Irish trawlers face being locked out of UK waters under a bill set to be introduced in the British Parliament.
The UK Government's Fisheries Bill includes a legal guarantee that the UK will pull out of the EU's Common Fisheries Policy by the end of the year.
Britain's environment secretary Theresa Villiers has said the bill "takes back control" of British fisheries.
Seán O'Donohue, CEO of the Killybegs Fishermen's Organisation, said he expects fishing rights to be strongly defended by the EU in trade talks.
He said that he was "confident" that the EU would "sign off on their mandate in February".
It will make it very explicit again that fisheries will have to be negotiated in the context of the wider trade negotiations.
"If that is the case we would expect that there will have to be concessions," he said.
