Shark researchers track world’s biggest fish with pet tags
By Juliet Eilperin,
Scientists working in Indonesia are inching closer to understanding whale sharks — using the same kind of radio-frequency identification tags that many Americans put on their pets.
Late last month, researchers from Conservation International, WWF-Indonesia, Hubbs Sea World Research Institute and the State University of Papua inserted RFID tags on 30 whale sharks in Indonesia’s Cendrawasih Bay National Park, where the hulking giants have been gathering in recent years to feed on silverside baitfish.
Mark Erdmann, senior adviser to CI-Indonesia’s marine program, said in an interview that the tiny tags have “never been used on big free-roaming animals in the ocean” because they can only be read by a receiver wand waved near a tagged animal. But Brent Stewart, senior research scientist at Hubbs, suggested doing it because the sharks routinely return to the same place so they can consume the creatures that local fishing operators are also targeting.
Researchers have assumed that whale sharks — the biggest fish in the world, measuring as large as a school bus — primarily feed on plankton. But this amazing footage shows how these filter feeders are happy to gorge on silverside baitfish caught in lift net, or bagan, fishing platforms.
Erdmann said that in recent years, it “became increasingly obvious the sharks have become a little too friendly with the nets.” During this recent trip, he and others had to spend 10 minutes helping extricate a whale shark from one of the nets.
Researchers have spoken with area residents about modifying the nets they use to prevent this from happening, either by inserting mesh or attaching additional ropes so only small fish, such as the three-inch baitfish, can get through.
The group used two ways to attach the pill-size tags to 30 sharks, 29 of which were adolescent males. One method uses a pole spear to penetrate the shark’s thick layer of blubber; the second uses a large-bore syringe. “That one proved to be much more difficult with the animals because they tend to feel it a little more, and they tend to rapidly knock you off,” Erdmann said. With the pole spear, he said, “They don’t even flinch.”
While Cendrawasih Bay National Park has enjoyed government protection for nearly two decades, the aggregation of whale sharks has become so popular with the public that Indonesia decided this month to make them a nationally protected species. The move is significant because Indonesia ranks as the world’s largest shark exporter.
“Whale sharks are just fantastic ambassadors for all sharks,” said Greg Stone, Conservation International’s chief scientist for oceans. “These don’t hurt anybody. . . . They’re an entry point for helping people understand the importance of sharks in the world.”
Researchers continue to weigh the public’s attitudes toward sharks. In a new article in the journal Marine Policy, two University of Sydney researchers report that a pilot survey of 100 South Africans living near Cape Town shows that attitudes toward great white sharks remained unchanged even after one bit a man last year.
In May 2011, researches asked residents in the Cape Town beach suburbs of Fish Hoek and Muizenberg how much “pride” they had in the local white shark population. Following a serious but nonfatal shark attack on British expat Michael Cohen on Sept. 28, the survey was re-administered at each location in October.
Lead author and University of Sydney doctoral candidate Christopher Neff, who recently delivered a TED talk about his research, said 31 people had “average or a lot of pride” in great whites before the incident and 33 had “average or a lot of pride” afterward. Negative attitudes toward the animals remained similar as well: 19 people had “little pride” in sharks beforehand and 17 had “little pride” in the follow-up survey.
Neff wrote in an e-mail that the survey shows that many South Africans “know that entering the ocean is putting yourself in the middle of an active and dynamic ecosystem. They see the ocean as the wild and give it the respect it deserves. That is an important lesson that we all can take away.”
On Saturday, a 24-year old resident of Perth, Australia, surfing off Wedge Island, was killed by a white shark. Benjamin Linden’s death was the fifth shark fatality in the region in the past 10 months. Now, officials in Western Australia are questioning whether the country should revoke great whites’ protected status.