Mike stands on the duckboard at the back of the Undersea Explorer shaking a coconut rattle — a bamboo stick with a bunch of coconuts on the end that rattle together. “This has been used to attract sharks throughout Polynesia and Micronesia for millennia,” he says. “Well, actually I just made this one.”
Sanjayan, Richard and JR throw some small dead fish into the water to attract sharks toward the boat, and once they approach, they shake the rattle at the sea surface to lure them even closer. Scientists once discounted this as folklore, but turns out the age-old practice actually works.
“When we shake the rattle, the sharks tend to swim faster and come to the surface,” explains Mark. “It gets them into a frenzy.” Apparently it’s the vibrations from the rattle that interests the sharks and it’s probably because it mimics the thrashing around of a dying fish. They use the rattle in addition to the fish because they often can’t tell grey reef sharks from similarly sized silvertips unless they come close enough to see the fin markings and body shapes.
Richard sticks his head completely under the water. I’m wondering if he’s out of his fool mind. He’s apparently looking around to see what the sharks are doing underwater, with his Scuba mask on so he can see. “There are three greys out there,” he says to everyone, pointing. During these shark catching experiences, nearly everyone hangs out near the duckboard. There’s several crew filming, soundman Cam McGrath recording sound with his mop-looking microphone, scientists baiting or handling sharks and others just watching.
I look out into the water and can make out three fusiform grey bodies, twice as big as whitetips, swimming gracefully around just off the boat. They have slightly darker markings on their tail fins, and white bellies that become visible as they turn directions underwater. I’m not seeing their infamous dorsal fin sticking out above the water, the classic image that comes to mind of a shark swimming near the surface. Enter JAWS music in my head….dun dun…dun dun...
Richard sticks his head back in the water, looking around, wondering why they’re not coming closer. In an instant he jumps back out of the water and screams. Sanjayan jumps back and shouts in reaction. Richard starts to laugh—just one of the many practical jokes that have been played since we’ve been out at sea.
Several different species may come to the bait, but each day the crew has a plan of action and know which species they need to capture. Today it’s gray reefs. As the sharks draw in closer, Richard and JR take turns throwing out a giant tuna head on a rope, slapping it down hard on the water. He’s hoping one will take a bite so he can pull the shark back on board. But unfortunately they’re just not biting. After an hour or so of trying to attract them, we abort the mission.
We try this method the next day also, and the same thing happens. Sharks come in to check out the scent and sound, but they just aren’t that into the giant tuna head on a rope. We’re at North Horn now, and Richard makes the call to try this plan at night back at Admiralty Anchor where we moor at night.
In the meantime, Cat and I take a dive in the lagoon with JR to install one of the four additional receivers that they need to get their total number to 32 around Osprey. On this trip, the plan is to install four new receivers inside the giant shallow (80 foot deep) lagoon that makes up the center of the 150-square mile Osprey Reef to complement the receiving stations placed all around the reef exterior.
“The main thing we’re trying to figure out is how far they move around the reef,” explains Richard. “Another thing we want to figure out is whether the grey reef sharks move in and out between the lagoon and the outside of the reef.” These receivers record whenever any shark with a pinger swims by. Not only that, JR later tells me the same receiving stations can record IDs of any individual of any species with a pinger. On Osprey, they’ve put the pinger ID tags inside of several giant potato cod and chambered nautilus, but eventually plan to also put them on Maori wrasse, coral trout, and Queensland grouper. “This is amazing, honestly,” says JR. “Now we can collect data on the biology of all these species that no one knows anything about. And that will help with management.” A similar grid system exists within the Great Barrier Reef Marine Park and JR says that they will be able to compare data from here to there to see whether the species behave differently on this seamount reef. (The Osprey reef map shows the location of each of these receivers as red dots).
It only takes about 15 minutes to complete the whole dive. We drop down and JR wraps the rope around a coral island, and the receiver – which looks like a large plastic bottle painted grey – is tethered to buoy which drifts above. While down there, we see a giant moray eel hiding in a coral crevice.
We ascend, take our gear off, and have a shower. We have dinner and after dark, the guys are out on the back deck fishing for grey reef sharks again. Because no filming is going on, fewer people are out there, and I didn’t even realize what was going on until they had already caught and tagged two. They catch a third – using the same coconut rattle and tuna head technique as during daytime but it’s working like a charm now, probably because they generally feed more at night. I watch as Richard hauls one on the duckboard and lays her upside down. These grey reef sharks’ skin looks thicker and quite different from the whitetips, which have flattened bodies from hanging out mostly on the ocean floor. But grey reefs have a rounder, more classic shark shape and nostrum. They’re just beautiful animals. I feel incredibly blessed to be here.
Images: Mike with coconut rattle; Osprey Reef map, featuring pinger stations.
Photos: Cat Gennaro/DCL
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