Loughs Agency has confirmed an illegal fishing net was recently seized on the River Foyle near Lifford.
Fishery Officers were alerted by a member of the public through the WaterWatch app and arrived at the scene within 15 minutes.
Four Atlantic salmon were found in the net. Two were returned to the river unharmed, while two could not be saved.
Loughs Agency is urging anyone who witnesses or suspects illegal fishing to report it through the WaterWatch app or its confidential 24-hour hotline.
It says information from the public is vital in helping officers prevent and deter illegal fishing and protect salmon stocks.
