350 species of sharks swim the earth ...

Sharks have been around since before the dinosaur.  The modern shark evolved in the Jurassic period (200 million years ago), joining dinosaurs and the first birds.  Sharks are cartilaginous, meaning they have no bones, and the few fossils that remain of early species are mostly from teeth and their famously tough skin.  Though all sharks are carnivores, some (like the whale shark) are filter feeders with large sieve-like mouths that draw in huge quantities of tiny animals, fish eggs and plants.

Basking shark
Basking shark (second largest, 33 feet)
also called the elephant shark
Whale shark
Whale shark (biggest, up to 50 feet)
Both sharks are filter feeders

Only 25 shark species have been known to attack people, and half of all shark species grow no bigger than 39 inches (1 meter).  Some have anatomical features besides teeth that help them hunt: the hammerhead shark uses its T-shaped head to hold down rays while eating the wings, and the thresher shark uses its long tail to corral and stun prey.  Some kinds of pelagic (open ocean) sharks migrate as far as 1000 miles; others are benthic and stay on the ocean floor.  Great whites are classified as pelagic, but are most often found in coastal waters.  Makos and great whites are endothermic, generating their own body heat, which allows them self-regulated bursts of speed and energy.  Most sharks give live birth from eggs that hatch inside the female.  Males use "claspers" on their pelvic fins to transfer sperm into the females to fertilize their eggs.

Thresher shark
The thresher shark stuns prey with its tail
Hammerhead shark
The hammerhead shark holds prey
down with its snout

Health Insurers of the Ocean

Predatory fish, by thinning the ranks of everything down the food chain, are guardians of the ocean's health.  Research surveys tell us that overfishing (obviously the work of industrial man) has deprived the oceans of 90% of their predatory fish in the last 100 years. Of the 350 shark species, only three -- the great white, the whale and the basking (see pictures above) -- are protected by international regulations.  The rest of the world's fast-dwindling shark populations may be viewed as unimportant, but as researcher Ralph Collier says repeatedly, "Sharks are the street sweepers of the ocean."

What would happen if we never cleaned our own streets or yards or houses?
  Predatory fish also serve as "scatterers" of other species, keeping the oceans evenly populated.  They are our biodiversity insurers.  They "take care of" the sick and weak (by convenient removal).  Just as the ecosystem is dependent on the balance and health of our oceans, our oceans need their predatory fish and sharks.


Alaskan fishing boatTo remind you (and you will see this on the other pages of this site), industrial man has been responsible for the depletion of more than 90% of our oceans' sharks.  Nearly half of the sharks that are caught each year are discarded as "bycatch" -- the term for unwanted fish caught in nets or lines by commercial fishing boats. 

The "cascade effect" is the end result of an imbalance within a system.  Sharks longer than two meters are known as "greats."  As the greats are taken out, the species they hunt are allowed to thrive.  For instance, thresher sharks, scalloped hammerheads and great whites on the east coast of the US have dropped by 75% in the last couple of decades.  Their food source is skates, rays and smaller sharks, which have grown vastly in number.  Their food -- scallops, clams and oysters -- are now being consumed in ever greater quantities.  Scallop fishing is nearly a thing of the past.

What will happen to the food sources for oysters and clams?  They will increase in number as they are not consumed, and as they over-consume what is under them, eventually the life forms at the very bottom of the food chain will be able the only ones left.  The ocean will be a vast, murky mess, crowded with microscopic life forms.

Habitat transformation

Mussels
Bivalves like mussels are named
for their two-part shells

The food source for rays -- bivalves (scallops, clams, oysters, mussels) -- feed on phytoplankton and act as a filter system for the ocean.  Many coastal areas are seeing an increase in algae blooms (e.g., red tides) that signal the absence of creatures that keep these single-celled plant-animals in check.  Too many of one species can stress aspects of a habitat such as sea grass (rays and dugongs will uproot this), causing the ocean to suffer physical damage or destruction.

When I first began to swim in Southern California, you could see to the bottom almost every day.  Today, when other swimmers tell me the "visibility is great!" I enter the water knowing I will not be seeing what I saw in the late 1980s.  And sure enough, a few dim shapes wave beneath me -- kelp masses and rocks that I can barely make out.  That's our "great visibility."  Gone are the days of shafts of sunlight streaming to the ocean floor, stingrays basking in their gleam.  Gone are the days of swimming with the ripples in the sand, and the baitfish swarming like flies.  I feel sorry for the giant fluttering bat rays, having to blunder along next to each other in a dark, murky swill.  Gone are their days of enjoying the pleasure of the first few feet below the surface.

