Sydney, Oct 23 (IANS) Big fish like whale sharks can dive to chilly waters hundreds of metres deep but also swim back to the surface to warm up, according to an Australian study.
Michele Thums from the University of Western Australia's (UWA) Oceans Institute said the findings delivered new insights into the little-known behaviour of these gentle giants of the sea.
For instance, whale sharks have been known to undertake regular dives to around 100 metres and then return to the surface relatively quickly. It is called "bounce" or "yo-yo" dives, the Journal of the Royal Society reports.
But the research team, which included Mark Meekan, an adjunct professor of the Australian Institute of Marine Research, discovered that whale sharks could also undertake very long, deep dives lasting more than two hours, according to an UWA statement.
"When we looked at our data, we found that the whale sharks spent regular intervals at the surface between diving bouts. This pattern of returning to the surface looked similar to the patterns seen in air-breathing marine animals, so we were curious as to why fish that do not breathe air would do it," Thums said.
The sharks were tagged with time-depth recorders which also recorded water temperatures.
The researchers found that after the deepest and coldest dives - an average 340 metres deep with temperatures of about 14 degrees Celsius - the sharks spent the longest time at the surface, an average of 145 minutes.
Thums concluded that they need to do so to regulate their body temperature to warm up after spending time in the deeper and colder parts of the sea.
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