A Queensland inquest into the deaths of two fishermen on a trawler that sank in rough seas has heard a common screw breaking could have caused the tragedy.

March 20, 2019

A simple turnbuckle breaking under load in heavy seas could have caused the deaths of two Queensland men who disappeared when their converted prawn trawler sank three years ago.

The bodies of skipper Matt Roberts, 61, and crewman David Chivers, 36, have never been found and an inquest in Gladstone is investigating their deaths when FV Cassandra sank on April 4, 2016.

It heard on Wednesday a common turnbuckle, which connects the boat’s heavy seven-metre boom arm and net via chain to its hull, is thought to have straightened in the rough seas off Fraser Island.

It would have caused the boat to roll violently as massive, heavy prawn nets were suddenly released from the port side of the vessel.

Expert witness Barry Ehrke, who was commissioned by Maritime Safety Queensland to report on the sinking, says video of the boat 47 metres below the surface shows there had been a net “hook-up” on the ocean floor before the vessel capsized.

“The bridles (60-metre wire) were on the winches and from there on, something has let go,” he told the inquest.

“The hook-up would have let go.”

The inquest is exploring whether the vessel was structurally sound if there was adequate safety equipment on board and if the search and rescue operation was sufficient.

Huge swells prevented rescuers reaching the stricken vessel, which is believed to have rolled after one its nets snagged on rocks or reef on the sea bottom in the early hours.

Earlier, Mr Ehrke said the vessel should not have been in the notoriously rough stretch of ocean 10 kilometres off Waddy Point.

“In that area, there’s a lot of currents and there are numerous hook-ups on obstacles on the bottom,” he said.

Southeast winds smash into southerly tides and make the water’s surface “disturbed”.

In those conditions, the Cassandra’s “quad” net set-up, which hung from the end of its seven-metre boom arms, was too unstable, the retired fishing boat owner and industry advocate said.

The inquest has heard it’s likely the two fishermen were in the wheelhouse as it rolled.

Despite this, the vessel’s two emergency radio beacons also weren’t activated.

The video shows almost all the boat’s safety gear had failed, counsel assisting the coroner John Aberdeen said.

The boat’s former manager Dennis Markwell has painted a bleak picture of the prawn trawling operation onboard the boat.

He had welded shut an emergency exit and contracted an unqualified boatbuilder to refit the fishing boat as a four-net prawn trawler, without discussing the potential ramifications of the massive top-heavy weight.

The boat’s owner, Paddockmist Pty Ltd, had no knowledge about the safety requirements and didn’t provide its crew with safety training, the inquest heard.

The vessel’s safety management system lacked key information for dealing with net “hook-ups” despite being ordered to have it by the Maritime Safety Queensland.

The inquest continues.