Six Shetland fishermen have admitted illegal landings of thousands of tonnes of "black fish" worth more than £14m.
David Hutchison, Robert Polson, Thomas Eunson, Allen Anderson, John Irvine and Allister Irvine admitted the offences at the High Court in Glasgow.
Shetland Catch Ltd admitted helping the men give false information about catches landed by three boats.
The Scottish Fisheries Protection Agency discovered the crimes in 2005. Sentence was deferred until November.
Advocate depute Peter Ferguson QC, prosecuting, told the court: "The criminal conduct being prosecuted here is the making of false declarations by individual skippers."
Speaking after the hearing, Scott Pattison, the director of operations at the Crown Office, said: "This prosecution is part of an extensive and complex investigation.
"The legislation is to protect the marine environment for the good of all and to safeguard the fishing industry.
"We will continue working with police and other agencies to prosecute those individuals or organisations who disregard it for their personal gain."