Dolphin found dead in the Thames at Mortlake

Dolphin in the Thames outside the Bell & Crown at Strand on the Green on Wednesday; Photograph Fiona Sparkes

Seen swimming at Strand on the Green the day before it was found dead

A dolphin was seen swimming in the River Thames outside the Bell & Crown pub on Wednesday. It is presumed to be the same one that was found dead the following day on the riverbank at Mortlake, as dolphin sightings are rare.

The Port of London Authority confirmed the common bottle-necked dolphin has been found dead, adding:

“Unfortunately, when dolphins are sighted this far up the Thames it can often indicate they are already in distress.”

The dead dolphin at Mortlake; Photograph CSIP

The Cetacean Strandings Investigation Programme (CSIP)  team from the Zoological Society of London (ZSL) came and took it away and will investigate how it died.

ZSL is a world-leading conservation science research centre and the CSIP team is funded by the government to collate, analyse and report data for all cetacean strandings around the coast of the UK.

Rob Deaville of the CSIP thanked British Divers Marine Life Rescue and Tideway Scullers for their help.

In a Facebook post on Thursday (2 July) the CSIP team said:

‘A CSIP team from ZSL recovered the body of an adult male short-beaked common dolphin from the Thames earlier today. This is believed to be a common dolphin that had been sighted at various locations across the Thames over the last few days.

‘Unfortunately, it live stranded and died at Mortlake earlier this morning- a #CSIoftheSea examination will be carried out soon to try to learn more about the dolphin and possible causes of its live stranding.

Photograph CSIP

‘This is an unusual stranding for the region- common dolphin strandings have been rarely reported within the southern North Sea over the last 35 years since the inception of the CSIP in 1990.

‘However, they have been increasingly recorded in the region in recent years, potentially due to climate change driven shifts in distribution- the last strandings recorded in the Thames were a pair of individuals in August 2024’.

Photograph CSIP