Crown-of-thorns starfish on wane at Great Barrier Reef

Drew Cratchley, Courier Mail news.com 18 Jun 08;

THE potentially devastating crown-of-thorns starfish is in retreat on the Great Barrier Reef, with its numbers hitting a 20-year low, researchers say.

Findings from the Australian Institute of Marine Science released Tuesday, June 17, indicate the latest outbreak of the coral-eating pest is near an end.

Surveys of the Reef in 2007 detected fewer crown-of-thorns starfish than in any year in the past two decades, the head of AIMS' long-term monitoring program, Hugh Sweatman, said.

"There were outbreaks on 6 per cent of the 104 reefs surveyed in 2006, and on just 4 per cent of the reefs we surveyed in 2007," he said.

"Historically, the numbers of the starfish have increased drastically every 15 years, and in 2000 up to 17 per cent of the reef was afflicted."

However, the crown-of-thorns starfish remains a "mysterious phenomenon", according to AIMS, and it is not known when the next outbreak could begin.

AIMS researchers have also detected a fall in coral cover on outer sections of the Reef due to coral diseases, particularly a disease known as white syndrome.

The cause of the disease was unknown but it killed off massive areas of coral on previously healthy reefs, Dr Sweatman said.

"The disease is found particularly where hard coral cover is high," he said.

"What we see is that the healthy reefs with lots of coral cover are the ones at risk."

Seven reefs in the Capricorn-Bunker sector and six in the Swain sector of the Great Barrier Reef were surveyed.

No crown-of-thorns starfish were recorded on Swain reefs but scuba surveys found the starfish for the first time at Fairfax Reef in the Capricorn-Bunker group.