The Sea-Fisheries Protection Authority (SFPA) has issued a warning about the catching of Bluefin tuna following the landing of the protected species in Donegal.
The SFPA issued the warning after a privately owned pleasure boat on its arrival at Teelin pier was found by SFPA officers to have Bluefin tuna on board.
Those on board the boat were questioned and a file is being prepared for submission to the Director of Public Prosecutions.
It is also understood a number of other similar incidents are currently under investigation.
Bluefin tuna is a protected species due to declining stocks worldwide and the fish are specifically protected under Irish law due to European conservations measures and it is illegal to catch, land or sell this fish.
The SFPA is also reminding recreational fishing businesses that it is illegal to advertise fishing/charter trips targeting Bluefin tuna.
The fish visit Irish waters during the late summer and autumn.
Some EU member states issue permit for the fishing of Bluefin tuna in their waters under strict guidelines.