Researchers are “stunned,” said one of several articles recently reporting on sharks in the Pacific reaching “insane” sizes. The articles all linked to a new National Geographic documentary. He is said to have found out that tiger sharks in the South Pacific grow about a third larger than other tiger sharks. In addition, great white sharks are also said to grow to enormous sizes: Specimens over six meters long have been spotted in the region – we are talking about Hawaii and French Polynesia.
According to media reports, the researchers attributed “this size boom” to protection zones in which the predatory fish found significantly more prey. In addition, even there they would be spared from the fishing industry. But are great white sharks and tiger sharks actually getting significantly larger – and thus potentially more dangerous for humans? A fact check shows that the claim, which has been published in numerous media outlets, is at least a simplification.
Kori Burkhardt, a marine biologist who is also featured in the documentary, was quoted in a press release by National Geographic, although she says she “didn’t give any interviews” for it. A quote that some media used, and in which so-called “mega sharks” was mentioned, did not come from her, stressed Burkhardt. Rather, this term was used purely by the PR people. From there on, the assertion then became “independent”.
“Sharks don’t exploit protected zones to grow into monstrous or ‘mega’ sizes,” says Burkhardt. There are protected zones so that sharks can reach their natural and ecologically important size. Before that, they were slaughtered because of the “true monsters” – namely humans. The so-called “mega sharks” are not a genetic variation. “It has been scientifically proven that tiger sharks are larger in the Pacific than in the Atlantic,” Burkhardt wrote in an email. However, the differences are not very large.
“The shark in the documentary is the largest tiger shark recorded underwater, but it’s not the largest ever spotted based on fishermen’s catch data,” she said. In their eyes, it is “highly irresponsible” to claim that “mega sharks” would create protection zones. Because this could trigger fear in the public and even discourage some people from conservation.
Christopher Lowe, an American shark expert and director of the Shark Lab at California State University Long Beach, who is also mentioned in the articles with a quote from a different context, emphasized in a video call that he believes that marine protected areas are too larger great white sharks and tiger sharks would not agree. “Most marine protected areas have not existed long enough to provide this type of benefit, and it takes sharks a long time to reach such enormous sizes — 30, 50, even 70 years.”
Great white sharks and tiger sharks are also species that would not stay long enough in these relatively small protected zones because they would migrate. And: “There are no protection zones large enough to make such a difference.” Protecting some food sources is most likely not enough to create so-called “mega sharks”.
The fact check in South Australia – another region with many large shark species and marine protected areas – could not confirm the claim. Andrew Fox, an Australian who organizes shark tours in South Australia while also working to protect predatory fish, said he hadn’t noticed any increase in size in the great white sharks around South Australia’s Neptune Islands, nor in other large species . “It’s probably the less dangerous and smaller reef sharks that benefit most from sheltered waters,” Fox said.
Basically, however, his experience shows that marine protected areas support the growth of all species and that a healthy shark population corresponds to a healthy ecosystem. However, he does not believe in significantly larger sharks because of the protection zones, since apex predators would tend to regulate themselves. The latter probably ensures “that these animals do not overexploit the resources”. In addition, larger great white sharks do not necessarily pose an increased danger to humans, since it is often not the larger, more mature sharks that are responsible for attacks on humans, but the younger, less experienced animals. “Older great white sharks often stay further out to sea.”
Charlie Huveneers, a marine biologist and shark researcher at Flinders University in Adelaide, South Australia, echoed Fox’s assessments of the region while stressing the importance of protected areas for wildlife. “Well-designed and regulated marine protected areas can increase the diversity, abundance and size of fish, as well as their resilience to climate change,” he said. In general, marine protected areas would offer the most benefits to animal species that live in the region – but animals that only come to the region to spawn or raise their offspring would also benefit from protected areas.
