The volume of Roll-on-Roll-off (RoRo) traffic at Republic of Ireland ports dropped by 2% to 291,879 units between July and September when compared to the same period last year.
A new report shows that traffic to ports in Great Britain and ports in mainland Europe both fell by 2% each.
The data from the Irish Maritime Development Office (IMDO) shows that all three Irish RoRo ports - Dublin, Cork and Rosslare Europort saw a decline this quarter.
According to the report, passing 1.2m RoRo units for the full year, as was achieved in 2022, is now unlikely.
But it said shipping operators and ports will be hopeful that the busy months of October and November can recoup some of the losses from this year.
In the Lift-on/Lift-off (LoLo) market, traffic declined by 6% to 277,60 TEU's.
For each of the three Irish LoLo ports, the report states that this is the lowest third quarter performance of the post-Brexit era .
It said the main factor driving declines in the RoRo and LoLo markets are high inflation and interest rates,a along with "heightened geopolitical uncertainty".
"Higher prices, higher borrowing costs, and greater uncertainty serve to suppress demand for finished products such as those transported by the unitised shipping sector," the report states.
In Northern Ireland, RoRo traffic performed strongly in the third quarter of this year, as volumes rose by 3%.
In the LoLo sector, traffic was roughly equivalent to the same quarter last year.
"This is a resilient performance from Northern Irish ports in the face of difficult economic headwinds," the report states.
