A dead Pacu fish, native to the Amazon in South America, has been found in Lough Garadice near the Cavan-Leitrim Border.
Inland Fisheries Ireland said it is examining the 2kg Pacu after its discovery by angler Steve Clinch at the weekend.
Barry Fox, Head of Operations with IFI told RTÉ's News at One that protecting Irish waters from invasive or non-native species is ongoing.
Mr Fox said that a research team from Inland Fisheries Ireland are examining the fish, using analysis to confirm that it is a Pacu fish.
He explained that the fish is a vegetarian, and consumes plants, nuts and aquatic growth using its large mouth.
The Pacu is a relation of the purana, and Inland Fishers Ireland suspect it may have been held in an aquarium but outgrew its location.
The team also carried out stock assessment of the lake and found no additional fish were identified there up to this point.
He said that the finding of non-native species happens from time to time, but is on the increase.
He added that some of the non-native species can become invasive and can impact on the natural fish or flora that populate the locations, which can have a significant impact on natural biodiversity.
He said managing invasions are costly, but that Inland Fisheries Ireland uses methods of traps or electrodes to get fish into a net and remove the non-natives, but release the natives back into the water.
