Local finds marine pest in island bay
A destructive Australian marine pest has been found in a Waiheke Island bay, so boaties are being warned to check their hulls.
An island resident reported an infestation of the Australian droplet tunicate, Eudistoma elongatum, at Oakura Bay off Te Whau peninsula on the western coast of Waiheke in May last year.
The Ministry for Primary Industries has confirmed the pest, which breeds in clusters of slimy white tubes, is present in the bay.
Auckland Council marine biosecurity advisor Samantha Happy said Eudistoma posed a serious danger to the marine environment.
It couldsmother beaches, rocks and tidal pools and posed a threat to marine farms.
‘‘The pest will change our beautiful foreshores as we know it, forever, and is nearly impossible to control once it’s established,’’ Happy said.
‘‘Preventing the pest spreading is something every Kiwi, especially sea farers and boat owners, needs to be part of, so we can keep our treasured marine playground pest-free for future generations.’’
The clusters of white or cream cylindrical tubes die back in winter, so the council planned to assess the problem this summer.
The Ministry for Primary Industries tried to remove Eudistoma from Northland in 2007 and 2008, until the tubes disappeared after a flood. The pest is vulnerable to salinity changes due to rainfall.
‘‘Any attempts to smother or treat populations will also have an impact on non-target species, and Eudistoma can fragment easily, facilitating its spread,’’ Happy said.
The pest, which can grow from five centimetres to more than a metre long and from five millimetres to two centimetres thick, has been spreading throughout the North Island.
The first Auckland bay where Eudistoma was found was Sandspit in 2010 and it has since been spotted in Mahurangi Harbour.
The tunicate reproduces quickly and spreads easily, because it has a free-swimming larval stage and each ‘‘slimy saus- age’’ contains numerous individual organisms that can break away and form new colonies.
It looks similar to the native colonial sea squirt, Didemnum spp., but the native species forms mats, while Eudistoma remains in separate tubes and sometimes has orange flecks from its larvae.