Land and Marine Life
Hawaiian Sea Turtles
What kind of an animal is a sea turtle? Sea turtles are reptiles. There are only 7 marine species world wide out of the 225 species of turtles that live today. Brain size may not have anything to do with longevity considering the turtle’s brain is smaller than a grape, and it has survived 225 million years. The largest turtle ever swam in the ancient seas that covered Kansas and South Dakota, weighed over 6,000 lbs. and its shell measured 12 feet in length. We see these curious sea turtles along our route off shore Kauai.
How many kinds of sea turtles live around Hawaii? There are three native Hawaiian sea turtles. The Green turtle, or Honu, is the most common. There are very small numbers of Hawksbill, or Ea, found around the islands of Molokai and Hawaii. The third turtle is the most rare, the Leatherback, and it is usually seen on the open ocean where it feeds almost exclusively on jelly fish. There was one documented case of a Leatherback laying eggs on the shores of Kauai four years ago – high surf washed the eggs away.
Are all Hawaiian sea turtles endangered? The Green sea turtle is threatened which means it isn’t likely to go extinct as the Hawksbill and Leatherback which are both endangered . However, all of the sea turtles are federally protected and the penalties are severe if you bother these turtles in any way.
How did the green sea turtle get it’s name? The fat of a green sea turtle is yellowish green and turns bright green when cooked (probably due to the green plant food that makes up the diet of an adult sea turtle).
Are there green sea turtles that actually nest on Kauai? Yes, there are between 6-8 nesting females that lay their eggs on both the north and south shores of Kauai. The females are on a two year nesting cycle and usually lay over a hundred eggs every two weeks from the end of May to September (a total of 1200-1400 eggs in a season!). Most of the green turtles swim over 800 miles to nest on the French Frigate shoals which are apart of the North West Hawaiian Islands.
What do green sea turtles feed on? As juveniles they feed on the small animals and plants that live among these clumps of vegetation. Eventually, the green sea turtles begin to forage near the coast and feed primarily on algae or limu which grows on coral reefs and on rocks close to shore at high tide. Like cows, green turtles depend upon bacteria in their guts for digestion of their food. As adults, the turtles are herbivores or vegetarians weighing as much as 500 lbs. (average is around 350 lbs. for Hawaiian green sea turtle).
How fast can they swim? 25mph (dive the length of an 80 story building or 800 feet).
How long do they live? No one knows for sure, possibly 100 years.
How long can they hold their breath? If they are resting, turtles can stay under water for days even weeks. However, for active greens 3 hours is maximum documented time. Greens in the Atlantic ocean can actually hibernate during winter, they will partially bury themselves in the mud to help keep warm. The critical temperature is 6.5° Centigrade, any colder and the turtles cannot survive for more than a few hours.
How do you tell the difference between male and female green sea turtles? The male has a tail that is almost a foot long extending beyond the shell or carapace where as a female’s tail does not extend past the shell or carapace. However, you can only tell if you are looking at a male or female if they are sexually mature – 25-30 years of age for a green sea turtle.
Why does the male have such a long tail? The male uses his tail to hold onto the female during copulation, turtles are known to copulate for hours. It is thought that during this time the couple emits some type of shark repellent because sharks will not bother copulating turtles. Often, the male is fertilizing next years crop of baby turtles because the female can store the sperm for more than a year (this is common ability for reptiles).
Who eats the turtles? Man is the major predator of turtles and this is still a problem on Kauai. Turtle remains are often found discarded in the rivers. Unfortunately, unless the turtle is an adult, the turtle poachers don’t know that they are killing valuable females who only begin nesting at 25 years of age. Tiger sharks are the natural ocean predators of the green sea turtles.
Do turtles get caught in nets, if so, what kind of nets? Dr. Don Heacock from Aquatic Resources on Kauai gets a call once a week about a green sea turtle entangled in some type of fishing line or net. Only 10% of these turtles survive, which means we lose around 50 turtles a year to nets alone. The ones that don’t get tangled in nets, may die from ingesting plastic bags, pieces of plastics, or die from the dreaded disease fibropapilloma.
