Behemoths of Baja : Mysterious Whale Sharks Living Large in Plankton-Rich Waters of La Paz Bay

The giant shark emerges from the green haze of the bay almost immediately after the diver has stepped off the boat.

The diver has plunged directly into the path of the beast. It’s swimming right at him . . . with its mouth wide open . . . and it’s only a few feet away.

The diver’s reaction?

Well, I recall cursing into my snorkel and remaining motionless, awed, as the enormous brown shark veered to my left and passed directly before my eyes, which no doubt were filling my mask.

Spellbound, I followed, eventually positioning myself above the slow-moving creature, thinking to myself how fortunate I was that the Almighty didn’t give this gargantuan specimen--30 feet long and as big around as a bus--the same teeth and tenacity possessed by most other sharks.

Then I thought how remarkable it is that something so large can sustain itself on something so small--plankton. The tiny organisms that make up plankton are flourishing here, turning sprawling La Paz Bay into a giant bowl of soup and attracting all sorts of magnificent creatures, among them perhaps the most magnificent of all, the whale shark.

The largest of all fishes, growing to more than 40 feet and 10 tons, whale sharks in recent weeks have generated considerable excitement on the shores of this bustling city in southern Baja California.

Their presence is nothing new. They enter the Sea of Cortez every spring and fall. Dive boat captains spot them occasionally, and when they do their divers jump in and try to befriend the big lugs, swimming with them and, yes, climbing on their backs for the ride of a lifetime.

But such encounters have always been considered merely a bonus--because they are so uncommon.

Or at least they were.

The situation changed last fall, perhaps because of the warming of the bay caused by El Nino, and the subsequent plankton bloom. More whale sharks came and were seen frequently for about three weeks. They returned briefly last spring, and began to show again in late September.

But what’s astonishing about this season is that it’s still in progress, although the north winds are beginning to blow, which means the end is near.

Whale sharks of 15-35 feet have been seen in the bay almost daily for the last nine weeks, making La Paz one of only a few places in the world where they are so readily found.

“We usually start seeing them at about noon, when the sun is high enough to make it easy to spot them,” says Rocio Lozano, 30, general manager of Baja Quest, a dive company.

“The last time we had this many was in November of 1992. But they did not stay this long in the bay back then. For some reason, the plankton blooms [this year] have been intense, constant and in a relatively small area. Therefore, we have easily seen them.”

Very easily.

Most of the sightings have been only 20 minutes from the docks. Lozano has seen as many as 12 whale sharks in one day and estimates that there are about 15 in or around the bay at a given time.

She also believes, based on personal observation, that the sharks are not the same animals that were here in the spring, meaning there probably are two groups using the bay.

In any event, the presence of the gentle giants is exciting from a scientific, as well as a recreational, standpoint. Only at Kingaloo Reef in Western Australia are whale sharks as easily accessible.

Jim Knowlton, a photographer for Thomas Horton Associates, a Santa Barbara production company that specializes in documentaries, got a call from Lozano earlier this season, flew here the next day and spent four hours filming whale sharks for a program on the Discovery Channel’s popular “Shark Week” special.

His footage shows whale sharks cruising around with their mouths open, occasionally turning their heads from side to side, sucking in water and filtering it for plankton.

In one instance, a whale shark positioned itself vertically in a shallow portion of the bay and gulped plankton concentrated at the surface. Vertical gulp-feeding is an event not often witnessed, Knowlton says, so the trip was a huge success.

Not that it wouldn’t have been otherwise. The whale shark is one of the most elusive and mysterious of fishes. Researchers in the first half of the century considered themselves fortunate if they were able to inspect a live specimen. Even today, little is known about whale sharks because until fairly recently they were so difficult to locate.

Scientists can tell you that whale sharks bear live young, which hatch from eggs internally. They learned this a few years ago, after 300 embryos, many of them already hatched, spilled out of a large female harpooned off Taiwan, where the sharks are hunted for their meat and livers.

They can tell you that whale sharks are found in tropical and sub-tropical regions throughout the world.

But they have little knowledge of migration patterns, how old the fish get--though it is believed they can live at least 60 years and perhaps much longer--how deep they swim or how many there are worldwide.

“We just know that they can travel great distances and go to great depths,” says Diane R. Nelson, a marine biology professor at East Tennessee State University.

