An invasive fish species has reappeared in the River Inny in Co Longford, causing concern for local biodiversity, Inland Fisheries Ireland (IFI) has said.
Chub, more formally known as Squalius cephalus, has the potential to compete with native fish for food and space and are potentially a carrier of fish diseases and parasites.
The threat of Chub spreading through the Shannon system, of which the River Inny is a tributary, is of “real and pending concern” to the biodiversity of Ireland’s biggest catchment, IFI said.
The organisation added that it is investigating the extent of the invasion and assessing strategies for eradication and control.
The fish was captured on rod and line at a targeted location identified by IFI staff who recorded potential sightings at several locations.
The initial inspection followed reports submitted to IFI and the National Biodiversity Data Centre by members of the public.
Chub are non-native in Ireland, and the River Inny is the only Irish river in which they have been recorded.
The species was subject to removal operations between 2006 and 2010 and it was hoped that it had been eradicated.
It is unclear at this stage whether these fish represent growth in the original population or are as a result of a second introduction.
IFI is trying to establish the status and distribution of the species within the catchment which will help inform potential management programmes.
Dr Cathal Gallagher, head of research at IFI, stated: "Ireland's rivers are ecologically important ecosystems, which support significant recreational fisheries for native and established fish species.
“Non-native fish species threaten these ecosystems and the game and coarse fisheries that they support – potentially in unforeseen ways – and are thus a cause for concern,” he added.
Dr Gallagher has appeal to anglers to “protect our fisheries” by not moving fish between watercourses and to submit any sightings directly to IFI or through the IFI hotline (1850 34 74 24).