Illegal fishing netting measuring the length of six Olympic swimming pools were discovered on Lough Swilly in recent days.
The netting was found by officers from Inland Fisheries Ireland (IFI) while on sea patrol on Sunday.
The two nets, used to poach salmon, measured 200 metres and 100 metres in length.
The illegal nets, which were set from buoys, were found in the inlet at Leenan Bay.
The IFI said the seizure was made as part of ongoing surveillance off the Donegal coast.
Dr. Milton Matthews, IFI’s North Western River Basin Director, said: “IFI have noted an increase in illegal fishing activity in recent weeks associated with improved runs of wild Atlantic salmon this summer.“IFI Fisheries Officers remain committed to the safeguarding of Atlantic salmon returning to their rivers of origin to spawn.
“Any person engaged in illegal fishing activity is liable to prosecution, fines and possible conviction.
“Protection of wild Atlantic salmon stocks remains of vital importance in terms of conservation and restoration of this iconic species, so that future generations can experience and enjoy this marvel of nature.”
The IFI said it continues to urge the public to report illegal fishing activity, habitat destruction, water pollution, fish kills, or other issues of concern in their local rivers/lakes, to its confidential 24/7 number, 0818 34 74 24.