristics & Facts: Characteristics & Facts Largest shark in the world is the Whale Shark(Rhincodon Typus)- Average length- 15 meters(may exceed 18m) Average weight- 10 tons Typically found in tropical waters Feeds mainly on plankton Harmless to humans * Not certain which shark is the smallest in the world, among them is the Midwater Shark which is 22-25 cm (8-10 in.) and weighs only a few lbs. Characteristics & Facts: Characteristics & Facts Sharks are believed to have developed approximately 350 million years ago. Due to their advanced evolutionary state, they have remained virtually unchanged for the past 70 million years. Large sharks generally cruise at a speed of 1.5 mph. Great White sharks are believed to swim at a top speed between 40-50 mph. The Shortfin Mako is thought to be the fastest shark, calculated top speeds have ranged anywhere from 30 mph to around 70 mph. Characteristics & Facts: Characteristics & Facts Sharks typically have what is called a ‘fusiform’ body shape (cylindrical / rounded with tapering at each end), which makes swimming easier by reducing drag and minimizing effort. Usually sharks have different colors on their dorsal and ventral sides. When a shark is darker on the dorsal side and lighter on the ventral side it is termed ‘countershading’, which makes it more difficult to see from above and below. There are five fin types on sharks- Pectoral fins- help lift shark as it swims Pelvic & Dorsal fins- stabilize the shark during swimming Anal fins- provides further stabilization Caudal fin- propels the shark through the water Physiology: Physiology Skeletons are made of cartilage, a fibrous tissue, which is lighter and ½ as dense as bone tissue- Lighter structure makes it easier for shark to move and support its weight Sharks have no ribs, not needed because much of their weight is supported by the water Muscles are attached directly to the collagen matrix which makes up the skin and outer shell of body, allows skin to act as an external skeleton making swimming motions much more efficient for the shark Physiology: Physiology Sharks have an S-shaped heart that consists of two chambers. Blood is pumped from the heart to the gills, where it is oxygenated, then flows throughout the body. The liver of a shark may account for up 25% of its body weight because of stored oils and fatty acids which provide energy and increased buoyancy. Two muscle types- Red- for slow, cruising actions (slow twitch) White- for faster, rapid swimming, speed bursts (fast twitch) Sharks are cold blooded which results in a significantly lower metabolism than warm blooded animals. Therefore- They typically eat less than animals of their size Eat between 1% and 10% of their own body weight weekly Capable of going several weeks without food Shark Sensory: Shark Sensory Smell: Smell Organs for scent located near front of the snout in nostrils Nostrils shaped for continuous water flow Odorants in water stimulate nerve cells in scent organs Most odorants in water are indictable to sharks Super sensitive to those produced by predators, prey or mates and most receptive to body fluids and secretions produced by injured or distressed prey Sound: Sound Use lateral line and ear to detect ripple of water pressure Receptor cells in the ear are very similar to those of humans Two tiny holes located behind eyes Hear better at lower frequencies, especially irregular noises like those generated by injured, thrashing animal and can hear up to 650 feet away Slide10: The lateral line is a tiny canal just under the skin which detects movements on the outside They also react to variations in water currents around the shark and pressure waves from underwater sound Allow for the detection of current flows around underwater feature or the swishing of a fishes tail Most similar to our ability to detect wind Touch: Touch Sense of touch in sharks in ot highly sensitive Mainly used to detect: Large changes in temperature Presence of noxious or corrosive chemicals Physical damage or trauma Electro-Sensors: Electro-Sensors Sharks can detect electrical fields emmitted by all animals with organs call Ampullae of Lorenzini Tiny pours in skin around the head and front end Nerve cells in the pours react to electrical stimuli, as well as changes in water pressure and temperature Slide13: This sense is relied upon more than any other when sharks are hunting and close to the prey Salts and minerals in leaking body fluids of injured animals create certain types of electrical signals This explains why sharks will repeatedly attack a victim during rescue and ignore the rescuer Shark Attacks: Shark Attacks Threat of Sharks When, Where and Why they Attack Most Common Sharks to Attack How to Reduce Risks of Being Attacked Threat of Sharks : Threat of Sharks About 80% of shark attack victims survive Most often the shark carries out an exploratory attack Globally, people are almost 1,000 times more likely to drown than be attacked When, Where and Why They Attack: When, Where and Why They Attack Most attacks occur in warm and shallow waters near resorts. Statistics are only recorded in affluent countries A lot of sharks feed of bigger prey such as sea lions; a human on a surf board or floating at the surface of the water can be