What is fibropapilloma disease? In humans a papilloma tumor is a benign growth that is spread by a virus, i.e. an ordinary wart. When they develop predominantly on fibrous tissues, they are called fibropapillomas. Fibropapilloma only attacks green sea turtles and these tumors debilitate and disfigure the turtle within a few years. These tumors are lobe shaped and grow on all soft parts of the turtle. Scientists do not know what causes this disease. They only know that it is a viral infection and it is caught in the wild (captive turtles don’t contract the disease even when in close contact with diseased turtles). Green turtles in Florida and the Bahamas are also suffering in epidemic proportions from this disease. It is feared that if a cure is not found soon for this disease that it may wipe out this species of sea turtle completely. 10% of the green sea turtles tagged off Kauai have fibropapilloma compared to over 90% of the greens tagged off Maui. It is not known how this disease is spread but it would appear that females maybe more likely to contract the disease than males (at least, this is true for the turtle population in Maui).
Do boat captains have to worry about hitting green sea turtles, and how many actual documented cases are there of mortality caused by vessel impact? There have been 7 documented cases of green sea turtles dying from vessel impact over the last 10 years. Most of these turtles were found having seaweed in their mouths which means they were hit when they were feeding. Two of the cases were turtles that washed up in Haena. Whether these turtles were hit by commercial boats will never be known. According to Dr. Heacock, “Speed kills and it is important, to drive slowly and safely where turtles are known to be resting and feeding along the Na Pali Coast.”
The only time it is ok, legally to approach a turtle, is if you see a turtle entangled in a net and can not get to a phone to call: 274-3344 or 241-6711 Dispatch for help. Then you should try to cut the net off the turtle (avoiding the head of the turtle i.e. the mouth) to free it.
Hawaiian Sea Birds
Hawaii’s only un-waterproof sea bird – our “Noddie” Tern
(Referenced from Seabirds of Hawaii by Craig S. Harrison)
What: Noddies are distinguished from terns by their distinctive nodding and bowing behavior during mating ceremonies, but “tern” properly includes noddies.
Where: There are over 9 million noddies and terns (3 species of each) that make up the 15 million seabirds of Hawaii. Noddies are widespread in all tropical oceans and once bred in virtually every island group in the tropical Pacific.
How come they aren’t waterproof? Unlike other seabirds, they lack substantial oil glands at the base of their tails. Thus they can become very bedraggled and even drown if they alight on the water for more than a few minutes.
What do noddies look like? Black noddies are dark with white capes, long pointed bills, and slightly forked tails. These birds have two color phases in Hawaii: in the light phase black noddies are dark gray-brown with pale gray tails, in the dark phase they are a uniform sooty black. Unlike black noddies elsewhere, the Hawaiian population has yellow-orange legs and feet.
What do they eat? Black noddies feed inshore over schools of near shore predatory fishes such as little tunas and jacks, often within a few meters of the shoreline. Black noddies eat virtually all fish; larval and juvenile forms of goatfish, Foster’s lizard fish, round herrings, flying fish and gobies.
Where and when do they have their babies? Black noddies nest on available cliff ledges and rocky pinnacles throughout the Hawaiian archipelago. Many colonies are located in rocky sea caves where nests are constructed above the surge of the high water. They will also nest in ironwood trees, beach heliotropes and bunchgrass.
Noddies will feed each other as part of the mating ritual: All terns and noddies have ceremonial fish flights in which one bird presents and sometimes transfers a fish to its partner. The nodding and bowing typical of noddies occurs when a male feeds his mate before she lays her egg.
How many chicks do they have at one time? The nod die typically lays one egg in the winter and spring, the egg representing almost 27% of the female’s body weight. Black noddies grow the fastest out of all of the terns and noddies, and average 38 days from hatching to first flight.
How long do noddies live? It is believed that Black noddies live to 25 years of age.
Did you know that Kauai used to be where the Big Island of Hawaii was about 5 million years ago. Kauai at the present moment is 500km or 300 miles northwest of the Big Island.
Kauai used to be over 9,000 feet tall at its highest point. At the present moment the highest point is 5,243 feet at Kawaikini point.
Can you guess who the vegetarian is: monk seal, humpback whale, green sea turtle, or spinner dolphin?
Green Sea Turtle Who swims faster the monk seal, the humpback whale or the green sea turtle?
