Pyura

Pyura doppelgangera (formerly known as Pyura stolonifera praeputialis and Pyura praeputialis)

Pyura (known in its native Australia as Cunjevoi)

Pyura (known in its native Australia as Cunjevoi)

Legal Status: No Status
Status in New Zealand: Established
Organism: Water snails, crabs, shellfish, starfish, and other aquatic

This species is present in New Zealand. It has been detected growing on rocks in a number of locations in the far north of Northland.

If you suspect you have found this organism in any other location in New Zealand, please report this by calling 0800 80 99 66.

Pyura
Pyura, Twilight Beach
Photo: Bruce Hayward

Description

Pyura at low tide, Te Werahi Beach.  
Pyura at low tide, Te Werahi Beach.
Photo: Bruce Hayward

Pyura (known in its native Australia as Cunjevoi) is a marine animal called an ascidian (a type of sea squirt). Individual Pyura live in dense colonies or groups which form a mat over rocks and are often highly visible at low tide. Pyura adults are comprised of a sack-like body, with a brown, or reddish-brown, leathery skin.

There is sometimes sand and shell material incorporated into the outer skin, and other sea life such as sea lettuce can grow in and around the individuals. Pyura can be found either attached to the rocks or on other hard surfaces such as mussels. Each sea squirt has two siphons or holes for inhaling and exhaling sea water. Adults grow to about 15 cm or more in height and around 3 - 5 cms in diameter.

Habitat - where Pyura is found

map of northern tip of the North Island 
Locations of Pyura in the far north (note that
this sea squirt has recently been found in the 
Hokianga Harbour and the Bay of Islands).
Click to enlarge.

In New Zealand, populations of Pyura have been identified in Northland on rocky intertidal reefs and in the shallows at Twilight and Te Werahi beaches near Cape Reinga; the Bluff on Ninety Mile Beach; the Tauroa Peninsula; north of the Hokianga Harbour at Mitimiti; near North Cape and at Whareana Bay on the east coast, in the Parengarenga and Houhora harbours; and at Rangiputa near the entrance to Rangaunu Harbour.

In December 2013, it was found for the first time in the Bay of Islands (growing on rocks near the Russell car ferry dock, opposite Opua) and in March 2014 it was found near the entrance to the Hokianga Harbour.

When first detected in Northland’s far north in 2007, this species was identified as Pyura stolonifera praeputialis. Recent genetic research work has reclassified the species as Pyura doppelgangera, one of several native Australian Pyura species (Rius & Teske, 2013). Far north specimens were sent to the researchers to assist them with the identification.

There are other species of Pyura that are native to New Zealand, including the stalked Pyura pachydermatina - which is subtidal in cooler temperate waters and is known as 'sea tulip'. It looks quite different to the introduced Australian Pyura.

Impact

Pyura doppelgangera forms dense populations or mats, and can live in areas covering a wide geographical range. In its native Australia, it is found in Victoria, South Australia and Tasmania. In Chile, the visually similar and invasive Pyura praeputialis has become the dominant organism of the lower rocky shore in one region.

The overall impact of this Pyura species in the New Zealand environment is not known, however there is concern that, should it spread to a wide range of habitats and other areas, it could displace important native New Zealand species, including green shell mussels. There are also concerns Pyura could be inadvertently spread to marine farms outside the Northland region.

Pyura doppelgangera forms dense populations or mats, and can live in areas covering a wide geographical range. In its native Australia, it is found in Victoria, South Australia and Tasmania. In Chile, the visually similar and invasive Pyura praeputialis has become the dominant organism of the lower rocky shore in one region.

The overall impact of this Pyura species in the New Zealand environment is not known, however there is concern that, should it spread to a wide range of habitats and other areas, it could displace important native New Zealand species, including green shell mussels. There are also concerns Pyura could be inadvertently spread to marine farms outside the Northland region.

Ministry for Primary Industries (MPI) response

In October 2009 MAF Biosecurity New Zealand (now MPI), undertook a survey to scientifically assess the extent of the Northland Pyura population.

The organism was found at 21 locations in the far north and later, it was reported from a further 5 locations, as shown on the map above.

