Sea fishing watchdogs do not have the power to adequately police the world's biggest super-trawlers in Irish waters, it has been claimed.
The warning came as conservationists called for independent observers to be put on board and tens of thousands of people signed an online petition over the presence of the Margiris, the second largest fishing boat of its kind.
The 142m freezer-trawler - off Donegal for the last two days - fishes for pelagic species like herring, mackerel or scad and uses quotas from Lithuania, where it is registered, or others sourced by its Dutch owners.
Its nets are reputed to be bigger than a football pitch.
The Sea Fisheries Protection Authority said the boat, owned by Parlevliet & Van der Plas, is likely to be inspected while in Irish waters.
Francis O'Donnell, chief executive of the Irish Fish Producers Organisation (IFPO), said authorities were powerless to adequately monitor and assess super-trawlers because of the European quota system.
"The issue with a boat that size is that it has a massive capacity to catch fish," he said.
"They are fishing on licence and with a quota but the real worry I would have is that they are not being controlled properly by Irish authorities in Irish waters."
Mr O'Donnell said: "The real question that needs to be asked when a sea fisheries officer goes on board is do they know whether or not the vessel has a quota and what is available to it at that moment in time."
Margiris has a gross tonnage capacity of 9,499 tonnes.
The trawler is owned by the same company as the 144m Annelies Ilena, formerly the Atlantic Dawn when it was registered in Ireland, and both vessels have faced criticism for fishing in Irish waters in recent years despite having full clearance from Europe under the Common Fisheries Policy.
The Irish Wildlife Trust wrote to the SFPA and m inister for the marine Simon Coveney to confirm if an independent observer was on board to monitor for the catch of non-target species, such as whales, dolphins, turtles and sharks, as required under EC regulations.
Irish Wildlife Trust campaigns officer Padraic Fogarty said: "Irish waters were designated as a whale and dolphin sanctuary by Charlie Haughey in 1991.
"It is simply unacceptable that enormous boats like this can move into our waters and hoover up marine life."
A target of 25,000 signatures was set for the uplift.ie online petition against the Margiris in Irish waters.
The SFPA said: "This vessel has a quota entitling it to fish for scad (horse mackerel) within EU waters and is authorised to conduct fishing activity in this area.
"As with all vessels, it is required to record its catches and set them against quota in compliance with EU sea-fisheries legislation."