Green Sea Turtle 25mph
Hawaiian Spinner Dolphins
Hawaii’s Spinner Dolphin(referenced from Kenneth S. Norris’s Dolphin Days and Peter G. H. Evan’s The Natural History of Whales and Dolphins)
What: Stenella Longisrostris the Latin name meaning long-snouted Spinner dolphin. The Hawaiian Spinner is considered one of 4 species of Spinner dolphins that live around the Hawaiian Islands.
What do Spinners look like? The slim spinner dolphin averages between 5-7 feet and its weight ranges between 110-160 pounds. There are three parts that make up the color pattern of the spinner; a dark back, pearl-gray side panels, and pure white belly. Their long, slim, blackish beaks are lined with 180 or more delicate interlocking conical teeth.
Where: Spinner dolphins can always be found in dolphin schools ranging from four to over 250 individuals in shore. The “school” is where dolphins give birth, raise and instruct their young, find and catch food, sleep; and schools of dolphins never stop moving, even during rest.
What is echolocation? Echolocation is how dolphins send and receive back as echoes. The form of echoes, including their loudness, can inform a dolphin of the size, shape and surface characteristics and movement of the object. The time lapse between emitting the signal and receiving the echo indicates how far away an object is.
So what, if dolphins echolocate? Because of echolocation, dolphins are able to search for, chase and catch fast swimming prey in total darkness. In captivity, a blindfolded dolphin can not only swim round a pool without ever hitting the walls but also can distinguish, for example, between balls of slightly different sizes or between, for example, between balls of slightly different sizes or between a hollow and a solid ball of the same size at 400 feet away. If you swim with a wild population of spinner’s they know how much you weigh, if you’re male or female, and if you’re pregnant.
Why do Spinner dolphins spin? The dolphins who spin are letting the rest of the dolphin school know exactly where they are and in turn, serve as a local “geographical markers” and in group, mark out the dimensions of the school. Before spinning, a dolphin will produce a barking like sound well below the surface of the water thus, informing other dolphins when and where a spin is about to take place. With a listening dolphin’s attention focused in the proper direction by the barks, the re-entry slap confirms that it was indeed a spin, and the bubble plume makes an excellent echolocation target, providing range and bearing for an echo locating school member.
How can you tell the difference between male and female spinner dolphins? Male spinners have deep muscular tails and are usually larger than the females. Males also have a peculiar ventral hump of tissue that looks like a radar dome, set just behind the anus. The curious post anal hump, marks the sex, and to a degree the age of the spinner dolphins that bears it. Big, old males have the largest humps.
What do they eat? Spinners eat a lot of very small food items: two-inch, bioluminescent lantern fish, deep-sea shrimp, and thumb-sized squids. Some of these squids never venture closer than 500 feet to the surface of the water. Spinners can dive to almost 1000 feet hunting for food.
Where and when do they have their babies? On average, newborn dolphins are most abundant in the late spring and summer, pregnancy lasts about 10.5 months and the babies are born within the school of dolphins. It is speculated that sexual behavior in these dolphins might be cued chemically probably by taste during mating season (late spring and summer). Females cycle through very brief peaks of sexual readiness (females who just ovulated), lasting just days. The male hormone patterns are quite different and they are sexually active throughout much of the mating season.
Can dolphins have twins? Yes, they can have twins but less than 1% have twins. Other adult females within the dolphin school will take care and feed the baby.
How long do the Spinner dolphins live? On the average, 20 years of age.
Loaded Gun Theory: Dolphins using their sonar to create “bullets” made out of sound. They direct their sound “bullets” in unison, at their prey. They can actually kill their prey with sound. Thus large school of dolphins, sometimes numbering in the thousands, in the open ocean represents a powerful hunting group. This theory has been documented with captive bottle nose dolphins using nose dolphins using their sound to kill anchovy.
Which whale or dolphins dives the deepest? The sperm whale which has been spotted off shore of shore of the Hawaiian Islands will dive over 12,000 feet (over 2 miles) for squid and can hold its breath up to 3 hours.
Dolphins are awake 24 hours a day. Dolphins alternate their brain halves when they sleep. In other words only one side of their brain is sleeping while the other side is wide awake. Then they alternate brain halves. Dolphins are conscious breathers and have to “remember” to come to the surface of the water to breath and they need to be able to respond to any danger signals i.e. sharks.
