June 8 (UPI) -- New research explains the allure of the handful of whale shark hotspots around the world.
Though the endangered whale shark, the biggest fish in the world, travels long distances, young sharks congregate at just 20 locations across the globe. Until now, scientists couldn't figure out what made these places so attractive to the giant fish.
New analysis of the species' hotspots suggests all 20 locations host warm, shallow water and a sharp sea-floor drop off leading to deep water.
The sharks are able to filter feed in both deep and shallow water, and importantly, bask in the sun at shallow depths, warming their cold-blooded bodies.
"Sharks are ectotherms, which means they depend on external sources of body heat," Bryce Stewart, researcher at the University of York, said in a news release.
Whale sharks routinely dive to great depths, where the water is cold, so they need a place to rest in warmer water. The hotspots surveyed in the latest study -- published Friday in the journal PeerJ -- have ideal places to recharge and warm-up after a frigid dive.
"Steep slopes in the sea bed also cause an upwelling of sea currents that stimulate plankton and small crustaceans such as krill that the whale sharks feed on," Stewart said.
Hanging out in warm shallows has its risks. While basking, whale sharks are more likely to expose themselves to human activity. They're more vulnerable to boat strikes and fishing nets.
By better understanding where whale sharks like to hang out and why, scientists can improve regulations and conservation initiatives designed to protect the species.
"The more we know about the biology of whale sharks the more we can protect them and this research may help us to predict where whale sharks might move to as our climate changes," Stewart said.
Researchers say there are still more whale shark mysteries to solve. While the latest study looked at the aggregation of young whale sharks, less is known about where older sharks hang out.