Fishing company Talley's has been fined $73,520 and ordered to pay $21,000 in reparations to the family of a crewman decapitated by a faulty rope.
Leighton Muir, 24, was killed in 2014 when the rope, which had snapped three weeks earlier, broke and whipped back while a net full of tuna was being hauled in Kiribati's exclusive economic zone.
Talley's pleaded guilty to a charge of failing to take all practicable steps to ensure the safety of its employees while at work.
Maritime New Zealand compliance manager Harry Hawthorne said a knot had been used to join the rope, even though there was a replacement rope onboard.
When the 50mm-thick safety rope broke a second time, it killed Mr Muir.
"Clearly not replacing the rope was one of the aspects we took into account in considering prosecution," Mr Hawthorne said.
"Our view was that the rope should have been replaced, and since the incident we've been working with Talley's to ensure that rope management is improved."
The deep sea fishing industry did not have to be dangerous, if there were good safety management schemes in place, he said.
In 2012, another crew member died on the same vessel, the Captain MJ Souza, after falling nearly 7m through an open hatch on the deck.
In a statement, Talley's general manager Tony Hazlett said Mr Muir's death was caused by "catastrophic gear failure" and a failure by two senior officers to ensure rigging safety.
An independent expert found the rope had a latent defect that meant it was half as strong as certified, he said.
"Despite the gear failure and that unknown defect, the standard of conduct by two senior officers on the board the MJ Souza that trip were below the standards required."
Mr Hazlett said the rope was not rigged safely by the bosun, and the captain failed to check on it.
He said neither of the two officers had worked for the company since Mr Muir's death, and both had refused to return to New Zealand to cooperate with the investigation.
He acknowledged that Talley's was legally liable for the officers' failings, but said the company was also looking at what it could do to hold them personally to account.
"Leighton was a well-respected fisherman highly regarded by his fellow crewmen and colleagues. He remains deeply missed by all today and our thoughts remain with the Muir family for his tragic loss."