Whales, how many are there and how did they evolve to their modern form? There are 78 species of whales, dolphins and porpoises and the scientific name is Cetacean (pronounced se-TAY-shun) which comes from an ancient Greek word “ketos” meaning whale. All whales are mammals and they breathe air, give birth to live young and nurse their young with milk. There is amazing diversity from the largest adult Blue whale which is 20,000 times heavier than the smallest newborn Vaquita porpoise. Modern cetaceans carry with them remnants of their terrestrial (land) ancestry. If one examines the internal structure of a whale’s side flipper-it resembles a huge hand complete with finger bones. Most whales also possess internal remnants of a functionless pelvic bone and hind leg bones. Whales evolved from hoofed land mammals about 50 million years ago.
The sea within us – a 155 pound human carries 16.5 quarts or a little over 4 gallons of salt water in his/her body. Some 3 quarts make up the blood plasma – the watery part of the blood flowing through veins and arteries. The rest serves as interstitial fluid in the spaces between all the cells of the body.
If we drained all the world’s oceans how much salt would there be? There is enough salt in the oceans to cover all the continents of the earth in a layer of salt the height of a 50 story skyscraper (or 500 feet).
No way to get rich fast – There are 9 million tons of gold dissolved in the world’s oceans – some 180 tons more than all the gold mined on earth throughout history.
What exactly is an ocean mammal, a whale? A whale is a mammal similar to a land mammal except that is lives in the water, specifically the ocean, which is very salty. So ocean mammals have evolved differently than land animals. Ocean mammals cannot breathe oxygen out of the water like fish. Ocean mammals, like whales, have to come to the surface to breath. Respiration is an exhausting activity and energetically expensive for mammals that have the same kind of lungs as human beings do (they’re called ventilation lungs) except that whale lungs are extremely efficient. With each breath the whale takes, there is over 90% exchange of the content (carbon dioxide for oxygen) of its lungs, a respiratory rate 5-6 times more efficient than human lungs. The lungs of a humpback whale make up only 1-3% of their total body weight vs. 7% in a human.
How are whales able to grow to such large sizes? In a medium of water, the whale is able to grow to huge sizes. In fact, the Blue whale is almost twice the size of the largest dinosaur that ever lived on Earth. It averages 100 feet in length and can weigh from 120-150 tons. You can think of a Blue whale as being as long as 3 railroad cars and weighing as much as 1600 people or 30 elephants. Whales, especially the Humpback whale, have very thick layers of fat or blubber (6-8 inches) which keeps them warm in polar waters and helps them float. The fatty tissue provides enough buoyancy to offset the negative buoyancy of the whale’s muscle and very light skeleton. The bones of a whale will actually float because they are filled with fat (which is quite different than the bones of a seabird which are filled with air). Whales don’t have to worry about supporting their great weight because they are in a medium of water and between their very light bones and built in “fat life preservers” they are very buoyant. But if a whale is beached they have a limited amount of time (depending upon the size) before the mammal will be crushed by its own weight.
Besides the more efficient lungs that a cetacean has over a human being, what other features do they possess that enable some cetaceans i.e. Sperm whale to hold their breath for as long as 3 hours? The sperm whale, the cetacean with one of the most impressive of all underwater capabilities has been documented as diving over 12,000 feet (more then 2 miles) for as long as 3 hours. It seems that cetaceans are able to take more oxygen down with them than a human diver can. One factor in this performance is the cetacean’s considerably greater volume of blood: up to 2-3 times more blood per unit of body weight than in human beings. The cetacean’s blood also has a somewhat greater oxygen-carrying hemoglobin of the red blood cells) is responsible for the muscle’s characteristic dark red color. Myoglobin is present in the muscles of terrestrial mammals too, but in much smaller amounts than cetaceans. In some cetaceans species more oxygen is carried in the muscles than in the animal’s red blood cells. Another key factor for cetaceans is its highly developed vascular systems – the fast circulation which rapidly reloads the red blood cells with oxygen. This fast circulation is demonstrated by the faster heart rate when a whale comes to the surface to breath after an extended dive. The whale has a powerful heart and a circulatory system that features large networks of capillaries (retia mirabilia or wonderful nets) and large sinuses in the venous system. The ability to recharge red blood cells with oxygen fast constitutes the fundamental respiratory difference between cetaceans and terrestrial mammals, whose breathing is usually regular and whose blood flow is relatively smooth. For example, humpback whale exhales its breath at 300 miles per hour then inhales around 2,000 liters of air per minute.
