Experts say that the animal, which they have named Elfina and is believed to be at least three weeks old, was showing signs of being underweight and had bite marks on the back of its neck.
After being transported to New Era Veterinary Hospital in St Saviour, Elfina was taken to an RSPCA hospital in the UK.
Clive Armstrong, of British Divers Marine Life Rescue, said that with the tide coming in, they had to make a decision as to whether to allow the seal to try to survive by itself or bring it in.
