The cooler sea temperatures and associated improvements in underwater visibility have brought another visiting species to Opua Marina - specialist divers hunting out unwanted Mediterranean fanworm (Sabella spallanzanii).

Contractors discovered a single specimen of the marine pest while working in the Opua area last winter and divers were immediately called in to investigate, discovering and removing more than 100 fanworm from the marina and surrounding area over the next several weeks.

The divers were then stood down as biosecurity experts analysed the findings and considered the best management approach, with the maturity, numbers of fanworm and their spread indicating what many people have feared — they may have been in the area, having hitchhiked in on a visiting vessel with a dirty hull, for several years.

Unwanted - Mediterranean fanworm.
Unwanted - Mediterranean fanworm.

Northland Regional Council (NRC) committed $60,000 and Biosecurity New Zealand $40,000 towards a second, roughly month-long, weather-dependent effort which began in late November to try to eradicate the pest.

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Bruce Howse, NRC's Environmental Services group manager, said the divers were forced to stand down only after a few days due to poor visibility.

The summer drought conditions may have been more advantageous for fanworm, as divers who went back to the scene last Tuesday might find.

The team of three divers and two support crew expect to spend another three weeks or so searching the seabed, structures and vessels both in and around the marina and associated commercial wharf, and removing any fanworm they find.

Howse said the council is writing to local mooring owners to update them on the latest developments, and while the NRC carries out regular hull inspections Northland-wide, it also urges people in and around Opua in particular to avoid spreading fanworm.

It is vital boaties ensure their vessel and any associated equipment – moorings and their rope/chain and fishing nets – is clean and free from fouling which may contain marine pests like fanworm.