The chart-topping star and his bandmate Chris de Margary acquired some rights to the River Finn outside Ballybofey in 2006 after they bought the Glenmore Rivers estate.
Both are keen anglers and saxophonist De Margey even set up home on the estate.
Hucknall, 51, often stays on the 24,000 acre Co Donegal estate where he is popular with locals.
But the agency which looks after the river which runs through the heart of the estate has revealed the number of salmon has dropped from 6,000 in 2006 to just 2,000 recently.
The salmon and trout season on the River Finn starts on March 1st and ends in September.
But the most worrying part for the ‘Money’s Too Tight To Mention’ stars is that nobody knows why the salmon are disappearing.
Commercial fishermen had been banned from placing drift nets on Lough Foyle leading to the River Finn.
But drift-net fishermen say they are not to blame.
Billy Doherty, a drift-net fisherman on Lough Foyle, has been stopped from catching salmon since June 2010.
He said the ban won’t help stocks to recover.
“The so-called experts now realise that there are other factors that are causing the decline in the salmon,” he said.
“It wasn’t solely the drift-net fishermen.
“I think to be honest someone somewhere needs to ask vital questions. Why are the stocks still declining after so much public money has been spent?”