Styela sea squirt response: update
Styela clava
As part of the Styela clava response, Biosecurity New Zealand (BNZ) is running a range of research projects aimed at understanding how the organism operates in the local environment, and how it could be managed here. This research will ultimately inform the longer term management plan for Styela. The long-term management strategy for this marine pest will ultimately involve consultation with the wider group of industries and stakeholders affected by Styela.
Potential Styela presence in Wellington
BNZ is currently investigating the possibility of the spread of Styela into Wellington Harbour. A heavily fouled yacht was moored in the Port Nicholson Marina for more than six months; the fouling included mature specimens of Styela. The vessel was removed from the water and thoroughly cleaned.
With the proximity of the high-value Marlborough Sounds and Nelson areas, this discovery is a concern. BNZ is organising an inspection of the marina around where the yacht was moored, to check for Styela.
The vessel apparently began its journey in Auckland, before heading to Wellington via a couple of months' lay-up in Napier.
Communications
Work is currently underway on new information resources for marine users, again stressing the importance of vessel hull cleaning. The objective will be to help prevent the further spread of Styela and other marine pests. Development of the new resource involves some research into the boating habits of both recreational and commercial users.
Population management trials
Field surveys for Styela clava (using both above water and diver searches) have been completed at Lyttelton Port and Marina and Tutukaka Marina. Styela was found at all three locations, but in highly contrasting densities. The population within Tutukaka has remained low, while the populations in Lyttelton appear to have increased considerably since the last survey in 2005. The survey results are currently being analysed and databases searched for patterns of vessel movement.
High-value areas of concern to each of the three survey locations have been successfully identified and efforts are now focusing on identifying potential management strategies to protect the high-value areas.
Assessment of reproductive activity
Research on the reproductive biology of Styela clava is continuing in Auckland. To date, results suggest Styela has two or three periods of high reproductive potential throughout the year, mainly through spring, summer and autumn. However, no larvae or young recruits have been detected in the water column or on settlement plates in the sampling areas, despite the presence of reproductively active adults in the vicinity. Sampling and analysis of results is ongoing.
Genetic diversity of Styela in New Zealand
An analysis of the genetic lineages in Styela populations in New Zealand is underway. Results will be compared with samples from overseas, with a view to determining possible pathways by which Styela may have arrived here. Early results suggest multiple introductions, with North and South Island populations showing slightly different genetic patterns. Samples from a number of additional locations have recently been collected, mainly from the North Island, with emphasis on the Hauraki Gulf.
- Lesley Patston, Senior Communications Adviser, Biosecurity New Zealand, phone (04) 894 0163, (029) 894 0163, lesley.patston@maf.govt.nz
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Page last updated: 30 April 2008