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Warmer oceans found to be baby sharks' "kryptonite"  


Warmer oceans are causing baby sharks to be born smaller, exhausted and undernourished, according to a new study.

A team of The James Cook University researchers have been working with the epaulette shark since 2012, a species only found on the Great Barrier Reef.

Associate Professor Jodie Rummer says the species was chosen for the study because of the challenging conditions it is able to survive in, but rising ocean temperatures seem to be their "kryptonite".

“The epaulette shark is known for its resilience to change, even to ocean acidification,” she says.

"If they were growing up in warm water, they would hatch with a weird colouration pattern that was not their typical stripes and dots.

“So, if this species can’t cope with warming waters then how will other, less tolerant species fare?”

The shark embryos were tested in waters up to 31°C.

Hotter conditions caused the sharks to develop faster and use their yolk sac quicker, causing them to hatch quicker.

Dr Rummer says that while faster development may sound like a good thing, it actually means the sharks were hatching undernourished, smaller and very hungry.

"If a shark hatches and it's hungry immediately and has to learn how to hunt immediately, that's going to put a really interesting tax or toll on that ecosystem," she says.

The research suggests that live-bearing shark species may be able to deal with the affects of warmer water better than egg-laying species.

Dr Rummer says this a concern because around 40 percent of all sharks are egg-layers.

"Egg-layers probably are at a little bit more of a disadvantage, because when the mother lays those eggs, they have to tolerate whatever conditions come their way," she says.

"They can't just move because conditions are not favourable."

While over-fishing is the biggest threat posed to sharks, marine parks and sanctuaries to protect them won't be able to save them from the affects of climate change.

Sharks are an integral part of their ecosystem, but because they grow slower and produce less young than other fish species, researchers are concerned they might not be able to adapt to climate change and oceans getting warmer.


Image: Supplied by E.Moothart