Approximately 2,000 of the escaped fish have been recaptured.
Norwegian salmon producing giant Lerøy is missing 15,000 rainbow trout, General Manager Morten E. Fjaereide told local newspaper Marsteinen.
Workers at Lerøy discovered a large hole in a net at their Naveide site on August 31, after reports of steelhead being caught across four Norwegian municipalities.
As of September 11, approximately 2,000 of the escaped fish have been recaptured. The cause of the net breach remains unknown.
The Norwegian Directorate of Fisheries has initiated an inspection is encouraging the public to report any catches, while Lerøy is offering a NOK 250 ($25) reward per recaptured fish.