Marine pest could threaten Cook Islands

Monday October 23, 2017 Written by Published in Local
There are fears the sea squirt could be inadvertently introduced to the Cook Islands through visiting yachts and container ships. 17101901 There are fears the sea squirt could be inadvertently introduced to the Cook Islands through visiting yachts and container ships. 17101901

New requirements for international shipping in New Zealand next year could save the Cook Islands marine environment from an invasive marine pest that threatens the country.


This follows concerns that the Australian droplet tunicate, a type of sea squirt, could spread to the Pacific Islands on visiting container ships or yachts after gaining a foothold at some Auckland beaches.

The pest has been spotted in Mahurangi Harbour, Sandspit and Oakura Bay on Waiheke Island. It grows on sand, mud, and seagrass beds, and can latch onto hard surfaces like rocks and shells.

Usually found in tropical climates it is thought that the sea squirts arrived in New Zealand on the hulls of uncleaned boats.

Auckland Council has recently warned that the region’s marine environment is under serious threat from the destructive Australian pest.

Marine biosecurity advisor Samantha Happy said: “The Australian droplet tunicate (Eudistoma elongatum) grows in clusters of slimy white tubes.

It can quickly smother entire beaches and foreshores, and damage or destroy marine farms.” The Australian droplet tunicate is difficult to get rid of once established, as the tubes grow back and spread from broken pieces, and have a free-swimming larval stage.

“This pest will change our beautiful foreshores forever, and is nearly impossible to control once established,” said Happy. To mitigate the threat of this and other invasive marine pests, the New Zealand government has released new biosecurity requirements for all incoming vessels, although they do not come into force until May 2018.

The new Craft Risk Management Standard will require vessels to have a clean hull when arriving in New Zealand. For most vessels ‘clean’ means no biofouling apart from a slime layer, but for fast turnaround vessels, which only visit the official ports of arrival, allowance is given for a slight amount of biofouling. There are fears the pest could arrive in the Cook Islands on container ships such as Liloa II and Imua II or other visiting vessels.

Both of those ships routinely circumnavigate the pacific via Fiji, Samoa, Tonga, Cook Islands and Niue from Auckland.

They are part of the Matson international shipping company. CINews contacted them recently for confirmation that they are already meeting, or soon plan to comply to biofouling regulations, but had not received a reply by the time of publishing.

Earlier this year the Fijian Biosecurity Authority stopped a Korean cargo ship from entering Fijian waters after it was ordered to leave New Zealand after destructive tube worms were discovered on its hull.

Regarding the possible arrival of the Australian droplet tunicate to the Cook Islands, Auckland Council’s Happy said “impact assessments and horizon scanning exercises” were underway. She added that research in Northland, New Zealand, showed the main vector for dispersal was fisheries based.

“We have observed the species on hulls, so the potential is there, however more commonly it is observed on structures (including piles, wharves, pontoons), therefore there is a risk of introduction from any of those vectors.”

In the Cook Islands the Ministry of Transport administers the Prevention of Marine Pollution Act 1998 (Cook Islands) but relies on the checks of ships’ hulls to first be undertaken in New Zealand.

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