The ones that got away: say ‘goodbye’ to the Irish salmon

IRISH scientists used cutting-edge DNA techniques to discover how endangered salmon are failing to make it past manmade barriers into the spawning grounds of Irish rivers.

RTÉ’s Eco Eye programme will show how the populations of wild salmon in Irish rivers have collapsed in recent years, with the iconic fish now placed on the International Union for the Conservation of Nature’s red list of endangered species since numbers started falling in the 1970s.

Salmon have to leap up to ten feet in the air to clear waterfalls and other barriers but these man-made structures are taking a toll on the species.

The programme reveals how obstacles such as dams and weirs which were built hundreds of years ago play a major part in stopping the wild Atlantic fish from returning to their spawning grounds.

In the programme, the chairperson of the Thomastown Anglers Association, Tom Moylan, says he fears salmon could die out in the once salmon-rich River Nore in Co. Kilkenny.

He said: ‘I think in a couple of years’ time we’ll be in trouble. We might have no salmon in our system here, that’s the way it is looking.’ Siobhán Atkinson from UCD’s reconnect project, which maps barriers in rivers around the country, said environmental DNA taken from rivers can now show how fish negotiate barriers to get to their spawning ground. ‘We extract DNA and see if we can detect specific species,’ she said. In a recent case, they found salmon DNA below a bridge but none above, showing the fish never made it over the barrier. Ms Atkinson said there are 508 structures such as waterfalls or weirs along the Nore for salmon to get past before they get to the spawning ground.

She said: ‘Only 11 of those structures are natural barriers, the rest are all man-made. The cumulative impact of these structures really needs to be considered.’

The documentary reveals that stocks of salmon in the River Shannon have plummeted steadily since the building of the Ardnacrusha hydro-electric dam in Co. Clare in 1929.

‘One hundred years ago, well over 100,000 came up and 100 years before that probably 700,000 so it’s been a decline through those decades,’ said ESB biologist Dennis Doherty.