The share prices of leading Norwegian salmon farmers fell sharply on Thursday after results of a preliminary investigation into breaches of antitrust rules sent alarm bells ringing with the companies facing the prospect of fines running into the hundreds of millions of euros.

On Thursday, the European Commission told Mitsubishi-owned Cermaq, Grieg Seafood, Bremnes, Leroy Seafood Group, Mowi and SalMar that they breached EU antitrust rules by colluding to distort competition in the market for spot sales of Norwegian farmed Atlantic salmon in the EU, according to the probe's preliminary findings.