KEY POINTS:
Tourist boats are endangering a unique community of bottlenose dolphins in Doubtful Sound, the Department of Conservation (DoC) says.
It is predicting the marine mammals will be wiped out within years and wants increased protection for them in Fiordland.
The region is one of the most popular areas for eco-tourists coming to New Zealand but a DoC report released yesterday revealed vessels in Doubtful Sound are hurting the dolphins.
"It is highly likely that the existing range and intensity of impacts will lead to the Doubtful Sound complex dolphin population becoming extinct within 45 years," it said.
There were 69 dolphins in the Doubtful Sound community in 1994, but by 2006, that had dropped to 56, with more dolphins dying or being killed than were being born.
"This decline is one of the steepest ever recorded for a dolphin population that is not exposed to direct or indirect takes from fishing," said DOC, which has issued eight marine mammal "viewing permits" for the dolphins.
The Doubtful Sound dolphins remain in the fjord year-round - with most never leaving for more than a few hours - and they have distinctive social and cultural characteristics.
Scenic cruises take place year round on vessels ranging from kayaks - usually in groups of five or six - to a 40m catamaran with twin diesel engines powered by twin diesel engines.
One company commissioned a giant glassed in boat to take up to 175 people at a time.
Some operators conduct tours in the fiord only during the winter.
Otago University marine ecologist David Lusseau - who studied the Doubtful Sound dolphins from 1999 to 2002 - has shown some dolphins were diving for longer to avoid boats.
His study showed boats were violating the Marine Mammal Protection Regulations, and DOC said this was tiring for female dolphins and could harm reproduction.
Stillbirths rose significantly between 1994 and 2006.
Other threats were boat "strikes". In Milford Sound - where there are five times as many cruises as in Doubtful Sound - 7 per cent of Milford Sound dolphins bear scars from propellers and dolphins leave the fiord when there is too much traffic.
"The current level of surface water activity in the Doubtful Sound complex may already be too high for the resident population of bottlenose dolphins," DOC said.
Protection measures being considered in Doubtful Sound included no-boat zones, zones accessible by permit only, or where dolphin encounters may not be sought.
Commercial trip allocations could be cut, research limited, and permits or consents required for recreational boats. Speeds could be restricted, and skippers constrained from radioing the location of dolphins to other boats.
- NZPA
