Members of the Environment Agency’s Great Ouse and Fenland Fisheries team restocked a stretch of the River Ouse through Buckingham with thousands of fish on Friday July 12.
Five thousand chub and 20,000 thousand dace from Calverton Fish Farm were stocked at nine locations across the river.
The fish were funded by anglers via income received from fishing licences.
The restocking forms part of a recovery plan for the river in the aftermath of a chemical spill which affected a 25km stretch of the river almost a year ago.
Further fish have been ordered and the next batch of roach, dace and chub are due to be added to the water at the end of the summer.
An Environment Agency spokesman added: "Whilst delivering fish we saw encouraging signs of natural recovery with large shoals of minnow on the upper reaches in Buckingham and young roach and dace at the lower end around Thornborough.
"This is great news for the fishery as our main aim is to ensure a sustainable river that can support itself."
Investigations into the exact cause of the chemical spill are continuing.