Gloria Davis, the sole director of AZ1 Enterprises, was facing the charges after the fishing boat, skippered by her husband Rewai Karetai, 47, sank off Stewart Island in March 2012, killing all but one person aboard.
It was New Zealand’s deadliest maritime disaster since the sinking of the Wahine in 1968 when 51 people lost their lives.
She was found guilty of operating the Easy Rider knowing her husband did not have the appropriate skipper’s certificate, that she caused or permitted the Easy Rider to be operated in a dangerous manner, and that she failed to take all practicable steps to ensure that no contractor or subcontractor was harmed on board the boat.
AZ1 Enterprises was found guilty of the same charges.
Judge John Strettell issued his reserved decision on Wednesday after a trial in January. A sentencing date has yet to be set.
Maritime New Zealand, which brought the prosecution after acknowledging Ms Davis had lost her husband, said the verdict should serve as a warning to those operating in the fishing industry.
“It was very important that action was taken that reflected the extent of harm – the loss of eight lives – and the very real responsibilities of those operating in the maritime sector,” director Keith Manch said.
The sole survivor of the muttonbirding trip, crew member Dallas Reedy, was rescued after clinging to a petrol can for 18 hours.
Mr Karetai, Boe Taikawa Gillies, 28, John Henry Karetai, 58, Peter Glen Pekamu-Bloxham, 53, Shane Ronald Topi, 29, Paul Jason Fowler-Karetai, 40, David George Fowler, 50 and seven-year-old Odin Karetai died.
Accident investigators said the 12-metre boat was badly overloaded when it was struck by a large wave.
Mr Karetai did not have the required maritime qualification to be in charge and his deckhand certificate did not cover the fundamentals of stability.
The boat was also illegally carrying six passengers when it was operating as a commercial fishing vessel, investigators said.