Cork County Council engineers estimate the repairs and upgrading of the weir in Fermoy could top €3m.
However, angling clubs and private fisheries said preliminary works, such as clearing increasing deposits of sediment around the weir, would ease increasing concerns about the safety of salmon stocks.
Youngsters from the north Cork town’s river rowing club, along with sub-aqua and triathlon clubs also joined in Saturday’s protest which coincided with World Fish Migration Day.
One protest group, represented 11 district angling, community, and watersport clubs.
Organiser Jason Mac Corcráin, of Ballyduff Bridge Salmon Fishery, insisted there was a simple solution, in advance of the council’s proposed major restoration works.
“For decades, the big mound of gravel on the river bed had been removed regularly by horse and cart before the former town council and the fishing authorities took over the responsibility,” he said
“But there has been no sediment clearance works or any form of action for a number of years and that’s the problem.
“I’m more concerned about the health risks of the fish than any risk to our family business.”
Mr Mac Corcráin also noted the concerns of the townspeople of Fermoy and dozens of angling clubs and sports bodies.
“Very simply, with the damage, the migratory salmon can’t clear the weir and they die, not only due to exhaustion from their attempts but also from diseases caused by the build-ups of sediment.”
He suggested a ‘rock ramp’ could be installed and also warned that steel pylons are killing many of the salmon that make the leap and collide with the steel.
“Fish can handle an impact with stones but not steel,” he said.
Mr Mac Corcráin said the morning protest through Fermoy had been registered as an official event with the international fish migration day, a global-local event to create awareness of the importance of open rivers and migratory fish.
Meanwhile, the rapidly crumbling weir issue was raised at the Fermoy-Charleville municipal district meeting. Council official Pauline Moriarty said the Fermoy-Charleville body will meet with assistant county manager James Fogarty to seek funding.
Fianna Fáil councillor Deirdre O’Brien demanded the OPW come on board, while Fine Gael councillor Noel McCarthy insisted funding should also be sourced from the Department of the Marine, Inland Fisheries and others.
Fianna Fáil councillor Frank O’Flynn said: “Time is not on our side. It is collapsing by the day. Salmon are dying downstream of the weir and many international tourist anglers have already decided not to fish the Blackwater this season.”