Coral reef changes

Algae on reef
Plant life takes over a reef
Dead reef
A dead, algae-covered reef
Coral reef
A coral reef


The loss of sharks in Jamaican waters has caused its reefs to be covered with microalgae as the coral has slowly died.  For coral to thrive, herbivorous fish are needed to feed on the algae that competes for space with the coral.  As the sharks go, the groupers thrive and eat the herbivores.  Without herbivores to keep the algae in check, Jamaica can no longer boast a coral-dominated sea-system -- it has an algae-dominated one.  Imagine the difference -- in looks alone!

Great white sharks (carcharadon carcharias) are not the biggest of sharks by any means, but they are among the rarest and most feared.  They are now a protected species, in part due to fanatical hunting in the wake of Steven Spielberg's movie Jaws (1975).  Whites are actually not white except on their bellies; they are predominantly dark gray.  Fully grown, they range from about 12 feet to 20 feet in length.  They have a robust "jumbo jet" shaped body, jaws that unhinge, and 3- to 4-inch serrated teeth.  Females (15-foot range) are larger than males (12-foot range) due to the fact that they give live birth to pups about 3 feet in size.  Great whites are the only sharks known to poke their heads out of the water to scope the scene around them.

White shark underbelly Great white, coloration

The great-grandfather of carcharadon carcharias was carcharadon megalodon, a prehistoric megatoothed shark believed to have become extinct some 1.5 million years ago.  Megalodon was 2 to 3 times bigger than most great whites -- about 50 feet in length.  Megalodon teeth fossils are highly prized today and bought by collectors.

Though much smaller than their ancestor, great whites are the largest predatory fish in the ocean today.  Preferring cooler water, they are rarely found in the tropics, where tiger and bull sharks are plentiful.  Whites, like bull sharks, are coastal.  Bull sharks are indiscriminate hunters; white sharks feed primarily on pinnipeds (seals and sea lions).


Baby whites

Pregnant great white females have no placenta to nourish their developing babies (called pups), who consume unhatched eggs and each other as they gestate.  Very few pups survive as a result of such competition in the womb, which is also why the great white species is so rare.  Mothers abandon their young almost immediately, leaving them to forage and grow up on their own.  Thus, most white sharks are loners.

Baby whites or juveniles are born live, one or two to a litter.  Females will migrate to warmer waters to give birth, where food for pups is plentiful.  Newborn whites are about 3 feet in length and like to feed on small fish like grunion.  Grunion themselves are West Coast fish that are famous for their on-shore spawning (egg laying and fertilizing) through the spring and summer.  Shark researcher Ralph Collier has discovered that Pacific Coast whites travel to Southern California to deliver pups who can feed on the plentiful Southern California grunion.


Juvenile white feeding
A juvenile white shark feeding (click to enlarge)


On the West Coast, birthing season for female whites occurs in the spring.  A birthing mother can become very aggressive and clear a chosen cove or shallow area of predators (i.e., anything larger than her 3-foot pup) prior to delivering.  The gestation period for white sharks is thought to be a year or longer (14 months), and females may only deliver once or twice in their lifetimes.  Surprisingly little is actually known about white sharks, despite all the Shark Week specials on TV.

Juvenile whites normally do not pose a threat to people, although the bite on her foot that Bethany Edmund received in Carlsbad, California in August 2009 was most likely a juvenile white shark asserting territory as he fed on grunion.  (Popular opinion blamed her bright green nail polish.)

Bethany Edmund's bitten foot
Bethany Edmund's bite marks from a juvenile white


As baby whites grow, they begin to feed on rays and bigger fish, and eventually turn to pinnipeds (the seal family) when fully grown for optimal fuel.  Many Southern California sightings of upright dorsal fins on small gray sharks by surfers and reports of dark, shadowy fish of 5 to 6 feet by swimmers are juvenile whites in coastal waters where their primary food source lives.

Juvenile white shark
A juvenile white shark with its
characteristic "straight" dorsal fin

Whites are warm-blooded for speed in hunting, unlike most other fish, so dietary fat is an imperative.  See our "Seal Problem" page for a significant reason behind recent changes in the migratory pattern of Pacific white sharks.

Seals have now become plentiful on both coasts.  Due to the abundance of the white shark's favorite fuel source crowding the beaches of Southern California these days, in the form of grunion for the juveniles and pinnipeds for the parents, it is not surprising that people frequenting the ocean are spotting and encountering higher-than-normal numbers of what appear to be great whites.  An ever-increasing pinniped population will ensure increasing numbers of mature white sharks, ready to conceive and give birth.  In addition, the large number of recent sightings suggests that adult whites that migrate south to give birth are remaining in the area to feed on pinnipeds instead of returning to the central and northern waters they came from.


Swimmers and surfers often spot a fin sticking out of the water, which can be frightening.  Dolphins' fins, although dark in color, have a noticeable arc to them, and dolphins themselves tend to swim in arcs, curving up and down as they periodically break the surface.  The dark fin of a white shark points straight up, and the shark moves directly.  A glimpse of a fin may be all you get and panic may ensue, but the nature of the movement is often what will clue you in, and dolphin sightings are far more frequent than those of Mr. White.  (The raggedy edge of the fin pictured below is a result of wear and tear; sometimes fins show nips from other sharks.)

