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SHARK The Inside Story

Accidental death provides opportunity to take apart a protected great white and extract some knowledge

Monday, January 22, 2001

(01-22) 04:00 PDT Santa Cruz -- Pangea lived fast, died young and left a corpse that was, if not exactly good-looking, at least relatively sweet-smelling. And the people who performed her necropsy yesterday were grateful for that.


A team of scientists and volunteers peeled open a 1,703-p...This shark's tooth was more than an inch long. Chronicle ...A 1,703-pound great white shark was wrestled onto the tab...

"I'm delighted by the shape she's in," said Corrine Davis, a pathologist with the University of California at Davis. "Her tissues are in far better condition than I expected."

And a lot of tissue it was: about 1,700 pounds worth. That's not particularly big for a great white shark, but then, Pangea was a mere adolescent. At 10 to 12 years of age, she was not even sexually mature.

Still, she had what it took to be a fearsome ocean predator: a 14-foot length, jaws that could extend to a 24-inch diameter, and a maw bris with teeth close to 2 inches long.

When alive, she no doubt sheared the head off many a harbor seal -- a favorite killing technique of great whites. Had she chosen, she could have done the same to a surfer.

But now she was only so much sashimi, the victim of a commercial fisherman's gill net near Morro Bay. Being apex predators, great white sharks are quite rare. Still, they occasionally entangle and suffocate in nets set for halibut.

Biologists consider such incidents great opportunities. Despite all the hoopla, relatively little is known about great whites, and it is difficult to obtain specimens for dissection.

"We first heard about Pangea when we found out she was being offered for sale on EBay," said Sean van Sommeran, executive director of the Pelagic Shark Research Foundation, a Santa Cruz group devoted to the conservation of Pacific fisheries. "Most of the time you don't even hear about these nettings. The fish are chopped up and sold surreptitiously. The meat, fins and jaws all bring a lot of money."

Bids for Pangea -- named by researchers after an ancient continent that once dominated Earth -- reached $4,200, but Van Sommeran said he was able to obtain the critter for $700 after negotiating with the fisherman who captured her.

So biologists from state agencies, the University of California and environmental groups gathered at California Department of Fish and Game laboratory to see what could be learned from Pangea by dismantling her.

Great whites are protected under state law, Van Sommeran observed, but the regulations are vague about what can be done with fish caught while legally fishing for other species.

Gill nets aside, researchers said they hoped to learn a lot about great whites through Pangea.

"Among other things, we're going to take vertebral and DNA samples from her to compare them with samples from great whites taken in other places, such as Australia and South Africa," said Dave Ebert, a shark researcher who led the dissection.

Great whites are distributed worldwide, observed Ebert, but it is not yet clear if there are significant genetic differences between the populations: whether there are distinct subspecies and races, in other words.

"My sense is there isn't," said Ebert, "but that's why we're doing the research."

The dissection tools used on Pangea weren't particularly delicate. Butcher knives were the favored device, and pruning shears and meat saws also were available.

Every inch of Pangea was meticulously measured, and samples were taken of her tissues to test for environmental contaminants.

Researchers weighed her gigantic liver, which constituted almost a fifth of her weight.

"Great whites store lipids (fat) in their livers, which serve them both as a buoyancy device and a source of energy," explained Van Sommeran. "They can go a long time without eating because of the reserves in their livers."

But that doesn't mean great whites like to fast. Quite the contrary. With a few related species such as porbeagles, salmon sharks and makos, great whites are unique among sharks: They are essentially endothermic, or warm-blooded.

"They can maintain body temperatures 18 degrees above water temperature," said Scot Anderson, an independent shark researcher who has worked for the Point Reyes Bird Observatory and the Gulf of the Farallones National Marine Sanctuary.

Maintaining such internal temperatures keeps muscles warm, allowing great whites to move rapidly and decisively while hunting, Anderson observes. But temperature regulation is also expensive in terms of energy expenditure -- which is why great whites love to eat seals.

"Seals are really fat," said Anderson. "They're just like big sticks of butter, loaded with energy. When great whites sense seals, they get really turned on. With fish, they may eat them, may not, but they always go for the seals."

Great white sharks find seals by smell, homing in on urine and feces trails through the water.

"They have very large olfactory bulbs (in their skulls), so we know that odor plays a major role in finding prey," said Davis, "and they also use other senses."

Sight, for one. Great whites see well. But they also use little bumps on their snouts called ampullae of Lorenzini.

"They determine water pressure, temperature and electrical impulses from the ampullae," Davis said.

There were other things on Pangea's head: scars, lots of them, including two fresh rakings that matched the typical tooth patterns of a sea otter.

"Great whites eat marine mammals, and marine mammals have teeth and claws and fight back," Van Sommeran said.

Pangea disappointed the researchers in one regard: Her stomach was empty. No elephant seal teeth, sea otter bone fragments or corroded Rolexes.

Great whites are handsome animals in the water, graceful and subtly colored in gray and white; Pangea, in the end, was reduced to a pile of fish fillets, though ones carved with science in mind, not the seafood counter.

Still, the researchers didn't lose sight of the fact that they were dealing with an animal that remained compelling even in death.

Davis rubbed her finger along Pangea's skin, noting the sandpaper texture.

"The skin is composed of denticles, which are actually tiny teeth," she observed, "I mean, literally teeth. They're essentially identical to the teeth in her mouth, though smaller. Actually, you can say her teeth are modified scales."

Brandy Faulkner, director of molecular biology for the Pelagic Shark Research Foundation, said she hopes more people become educated about the true nature of great whites.

"Of course they're a top predator, but what isn't recognized is how intelligent and well-behaved they are," she said. "They never rush the bait bag or the boat when we're tagging them. They're incredibly wary. They spy hop:

stick their head out of the water and look around, like whales. They're not dumb fish."

E-mail Glen Martin at gmartin@sfchronicle.com.

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