Article reprinted with permission from Oceanspace, formerly located at http://www.oceanspace.co.uk

Issue 150 Monday 28th June 1999
Seastars Invade Australia Waters

A marine invader has established itself in Australia, and is rapidly expanding its numbers and its range, Australian scientists report. The Pacific seastar, Asterias amurensis, poses a serious environmental threat to coastal centers from New South Wales to Western Australia, the scientists conclude.

The sea stars have enjoyed a major range expansion recently. First found in Tasmania in 1986, experts estimate that there are around 30 million in the Derwent Estuary today. The species has reached 12 million in the two years since first detected in Port Phillip Bay, across the Bass Strait in New South Wales. Early efforts to destroy the pest failed, and scientists concede that expansion of its range to South Australia and NSW seems inevitable.

The seastar almost certainly was brought to Victoria in the ballast water or on the hulls of domestic shipping or boating. In Australia, there are no management strategies in place right now to prevent the transport of seastar larvae in ballast water. New Zealand - which does not yet have the seastar and has designated it an undesirable pest - has banned the discharge of ballast water from ships coming from Tasmania and Port Phillip Bay. Restrictions on ships from other areas along the Victorian coast seem likely in the near future.

"No single method offers us any prospect of control of the seastar in Australian waters at this stage of investigation," says Dr. Louise Goggin, a scientist at the CSIRO Centre for Research on Introduced Marine Pests, who has done extensive work on both the Pacific seastars and introduced pests. CSIRO is Australia's primary agency for scientific research. "Genetic methods are the only technique that could in theory eradicate the northern Pacific seastar with little or no risk to native seastars. However, these methods, which would be state of the art, would take up to five or more years to develop."

Scientists believe that biological control is probably the only realistic long-term means of controlling the seastar's numbers around the Australian coast. Goggin has been working overseas for several years searching for possible natural parasites or diseases for the seastar.

One parasite in particular, a ciliate called Orchitophrya, that invades and destroys the seastar's gonads, looks promising, but still needs to be rigorously tested for safety and effectiveness, says Goggin.

"To be useful, any control method must have little or no impact on our native animals, has to be practical and, ultimately, it has to be socially and politically acceptable," Goggin says.