Dolphin deaths remain a mystery

The deaths of eight dolphins in the Hauraki Gulf, a coastal feature of the North Island of New Zealand look set to remain a mystery. This coincided with the death of several dogs around the same time on Auckland beaches.

As part of an investigation into the cause of the recent dog deaths an inter-agency team led by the Auckland Regional Council has conducted initial investigations into the dolphin deaths, these independent laboratory tests have proven negative for the presence of domoic acid - an algal toxin known to be a common cause of dolphin deaths. The team also quickly ruled out any link to brodifacoum, the rat poison used by DOC in its recent restoration programme on Rangitoto and Motutapu islands, after autopsies on the dolphins showed no signs of internal bleeding.

Investigations into the dolphin deaths were sparked after eight dolphins died over a three-week period in the Auckland region. Strandings data analysed by Massey University from the 1950s onwards suggested that single stranding events of common dolphins normally occurred about once or twice a month for the entire New Zealand coastline. Massey University marine biologist Dr Karen Stockin who has studied the dolphins in the area for many years is disappointed with the findings but agrees the deaths will have to remain a mystery. Massey University had conducted post mortems of dolphins as part of a long-term research programme since 2002.