Basic Shark Biology
Is a shark a fish? Yes, it is a type of fish in which the skeleton is made out of cartilage, instead of bone. Cartilage is a flexible, semi-transparent elastic material full of cell spaces. Cartilage is formed from a complex protein which encloses a network of connective tissue fibers. Sharks and their relatives the skates, the rays, and chimaeras, are separated from the 26,000 species of bony fishes, because they are cartilaginous fishes, known collectively as the Chondrichthyes. There are between 344-368 different species of sharks and some have fossils dating back 400 millions years (dramatic compared to man which is only 2 million years).
How well do sharks see? Most sharks have a well-developed sense of vision. Their eyes can adapt to low light environments because they have a special structure in the eye called a tapetum. This reflective layer beneath the retina amplifies the light signal. Sharks have the ability to distinguish individual flashes of flickering light down to 45 impulses per second (less than a dragonfly which is 220/second, but similar to cockroach at 50/second). This enables sharks to discern the brief, flickering movements of prospective prey in the dimly lit undersea world. Some species, such as the great white shark, have been shown to have color vision. The corneas of sharks have been successfully transplanted in human eyes.
How well do sharks hear? Sound travels 4-5 times faster in water than air and is an important medium for all sea life – the shark is no exception. Sharks have very sensitive hearing, primarily in the low frequency range. Many sharks can “hear” potential prey more than a mile away. Sharks have very sensitive ears and dolphins will actually use loud “sound bursts” as weapons of defense, successfully discouraging shark attacks.
Do sharks taste what they eat? Yes, although they don’t really chew their food much. Once, the taste has been identified as acceptable, they will swallow the prey practically whole.
How well do sharks smell? It depends upon what the smell is. If it is tuna, some species of shark (i.e. gray and black-tip reef sharks) can detect a dilution of 1 part in 10 billion (ppb)!, though other sharks detect a “mere” 1 part in 25 million. Needless to say, sharks have an excellent sense of smell. They are not normally attracted to the smell of human blood, but more likely they are investigating sound or electrical signals. With an ability to detect 1 in 10 ppb, sharks can probably smell a partially digested seafood meal. If you ever meet a shark bite victim you might ask them, “Did you eat seafood recently?”
Besides the shark having an excellent sense of smell, sight and hearing, how else do they hunt for prey? Sharks have an ability to detect electrical signals. In fact, they are considered to have the highest known electrical sensitivity of any living animal – 5 billionth of a volt per cm. So if they can’t hear, see or smell their prey, they can still detect the electrical currents. These are given off by contracting muscles of all living prey – from shrimps to seals.
Do sharks make any vocalizations similar to the dolphin or humpback whale? I guess you can’t have everything. Sharks are not capable of making any acoustic sounds, and have absolutely no sound -making apparatus. However, that does not mean they can’t communicate with each other, it just means, they have evolved to use other mediums.
Are sharks intelligent? It would seem that they are more intelligent than previously thought. The larger, faster moving sharks generally have larger, more complex brains compared to some mammals and birds (specifically ratio of brain weight to body weight). In captivity, some sharks have been trained to hit specific targets for food depending on the shape and color of the target. Also, “play” has been observed with some species of sharks.
How often does a shark have to eat? It depends upon the species of shark but it may be that they can store ingested prey in their stomach for limited periods. Also they can regurgitate only unwanted items (i.e. the shell of a turtle). The Great White sharks can go 3 months without a meal.
What determines the size of a shark and how large can they grow? The liver is the key organ which determines the overall length of a shark, and it is filled with oil that is lighter than sea water. Livers from some of the largest whales weigh 200 pounds and contain more than 18 gallons of oil! Because sharks are the muscle machines (unlike the ‘blubbery’ humpbacks who use their blubber for buoyancy) – how is it that they can float? While most other types of fishes have a swim bladder which they fill with air for buoyancy; the shark has adapted its liver and specifically the liver oil. But there are limitations to how much room the liver can have within the body cavity of the shark which has other important organs to house as well. Thus, the liver can only be so large, and it limits the overall size of the shark.
