Staff at the Cornish Seal Sanctuary said they were shocked and saddened to hear of the death of a baby seal which was released back into the wild from the centre just last month.

Sponge Bobby was found dead on a beach in Bournemouth with serious facial injuries - it is thought she was struck by a jet ski.

Animal care supervisor Tamara Cooper from the centre in Gweek said they had spent three-and-a-half-months bringing the animal back to health after it was rescued from a beach in North Cornwall in November.

She said: “When she was first rescued they thought she was a boy so they called her Sponge Bob. When we found out she was a girl we changed it to Sponge Bobby.

“She had a cough and some nasty cuts when she was brought in. We always try our best to give them a second chance."

She said Sponge Bobby was fighting fit when she was released last month and staff gave her a little “pep-talk” as they let her go.

She added: “We were very sad to hear what happened but it's amazing that in just a few weeks she had gone from the North Coast of Cornwall, travelled around Land's End and the Lizard and ended up in Bournemouth”

Conservation experts traced the animal using the identification tag on its flipper after she was discovered at Hengistbury Head on Monday.

Wildlife photographer and environmental campaigner Steve Trewhella, of UK Coastal Wildlife, said the animal had suffered serious injuries to its face, believed to have been caused by a boat or jet-ski.

Urging people to keep their distance from seals, as well as other sea animals, he added: “They are wonderful creatures – watch them, film them and enjoy the spectacle but you have to respect the fact that they are vulnerable animals.”

Emma Rance, marine conservation officer at Dorset Wildlife Trust, said the animal had sustained severe head injuries.

She said: “She had suffered a lot of trauma to the head area and we assume that is the reason for her death.

“It’s quite likely she would have been hit by a propeller.