Hector's dolphins, which are found only in New Zealand waters, continue to slide towards extinction, according to Otago Zoology Associate Professor Elisabeth Slooten.

The Hector's dolphin is one of the best studied dolphins in the world and Slooten says research conclusively points to entanglement in fishing gear - particularly gill nets - as the main threat to the species.

This is supported by a new analysis she has completed with Associate Professor Steve Dawson (Department of Marine Science) which shows that the number of Hector's dolphins caught in commercial gill nets is 10 times above sustainable levels. Effectively, the death toll - estimated by NIWA to have been between about 110 to 150 dolphins each year between 2000 and 2006 - exceeds sustainable impact by more than 10 times.

This Otago study used the Potential Biological Removal method of analysis, developed by the US National Marine Fisheries Service, which is a commonlyused standard for determining levels of human impact on marine mammal populations.

A Hector's dolphinSlooten says Hector's dolphins are regarded as endangered in the World Conservation Union's (IUCN) recentlyupdated endangered species list - and the North Island population (Maui's dolphin) is listed as critically endangered.

Current population levels of just over 7,500 are only about a quarter of what they were. "If the recent level of bycatch continues, Hector's dolphins are expected to further decline to around 5,000 individuals over the next 50 years," she says.

In May, the New Zealand Government announced a range of protection measures (which are now being challenged by the fishing industry). They include regional bans on set netting, trawling and drift netting in some coastal waters, as well as increased monitoring of commercial fishing vessels and the establishment of four new marine mammal sanctuaries.

Slooten and Dawson analysed the effectiveness of these measures and concluded that there would be a slowing of population decline to about 7,000.

"It would be a major step forward, but not enough yet," says Slooten, who has received the Royal Forest and Bird Protection Society's "old blue" award for her contribution to marine conservation.

"Our research shows these measures would slow the Hector's dolphins' slide towards extinction, but more would need to be done to achieve population recovery." She adds that full protection from by-catch in gill nets and trawl fishing would help the population almost double by 2050, recovering to more than 15,000.

Based on their research, she recommends a shift to more selective, sustainable fishing methods. "This would have benefits not only for Hector's dolphin conservation, but also for other dolphin species and seabirds caught in these fisheries and, in the long term, for the fishing industry itself."