A Hector's dolphin at play.
Photo: Supplied
The institute has been monitoring increasing amounts of noise created by pile driving, ports and recreational boats, and found it can cause temporary or even permanent deafness in whales and dolphins.
A biologist with the Cawthron Institute, Dr Simon Childerhouse, said noise pollution got in the way of them communicating with each other and could cause stress, leading to declining birth rates.
"Loud noises have the potential to physiologically injure them and their hearing either temporarily or permanently, which obviously has big implications for survival. Some of the really loud noises like seismic surveys or military sonar can also actually directly kill marine mammals."