Irish fishermen joined French, British and Danish colleagues in a blockade of European ports in protest at an EU decision to cut quotas for badly depleted fish stocks.
The French ports of Boulogne-sur-Mer, Calais and Dunkirk were blockaded by dozens of trawlers, halting ferry services between Britain and France and all other commercial vessels trying to enter or leave the harbours.
The Belgian ports of Ostend and Zeebrugge were also to be hemmed in by local fishermen.
The protesters said the blockades would stay in place until 3 p.m. Irish time
The fishermen were protesting moves by the European Commission to cut quotas for cod, whiting and sole by up to 80 per cent.
A delegate of France's CFTC fishermen's union, Mr Jacques Bigot, said in Boulogne-sur-Mer that the protest was a loud shot across the European Commission's bows.
"It's a success, there is an incredible amount of chaos. Cargo ships are slowing right down, some are even getting in the wrong shipping lane," he said as he met counterparts from Belgium, Britain, Denmark and Ireland to plot their next moves.
In the Dáil, the Taoiseach Mr Ahern said the Government was in contact with the European Commission about the quota cuts.