Global effort gives depth to shark study
Sharks can dive to depths of nearly 2km, some six times lower than the deepest scuba dive, a global study reveals.
Sharks can dive to depths of nearly 2km, some six times lower than the deepest scuba dive, a global study reveals.
Led by the Zoological Society of London and Stanford University’s Hopkins Marine Station, a global team of 171 researchers at 135 institutions around the world fitted hundreds of tracking tags on 38 species of sharks and rays.
Gathering a wealth of knowledge from Australia’s diverse marine life, co-author Charlie Huveneers from Flinders University said the immense scale of the study allowed for a breakthrough in understanding the animals.
“This is the first time such a large amount of data on the vertical movements of sharks and rays has been put together,” Professor Huveneers said.
“Our collaborative team put together 96,169 days of data from 989 sharks and rays (to) tell us about how they use the ocean.”
The study reflects a breakthrough in methodology, mapping the movement of the animals along a different axis to focus on movement vertically through the depth of the ocean as well as horizontally across it.
It found that while 26 of the 38 species surveyed spent 95 per cent of their time less than 250m from the water’s surface, 13 species were found to dive more than 1km beneath the surface.
Whale sharks were seen to dive to depths of 1896m, while the deepest-diving ray recorded was the sicklefin devil ray, which reached a depth of 1637m.
Professor Huveneers said the study’s aim was to understand the depths the animals move at, in order to prevent sharks and rays being accidentally caught by commercial fishing operations.
“We’re lucky in Australia that most of our commercial fisheries are relatively well-managed, and that many of the shark and ray species threatened with extinction in other parts of the world are safe here, but some shark and ray populations are at risk of extinction in Australia,” he said.
“Our increased knowledge of their depth use will help managers better understand and mitigate threats.”
The study’s co-lead author, David Curnick from the ZSL Institute of Zoology, said he hoped the wealth of knowledge offered up by the study served as a breakthrough for taking care of the animals.
“Knowing just how deep some species dive – or don’t dive – will help us inform much-needed conservation plans for these species and their relatives,” Dr Curnick said.
“It will also help us understand how these animals are likely to respond to the predicted climate-induced changes to our oceans.”
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