Investigations into managing Pyura

Field team working at entrance to Parengarenga Harbour
Field team working at entrance to Parengarenga Harbour (August 2010)

As a result of the 2009 survey, MPI determined that eradicating this well established sea squirt was not feasible. Due, however, to a high level of interest in the local community, MPI saw merit in attempting elimination of the species from some sites where population numbers were relatively low to see if clearing Pyura was a feasible approach to managing this invasive species.

MPI began a one year pilot treatment programme in August 2010. As part of the pilot, local people were engaged by MPI to work with a marine scientist clearing all visible Pyura from two locations - the Bluff at 90 Mile Beach and Whareana Bay on the eastern coast. The field team received training prior to starting the clearance work. The team made excellent progress clearing Pyura from these two sites.

As well as these two locations, a scientific reference site was established at the entrance to Parengarenga Harbour, where a large population of Pyura was found. Permanent quadrats were set up there - some of the quadrats had all visible Pyura removed from them and the others were left alone, for comparisons to be made in the future.

North Island map showing elimination sites at Whareana Bay and The Bluff, and a scientific control site at Parengarenga Harbour
Pyura pilot treatment sites

The Pyura elimination treatment trial field guide Link to PDF document (4936 KB)

In late March 2011, MPI returned to the study sites to evaluate the effectiveness of the clearance work. Members of the local community comprised the field team, as with the earlier field visits. The results gave MPI confidence that Pyura populations can be maintained at low densities at semi-isolated localities, such as the Bluff and Whareana Bay sites. By way of comparison, the results of the Parengarenga Harbour reference site suggested this population had increased in density over the previous six months, although the total area covered by Pyura had not changed and no new Pyura individuals were found in the quadrats that were cleared in 2010.

The final stage of the pilot treatment was carried out in August/September 2011.  Again, members of the local community were engaged as the field team.  In addition, MPI was supported by the Northland Regional Council and the Department of Conservation.  We found that the populations at the Bluff and Whareana Bay treatment sites had continued to decline to very small numbers.  However, Pyura numbers had substantially increased at the Parengarenga Harbour entrance reference site since March.  This was an important result because it showed measurable population decline at the sites where we were actively removing Pyura, compared with the scientific reference site where there was no active clearance of the population.

The results of the full pilot treatment programme can be viewed in the attached reports, which can be downloaded.

Report of the Stage One Pyura treatment trial Link to PDF document (4408 KB)

Report of the Stage Two Pyura treatment trial Link to PDF document (3801 KB)

Report of the Stage Three Pyura treatment trial and data analysis (full report) Link to PDF document (14114 KB)

Collaborating to manage Pyura in the far north

During 2012, members of the local community, Te Hiku o te Ika Fisheries Forum, Northland Regional Council, Department of Conservation and MPI collaborated to continue work at the three sites.  They found that Pyura continued to decline at the Bluff and no Pyura was found at Whareana Bay.  The Parengarenga Harbour entrance reference site proved to be very interesting.  Where, during the previous year, numbers had been increasing, the results in 2012 showed a massive retraction of the population to less than 1% of that recorded in 2011. Anecdotal reports suggest that a combination of frequent rough seas bringing fine sand ashore may have resulted in smothering the sea squirts and killing them.

Change in cover of Pyura at the Bluff, Whareana Bay and Parengarenga Harbour 2010 - 2012 Link to PDF document (249 KB)

Rius & Teske, 2013. “Cryptic diversity in coastal Australasia: a morphological and mitonuclear genetic analysis of habitat-forming sibling species.” Link to PDF document (1104 KB)

Pyura on rocks at Twilight Beach.
Pyura on rocks at Twilight Beach.
Note organisms squirt water when compressed.
Photo: Bruce Hayward

What can I do?

Pests such as Pyura can be spread from location to location on fouled vessel hulls, marine farming equipment and discarded shell hash. Please ensure you keep your moored boat’s hull clean and your antifoul coating in good condition.

Until more is known about Pyura and how much of a pest it is in New Zealand, MPI advises that it is not touched or squashed as this may further spread the population.  If people wish to assist with managing Pyura, we advise that it is carefully scraped from the rocks as whole animals (i.e. don’t chop it up as it may release young), secured in leak-proof plastic bags and taken on land where it should be buried. 

If you believe you have seen Pyura in any other location, please advise MPI on 0800 80 99 66.

Page last updated: 20 June 2014