By Diarmaid Fleming
BBC Northern Ireland
The salmon is now one of Ireland's rarest fish, but in one of the Republic's rivers they could become rarer still.
Salmon on the River Nore in County Kilkenny have been prevented from swimming upstream to spawning grounds, blocked by a new weir, built as part of a flood prevention scheme.
Fish leaping at the new weir has brought dismay
It is called a "fish pass", but for the salmon supposed to use it in one of Ireland's most famous rivers, it is been more of a barrier.
The sight of salmon leaping in the River Nore usually brings delight to the people of Kilkenny.
They are proud of the rich environmental jewel running through their city, but also the sporting heritage it bestows, bringing anglers like leading golfer Tiger Woods in search of the prized salmon who swim through its waters.
But this year, the sight of hundreds of fish leaping at the new weir has brought dismay.
Hurtling in vain against the weir at the beginning of January, fish tried desperately to leap the weir, returning home to their native river to spawn after thousands of miles at sea.
For some, it was to be the end of their journey - for having survived predators, trawlers, drift-nets, poachers and anglers - a man-made weir was to prove their end. Fish who did not make it were found dead downstream.
Installed as part of a £33m flood protection scheme in a new weir in Kilkenny city, the new fish pass on the River Nore only appears to work when the river level is unusually high.
The pass is like a channel in the weir, with a shallower slope and designed to slow the current to help the fish swim upstream.
Fish can pass through when water levels are high
Brian Sheerin, chief executive of the Southern Regional Fisheries Board, said as part of the flood protection scheme, the weir was taken out and replaced with a fish pass designed into it.
"But unfortunately the bottom rungs of the fish pass don't extend into the water at low level or average low level," he said.
"So therefore, it's like the stairs in your house - the two bottom rungs are missing and you have to step up. That's what the salmon have to do and they have a difficulty doing that."
Fish can pass through when water levels are high - but this also means that repair works to add new rungs to the bottom of the pass cannot be done as it is too dangerous to work.
'Disastrous for salmon stocks'
Anglers are furious. Local salmon fly-fisherman Jim Brown - who moved from Scotland to Kilkenny almost 20 years ago because the fishing on the Nore was even better than home - said he would never forget the sight of the fish leaping in futile desperation at the pass.
"I was sick to see those beautiful creatures that swim 3,000 miles down past the west cost of Scotland all the way round to Ireland to come up our river, stuck at a man-made dam, bashing their heads against the rocks.
"It's a sickening sight to see those beautiful creatures struggling, I really feel gutted about it."
Jim Brown: "It's a sickening sight"
Other fisheries experts say impeding the fish could be disastrous for the salmon stocks.
Bob Wemyss of the South East Salmon Federation said: "The scientists have told us that less then 30% of the fish needed to maintain salmon stocks are coming to the river Nore.
"Now that they have found this impassable barrier, it can only make things worse."
It's become a hot local political issue too. Kilkenny mayor Martin Brett said: "We in Kilkennny have a very good tourist industry here based on fishing and we need the situation alleviated as soon as possible.
"I'm not interested in who fixes it - all I know is that it has to be fixed."
Who is to blame for the debacle has yet to be determined.
The state's Office of Public Works carried out the project and investigations are ongoing to see if the design was at fault, or if the pass was not installed or built correctly.
Irish mythology tells the story of Fionn MacCumhaill who was bestowed with superhuman wisdom having tasted the Salmon of Knowledge, a fish giving anyone who caught and ate it such powers.
The people of Kilkenny may feel a few portions could come in handy in the sandwiches of those responsible for the pass the fish could not pass.