Picton survey for clubbed tunicate (Sea Squirt)
Scientists from NIWA will be diving in Waikawa Marina, near Picton, on Friday 14 October to check for the presence of an invasive sea squirt, known as the clubbed tunicate (or Styela clava). The work is being conducted for Biosecurity New Zealand so that they can assess the need for further investigation.
The aim is to determine the distribution of the sea squirt in Waikawa Marina, where it was provisionally identified on a boat recently arrived from Auckland. The survey team from NIWA will use scuba searches for the sea squirt, allowing the team to sample a variety of habitats quickly. A further survey will search the wider Picton Harbour.
About the clubbed tunicate
The clubbed tunicate is a fast-growing organism, which filters suspended plankton and organic materials from the water. It can grow up to 160 millimetres long and reach densities of up to 500-1500 individuals per square metre.
It is thought to be native to the coastal waters of Japan, Korea, Northern China, and Siberia, and is known to have spread to parts of northwestern Europe, USA, and Australia. While it mostly occurs in shallow water, the clubbed tunicate can live in water as deep as 25 metres.
It competes for space and food with native and aquaculture species. It can also be a nuisance by fouling marine farming lines, vessel hulls, and other structures.
It is also known as the Asian sea squirt, leathery sea squirt, or Pacific rough sea squirt.
Invasive Sea Squirt (Styela clava) Fact Sheet
Background on the clubbed tunicate is also available at: crimp.marine.csiro.au/nimpis