A company at the heart of the black fish scam has claimed their participation left them millions of pounds out of pocket.
Shetland Catch Ltd has admitted processing illegal landings of mackerel and herring worth £47.5m at its Lerwick plant between January 2002 and March 2005.
The company now faces legal action at the High Court in Edinburgh to strip the company of any financial proceeds gained illegally.
At the start of the hearing on Tuesday, Lord Turnbull was told that the company is resisting the Crown's effort to confiscate around £6m.
Advocate depute Barry Divers said that the sum - a third of Shetland Catch Ltd's profits during the three years in question - was made through the illegal landings.
Defence solicitor David Burns QC agreed that the company made £6.157m through the black fish scam, but insisted his clients had paid tax on their illegal earnings.
The processing company also claims that once the fraud was uncovered, quotas were slashed in following years, plunging the company into debt totalling around £11m.
Annual profits of around £3m were turned into losses of more than £2m, the court heard.
A report by the company's accountants said: "The quota claw-back had a direct and inititally catastrophic effect."
Mr Burns also asked the court to take into account the thousands of pounds lost when the processing plant was closed for three days while it was being investigated, and the cost of restructuring the company because of its losses.
Shetland Catch Ltd will also be fined for its part in the black fish scam but this cannot be done until the court decides how much money will be confiscated.
Last December fishing boat skippers were told to hand over nearly £3m to settle confiscation demands in their own cases.
In February 17 skippers and a Peterhead-based fish processing company were fined a total of £1m for defying quota regulations.