Waikato Regional Council takes on fight against marine pests in Coromandel

Marine pests like the mediterrainian fanworm pose a major threat to the ecological, cultural, economic and recreational values of the marine environment. Photo / Supplied

Waikato Regional Council is taking on the fight against marine pests by engaging a dive team to survey coastal marine areas around the Coromandel Peninsula.

The dive team will determine the presence and extent of marine pest species and particularly target Mediterranean fanworm (Sabella spallanzanii) and clubbed tunicate.

This biosecurity surveillance work will extend until 2022/2023.

Marine pests are species that are not native to New Zealand and are introduced to coastal marine areas by human activity through 'hitchhiking' on incoming vessels and then being spread via domestic vessel movements.

They harm the natural environment and resources and therefore pose a major threat to the ecological, cultural, economic and recreational values of the marine environment.

They can out-compete, smother, predate on or otherwise adversely affect native species and habitats.

Once established, marine pests are extremely difficult and costly to eradicate or contain, so prevention is far more effective.

As marine pests are mainly spread by heavily fouled vessel hulls, the dive team will target pathways of boats and check vessels, marine structures like wharves and jetties, popular anchoring spots, as well as mussel and oyster farms. If the team finds infested vessels, owners may be requested to remove and antifoul them.

Although previous surveys have shown that the eastern side of the Coromandel is free of marine pests, the west coast of the peninsula is looking not so good.

Especially the natural spread of Mediterranean fanworm is continuing up the coast from Coromandel Harbour. During the last survey in 2018/19, the worm was found as far north as Colville, up from Papa Aroha.

Biosecurity New Zealand has placed a controlled area notice (CAN) on Blind Bay, Tryphena Harbour and Whangaparapara Harbour to minimise the spread of Caulerpa brachypus, a seaweed native to the Indo-Pacific region. Ngāti Rehua Ngāti Wai ki Aotea has also imposed a rāhui (tapu restricting access) on the same areas.

The CAN and rāhui are in place until June 30, 2022, and make it illegal to take any marine life (fish, shellfish, crays, seaweed) from the three affected harbours. If you anchor in those areas, you must have a permit from Biosecurity New Zealand to move on.

The seaweed was discovered for the first time in New Zealand in August this year and can be spread by fragments being carried by coastal currents or through vessels when pieces get tangled in or stuck on equipment like nets, dive and fishing gear, and cray pots.

Caulerpa can also be broken into little pieces by wave action or when anchors and fishing gear are moved through weed beds. The species can even survive out of water for up to a week or more if it's in a moist location.

Waikato Regional Council regularly checks for marine pests to see how much of a problem they are, but you can help to prevent spread by making sure your hull has been checked, cleaned and antifouled before heading away.

If you don't know what a marine pest is, check out marinepests.nz for some of the pests to look out for.