Ocean fish around the world risk becoming lost at sea if carbon dioxide concentrations in seawater continue to rise on current trajectories, a study from the University of NSW has found.

The study, published in the journal Nature, is the first global analysis of the impact of rising carbon dioxide emissions from fossil fuels on natural variations in carbon dioxide concentrations in the world's oceans.

It found that carbon dioxide concentrations could reach levels high enough to disorient and "intoxicate" fish, a condition known as hypercapnia.

"Essentially, the fish become lost at sea," said the study report's lead author, Ben McNeil, of UNSW.



"The carbon dioxide affects their brains and they lose their sense of direction and ability to find their way home. They don't even know where their predators are."



Hypercapnia research in fish is relatively new, starting about 6 years ago.



In the case of ocean fish, high levels of carbon dioxide affect receptors for GABA, "the main inhibitory neurotransmitter in the vertebrate brain".