| # | Species | Year | Period | From - To | Reason | Established in the wild | Ref. no. |
| 1 | Dactylogyrus vastator | 1950-1974 | Europe - Fresh water areas of Ireland | angling/sport | no | 074339 | |
| 2 | Gammarus pulex | 1958 | 1950-1974 | Europe - Fresh water areas of Ireland | other reasons | yes | 074339 |
| 3 | Hirudo medicinalis | 18th century | Europe - Fresh water areas of Ireland | other reasons | no | 074339 | |
| 4 | Proasellus meridianus | 1925-1949 | Western Europe. - Inland Waters. | Lessepsian migration | Unknown | 003700 |