Rocco, who was believed to be about five months old, was severely underweight and dehydrated and is believed to have had a respiratory infection.
The pup was initially cared for by members of British Divers Marine Life Rescue and vets from New Era before being transferred to Guernsey on Monday.
Steve Byrne, GSPCA manager, said: ‘We are all heartbroken that Rocco passed away in the early hours of this morning.
‘If the Jersey BDMLR team hadn’t have rescued her it is likely she would have passed away where she was found, as she was extremely weak and had a number of health problems.’
Rocco was found on the same day that a seal rescued over Christmas was released back into the sea.
