It could carry disease and parasites.
An invasive fish species has re-appeared in the midlands.
Inland Fisheries Ireland says Chub - which is common in the UK - has been found n the River Inny in Longford, which is a tributary of the Shannon.
It says the fish competes with native species for food and could carry disease and parasites.
Head of Reseach at IFI, Dr. Cathal Gallagher, says there's a real concern it could spread into the Shannon and that an investigation's now underway to see the extent of the invasion:
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