There have been reports of stones being thrown at Marra

Marra became a celebrity in February when it had to be rescued from Maryport harbour, in Cumbria, where it had been stranded for nearly a month.

Now it has been spotted off the coast at Silloth and conservationists have received reports from the public of stones being thrown at the mammal.

They have put up posters warning that the dolphin is a protected species.

Poor health

Trevor Weeks, of British Divers Marine Life Rescue, also urged watchers not get close to Marra or throw food at it.

He said: "Our biggest concern is that Marra could become a humanised dolphin which would not be good for it. We want people to enjoy Marra as a wild, natural dolphin.

"Watching any dolphin from the harbour walls is okay, but we don't want people going out in boats chasing after and interacting with the dolphin as this is not natural."

Marra, named after the local word for "mate", had to be rescued because of its flagging health in the cold marina.

The RSPCA, the Whale and Dolphin Conservation Society and the British Divers Marine Life Rescue helped design the warning poster.