Bottlenose dolphins are at risk of being driven out of the Bay of Islands because of boat traffic in the area, according to a new report.
The study conducted by Massey University for the Department of Conservation (DOC) found both commercial and private boats are altering the behaviour of the nationally-endangered bottlenose dolphin in the area.
Over the past 15 years the local population had fallen from more than 250 to fewer than 100 according to the department.
On average those dolphin spend 86 percent of daylight hours in the presence of at least one boat which is adversely affecting their behaviour.
DOC director of operations Sue Reed-Thomas described the Bay of Islands as a boating Mecca.
"This is very disruptive for the dolphins. It means they spend far less time feeding, nursing their young and sleeping."
The majority of interactions involved private boats and commercial vessels taking tourists around the Bay of Islands. These boat owners interact with dolphins when they see them while cruising.
Ms Reed-Thomas said it was very difficult to manage a group of wild animals swimming freely.
"Everyone who puts a boat on the water in the Bay of Islands needs to be aware of the problem so they play their part in protecting the local dolphin population."
The study was undertaken between December 2012 and April 2015.
It found 75 percent of bottlenose dolphin calves observed were suspected to have died before reaching independence, compared with 52 percent in a 2009 study.
It said the the trajectory of decline in the population was not good news for the region, or the long-term viability of the local marine mammal tourism industry.
The report recommends improvements on how boats are managed in the area, including simplifying permit conditions, no interaction zones, community engagement, education and enforceable regulations.
DOC has begun working with boat owners, iwi and the wider Bay of Islands community to improve the management of boat interactions with the local bottlenose dolphin population.