Environmental experts have used electric currents to drive fish upstream from Aylesbury town centre’s canal basin.
The operation to replace 10,000 fish that died after a mysterious outbreak of pollution last year was launched this week.
It began on Tuesday when 1,000 fish, weighing about 400 pounds, were transported from the town centre down the Grand Union Canal to the Tring Anglers Puttenham fishing site.
They were moved after being stunned in a technique known as electrofishing, where an electric current temporarily stops them swimming so they can be scooped up in a net.
John Ellis, national fisheries and angling manager for the Canal & River Trust, said: “The fish are stunned for no more than five minutes.
“Research has shown no more long-term damage.
“It may be similar to having a local anaesthetic when you go to the dentist.”
But it will still take up to 10,000 extra fish, weighing 2,640 pounds, to restore the mile-and-a-half stretch of Puttenham waterway to its natural capacity.
A recent Environment Agency fish survey found
just 20 pounds of fish in the area.
Mr Ellis said that 99 per cent of its fish population was wiped out by a mysterious pollutant in February 2013.
A member of the Tring Anglers found all of the fish leaping about and dying on the surface of the water while driving over a bridge in the area.
Club spokesman Dick Pilkinton said: “I got over there as soon as I could.
“You always feel devastated when you see things like that happening.
“It leaves a strange empty feeling, because you know it’s not going to be possible to replace the fish immediately.”
When the Environment Agency arrived to investigate, the toxic substance had already been diluted by the water – so nothing was
If the polluter could have been found, legal proceedings could have been launched to fund the replacement of the fish – expected to cost £20,000.
It would take about eight years for fish to return there naturally from other parts of the canal.