This past summer, Professor Aaron Wirsing of the School of Environmental and Forest Sciences (SEFS) helped initiate a pilot research program to study the biology of reef sharks on a tiny atoll in the South Pacific. Tetiaroa, located about 33 miles north of Tahiti in French Polynesia, is comprised of a ring of 12 coral islets—also known as motus—surrounding a shallow lagoon. Largely untouched by human development, the lagoon is home to several shark nurseries, or areas where shark pups spend the first part of their lives, making the atoll ecosystem an especially promising site to study shark behavior and development under natural and nearly pristine conditions.
“In most parts of the world, shark populations have been heavily impacted by people,” says Professor Wirsing, who got to spend 10 days on the atoll in August. “So what tantalized us about Tetiaroa is that it’s close to Tahiti and fairly easy to reach, yet at the same time it’s remote enough to have very little human contact.”
French Polynesia, after all, is a collective of more than 100 islands spread out across a vast water area about the size of Western Europe, though with a total land area only about as big as Rhode Island. Within this sprawling network of archipelagos, moreover, sharks play an important role in traditional and modern Polynesian culture, and the government has established a moratorium on shark fishing. The result is effectively the world’s largest shark sanctuary, about half the size of the United States, making Tetiaroa a paradise for the sharks that live there—not to mention for the researchers who get to study them in this stunning natural laboratory.
Quite a Site
The unique conditions of an atoll ecosystem require an enormous amount of time and very particular geologic circumstances to form. On Tetiaroa, that work started millions of years ago when volcanic upwelling created a land mass above sea level. Coral slowly formed around the edges of the island, and while the volcano eventually became inactive, the coral continued to grow, maintaining its structural shape even as the volcano gradually disappeared under the ocean. In time, all that survived of the original upwelling was a barrier reef surrounding a turquoise lagoon, which floats like a tropical wading pool in the middle of the Pacific Ocean.
How Tetiaroa evolved as a base for research operations—and how Wirsing got hooked into this project—began far more recently with the filming of Mutiny on the Bounty in 1961, when actor Marlon Brando first visited and quickly fell in love with the atoll. He ended up buying it in 1967, in fact, and aimed to preserve the natural wonders and biodiversity of the ecosystem.
Brando envisioned Tetiaroa as an ideal location for a luxury eco-resort and a small scientific community to support research and conservation efforts on the island. Though Brando never got to see his dream come to life, his estate—The Marlon Brando Living Trust, which owns Tetiaroa—has recently implemented much of that vision working with two partners: Pacific Beachcomber, which just opened The Brando, a highly exclusive eco-resort (where accommodations start around $3,600 a night), and Tetiaroa Society, a nonprofit scientific and cultural organization that now operates a research facility on the atoll.
Last year, in anticipation of The Brando’s opening, David Seeley of Tetiaroa Society reached out to the College of the Environment and expressed interest in bringing more researchers out to Tetiaroa. A number of projects are already under way on the atoll, including the work of Oceanography professors Julian Sachs and Alex Gagnon, as well as recent Oceanography alumna Lauren Brandkamp, measuring the effects of ocean acidification on coral reefs. Another big project Seeley targeted—to be funded through a donation from his parents, Jim and Marsha Seeley, of Medina, Wash.—involved studying the atoll’s large population of sharks, including lemon sharks (Negaprion brevirostris) and blacktip reef sharks (Carcharhinus melanopterus).
Sharks tend to reproduce in remote areas that are hard to research, and many coastal areas that might have once served as nurseries have been degraded or destroyed. But Tetiaroa’s shallow lagoon—protected from the open ocean and only a couple feet deep in most places—provides a relatively safe habitat for juvenile reef sharks to learn and mature for roughly the first year of their lives before venturing out as adults. That sheltered basin, in short, can open a special window into the shark world. So when the College approached Wirsing about the possibility of setting up a shark research program on Tetiaroa, he jumped at the chance.
“Our work on Tetiaroa can help establish a vital baseline for how healthy reef shark nurseries function,” he says.
Wirsing’s first job was to assemble a team of international shark experts. Though much of his current focus is on terrestrial ecosystems, his doctoral research involved the effects of tiger shark (Galeocerdo cuvier) predation on dugongs (Dugong dugon) in Australia’s Shark Bay, so right away he brought in a long-time collaborator on that project, Professor Mike Heithaus from Florida International University (FIU). Heithaus, who hosted the National Geographic Crittercam television series from 2002 to 2003, runs the Marine Community & Behavioral Ecology Lab at FIU, and one of his postdocs, Jeremy Kiszka, has also joined the Tetiaroa crew. The other principal researcher is Dr. Johann Mourier from the Insular Research Center and Environment Observatory (CRIOBE), based in Moorea, French Polynesia.
Their next task was to establish whether Tetiaroa would in fact be a good base to set up a shark study, so Wirsing, Kiszka and Mourier spent 10 days on the atoll this past August. While they weren’t lucky enough to get a room at The Brando, the Tetiaroa Society Ecostation itself is an impressive installation, offering cozy lodging and lab space for scientists and students from around the world. (It also features a number of green innovations, including a Sea Water Air Conditioning system that pulls cold water from the deep ocean to provide low-energy cooling for all the buildings on the island, as well as a biofuel power station that runs on locally produced coconut oil.)
They initially set out to answer some very basic questions about the lagoon ecosystem, such as what kinds of sharks live there, how many there are, and why they’re using the lagoon. Since the lagoon is only seven kilometers across, the ecosystem is small and contained enough to map and study in its entirety—potentially to the point of counting every shark in there. Yet given the limited time of the pilot season, the team decided to focus on surveying and mapping two of the largest nurseries to get a sense of their physical structure.
Using a combination of aerial drone photography and underwater videography with stationary cameras, they were able to generate a wealth of spatial and population data. The drones allowed the researchers to run multiple transects over the water, providing a broad sweep and bird’s-eye view of the lagoon and its fish communities. The underwater cameras, meanwhile, captured a more localized and detailed look at the nursery environment (including the footage below of a curious blacktip reef shark jostling the camera!).
This first field season was fairly limited, and the researchers are still working through the data they collected. Yet thanks to another donation from the Seeley family, they’ll be returning to Tetiaroa this summer for a second trip. Professor Heithaus, who couldn’t make the first visit, will be joining the team and helping expand the operation. “This time we hope to actually catch, measure and sample the tissue of sharks to get a sense of what they eat,” says Wirsing, and down the road they might also be able to equip juvenile sharks with tracking technology so they can study their behavior and movements after they leave the nurseries.
“These nurseries are critical to reproduction,” he says. “One of our ultimate goals is to use this ecosystem as a reference point to guide restoration of areas that might someday serve as shark nurseries again, so the conservation implications are huge.”
Photos: aerial shot of Tetiaroa © Tetiaroa Society; blacktip reef shark © Johann Mourier; Professor Aaron Wirsing © Johann Mourier; Jeremy Kiszka and Johann Mourier with a drone © Aaron Wirsing; entrance to lagoon © Mourier.