Fish landings by Irish vessels in Irish and foreign ports declined by 5% in 2021, according to new figures from the Central Statistics Office.
Two thirds of landings happened between January and April and more than half of fish landings took place in Killybegs, Co Donegal.
The figures show the tonnage of fish landed by Irish vessels was 206,000 - down from 218,000 tonnes the previous year.
In Ireland, landings were down 3% or 6,259 tonnes and landings by Irish trawlers in foreign ports declined 19% or 5,655 tonnes.
Broken down via fish species the figures show the species with the largest tonnage landed by Irish boats was Atlantic Mackeral at 51,000 tonnes, followed by Blue Whiting at 36,769 tonnes, Horse Mackeral at 15,246 tonnes, Boarfish at 11,908 tonnes and Atlantic Herring at 1.78 tonnes.
The value of the Atlantic Mackeral landed is put at €60m.
Landings by foreign vessels in Ireland also decreased by 20,000 tonnes or 14% in 2021 compared with 2020.
Some 55% of fish landed by Irish vessels was landed in Killybegs, Co Donegal, amounting to 11,4000 tonnes.
An additional 90,000 tonnes of fish were landed in the port by foreign vessels, making it the leading fishing port in Ireland by some distance.
Castletownbere in Co Cork landed 11,239 tonnes of fish from Irish vessels followed by Dunmore East where 11,052 tonnes were landed.
Some 6,518 tonnes were landed in Dingle, Co Kerry, and 2,222 tonnes in Ros a Mhíl, Co Galway.
Foreign vessels landed an additonal 20,300 tonnes of fish in Castletownbere.
Sean O' Donaghue of the Killybegs Fishermens Organisation said the decline in fish landings is to do with Brexit and the loss of quota to Irish fishers when the UK left the EU.
"It's obvious it’s related to Brexit. We lost 12,000 tonnes of mackerel to the UK as part of Brexit and those transfers are obviously a significant cause of the reduction," he said.