Future too warm for baby sharks

Full article issued by the ARC Centre of Excellence for Coral Reef Studies at James Cook University.

New ARC-supported research has found that as climate change causes the world’s oceans to warm, baby sharks are born smaller, exhausted, undernourished and into environments that are already difficult for them to survive in.

Lead author of the study Carolyn Wheeler is a PhD candidate at the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University (JCU) and the University of Massachusetts. She examined the effects of increased temperatures on the growth, development and physiological performance of epaulette sharks – an egg-laying species found only on the Great Barrier Reef. She and her team studied the sharks as embryos and as hatchlings.

'We tested shark embryos in waters up to 31°C,' Ms Wheeler says. 'The hotter the conditions, the faster everything happened, which could be a problem for the sharks. The embryos grew faster and used their yolk sac quicker, which is their only source of food as they develop in the egg case. This led to them hatching earlier than usual.' 

This meant hatchlings were not only smaller, they needed to feed almost straight away – while lacking significant energy.

Co-author Associate Professor Jodie Rummer, a Discovery Early Career Researcher Award (DECRA) recipient from Coral CoE at JCU, says the waters of the Great Barrier Reef will likely experience summer averages close to or even in excess of 31°C by the end of the century.

The study suggests the sharks of the future will be born – or hatch, in this case – not only at a disadvantage but into environments that are already at the warmest they can tolerate.

 

Image Credit: M Johnson - Shark Embryo