Beach sea slugs sent for poison tests

Signs alert visitors at Narrow Neck Beach, North Shore. Photo / Richard Robinson

A hundred sea slugs collected off seven Auckland beaches are being tested to see if they contain the poisonous toxin tetrodotoxin.

Divers were searching for the grey side-gilled sea slug (Pleurobranchaea maculata) which can be a carrier of high levels of the toxin, known as TTX.

Slugs were found at seven subtidal sites around the Auckland region last week, the highest number at Narrow Neck Beach on the North Shore.

Auckland Regional Council spokesman Grant Barnes told the Herald there was a risk the slugs could be stranded on beaches if weather conditions were favourable.

"If we get prevailing wind conditions that push large waves on to Narrow Neck Beach there is a chance that sea slugs will strand."

Divers picked up 48 slugs at Narrow Neck, which was one of the high alert spots when the slugs were found on beaches last year.

Mr Barnes said researchers were investigating why Narrow Neck beach, in Devonport, was such a "hot spot" for the slugs.

"It seems that there are habitats immediately offshore that are particularly attractive to the sea slugs," Mr Barnes said.

He said divers were picking up the slugs from the sandy flats of Narrow Neck Beach rather than from rocky outcrops where they were usually found.

"There is something particularly funny happening at Narrow Neck," he said.

Underwater searches also found 16 slugs at Cheltenham Beach - also in Devonport - and 14 found at Illiomama Rock near Rangitoto Island.

Smaller numbers of slugs were also picked up at Browns Bay, Long Bay and Mission Bay.

Eighteen incidences of poisoning were reported last year between July and September, when there was a mass stranding of sea slugs on several North Shore beaches.

Five dogs died as a result of ingesting slugs on the beaches.

North Shore local Suzy Feeney said she walked her dog Gizmo on Narrow Neck Beach every day.

"I'm not really concerned about the sea slugs. I've only seen one slug about a month ago on the foreshore," she said.

A dog control officer from the North Shore City Council was patrolling Narrow Neck beach while the Herald was there, checking for sea slugs and handing out pamphlets to dog walkers.

Three signs warned beachgoers of precautions to take should they see or touch a sea slug.

The ARC and the Cawthron Institute are conducting research to determine whether the slugs are born with the toxin in their system or whether the toxin is acquired from an outside source.

Mr Barnes said testing had found TTX in egg mass, juvenile and adult slugs.

"This makes us think that the presence of TTX is part of the reproductive process. We tested all parts of the sea slug, the tissue, gut and reproductive system which we found all contain TTX."

No recent calls have been to the MAF helpline regarding animals affected by TTX.

The Auckland Regional Council says people should take extreme care on the beaches where the slugs have been found.

SEASIDE BLIGHT
* The slugs that have been collected are up to 7cm long.
* They are a mottled grey colour.
* When they are exposed to air they collapse, so may appear to be flat.
* They are mostly found in the wave wash zone of the beach, among other marine debris.