Dozens of dumped goldfish were removed from a village pond by the Environment Agency as part of routine maintenance work.
An agency team arrived at the weir in the heart of Warboys on April 9 to carry out some pre-emptive work ahead of what is expected to be a dry summer.
Low water levels can lead to low oxygen levels so the agency decided to remove some of the fish living in the pond, to reduce the risk when temperatures begin to rise in the summer.
During their work, however, the teams came across carp and goldfish they believe had been released by well-meaning former owners into the pond, sparking a warning from officials.
A spokesman said: “Village ponds can sometimes be a dumping ground for unwanted pet fish, and some very strange things can end up in these semi-urban watercourses. It's a shame that at one stage true crucian carp, an endangered species, once thrived in here, but illegal stockings of carp and unwanted gold fish have hybridised with the once resident population so heavily that none have survived.
“Please remember not to dispose of unwanted fish in rivers or ponds, it might feel like the right thing to do, but actually some species can cause huge problems and they also provide very real disease and parasite risks too.”
In all, the agency team removed 12 carp totalling, weighing 53lbs, the largest hitting the scales at 12lb. The carp were given to a local fishery for re-stocking. More than 40lbs of goldfish were also removed.
The spokesman said the goldfish would not be re-homed as they were “not suitable for a fishery or the wild”.
It is understood that goldfish will be used as part of the agency's ongoing education work, which explains what it does in watercourses across East Anglia.
According to the agency, Warboys Parish Council also plans to de-silt the weir later in the year to help with conservation efforts.