A marine pest discovered in Nelson harbour has prompted a warning to boat owners to check their vessels carefully.
The Mediterranean fanworm was found earlier in May on the hull of the vessel Manini as it was being prepared to be hauled onto the Calwell slipway at Port Nelson.
If the pest takes hold as it has in Auckland and Lyttleton the effects could be devastating to the local marine environment.
The organism was spotted by Bruce Lines, the manager of a commercial dive company.
He immediately called the National Institute of Water and Atmospheric Research, who informed the Ministry for Primary Industries.
Samples were taken and it has now been confirmed as Sabella spallanzanii, one of six unwanted marine organisms on the national priority list.
Mr Lines says Nelson was lucky on this occasion as the pests were too small to breed, and urged boat owners to take care.
"It's those little boats that get parked up in an estuary and left for years and years and they become massive reefs and holding points - they're the real trouble ones."