Climate change and overfishing could lead to higher mercury levels in fish

Mercury levels in popular fish — including tuna, salmon and swordfish — are rising, and climate change and overfishing may be to blame, a new study suggests.

That mercury levels would increase in fish is counterintuitive, given that government regulations have driven down the amount of mercury found in the air and the oceans over the past few decades.

“You would expect that as mercury was reduced in seawater, then it would go down in all the fish,” said the study’s lead author, Amina Schartup, who was a research associate at the Harvard School of Engineering and Applied Sciences when working on the study. “But there was variability. We were trying to tease out the different factors contributing to those differences.”