The Environment Agency restocked thousands of fish into the River Great Ouse just before Christmas as they made their annual trip to Calverton Fish Farm.
This was a four day exercise as part of a conservation programme and post-pollution recovery plan.
On the first day of the restocking, more than 1400 juvenile barbel were released into the upper reaches of the Ouse in carefully selected locations that would suit habitat conditions.
This is part of wider efforts to conserve barbel populations and improve vital habitat.
Officers then released 5000 dace, 7000 roach and 1000 chub into the river to replenish stocks following a pollution incident in Brackley in 2018, during which thousands of fish died.
Since the incident, the Environment Agency has released almost 28,000 fish back into the river.
Further stocking at this location is planned for 2020.
As well as the fish stocking, other measures have been taken to restore the River Great Ouse, including habitat restoration work, such as gravel enhancement and cleaning, improving cover for foraging and resting up, and improved opportunities for fish passage.
On the final day, 900 crucian carp and 500 tench were delivered to three separate still waters in Cambridgeshire, Norfolk and Bedfordshire and will promote work with the Angling Trust to conserve crucian carp populations.
Kye Jerrom, fisheries specialist for the Environment Agency said: “All of these enhancements should give these fish and others in the system the help they need to thrive.”