An investigation is under way after an otter was found dead in a net at a pool where fishing is banned.
The protected animal is believed to have drowned in the net while hunting in Loe Pool, near Porthleven, Cornwall.
Fishing is prohibited at the pool, which forms part of the National Trust's 50-acre Penrose Estate.
The charity described the death as "shocking" and said it been reported to the police's wildlife officer.
Lead ranger, Mike Hardy, said: "We believe the otter, looking for fish for food, has gone into the net and been unable to escape and then has sadly drowned."
He said it appeared the person fishing had then tried to hide the evidence.
Mr Hardy said he hoped it was an isolated incident but there was a need to be vigilant.
He added: "What may appear to be relatively benign - putting out a net for some fish - can have catastrophic implications for wildlife."
Otters were thought to be extinct from Loe Pool in the 1970s and 1980s, when the water there was suffering from eutrophication and algal blooms.
A survey in the early 1990s found signs of otter and the National Trust believes that since then the population has been slowly recovering.
A Facebook post by Penrose National Trust urged anyone with information to contact Devon and Cornwall Police.