The Risso's dolphin has not been seen since Monday
Marine conservationists have scaled down their search for a dolphin which swam up the River Clyde at the weekend.
The Risso's dolphin was last seen on Monday, far upstream from its natural habitat in the Atlantic.
An extensive search of the river and firth on Tuesday night failed to spot the mammal.
Experts said it was emaciated and had a bad cut on its head. They believed a lack of food and dehydration would make its chances of survival unlikely.
The search has been co-ordinated by the British Divers Marine Life Rescue.
Director Nick Duthie said: "On Tuesday evening we mounted a major search of the Clyde to try and find the animal but it was not located.
"We can only assume it has headed out to sea.
"Although this may sound like good news, we remain very concerned for the animal as it was in such a poor condition and was alone, rather than being in a social group."