Climate change to destroy sharks's hunting ability

With the increase in level of carbon dioxide (CO2) and warmer oceans, the hunting ability and growth of sharks will be dramatically impacted by the end of the century, a study warns.

Warmer waters and ocean acidification will have major detrimental effects on sharks' ability to meet their energy demands, the study said.

"In warmer water, sharks are hungrier but with increased CO2 they won't be able to find their food," said study leader Ivan Nagelkerken from Australian Research Council.

"With a reduced ability to hunt, sharks will no longer be able to exert the same top-down control over the marine food webs, which is essential for maintaining healthy ocean ecosystems," Nagelkerken noted.

The laboratory experiments, studying Port Jackson sharks and including large tanks with natural habitat and prey, found embryonic development was faster under elevated temperatures.

But the combination of warmer water and high CO2 increased the sharks' energy requirement, reduced metabolic efficiency and removed their ability to locate food through olfaction (smelling). These effects led to marked reductions in growth rates of sharks.

The results of the study provide strong support for the call to prevent global overfishing of sharks.

"One-third of shark and ray species are already threatened worldwide because of overfishing," professor Sean Connell from University of Adelaide said.

"Climate change and ocean acidification are going to add another layer of stress and accelerate those extinction rates," Connell pointed out.

The study was published in the journal Scientific Reports.