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El Niño triggered bleaching at Cocos El Niño triggered bleaching at Cocos, in which a coral polyp expels its symbiotic algae, turning it white.
Hammerheads or Bust
by Ken Mallory
September 23, 1998

Cocos Island is renowned for its hammerhead sharks. Typically, hundreds of scalloped hammerheads will congregate in the deep, current-whipped waters swirling around this ancient volcano. Yet during the first half of 1998, the warmer waters brought by El Niño had apparently kept the hammerheads and other large, ocean-going predators away (and caused serious bleaching of corals on the island's reefs). Hammerheads are camera-shy under the best of circumstances, but when surface water temperatures reach 82°F and higher, divers rarely see them.

So it was with some anxiousness that I arrived at Cocos Island last July. I had come to visit Howard and Michele Hall as they continued shooting their IMAX film "Island of the Sharks." The film is being funded in part by my employer, the New England Aquarium, and we knew that hammers might make or break the film. Had they returned?

Cocos Island was recently ranked as the number-one spot in
the Pacific Ocean for advanced scuba diving. Cocos Island was recently ranked as the number-one spot in the Pacific Ocean for advanced scuba diving.

Not long after I arrived I dove at a site known as Dirty Rock. My instructions were to follow the current along the coral-encrusted wall until I came to the far end. To see hammerheads, I was told, I would have to leave the relative security of the islet's flank and launch off into the blue. If I went in the right direction, I would find a submerged mountain after several hundred feet, and it was there I might find hammerheads swimming up from the depths. If they had returned.

Despite my aquarium credentials, I'm more comfortable on land than in the water, and the idea of going off into the blue was a little like doing a freefall blindfolded, with no assurance of where I might end up. I was deep enough not to be aware of the surface, and the sea was a rich blue all around me, with an even darker, murkier blue below. Peering through my face mask for some sign of life, all I could see was the slow paddling of the occasional black triggerfish.

Scalloped Hammerheads Scalloped hammerheads are typically wary of scuba bubbles.
Then I heard a dull but distinct sound. Someone was pounding on his scuba tank—the universal symbol among divers to pay attention. Following a pointed finger, I looked below and there, not 25 feet under my belly, was a parade of seven hammerheads. They were swimming in single file, swinging their peculiar boomerang heads back and forth and probing the water with their high-sensitivity snouts. One after the other scurried obliviously past me until each faded into the endless blue.

Hammer heaven Hammer heaven.

The hammerheads were back. To our dive masters, who study the currents around Cocos as a way of predicting where to see wildlife, the currents on that and subsequent days said "hammerhead." And the currents didn't lie. Over the coming days, the Halls used their 250-pound IMAX camera to film hammerheads and many other pelagic fish through the oily veil of thermoclines that send fingers of cold current through the surrounding warm water. At a dive site called Alcyone, they were even treated to a hammerhead gathering in the hundreds.

But seeing such large schools on the edge of one's vision and getting them close enough for the money shot in an IMAX format—as close as 10 to 15 feet in front of the lens—are two different matters. That was the challenge of the Halls' last few days in early August, and will be the focus of their final trip to Cocos over the coming days and weeks. Join them by bookmarking this site and following the expedition as it unfolds.

Kenneth Mallory is Editor-in-Chief of Publishing Programs at the New England Aquarium, which is co-producing "Island of the Sharks" with WGBH-TV. He is currently writing a children's book to accompany the film. Further dispatches in this series will be submitted by NOVA Online producer Peter Tyson, who arrives at Cocos Island with the Halls on September 25th.

Photos: (1-3) ©Michele Hall; (4) ©Howard Hall.

Hammerheads or Bust (Sept. 23)
Get Used To It (Sept. 25)
Nature Reigns at Cocos (Sept. 27)
The PIG and the Process (Sept. 29)
Hammerheads Sighted (Oct. 1)
Assault on Cocos (Oct. 3)
The Director's Cut (Oct. 5)
Swimming with Whitetip Reef Sharks (Oct. 7)
The Magnificent Seven (Oct. 9)
The Search for Lake Cocos (Oct. 11)
Courtship of the Marbled Rays (Oct. 13)
Of Booby and Beebe (Oct. 15)
Taken by Surprise (Oct. 17)
"This is Cocos, This is Cool" (Oct. 19)

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