Dolphin fin
A dolphin's fin is curved
Great white fin
The fin of a white shark is upright

I remember once seeing a straight dark fin coming out of the water to my left as I was swimming, and it appeared to be moving in a straight line.  I knew it wasn't a dolphin.  I was a quarter mile from the nearest lifeguard tower and a good distance from shore.  I told myself that if I could still see the fin on my next breath for air on that side (six more strokes), I would have to decide what to do.  It was gone the next time I looked, as well as the next.  I kept swimming.  "The shark came up to check you out," shark researcher Ralph Collier told me.  Sharks can see color, and have as many rods and cones in their eyes as humans do.  Their eyes are adapted to a marine environment, which basically means that what you and I see around us is the way sharks see things underwater.  The day I saw the fin was during a heavy red tide, which would explain why the shark might have come a bit closer to get more information.  ("Red tide" refers to an algae overbloom which turns the water a murky reddish brown.)

Another time, after returning from a swim by myself, the lifeguard exclaimed to me in awe about the number of baby dolphins that had accompanied me and formed a circle around me as I was swimming.  Amazingly, I hadn't seen a single one -- not even a fin!

See the Global Shark Attack File incident log for updated information and read more about all kinds of sharks here and here.




Finned shark
A shark without its fins
(photo by Henry Wolcott)


For every human being killed by a shark, how many sharks do you think are killed by human beings?
  Most people guess way below the mark.  Think of a number yourself -- right now.  What is it?  What could it possibly be?

The answer is 10 million.  There are only about ten shark attacks a year that result in someone being killed.  Yet humans kill as many as 10 million sharks each year.  Why?  Skins, meat, fins -- and the movie Jaws.  Released in 1975, it provoked an enormous public reaction.  People couldn't punish sharks fast enough.

And for no reason other than their fear of a movie.  Sharks themselves, particularly white sharks, are hardly our pursuers.  "There is this image of the shark as a super-aggressive, malicious fish," says one researcher who tags sharks off South Africa.  "I have worked with white sharks at close range. In their natural behavior, they are almost gentle, really shy animals."

Shark-fin soup, an Asian delicacy, has made its way to the fancy restaurants of America.  It is a traditional dish at Chinese weddings, and is said to confer prosperity and "the strength" of the shark.  Today, some restaurants sell a bowl for $100 or more.  Fishermen who supply what is now an illegal market set out lines to catch sharks, and because they have only so much freezer space on their boats, they chop off the fins and drop the sharks back in the ocean.  The fins are what bring in the money, but a shark without fins is destined to die a struggling and painful death.

Note: The number of sharks killed each year may well be higher than 10 million.  I have seen it reported as high as 100 million on the internet, with estimates frequently between 25 and 70 million too.  How could we know what this number truly is, as the shark-finning/trading industry is a very shady one in which no one reports anything.  I have asked shark researchers to estimate the number of great whites cruising the California coast, and even they cannot say what this could be.  So shark populations all over the globe?  How many, what kinds -- it's something to wonder about, but as the nets and soup bowls fill and the ocean goes to seed, it's a number that deserves to grow, if anything.  (Read an in-depth article about shark finning from the Vancouver Sun here.)

For a great documentary on shark finning, see Sharkwater by Canadian diver Rob Stewart.  Here's the trailer:



"Sharks keep the ocean healthy," says researcher Ralph Collier of the Shark Research Committee (www.SharkResearchCommittee.com).  They are guardians of the ocean's health and balance, and by extension, of our world.  "We cannot survive without healthy seas," wrote Peter Benchley in his introduction to Shark Life, a follow-up book and very different in nature to Jaws.  Some believe Benchley deeply regretted the panic created by his famous thriller and the blockbuster movie made from it, turning out Shark Life to make up for the damage.  "This book is about understanding the sea in all its beauty, mystery and power," the introduction continues.  "It is about respecting the sea and its creatures, many of which are exotic, complex, and more intriguing than anything ever imagined by the mind of man."

Ocean water
What will become of the great healing
waters that are so essential to our
planet if the creatures that live in them
are systematically destroyed?

The mind of man.  That's where the fear is born, and that's where misunderstanding forms.  The more we learn and the more we realize we are only a small part of this enormous, beautifully balanced world, we might be better keepers of its maintenance and future.  Fishing sharks out of the ocean by the hundred million has disrupted the entire ocean equation.  As you will see from the other pages of this website, all factors end up being intertwined.  Coral reefs are dying and becoming algae-dominated, which is because the lowest life forms in the ocean are becoming the most populous.  Fish of all species are disappearing.  See our pages on plastic in the ocean, Navy warfare testing programs, and the BP oil spill.