Udo Engelhardt, director of consultancy Reefcare International, claims his analyses of the crown-of-thorns (COTS) controls for 2013-15 demonstrated the "widespread and consistent failure" to protect coral cover.

This information was provided to the Reef & Rainforest Research Centre, which oversees the program contracted to the Association of Marine Park Tourism Operators (AMPTO). It is also under the oversight of the Great Barrier Reef Marine Park Authority.

But almost two years on, neither the report not photographs had been made public "despite the fact that both components were paid for using government funds", Dr Engelhardt said.

Dr Engelhardt is a former coordinator of the COTS program at the authority. He said the current $14.4 million program to cull the starfish should cease "immediately", including the tendering of a third vessel, until a comprehensive, independent review of recent operations had been completed.

"Since the start of current operations back in 2013, virtually none of the reef sites visited by the roving, vessel-based operations have received the recommended weekly visitation rate for COTS controls," he said.

Instead, site visits were typically separated by several weeks or even months, so infrequent as to virtually guarantee their failure to control numbers, he said.

Fairfax Media sought comment from the Reef & Rainforest Research Centre.

Post-bleaching

The latest outbreak of the starfish began in 2009 and has added to the woes facing the Great Barrier Reef.

The unprecedented back-to-back mass coral bleaching in the past two summer has led as much as half the corals on the reef dying, scientists say.

Col McKenzie, executive director of AMPTO, said the program had targeted starfish in about 70 key locations, particularly in a stretch from Lizard Island down to south of Cairns.

"The program was designed to protect key tourist sites," Mr McKenzie said. "It has achieved those objectives.

"After [the coral] bleaching, the best thing we can do is to prevent those starfish from eating the corals that have proved to be resilient."

'One at a time'

Jon Brodie, a professorial fellow with the ARC Centre of Excellence for Coral Reef Studies at James Cook University, said Dr Engelhardt's findings should be made public and the program formally reviewed.

"We've suspected for a long time there's no hope we can control the population level of the crown-of-thorns starfish by killing them one at a time," he said.

"We did believe them we could control them at small tourist sites...but it doesn't look like it works at that scale either," Dr Brodie said.

The Marine Park Authority referred questions to Josh Frydenberg, the federal environment and energy minister.

"Managing the crown-of-thorns starfish is a significant challenge given the Great Barrier Reef covers an area larger than the size of Italy," Mr Frydenberg said, adding that "solid progress" had been made in tackling the natural predator with more than 500,000 of the starfish killed by divers.

"Concerns around the length of time between control visits and a focus on a large number of reefs have been addressed since they were raised in 2015," he said.

Nutrient link

Dr Brodie said the current starfish outbreak was the fourth since 1962, with events beginning at about 16-year intervals, and each lasting about a decade.

While warming waters from climate change appear to foster their proliferation, research suggests nitrogen-rich run-off from wet tropics sugar cane farms that began in the late 1950s is the main cause of their waves of expansion, he said,

"The real solutions are being ignored, especially by the federal government," Dr Brodie said. "These are reducing emissions - the obvious one, and also managing water quality better."

State view

A spokesperson for Queensland's Department of Environment and Science said the government is "is concerned about crown-of-thorns starfish outbreaks, and other threatening processes affecting the Great Barrier Reef, particularly following successive years of mass coral bleaching".

During 2017, the Queensland Parks and Wildlife Service's Field Management Program was involved in efforts to maintain and promote live coral cover including the lethal injection of 14,460 COTS on Gator Reef in the southern Great Barrier Reef.

During the final four months of last year, the state's program undertook 2,955 manta tows covering 605 kilometres, and 675 Reef Health Impact Surveys.

Of 61 target locations surveyed for COTS, 50 were identified as having populations above outbreak threshold levels, the spokesperson said.

Starting Wednesday evening, QPWS and volunteer divers were beginning ten days at Swain Reef conducting both surveillance and control of the starfish, with the ship provided at no cost by a tourist operator.