Hopes faded on Monday for a young minke whale that became trapped in the River Thames near London, authorities said.
Rescuers trying to capture the whale said that by 5pm its condition had deteriorated rapidly and it would soon be stranded by the dropping tide near Teddington, in south-west London.
“Once the whale is beached a veterinary team will be on stand by to euthanise the animal to end its suffering,” the British Divers Marine Life Rescue said.
The group said the injured and exhausted calf would struggle to swim even if it made it back into deeper water.
Crews worked for hours before being able to free the whale early on Monday after it was stranded in a lock near Richmond, a few kilometres downstream of Teddington.
But as the mammal was being taken for further health checks on an inflatable pontoon, it slipped back into the water.
“This animal is very, very lost,” Port of London Authority spokesman Martin Garside said. “It’s like seeing a camel at the North Pole.”
Mr Garside said a whale had never been seen that far up the Thames, 150 kilometres along the river from its mouth.
The distance made the creature’s route back to safety extremely difficult.
The whale, which measured about four metres long, was first seen lying on the lock’s boat rollers on Sunday night.
Hundreds of people gathered along the banks of the Thames to watch the rescue operation as night fell.
The area is known for wide tidal swings of more than 5.5 metres.
Port staff were joined by firefighters, coastguard members and marine animal rescue divers.
Minke whales, which are more typically found in the northern Atlantic and Pacific Oceans, can grow to nine metres.
Last September, The National explained how whales can be stranded so far from home.
