Sea slugs may be victims as well

Narrow Neck Beach. Photo / Brett Phibbs

An expert on sea slugs doubts they are to blame for killing dogs, saying the slugs themselves are probably victims of something in the water.

Researchers are looking at whether toxic sea slugs found at Narrow Neck Beach, on Auckland's North Shore, killed dogs in recent weeks and made others ill. They believe the slugs may have eaten something toxic and passed it on to the dogs.

But Bill Rudman, senior research fellow and an expert on sea slugs at the Australian Museum in Sydney, said he would be surprised if slugs were responsible.

"I don't know how a sea slug would have ingested that much toxin without dying. The slugs are probably as much a victim as anything else."

Dr Rudman said sea slugs could store chemicals in their bodies, but their intention was to taste bad to predators, not to kill.

"They've developed the ability over the years to take the poison out of algae and use it to make them taste bad. They also use sponges."

He suggested an algal bloom, such as a red tide, was more likely to be responsible.

New Zealand scientists trying to discover what killed four dogs, pilchards, dolphins and penguins in the Hauraki Gulf have found no traces of toxic algae in sea water but have not ruled it out.

Further test results on the vomit of dogs that died, pilchards and sea slugs are expected this afternoon.

Although Dr Rudman doubted that sea slugs were the problem, he pointed to reports from Western Australia of dog deaths from a common type of sea slug, known as sea hares.

Dr Rudman said dog owners in other parts of Australia where sea hares washed up did not seem to have the same problem.

He said each species ate its own small and specific range of algae, so it was vital to find out which one had been found in New Zealand.

Sea slugs found on Narrow Neck Beach were too broken up for scientists to identify, but they were reported to be grey and looked like "shellfish without shells".

Health authorities will decide tomorrow whether people should go back in the water this weekend.

One planned event - the Winter Jolt fundraising dip at Mission Bay - was cancelled yesterday.

Organisers said the event - to raise money for youth programmes - would go ahead next year.