Why Do Deep-Diving Whale Sharks Hang Out Near the Surface?
Whale shark. Photo credit: Quenton Dokken, NOAA.
New research reveals why whale sharks and other large fish frequently return to the surface after deep dives.
Unlike whales, sharks, tuna, swordfish and many other large fish don’t need to return to the surface to breathe. It was thought that their surface-time following a deep-sea dive was primarily for feeding purposes, but it turns out that’s only partly true.
The team of Australian researchers determined that these animals swim to the surface to warm up after spending time in the cold, deep sea.
Michele Thums at the University of Western Australia’s Ocean Institute, and colleagues attached tags to four whale sharks in an attempt to gather regular information about the shark’s depth, the level of light, and the water temperature.
The found that the whale sharks made three types of dives
- Day and night ‘bounce dives’ which involve spending only 10-20 minutes at depth
- Extra-long, extra-deep dives lasting over two hours, followed by a long period at the surface
The researchers found that if the water was warmer during a dive, the sharks spent less time at the surface.
Thums explains that this is important research because it helps us learn more about what drives their movement, and “it will assist in predicting their responses to environmental change and ultimately developing effective conservation and management strategies.”
Whale Shark. Photo credit: NOAA.
To learn more:
- Check out this article from the Australian Geographic: Diving whale sharks surface to warm up
- Find the results, published this week in the Journal of the Royal Society, here: Evidence for behavioural thermoregulation by the world’s largest fish
Copyright © 2012 by Marine Science Today, a publication of Marine Science Today LLC.
