Shark Surgery

After hours of waiting, waiting, waiting things can happen fast around here. One minute Sanjayan’s playing in the kiddie pool, cracking jokes. Fifteen minutes later, he’s got a whitetip reef shark by its pectoral fins, pinned on its back on the duckboard with two whitetips are lounging in the pool. They’ve never used the kiddie pool as a holding tank for sharks before, but it works brilliantly.

Richard, Mike and Dean dove down below with a box full of fish, which attracts the sharks. Sometimes up to 40 sharks will swim in a flurry around the bait box, and then it’s time for shark rodeo! Richard goes in with a rope and lassoes the tail. If I’m lucky, I’ll get to go down with the crew while they lasso sharks in the next few days.

Richard is something of a shark superstar around Australia. He’s been in four documentaries and worked on 20, and he has a sixth sense about sharks. I’ve seen him stick his head right in the water with two or three grey reef sharks circling near. I know I wouldn’t be that bold. 

“I’ve worked with sharks every day for 6 years at the Manly Aquarium (in Sydney, Australia),” he says. “So, I know when to stop. I know when they’re about to get crazy or dangerous.”

But today, I’m staying topside, and about to take on my new role as “shark nurse,” handing Richard surgical equipment.  Richard will be testing a new hypothesis about whitetip diving behavior and we’ll even be able to look at that data before the end of the trip, after they catch these same three sharks again and retrieve the devices.

“We think they’re using their diving behavior to thermoregulate,” explains Richard. Data they’ve collected on Osprey Reef whitetips over the past two to three years shows that during the night-time, they spend most of their time at shallower depths, but then do quick swims down deep. On top of that, as the night goes on, the sharks start going deeper and deeper.

Richard’s hypothesis is that the body temperatures of these “cold-blooded” animals start to heat up as the night progresses because they’re feeding constantly, and then they cool off by diving to the cooler, deeper waters below. “We have to prove that there’s a temperature differential between inside the shark and outside.” That will suggest that the deep dives can indeed cool them down. They’ll do a rough test by comparing internal body temperature to external temperature on these three sharks. We’ll find out in a few days.

Three divers arrive back at the boat with three lassoed sharks and hand the ropes to Sanjayan.  Scuba gear comes off, then Richard and Mike pull one shark at a time out of the water. Richard grabs the 5-foot-long shark, which wriggles at first, then calms down as he carries it nonchalantly up the stairs into the kiddie pool. They repeat this for the next shark, but the third shark they place upside down onto a mattress – the “surgery table.” The mattress has an orange-sized rip in it where another whitetip had taken a bite. “They’ve got a mouth full of tiny razor blades,” says Richard. I ask if he’s ever been bitten by a whitetip, and he shows me several tiny bite mark scars on his leg.

I sit near the shark’s tail, which Mike holds in place. Sanjayan holds down the shark’s pectoral fins which is hard work. JR places a hose so that saltwater runs constantly through the shark’s mouth and hence over its gills. Since sharks are fish, they breathe by getting oxygen through water pumping past their gills.

The first order of business is to find out whether the team has captured this shark before. If so, it will already have a PIT —or passive integrated transponder—ID tag inserted by needle beneath the dorsal fin. Before he even swipes the PIT tag reader, Richard says “We’ve caught her before.” He can tell some sharks apart by their spots! Sure enough, after swiping the PIT tag reader, he confirms she’s “Twin Peaks” — so named after two spots on her flank. “Twin Peaks” has probably told us more about whitetips than any other shark. And with this new data, she’ll show us even more.

Richard squirts the shark’s abdomen with antiseptic. I hand him the scalpel and he cuts an inch-long incision through skin and top muscle layer.

“Females have tougher skin than males because it protects them during mating,” Richard explains. “They can get a bit rough.” They can also tell she’s a “girl” because she doesn’t have claspers, two sausage-like projections.

During the incision she flinches a couple of times and Sanjayan yells, “Watch out!” since he can feel her squirm before the rest. They quickly pin her back down, making sure no one has any fingers close by those razor-sharp teeth.

After Richard completes the incision, I hand him a 2 ½ inch long black capsule — a “pinger” which gives the shark a unique ID. Unlike the PIT tag ID, which they can only scan when they capture the shark, the pinger ID gets recorded any time it swims within 900 feet of one of 29 receiving stations (aka data loggers) the researchers have set up around Osprey Reef. They will be installing three more on this trip and I will dive underwater tomorrow to watch one being set up.

Data collected from these pingers will give a great geographical perspective on where the sharks spend their time on the reef. Combined with the time-depth-recorder, which gives a vertical perspective of how deep they dive, they’ll end up with an amazing three-dimensional view of how sharks use their habitat.

I hand Richard the internal temperature recorder, a 1-inch long white capsule. Next, a needle threaded with catgut with which he expertly sews up the incision, twisting it in place with clamps and cutting with scissors.

The next order of business is to attach another temperature capsule to the caudal peduncle — the base of the tail fin — with a cable tie. Last, he takes measurements of the shark’s total body length from head to tail. Then she’s ready to go back in the water.

After we finish all three whitetips, they switch to a new project— luring in grey reef sharks by pitching in fish and a tuna head on a rope just off the duckboard. If we can lure them in, we’ll also implant pingers and collect data on these guys. Mike shakes a coconut rattle —used for millennia by ancient cultures — to attract them. Within minutes, I see one in the water just off the boat. They’re about twice the bulk and size of the whitetips. Magnificent!

Images: Sanjayan holds whitetip for tag retrieval; Richard and Mike with lassoed whitetip; Wendee (bottom right) with team performing "surgery;" Richard sews up incision.

Photos: Cat Gennaro/DCL

Comments

[Chrstine Heinrichs]

Fascinating detail. Tracking ocean critters is so difficult. The question of large eyes is an interesting one. Is there more light from bioluminescence down there than we think? Are their eyes sensitive to a different spectrum from ours?

[samantha egnor]

Awesome surgery DOCTORS .