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  news.com.au 18 Jun 07
Jellyfish taking over the seas
Brian Williams

A JELLYFISH plague is threatening shipping and fishing worldwide.

Scientists believe depleted fish stocks have removed competition for jellyfish, allowing them to breed to plague proportions.

Jellyfish blooms – where the creatures multiply rapidly into untold millions – clog water intakes on ships and power stations, ruin fishing nets and can wreck engines.

Kylie Pitt, from the Griffith University School of Environment, said Japan was experiencing plagues of the giant jellyfish nemopilema. "At more than a metre wide and up to 200kg, they become caught in fishing gear and damage boat engines and mechanical equipment," Dr Pitt said.

The Port of Brisbane was experiencing blooms of catostylus or blue blubber jellyfish. In 2004, thousands of blue blubbers stopped the P&O cruise ship Pacific Sky from sailing from Brisbane after they were sucked into a water intake.

A jellyfish bloom also shut down a coastal power station in Manila in the Philippines in 2000.

A survey of Lake Illawarra, near Wollongong in NSW, found it contained 18,000 tonnes of blue blubbers.

The Moreton Bay Seafood Industry Association also had reported problems with jellyfish clogging Brisbane River trawler nets. "At times they are in absolutely enormous quantities," Dr Pitt said.

Port of Brisbane Authority environment manager Brad Kitchen said blooms were not a major issue for the port.

"It's mainly just the ships with bow thrusters (used to turn ships) that have to be careful," Mr Kitchen said. "Bow thrusters can get clogged."

Although Australia did not yet have the feared nemopilema blooms, jellyfish could spread quickly world-wide through ballast water.

Mr Kitchen said in an effort to avoid exotic species being transported to Brisbane, all ships entering the port were obliged to dump ballast and take on deep sea water off the continental shelf before entering Moreton Bay.
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