No dolphins were hurt in the making of a powerboat race in the Bay of Islands, but planning for next year's event will involve ensuring better protection of marine mammals.

Northland Conservation Board Chair Mita Harris said the board shared Department of Conservation and other agencies' concerns about possible disruption the New Zealand Offshore Power Boat Race - dubbed Thunder in the Bay - caused the endangered bottlenose dolphins' environment.

Preliminary reports from the Coastal-Marine Research Group at Massey University, state that bottlenose dolphins and young calves were present in and around the race course last Saturday.

"High-speed power boat racing in key dolphin habitat inherently creates a significant risk of collision between dolphin and speedboat," Mr Harris said.

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"The consequences of the animals being exposed to high levels of noise emitted by these vessels are also of concern.

"The local population is declining at 7.5 per cent annually and calf mortality is very high at 42 per cent. We cannot afford to lose even just one of these precious mammals."

Mr Harris said collisions of vessels with bottlenose dolphins do occur and often result in severe injury to or death of the animal.

The variety of effects of noise on whales and dolphins had also been well-documented.

"Marine mammals are protected by law.

"Commercial marine mammal viewing operators generally take due care and they have procedures in place that regulate marine mammal encounters.

"Apart from the obvious need to protect the Bay's marine mammals for conservation reasons, a significant portion of the Bay of Islands' tourism economy is also reliant on healthy dolphin populations frequenting the area," he said.

In planning future races it was important to weigh up the risks to marine mammals, conservation efforts, and the local tourism interests against the economic benefits this event brings to the region, Mr Harris said.

A different location or time of year, outside of the calving season, could be a solution to safeguard marine mammals.