Hitchhiking marine pest a risk to the Hauraki Gulf

Friday, 6 October 2017

Boaties help called for to slow the spread of the sea squirt Eudistoma.

As the weather warms up and the glistening Hauraki Gulf beckons, boaties are being asked to clean their hulls to slow the spread of the invasive sea squirt Eudistoma elongatum.

A native of Australia, it was first spotted in oyster farms in Houhora Harbour 12 years ago, and has now spread throughout the north.

Able to survive being out of the water between tides also makes it is a significant nuisance for mussel and oyster farmers.

Marine biologist Roger Grace found the invasive sea squirt Eudistoma elongatum at Sandspit in 2010.

While not poisonous or toxic, the squirt breeds in clusters of slimy white tubes that grow from five centimetres to more than a metre long and from 5 millimetres to two centimetres thick.

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The marine pest Eudistoma elongatum has been found at Sandspit and the Mahurangi Harbour.

* Marine pest found in Waiheke Island bay**

It accounts for about half of the marine waste on northern oyster farms during summer, Northland Regional Council Biosecurity Officer, Cameron Bunton said.

Largely dormant in winter the invasive sea squirt Eudistoma elongatum will cover much of the lower Sandspit Wharf structure in mid summer.

Sand, mud, wharf piles - the fast growing pest grows almost anywhere. It competes with native species for space, and filter feeds on the eggs and larvae of native marine life.

Warkworth marine biologist Roger Grace spotted it at Sandspit seven years ago.

He then raised concerns that dredgings, from the Sandspit Marina build, dumped near Cuvier Island, could help spread the squirts in the gulf.

Found in Oakura Bay on Waiheke Island last year, it is now in the Mahurangi Harbour.

The tubes are incredibly difficult to control or pick off, as they grow back and spread from broken bits, Auckland Council Marine Biosecurity Advisor Samantha Happy advised.

It is a particular risk to moored boats in marinas that may not get cleaned or taken out regularly, she said.

Some Sandspit boats already have the squirts on them, Grace said.

In an effort to slow its spread in the Hauraki Gulf, Auckland Council is asking boaties to check their boat hulls and keep them clean.

Pontoons have also spread the pest in the north, Bunton said.

'The pest will change our beautiful foreshores as we know it, forever, and is nearly impossible to control once it's established,' Happy said.

Anyone who sees marine pests outside of recorded sites can note the location, take a photo or sample and report it to the Ministry for Primary Industries on 0800 80 99 66.

For advice, contact Auckland Council biosecurity on (09) 301 0101 or biosecurity@aucklandcouncil.govt.nz.