Interfish employee Tomas Suchy was helping to clear up a fallen stack of frozen fish boxes in one of the cold store areas when another stack of stock fell on top of him.
He received multiple and severe injuries which proved fatal.
An investigation by the Health and Safety Executive (HSE) on October 18 2013 found there was no safe system of work or instruction to staff on how pallets should be stored.
The HSE also found there was no written procedure for dealing with falls of stock when they occurred.
The company – based at Wallsend Industrial Estate in Plymouth – pleaded guilty to breaching Section 2(1) of the Health and Safety at Work etc Act 1974 at Plymouth Crown Court.
It was fined £500,000 and ordered to pay costs of £24,800.
HSE inspector Emma O’Hara said after the hearing: “Safe stacking of stock is a cross-industry necessity and can often be overlooked when considering safe systems of work.
“Duty holders need to ensure that they are stacking safely and that they have a plan for dealing with any unforeseen circumstances such as a fall of stock.”
A statement from Interfish said: “Interfish has a good health and safety record, with no previous convictions and has fully co-operated throughout the HSE investigation.
“Interfish regrets the tragic events that occurred and has improved its cold store procedures in light of the accident. The HSE confirmed that the Interfish’s response to the accident had exceeded expectations.
“Interfish respects the decision of the court and will continue to use its best efforts to make sure that the business maintains the highest possible standards.”
Meanwhile, food waste disposal and recycling firm John Pointon and Sons was ordered to pay nearly £290,000 on June 10 for safety failings, after an HSE investigation found three employees were overcome by toxic gases.