Six fishing boat skippers have admitted participating in a scam to cheat European quotas to the tune of more than £15m.
Scottish courts have been hearing how tonnes of so-called 'black fish' were landed in Shetland ports to get around stringent limits laid down by the European Union to protect fish stocks.
Fish processing company Shetland Catch - the largest firm of its kind in Scotland - has also admitted helping to give the skippers false information.
A total of 14 fishing boat skippers have so far appeared in court in connection admitting their involvement in illegal herring and mackerel catches worth more than £37m.
In the latest case, brought at the High Court in Edinburgh on Monday, advocate-depute Peter Ferguson QC said one master had netted £5.6 million worth of 'black fish' - the highest individual figure to be admitted so far.
The scam came to light when Shetland Catch was raided in September 2005 after protection officers became suspicious that widespread illegal landings of mackerel and herring were taking place.
Accountants were brought in to examine the books of the eight processing factories in Scotland and discovered that the figures did not add up for Shetland Catch, Mr Ferguson said.
Fishermen and their agents have to submit log books, sales notes and landing declarations for scrutiny by the Scottish Fisheries Protection Agency (now called Marine Scotland - Compliance), who are responsible for enforcing quotas agreed between European Union states.
In the dock today were Laurence Irvine, 64, of Aviemore, Symbister, Whalsay; Gary Williamson, 51, of Norvag, Symbister, Whalsay; William Williamson, 63, of Westerlea, Symbister, Whalsay; George Henry, 59, of Noonsbrough, Clousta, Bixta; John Stewart, 55, of 57 King Harald Street, Lerwick, and Colin Leask, 37, of Vaarhjem; Simbister, Whalsay.
All six men admitted breaches of the Sea Fishing (Enforcement of Community Control Measures) (Scotland) Order 2000 and the Fisheries Act 1981, between January 2002 and March 2005.
Irvine, master of the Antares made 77 landings between October 2002 and February 2005 which included false declarations totalling more than £5.6m, more than a third of the fish he landed.
The case is due back in court in February when lawyers will report on progress they have made in trying to calculate the illegal profits made by the fishermen.
All those involved face an unlimited fine but they cannot be jailed for the offences.