A number of businesses and boats in Donegal, Galway, Cork and Kerry have been searched by gardaí investigating alleged irregularities in the Irish fishing industry.
Fishing vessels, fishing agents, co-ops, company offices and private premises were all targeted in the operation by the National Bureau of Criminal Investigation and the Bureau of Fraud Investigation.
Gardaí seized documentation during the operation and an incident room has been set up in Killybegs Garda station.
There were no arrests.
Several hundred gardaí were involved in the raids.
The raids follow allegations that fishermen in Killbegs have been fraudulently recordeding fish catches for years.
The claims, made by a Killybegs fisherman, Mr Pat Cannon, alleges that fishermen in the State's biggest fishing port have falsified logbooks, under-reported catches and ignored quotas and closed fishing areas.