MAF and iwi push to clear sea squirt from Northland waters

MAF and Northland iwi members go back to the rocky shore today in the final stage of a programme to trial the feasibility of removing an introduced sea squirt from the area’s harbours.

Pyura praeputialis (known as pyura) is known to be present on rocks and in rock pools at some 25 locations on Northland’s western and eastern coasts. Outside of its native Australia, pyura has been an aggressive species, overtaking native marine life and threatening food species such as mussels.

Senior marine adviser Kathy Walls says due to its widespread presence, pyura will never be fully eradicated from New Zealand. However, recognising local concern, MAF felt there was merit in testing removal techniques and trying to remove the species from some sites where population numbers were relatively low.

“The three stage programme sets out to tell us whether it’s worthwhile attempting to manage pyura at other locations with low density and it will also give local people the tools to carry on if they choose to do so.”

Stage one of the trail was this time last year when a team of local iwi, MAF and marine scientists spent several days manually removing the sea squirts from the rocks at the Bluff at 90 Mile Beach and Whareana Bay. At the same time, a scientific control trial was carried out on a population at the entrance to Parengarenga Harbour, where one marked area was treated and one left alone to compare results.

Some further work was undertaken in March this year to make a preliminary evaluation of success. At that time, some re-growth was found at the scientific site at Parengarenga but at the other two sites the sea squirt did not appear to have spread back. Now it’s time to revisit the areas, remove any pyura found and draw some final conclusions about the removal effectiveness.

The teams will be working at the treatment sites through to Thursday and will get together on Friday (2 September) to assess the results.

“We’re keen to know, for example, if it comes back with a vengeance, if it can be completely cleared, or if it will be like weeding a garden where you have to keep going back and removing it,” Kathy Walls says.

“Ultimately it will be up to the local community to decide if they wish to continue with management of this sea squirt into the future.”

Ms Walls says the teamwork involved in the programme is a good example of MAF’s focus on supporting communities to lead the long-term management of pest incursions. It also promotes greater local awareness about the arrival of species new to their coast and helps emphasise the importance of notifying MAF when new or unusual organisms are found.

Full information on pyura is at: http://www.biosecurity.govt.nz/pests/pyura

To report an exotic pest or disease call MAF toll free on 0800 80 99 66

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