Vigilance urged after two marine pests found in Whangarei

Northlanders are being asked to report sightings of any new or unusual marine life after the discovery of two unwanted pest species on the hulls of several commercial vessels moored in Whangarei.

Mediterranean fanworm (Sabella spallanzanii) has been found on the hulls of four fishing vessels in Whangarei, two of which had come up from Auckland where they had been berthed for an extended period, after being slipped and painted.

A second pest – the seaweed Undaria pinnatifida – has been found on one of those vessels, as well as another ship which had travelled from Timaru.  The fourth vessel is also believed to have last been in Auckland.  Neither pest is thought to be permanently established in Northland.

Don McKenzie, Biosecurity Senior Programme Manager for the Northland Regional Council, says three of the four vessels belong to the same fishing company which had been unaware of the infestations until alerted by the council and has been working proactively to manage the issue.

Mr McKenzie says divers hired by the regional council had removed the undaria seaweed from the hull of the shipping company’s largest vessel.  The company had also hauled its other two ships from the water and has had the fanworms and undaria removed and destroyed.

“Obviously with vessels of this size – roughly 20 to 30 metres long – you can’t just haul them ashore anywhere and the fishing company has worked hard with local slipway operators to make this happen”, says Mr McKenzie.

Ironically, the shipping company’s vessels were moored on commercial berths belonging to Port Nikau, whose owners include Northland Regional Council member Tony Davies-Colley, a keen advocate of better pest management for the region.

Mr McKenzie says the vessels were inspected at the suggestion of marine industry players attending a meeting of a regional council-organised marine industry stakeholder group, formed to improve awareness of marine pests.

Councillor Davies-Colley says his company had been unaware of the risks the fishing boats involved had posed.

“I’m pleased at the responsible approach the fishing company has taken on learning of these infestations and with the regional council’s handling of the matter,” says Cr Davies-Colley.

Councillor Davies-Colley believes the discovery of the two pests highlights the need for increased regional vigilance where marine pests are concerned and says his company will be doing everything it can to ensure such risk is reduced as much as possible in future.

Mr McKenzie says that while all four vessels are commercial, they could have just as easily been vessels from the recreational sector.  Northland’s coastal waters are particularly vulnerable to pest invasions given the big number of vessel movements and our closeness to Auckland’s ports.

He says Mediterranean fanworm is a marine animal typically found in estuaries or sheltered sites, at depths of anywhere between one to 30 metres.

Internationally recognised as a significant marine pest, it consists of a tough, flexible tube – often muddy in appearance and always anchored to a hard surface – which is topped with a single spiral fan.

They grow up to 40cm long and the fans are white, banded with brown and orange, and have an orange central stem.

He says the pest fanworm differs from New Zealand native fanworms in that it is larger and it has just a single fan.  “If you see what you think is a fanworm but it has two spiral fans, it’s not a Mediterranean fanworm and isn’t a concern.”

Mr McKenzie says staff from the regional council and the new Ministry for Primary Industries (MPI) have been working jointly to deal with the pest.

“The Northland Regional Council will carry out regular inspections of an extended area surrounding the infested vessels for the next several months to find and destroy any fanworm and hopefully eliminate the species before it becomes established.”

The port area will also be included in a detailed annual survey for marine pests that MPI carries out in Whangarei Harbour.  He says Mediterranean fanworms are unwanted because they can form dense groups that compete with native species for food and space.

Meanwhile, Mr McKenzie says undaria is native to Japan where it is cultivated for human consumption.  “It’s a highly-invasive opportunistic seaweed which spreads mainly by fouling on boat hulls and unfortunately it’s now present in almost all international ports and harbours.  High value marine areas like Whangarei Harbour which has a marine reserve are at risk.”

Undaria grows on any hard surface – including shells, reefs, ropes, wharf piles, vessel hulls, moorings and other artificial structures – and can form dense underwater stands to depths of up to 15 metres.

“These in turn can potentially result in competition for light and space which again may lead to the exclusion or displacement of native plant and animal species.”

Undaria’s appearance varies according to its maturity, with larger plants a brown/green/yellow colour, which grow up to one to two metres, with a very visible midrib.  Smaller plants appear as a single leaf, with the distinctive midrib starting to become apparent once the plant grows over five centimetres.

Mr McKenzie says restricting the movement of pests like Mediterranean fanworm and undaria is key to reducing their impacts on regions like Northland.

“Previously we’ve relied on boat owners to be vigilant but the risk of unwanted marine pests being transferred to Northland is increasing due to what appears to be less interest from authorities in the areas where these pests are already established,” he says.

“Vessels berthed in these ports then travelling to Northland pose a direct risk to our region so something different must be done to halt the decline of our marine environment.”

The council will issue a legal ‘Notice of Direction’ to vessel owners where it suspects marine pests could be found, to help ensure more vessels are inspected and cleaned.

The council is also asking anyone who notices strange or new marine life to report it to regional council biosecurity officers on (0800) 002 004 or the Ministry for Primary Industries (0800) 809 966 so it can be identified - and managed - if necessary.

He says information on pests generally is available from the council’s website via: www.nrc.govt.nz/nasties or the MPI website: www.biosecurity.govt.nz