Hopes are fading for a sailor missing at sea for more than 24 hours off the Otago coast.

The search is on hold for the man, who is presumed to have fallen overboard from bulk carrier vessel the Berge Rishiri.

The ship was scheduled to have left Bluff at 1am Saturday, according to South Port’s shipping schedule.

A Maritime New Zealand spokesperson said the Chinese national was last seen at 8am on Saturday when he finished his shift, and failed to report for duty at 4pm, prompting Maritime New Zealand’s Rescue Co-ordination Centre (RCCNZ) to be alerted.

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The crew searched the vessel, the ship returned along its route to look for him, and a helicopter and nearby vessel extensively searched along the Otago coast.

“A cold-water survivability expert engaged by RCCNZ believes there is little chance the person would have survived,” the spokesperson said on Sunday evening.

All “search assets” had been stood down, pending a search review and assessment.

“Our thoughts are with the family of the missing person. Broadcasts continue to shipping in the area, requesting all vessels maintain a sharp lookout.”

The loss of the crew member “is very concerning”, said Maritime Union New Zealand (MUNZ).

“We would like to know how long the seafarer had been at sea and on duty, and have assurances they were not kept on the vessel longer than their contracted period,” said national secretary Craig Harrison.

“We have seen huge mental health issues with seafarers basically kept captive on vessels for months and sometimes years.”

Harrison is calling on Maritime New Zealand to investigate whether the crew were having adequate rest breaks.

“These crew members are in New Zealand waters, their work is essential for New Zealand, and in our view their rights and welfare are often overlooked.”

Berge Rishiri is a 180m bulk carrier registered and sailing under the flag of the Isle of Man.

Napier Port schedules the vessel to arrive at 6pm on Monday, carrying logs from Bluff. It was then destined for Marsden Point in Northland.