Cool Facts (summarized from MARMAM, an internet e-mail group):
“Sea Lions Trained to Film & Tag Whales”, Researchers are training sea lions to become their spies of the deep. A 400-pound, 17-year-old male named Beaver and his 190-pound, eight-year-old female, sake, will take on the mission of videotaping and tagging whales off Monterey Bay. With six years training, Beaver will be the first to scale the ocean depths on hand and acoustic command – perhaps as early as this winter – aiming his video camera as his fellow sea creatures, gathering footage of the secretive giants at work, play, love or war, as never before seen by man. “We’ve got a biased view of what whales do because most observations have been done from shipboard,” said Jennifer Hurley of the Moss Landing Lab, who leads a team of 25-plus behavioral trainers. “In reality, whales spend 90-95% of their time under the sea. We need to know what’s going on down there. The whales are used to seeing sea lions, so by getting sea lions to be our filmmakers, we should be able to record what the whales are doing without any undue outside influence. Sea lions respond well to training and, we think, can learn the complex skills involved in swimming beside whales while wearing a harness with a video camera or carrying a tag in their mouths and affixing the tag to the side of a swimming whale.” The equipment the sea lions carry will allow instantaneous recording of depth, time, sounds and speed of the whales along with the video image. Underwater recordings will be used to analyze diving patterns, speed and underwater behaviors of gray whales, and depth, speed and feeding behaviors of humpbacks.
Can you tell the difference between a male & female shark? Yes, a male shark has two claspers which are modifications of the pelvic fin (located on the belly of the shark). A clasper can be as long as a person’s arm on a mature male. There are two claspers, each with visible hooks on the tips of the clasper. Normally only one clasper is inserted into the female. Once inserted, there is a rotation of the cartilage which results in a hook piercing the inner walls of the female oviduct, anchoring the male organ in the female; hence, the name “clasper”.
How do sharks mate & is there any courtship? For the large species of shark almost nothing is known about mating “where, when & how often” are unknown. There are only a few species in which actual copulation has been observed. For the white-tip reef sharks, the sharks engage in precopulatory courtship biting. The smaller male will grip the female’s pectoral fin in his teeth preparatory to entwining his body beneath her & inserting a clasper into her cloacal opening. The sharks will sink to the bottom until copulation is complete. It is thought that in some species the female gives off a pheromone, a sex attractant substance.
In some species of sharks, such as the Blue shark, sperm can be stored in a shell gland for later use until the eggs are mature or go directly to fertilize mature eggs.
How are young sharks born, live or from eggs? There are 3 possibilities for sharks. 1) Some species lay eggs usually encased in a leathery shell, they are expelled into the sea where the embryos develop for a period of 6-10 months hatching as miniature adults. This is considered the most primitive mechanism known as oviparous which means egg birth, & it is used mostly by bottom dwelling types of sharks such as the horn & cat sharks. 2) Ovoviviparous, meaning born live from egg, is the mechanism that occurs in the majority of sharks. The eggs develop from the nutrition of the yolk, & the embryos hatch inside the mother, to be born shortly after. With some species the developing embryos will actually feed on the other embryos inside the mother, cannibalizing one another till the most ferocious remain. This is referred to as ovophagy, which means egg eating & occurs with the Mako, Tiger, Sand & probably the Great White. 3) Viviparous, meaning live birth, is the mechanism in which there is a placenta-like growth contacting the embryo’s yolk-sac & provides a channel for transmission of nutrients direct from the female’s blood stream to the embryo (takes 9 months for development). This is the most sophisticated mechanism of development. It occurs in the Blue shark, Oceanic White tip, Black tip reef, Gray reef, & probably all of the hammerheads.
Some species of shark will not hesitate to eat their own young, thus females will not eat at all while they are in the nursery grounds during “pupping” season.
Is it true, that sharks have to swim to breathe? Sharks have been thought to be destined to a life without rest, because some need to swim continuously in order to move water past the gills to oxygenate the blood. However, a substantial number of species are quite capable of resting on the bottom in still water, while muscularly pumping water over the gills. It is probably the case for larger species, including the Tiger shark, Bull shark, and Gray reef shark.
How fast can sharks swim? They normally don’t swim fast & actually average less than 1 mile per hour. The fastest shark is the Mako shark which can swim to at least 22 mph, before leaping 20 feet into the air. Mako is the only shark fast enough to successfully hunt the Blue Marlin. Great whites & Blue sharks are also considered to be capable of short bursts of fast swimming.
