Pyura

Pyura stolonifera praeputialis

Pyura (known in its native Australia as Cunjevoi)

Pest and disease search

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, Twilight Beach
Photo: Bruce Hayward

Description

Pyura (known in its native Australia as Cunjevoi) is a marine animal known as 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 individual has two siphons or holes for inhaling and exhaling water. Adults grow to about 15 cm or more in height and around 3 - 5 cms in diameter.

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

Habitat - where Pyura is found

Pyura can be found in rocky intertidal areas and in the shallows growing on rocky surfaces.

In New Zealand populations have been identified in Northland on Twilight and Te Werahi beaches near Cape Reinga; around the Bluff on Ninety Mile Beach and the Tauroa Peninsula; at Whareana Bay, and in Parengarenga Harbour. Recently, it has been found north of the Hokianga Harbour at Mitimiti, in the Houhora Harbour and at Rangiputa. It is also present in Chile.

There are other species of Pyura and stalked sea squirts that are native to New Zealand - e. g. Pyura pachydermatina - which is subtidal in cooler temperate waters and is known as 'sea tulip'.

Impact

The species forms dense populations or mats, and can survive in a wide geographical range. In its native Australia, it occurs from southern Queensland to Western Australia and Tasmania. In Chile, it has become the dominant organism of the lower rocky shore in one area.

Its likely impact in the New Zealand environment is not known, but as it is appears to have aggressively covered the shore in Chile, there is concern that should it spread, 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 far north region.

MAF Biosecurity New Zealand response

In October 2009 MAFBNZ undertook a delimiting survey to scientifically assess the extent of the Northland Pyura population.

The organism was identified at 21 locations in the Far North as shown on the map below.

Pyura Location Map

*Since the survey, Pyura has been reported from 4 new locations.

As a result of the delimiting, MAFBNZ determined that fully eradicating this well established sea squirt was not feasible. Due, however, to a high level of interest in the local community, MAF saw merit in trying to remove the species from some sites where population numbers were relatively low.

In August 2010 a four day pilot treatment programme was undertaken at a couple of sites to gauge whether attempts to manage Pyura at other sites where numbers are low is worthwhile.

As part of the four day pilot, local people worked with a marine scientist engaged by MAF to clear all visible Pyura from two locations - the Bluff at 90 Mile Beach and Whareana Bay. Excellent progress was made at these two sites, but at the end of the work programme, a further large area of the sea squirt was found at the Bluff site. MAFBNZ returned at the beginning of September to attempt clearance of all remaining Pyura and was able to clear most of the accessible areas.

As well as these two locations, an experimental trial was undertaken treating a population at the entrance to Parengarenga Harbour. One marked area had all visible specimens removed, and a further marked area was left alone so results can be compared in future.

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

Full report of the Stage One Pyura treatment trial (4408 KB)

Report of the Stage Two Pyura treatment trial (3801 KB)

• Pyura pilot treatment sites (2451 KB)
• Parengarenga Harbour Pyura Scientific Control Site (966 KB)
• Whareana Bay Pyura Elimination Site (958 KB)
• The Bluff Pyura Elimination Site (1231 KB)

The Pyura elimination treatment trial field guide (1002 KB)

In late March 2011, MAF returned to the treated sites for further removal of Pyura and evaluation of the effectiveness of the treatment. Members of the local community comprised the field team, as with the pilot treatment last year. The preliminary results suggest it may be feasible to maintain Pyura populations at low densities at semi-isolated localities, such as the Bluff and Whareana Bay sites. The results of the treatment at the Parengarenga Harbour site suggest this population has increased in density over the last six months, although the total area covered by Pyura has not changed and no new Pyura individuals appear to have grown in the marked areas that were cleared last year.

The results of Stages One and Two can be viewed in the attached reports, which can be downloaded.

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 boat hulls. 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, MAFBNZ advises that it is not touched or moved as this may further spread the population.

If you believe you have seen Pyura in any other location, please advise MAF Biosecurity New Zealand on 0800 80 99 66.

Page last updated: 27 June 2011