Recent evidence--based on the tracking of one individual from La Paz to the mid-Pacific before the tracking device gave out--suggests that they do cross the Pacific.

In 1993, Nelson and renowned shark researcher Eugenie Clark, senior research scientist at the University of Maryland, spent a week in La Paz studying the feeding habits of whale sharks. They encountered seven animals in the bay, the largest about 17 feet.

It was Nelson’s first experience diving with the docile creatures, which are imposing despite their reputation because of their incredible bulk and because they are sharks, swimming in the same eerie manner as their more menacing cousins, lazily swinging their tails, staring blankly as they go.

Nelson didn’t curse into her snorkel, but recalls that after taking her initial plunge into the murky bay, the “Jaws” theme kept playing in her head.

“And I had to keep telling myself, ‘They eat plankton. They eat plankton. . . . ‘ “ she said.

She and Clark considered themselves fortunate, though, to have found so many whale sharks, even if they were all juveniles. They were able to locate so many because they lived aboard a dive boat and had a spotter plane for six days.

Had they conducted their research this fall, they could have done without such an elaborate production.

“I hear there are loads of them down there now,” Clark says.

There are indeed.

The day Lozano and I visited the whale sharks was a magical one from the start. There weren’t any other boats in sight, the sun was in the sky and there was only a whisper of wind.

A pod of bottlenose dolphins escorted the vessel Mantarraya to its first stop, alongside an actual mantarraya, a giant Pacific manta gliding gracefully beneath the surface.

We jumped in and kicked our hardest in an attempt to keep up, but the manta wanted no part of us. It flapped a little harder and soon disappeared into the deep.

We got back into the boat and spied another manta, which was a little more cooperative. It let us hover directly over its wing-shaped body, which spanned about 15 feet, before tiring of our presence, flipping upside down and reversing its course, passing only a few feet beneath us.

This all seemed to be happening in slow motion, surreal yet enjoyable. But Lozano wanted to find the whale sharks, so off we went toward the southern reaches of the bay.

It was lunchtime. And sure enough, the whale sharks were on the scene, leisurely sucking up plankton.

We jumped in and Lozano, who zips around like a fish, was over one large whale shark before I could even get my bearings.

I saw her turn sharply left so I swam fast in hopes of intercepting her and the shark. My plan worked. I had put myself directly in front of an oncoming monster with a mouth resembling a cave.

Several tons of shark went by, moving so slowly and effortlessly that it didn’t look real.

We soon found another whale shark, which seemed far less formidable, a juvenile measuring 15 feet. It had been feeding vertically, seemingly standing on its tail while taking gulps of plankton at the surface. It was uneasy around us, though, and soon disappeared.

By now, other boats were arriving. One of them had a dozen passengers, many of whom couldn’t swim well enough to keep up with the sharks, which were getting more skittish, apparently bothered by so many people.

Lozano was bothered too. The crowds have been getting bigger each week, and not everybody has the best interest of the whale sharks at heart: They sometimes chase them in their boats and harass them in the water.

The same thing happened at Kingaloo Reef until concern finally led to passage of a law forbidding people to touch the animals.

“Not all the dive operations in La Paz harass whale sharks,” Lozano says. “We tell our clients not to touch the animals because they will most likely swim away from the snorkelers and feel uncomfortable. We tell them just to swim around them and let everybody else have a close look.”

The other boats followed the two whale sharks to another part of the bay, but Lozano chose to let them be. Soon afterward, two others--a slender male measuring 30 feet and a slightly shorter but much stouter female--surfaced near our boat.

We jumped in and swam alongside them for 20 minutes or so. They didn’t seem to mind and one of them even stopped in a current and hovered motionless immediately beneath us, as if inviting us to take a ride.

Lozano gently grabbed its dorsal fin--just to show that you can, she later said--and the whale shark pulled her slowly through the bay. Thinking I might never get this opportunity again, I decided to give it a try, but the animal shook me off and swam away.

“Maybe it’s because she senses fear,” Lozano guessed aloud.

I insisted that there was no fear, perhaps just a little apprehension, but I’m not sure she bought it.

Baja Quest can be reached in the U.S. at (800) 298-9009, in La Paz at 011-52-112-35320 or on the Internet at https://www.bajaquest.com.

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* FISH REPORT, PAGE 15