mistaken for one. Most attacks are “hit and run” attacks Less common are “bump and run” and “sneak” attacks which more often than not end up in fatalities Where in the US: Where in the US WHY: WHY Most Common Sharks to Attack: Most Common Sharks to Attack These sharks are larger in size and consume larger prey Great White Tiger Shark Bull Shark Blacktip Shark How to Reduce Risks of being Attacked: How to Reduce Risks of being Attacked Stay in groups, sharks usually attack a animal that is alone Do not go in the water during night time hours, sharks have a competitive advantage then and are more likely to attack Do not wear shiny jewelery Use caution when near sandbars Avoid uneven tanning and bright colored clothing, sharks see color contrast well Feeding and Hunting Habits: Feeding and Hunting Habits Carnivorous Heterotrophs What do Sharks Eat?: What do Sharks Eat? No sharks are true herbivores Large irregular feeds .5-3% of body weight May attack humans, but they are not designed to feed off humans not around when sharks developed feeding habits What do Sharks Eat?: What do Sharks Eat? Specialized same thing over and over similar habitats offer similar foods Common Preys squid, shoals of fish, turtles, sea lions, crabs, small hard shelled animals What do Sharks Eat?: What do Sharks Eat? Facts Great Whites usually consumer 11 tons of meat per year 10% of all food consumed goes into making new shark growth and body maintenance Found in Tiger Sharks drums horses coal chickens cans of paint dogs coats cattle How do Sharks Eat?: How do Sharks Eat? Filter Feeding passes through bristles along the gills Four Methods too big to pass through bristles stick to mucus stick to bristles gravity sinks them into the filters How do Sharks Eat?: How do Sharks Eat? Use of Teeth pliable dentine covered by harder enamel Arranged in Rows lost teeth/rows replaced by the ones behind happens about every two weeks can go through 20,000 teeth in a life Do Sharks Hunt in Packs?: Do Sharks Hunt in Packs? Research in Ongoing Congregate to Feed with each feeding in its own way Smooth-Hound and Dogfish Sharks prowl in large packs This allows smaller sharks to hunt larger prey these reactions are more instinctive and responsive than planned Do Sharks Hunt in Packs?: Do Sharks Hunt in Packs? Silky/Dusky Sharks more instinctive behaviors herd shoals of fish together with fins into large central group swim inward with mouths open to feed Shark Conservation: Shark Conservation Why conserve sharks? What are sharks used for? Which sharks are endangered? Focus Whale Shark, White Shark, Smalltooth Sawfish Strategies used for conservation Why Conserve: Why Conserve Sharks are a natural by catch of many longline fishing industries fishing for tuna and billfish. Due to hazards imposed on the crew these sharks are often killed. Historically there was a wide market for Vitamin A, which is produced in the liver of sharks. Due to an increase in synthetic vitamins this market has fallen to the wayside. However, there is still a strong market in Asian communities for shark fins. Slide32: So why conserve? Many societies depend on shark fisheries to sustain their economies. Low reproductive capabilities. Gestation period long Mature at high age Due to over fishing some areas shark populations have become extremely low. (Stevens, 2000) What are Sharks Used For?: What are Sharks Used For? In the early 1900’s there was a big market for hides and livers off the coast of California These fisherman focused their efforts mainly on soupfin shark and the spinydogfish. The livers were used for the extraction of Vitamin A and the hides for clothing and meat. The onset of WWII created a demand for Vitamin A, and due to increased fishing pressures by 1946 populations were almost extinct. What are Sharks Used For?: What are Sharks Used For? The same kind of market developed on the East coast, but there focus species was the thresher shark. With the advent of synthetic Vitamin A pressure has been relieved on sharks in the US, however, many Asian markets will pay top dollar for shark fins. Which Sharks are Endangered: Which Sharks are Endangered http://www.iucnredlist.org/search/search.php?freetext=sharks&modifier=phrase&criteria=wholedb&taxa_species=1&redlistCategory%5B%5D=EN&redlistCategory%5B%5D=VU&country%5B%5D=all&aquatic%5B%5D=all®ions%5B%5D=all&habitats%5B%5D=all&threats%5B%5D=all&Submit.x=99&Submit.y=12 Whale Shark: Whale Shark Largest fish in the world Very lucrative industry in India Not much is known about reproductive capabilities. Listed as vulnerable on Endangered Species List. Great White Shark: Great White Shark Considered the most deadly shark to humans Often hunted for role in attacks. Little is known about breeding due to solitary lifestyle. Listed as vulnerable. Smalltooth Sawfish: Smalltooth Sawfish Once common throughout the eastern seaboard Almost completely extinct due to fishing pressure for saw. Listed as endangered. Little is known about this animal. Conservation Strategies: Conservation Strategies Listing at risk species on the endangered species list. Research into shark reproduction. Fishing regulations for “keeper” size sharks. Banning/boycotting goods produced from sharks in countries where it is legal to do so.