Rotting fish waste sparks toxic gas emergency aboard fishing vessel, report finds

Thursday, 23 July 2026

Four workers were hospitalised after a routine maintenance job aboard the Antarctic Discovery while the vessel was at Lyttelton Port on February 21, 2025.

Four workers were hospitalised after a routine maintenance job aboard a fishing vessel unleashed highly toxic gas when parts of rotten fish were accidentally pumped into a confined space, investigators have found.

The incident happened on the Antarctic Discovery while the vessel was in dry dock at Lyttelton on February 21, 2025.

According to a report released on Thursday by the Transport Accident Investigation Commission (TAIC), two apprentice fitters were working in the vessel’s bow thruster machinery space when contaminated seawater mixed with rotting fish offal suddenly began pouring down from an open hose suspended above the access ladder.

It is thought the incident occurred after a worker inadvertently pressed an unlabelled start button for the ship’s offal pump, pictured, which was covered in paint.

The report stated it was “about as likely as not” that one of the workers inadvertently pressed an unlabelled start button for the vessel’s offal pump while working immediately beside its control panel.

As the liquid poured into the confined space, hydrogen sulphide, a highly toxic gas produced as fish waste decomposes, rapidly accumulated.

The fitters escaped by climbing the ladder through the cascade of contaminated water before raising the alarm. However, the incident escalated when other workers attempted to investigate what had happened.

The vessel’s superintendent briefly entered the forecastle – the upper deck at the front of the ship – but was overcome by the gas and collapsed after retreating outside. Moments later, the chief engineer and second engineer entered from another access point and both collapsed inside the vessel.

Crew members wearing breathing apparatus rescued the chief engineer while the second engineer recovered enough consciousness to crawl clear. All affected workers, with the exception of the superintendent, were taken to Christchurch Hospital and later discharged after treatment for hydrogen sulphide exposure.

An illustration of how the apprentice fitters escaped from the bow thruster room by climbing through the flow of liquid.

TAIC acting chief investigator of accidents Tahlia Fisher said the immediate trigger was the accidental activation of the offal pump, but the investigation uncovered broader failures, with lessons extending well beyond the maritime industry.

“First, it’s essential that before work begins all machinery be made safe – and that includes not just the equipment being worked on, but also nearby systems that could create danger if activated.”

She said workplaces also needed to recognise and manage risks at any area with the characteristics of an enclosed or confined space, regardless of what it was called.

“In this case, the bow thruster machinery space had the hazards and characteristics of an enclosed or confined space but hadn’t been recognised and managed as one.”

The commission also highlighted the need for better coordination when multiple organisations share a work site.

TAIC acknowledged that vessel owner Australian Longline Pty Ltd had already taken extensive safety action following the accident but issued recommendations to both the company and Lyttelton Port Company aimed at improving management of safety-critical systems and dry dock operations.

“This accident demonstrates how routine maintenance in complex environments can escalate when overlapping responsibilities and weak procedural controls coincide,“ the report stated.