Anglers are threatening to blockade the River Thurne with their boats to stop the dredging of Heigham Sound, near Hickling, which they fear could devastate one of the country’s top pike fishing grounds.

Their worry is that disturbing sediment could trigger an outbreak of the deadly algae prymnesium parva, which decimated fish stocks in the Thurne system in 1969, writes Steve Pullinger.

There was no environmental impact when Broads Authority staff dredged a small area of Heigham Sound last summer during a trial to recreate a lost island at the entrance to Duck Broad.

However, John Currie, a committee member of the Norwich and District Pike Club, said there would be a “huge danger” of resuming dredging so quickly – and stressed the work would represent the biggest dredging project ever carried out in Heigham Sound.

He said the plan to start this month and continue over the summer was the worst possible timing as it was known there was a greater risk of triggering a prymnesium bloom in warmer conditions.

Mr Currie said feelings were running high and there was anger there had been inadequate consultation through the Broads angling strategy group.

He said: “We are urging the Authority to at least carry out the work over a two-year period so they can limit dredging to cold water conditions.

“Once you trigger a major bloom of algae there is no way of controlling it. It would be devastating to the economy; the Broads Authority’s own figures estimate that one third of holidaymakers fish.”

Mr Currie said unless the Broads Authority listened, there would certainly be legal protests and some anglers were likely to take the law into their hands – even though that would not be sanctioned by the clubs.

“As well as boat blockades some people have been talking about protesting at the Broads Authority offices in Norwich,” he said.

Trudi Wakelin, the Broads Authority’s director of waterways, said the success of last year’s trial and the effectiveness of their water quality monitoring had been fully reported back to the Broads angling strategy group in October.

She said it had also been made clear to anglers that dredging Heigham Sound was the number one priority as it was a major concern to yachtsmen.

“There have been regular reports of people running aground and there was a lot of concern for last year’s Three Rivers Race,” she said.

Subject to Natural England giving its approval, the dredging would begin later this month.