It is reported that the invasion caused the loss of as much as 40 per cent of the stock at Co Mayo aquaculture farm, located off Clare island.
Although Marine Harvest was unable to confirm exact numbers, what it could say was that the loss was estimated to be 20,000 specimens.
The firm opted for an accelerated harvest at its Donegal aquaculture farm in order to minimize losses on its farmed stock.
Scientists connect the the jellyfish invasion to warmer sea waters.
It is a phenomenon that has also been observed in other parts of the world.
Marine Harvest has been taking preventive measures such as giving its salmon less fish feed to keep them less active with gills covers closed as it worries about strandings of this jellyfish species from Donegal to Kerry.
Marine Harvest has nine fish aquaculture farms along the western seaboard at locations from Donegal to Cork.