Harmful Kelp Found In The Bay
The Age
Wednesday July 28, 1999
A noxious Japanese seaweed discovered near St Kilda Pier has sparked a search-and-destroy mission around the north-eastern rim of Port Phillip Bay.
Marine authorities have removed what they hope was an isolated outbreak of the seaweed, Undaria pinnatifida, but divers will begin searching north to Station Pier and south towards Brighton today.
The outbreak is the first reported outside an area close to Point Wilson where the seaweed was discovered in July 1996. The area, now infested with hundreds of thousands of plants, was quarantined until last year in the hope of containing the spread.
The ban on fishing or anchoring lapsed in the face of enforcement difficulties. Two commercial licences have since been issued to harvest the seaweed, which is used in Japanese cooking.
Undaria pinnatifida, one of the top 10 introduced marine pests in Australia, is known as the blackberry of the sea. It was found in Tasmanian waters in 1988 but the Port Phillip infestation is thought to have arrived through shipping from New Zealand or north-east Asia. The plant grows to about two metres tall during winter and then dies back completely in summer. It releases spores when disturbed, making removal difficult. It spreads rapidly and crowds out other species. It favors hard surfaces such as reefs, piers, hulls - even shellfish and blades of seagrass, which is essential habitat as a fish nursery.
An Environment Protection Authority marine scientist, Dr Stuart Campbell, said the muddy green undaria tended to take over disturbed habitats but so little was known about it in southern waters that its ecological implications were uncertain. ``But it really just changes the whole balance of the community it invades and displaces native flora and fauna - and that can't be good," he said.
The St Kilda outbreak was reported by a commercial fisherman in late June. Mr Mark Winfield, the Department of Natural Resources and Environment's flora, fauna and fish coordinator for Melbourne, said it was unlikely currents would have carried spores so far from Point Wilson.
``Our only thought was that a recreational fisher might have dropped anchor at Point Wilson, pulled it up and then it dropped off there (in St Kilda)," Mr Winfield said. About 200 plants had been pulled out.
Mr Winfield said divers from the Marine and Freshwater Research Institute were reasonably confident they had removed all the plants but would continue to check. The department would also enlist diving clubs to search south towards Brighton reef.
``If we find it at other sites, it would probably indicate we are unable to do anything about it at this time but we have our fingers crossed it is just a local infestation at this stage, and it can be eradicated over the next few months," Mr Winfield said.
* CSIRO scientists are investigating whether there is a link between water quality in Tasmania's Derwent River and the takeover of its estuary by 30 million Pacific sea stars, a prolific marine pest. They believe water and sediment pollution may be killing predators, allowing the sea star population to explode.
Beasties in the bay
* North Pacific seastar, Asterias amurenesis, voracious feeder on shellfish. Estimated population in the bay of 12 million.
* Pacific oyster, Crassostrea gigas,
escaped after an unsuccessful attempt to establish an oyster industry.
* Japanese kelp, Undaria pinnatifida,
found near St Kilda pier last month. First found near Pt Wilson, July 1996
* European shore crab, Carcinus maenus, possibly the first introduced species. Detected in 1856.
* European fan worm, Sabella spallanzanii, from the Mediterranean. Spread rapidly since the early 1990s.
© 1999 The Age
Share This