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