How deep do sharks dive? Some species of shark (i.e. Cookie Cutter) lie at the bottom of the sea more than 2 miles deep & then swim up in the evening for feeding.
How old do sharks live? Sharks are aged by counting the number of rings (annuli) added yearly to the sharks’ vertebral centra (annulus method). It is not an exact method as some species may differ in the number of rings they add each year. The Tiger shark can probably live 50 years & the Great White almost 100 years. The average is close to 25 years of age.
Are there any fresh water sharks? Yes, out of the hundreds of species, there are two that can live in fresh water the Bull & Ganges shark. The Bull shark is found in the Lake Nicaragua, & many rivers; including, Mississippi, Amazon, Ganges, & Tigris in Nicaragua. The Ganges shark is rare & is only found in the Hooghly & Ganges Rivers in India.
What is the largest shark? The largest shark & fish is the Whale Shark, & it is a filter feeder-practically harmless, similar to a Baleen whale except that it has 1000’s of tiny teeth arranged in over 300 rows. The whale shark feeds on plankton, shrimp & small fish. The average whale shark is around 50-60 feet & weighs 45 tons. The whale shark can have 300 eggs; it is thought to be ovoviviparous meaning born live from egg. The eggs are carried internally until they hatch inside & then the “pups” are born.
The smallest shark is the Dwarf shark or Spined pygmy which averages almost 4 inches in length, the longest recorded was 9.8 inches.
Is it true the Great White Shark is the only shark that lifts its head out of the water to inspect surface objects? Yes
Why is shark skin often called “skin teeth”? Shark skin is made up of tiny, hard, tooth-like scales called denticles (denticle means tooth). These denticles have a hard outer layer of enamel & are extremely abrasive. The shark’s “skin teeth” reduces water turbulences & increases laminar flow there by enabling them to move more efficiently in the water.
What shark holds the known record for the longest distance traveled? The Blue shark holds the record 3,740 miles, the distance from New York State to Brazil or a little more than one way trip to Alaska from Hawaii.
Shark Attacks in the Hawaiian Isles from 1779-1996 (taken from G. Balazs, National Marine Fisheries Service) There have been 115 attacks since 1779. According to type of activity – swimming/snorkeling (#1), surf boarding (#2), & getting swept out to sea from shore (#3) – give the highest statistics for shark attacks. The greatest number of attacks (26 out of 115) occurred from 1990-1995 & the second greatest number (24 out of 115) occurred from 1980-1989. With respect to the time of year, more shark attacks occur during April. June, November & December are all tied as having the second highest number of shark attacks. Oahu leads the islands in having the highest number of documented shark attacks including fatalities (47 out of 115 with 21 fatalities); Maui is second (27 out of 115 with 8 fatalities); the Big Island is third (17 out of 115 with 12 fatalities); & Kauai is fourth (15 out of 115 with 5 fatalities).
How did the Hawaiians view the sharks in their waters? The Hawaiians have always had great respect for sharks especially the Tiger & Great Whites. The mana or spirit of the Great White was embodied in the motif represented as an abstraction of the shark teeth (equilateral triangles) woven into the chief’s feathered cloak & also in complex tattoo motifs of the Hawaiian warriors. The teeth from the Great White presented the sharpest & thinnest edge used to cut designs for kappa or bark cloth bamboo stampers, wooden kappa beaters, & decorative bases for drum & gourds. Teeth fastened to heavy wood clubs were formidable weapons. Shark skin produces a leather that has 2-3 times the tensile strength of pig or cow hide & it was used to make head covers of the Hawaiian hula drums.
Thirty-three years ago, people paid to see young men riding on the backs of large Tiger sharks – it was considered a grand tradition of Oahu. It was the shark aquarium which is now a research facility of University of Hawaii to study captive dolphins.
What is the latest in technology for protecting humans from shark attacks? The U.S. Navy has designed and tested the “shark screen” – a large, dark, cylindrical plastic bag which is closed at the bottom, and has inflatable rings around the top. The idea is NOT to have any protruding areas (i.e. arms or legs), or any blood or body chemicals-only a large shapeless image is presented to the shark. “Shark screen” seems to be successful; probably a tent or sleeping bag would work as general survival gear.