Baby sharks are being born smaller, undernourished and exhausted as climate change warms the world's oceans, researchers say.

Researchers examined the effects of warming temperatures on the growth, development and physiology of the Great Barrier Reef's epaulette sharks off Australia, testing embryos and hatchlings in waters up to 31 degrees Celsius (87. 8 degrees Fahrenheit).

Over the last two decades, cloud-less, high-acidity conditions meant natural food sources such as krill, turtles and fish began to dwindle far more rapidly than they once were, says the study published Monday in the peer-reviewed journal PLoS Biology by researchers from Macquarie University in Sydney, the Australian Institute of Marine Science, Queensland University and the University of Aberdeen in Scotland.

They found that decades of ocean warming since the 1970s have given the reefs crowded with immature toothless fish, many more juvenile fish and smaller fish and sharks – thus exacerbating their habitat loss.

See also: Shark attack mortality jumps 10% at Great Barrier Reef

The young sharks do so little swimming than were once thought. Stringent experimental conditions – including suboptimal for preserving aquatic communities, according to the study – demonstrate that juvenile epaulette sharks, the pups of the epaulette shark family, do little swimming for longer than several hours at any given time.

Adult epaulette sharks "function as if they were in a hibernation state," says principal investigator Mary Davies, a marine ecologist at Macquarie University in Sydney. "They don't eat, sleep or dive of any sort."

Above, a great white shark off Australia's Great Barrier Reef in 2012. Media reports have suggested the shark population has declined 50% over the past 20 years. Credit: Tara Palmer/Flickr

Gone are fish that feed by shimmying onto shore and seizing the bait they inflate with mucous cells; the seals and fish that survive the feast are now pets for more precocious sharks. Gone are the often loud and crowded schools.

And gone are the giant, orange schools of feeding dolphins that number in the hundreds. Unless schools enjoy a flood of baby dolphins – for which the answer is not to bother feeding them, Davies says – the young sharks struggle little to muster enough energy to catch food, leaving the adult bottlenose dolphins to do all of the feeding on the Great Barrier Reef.

"Once an epaulette shark is seen eating by a harbor seal and then by another dolphin, he or she may not eat again for two weeks," says researcher Steven Glasser, a behavioral ecologist at the Australian Institute of Marine Science in Cairns, Australia.

With a population of an estimated 10,000 epaulette sharks, and few mature individuals in the population left, "this colonial niche is ripe for
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