Two Irish fishermen are accused of tampering with satellite transmitters so they could catch fish undetected in Cornish waters.
Trawlermen Mr Eric Murphy and Mr Donal O'Neill appeared in Truro Crown Court, Cornwall, charged with failure to maintain contact with fishing authorities while at sea in January.
Mr Sean Brunton, prosecuting on behalf of the English Department for the Environment, Food and Rural Affairs, said the two men deliberately tampered with transmitters on their vessels before they trawled for mackerel in a protected zone near Falmouth.
Under EU legislation it is compulsory for fishing vessels to have transmitters on board. They send an automatic hourly signal to fishing authorities with details of the vessel's location.
Mr Murphy, of Dunboy, Castletownbere, Co Cork, and Mr O'Neill, of Gour, Castletownbere, Co Cork, were also charged with falsifying official log sheets.
The court was told they did not declare the correct quantity of mackerel - a protected species - caught by the vessels Eilean Croineand Sparkling Starin waters off Falmouth.
The defendants pleaded not guilty to six charges.
PA