The noise from cargo, container and tanker vessels are causing communication problems for two key marine species on the Hauraki Gulf.
New research has found that the common reef fish and bryde's whales have had their communication space reduced due to the amount of ship noise on the surface.
The first-ever large scale investigation into the effects of ship noise in the waters of the Hauraki Gulf saw four hydrophone, or listening stations, track underwater noise contributed by shipping over a nine month period.
The study focused on reef fish and bryde's whales who use sound to communicate, and found that shipping noise overlapped their vocalisations up to 20 per cent of the time.
Every time a vessel passed within 10km of a listening station, it reduced communication space for bryde's whales by 87.4 per cent.
The reduction of communication space for marine life is becoming a big concern for scientists as more is learned about how sound is used among groups of species to ensure survival - including finding a mate, defending territory and warning of predators.
The biggest impact from ship noise was at Jellicoe Channel, the most regularly used shipping lane into Ports of Auckland, where vessel passages were recorded 18.9 per cent of the time.
This latest study shows that compliance with the 10-knot speed restriction within the Hauraki Gulf Marine Park area could benefit marine species, says University of Auckland researcher Rosalyn Putland.
"The voluntary speed limit of 10 knots is fairly recent but we believe is having a significant effect on helping reduce noise in the Gulf to allow species to hear each other," she said.
"Even so, when a ship is directly above marine animals, it reduces communication for those animals almost completely, or by 99 per cent."