Sharks are tired of cage diving … literally
New study shows pastime makes sharks exert far more energy than normal, doing them real harm
Shark cage diving may be exhausting for those brave enough to come face to face with the large predators, but it also takes a lot out of sharks.
Great white sharks can use 61% more of their energy when shark cage operators are in their area, according to a study published in the journal Conservation Physiology.
The study, which was conducted off the coast of Australia, found that sharks display increased dynamic body acceleration when interacting with cage divers, meaning they expend more energy.But more energy use isn’t necessarily a good thing, and cage diving may be sapping the sharks' wellbeing.
“Spending time interacting with cage diving operators might distract sharks from normal behaviours such as foraging on natural, energy-rich prey like pinnipeds,” said lead researcher Charlie Huveneers, a professor at Flinders University in Australia.
Huveneers said the energy of sharks increased only when they were close to the cage-diving vessels. When the boats were just in the general area, the sharks' energy use stayed the same, he said.
Researchers fitted 10 white sharks around Neptune Islands in South Australia with devices that tracked their swimming speed for about nine days.
The researchers noted that regulations prohibit operators from feeding white sharks, but that they do use “attractants” to entice sharks to come close to the cages.
“The interaction with cage diving tourists is, therefore, not rewarded by more food,” the researchers said.
The study suggests limiting interactions between cage divers and individual sharks, noting that it will reduce the industry’s impact on shark’s energy use. Further research is needed on how sharks’ energy is affected by the length of time they spend interacting with cage dive operators, they said.
The wildlife tourism industry has expanded in recent decades, according to the study. Some cage diving spots are used by as many as seven companies operating three times a day, according to the study.
South Africa has a large white shark population off the Western Cape, with Gansbaai and False Bay being popular cage diving spots. Alarms were raised last year after the number of reported shark sightings dropped. Scientists said at the time that the dip in numbers was due to an uptick in killer whale attacks.
Cage diving isn't the only way humans can cause harm to sharks. Populations have been decreasing in the long term as well, thanks to poaching, depletion of resources, pollution and shark nets that can tangle up the sharks.