Pond owners in Swansea believe that their pond fish are being stolen by mink, or possibly an otter, according to the BBC.
An unknown predator has been stealing fish from ponds in the Killay and Derwen Fawr area.
One attack resulted in around a dozen Koi being decapitated. The owners have now resorted to covering their pond with mesh to protect the remaining fish.
The owners of the Koi told the BBC that they knew of eight other ponds that had been visited by the predator but believe that many other cases may have gone unreported.