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First Thames seal pup survey conducted

The first ever survey of seal pups in the Thames Estuary has been carried out by marine biologists. Positive findings will now be used to provide evidence of the estuary’s ecological importance.

The inaugural harbour seal breeding survey was conducted via sea, land and air over a four day period (1-4 July), led by international conservation charity ZSL (Zoological Society of London). Seal pup numbers were recorded in key colonies along the Kent and Essex coasts, helping highlight the importance of this critical habitat for the UK’s native harbour seals.

The survey also took into account threats to seal populations, ranging from wildlife disease and pressures from coastal construction projects, to plastic pollution and inter-species competition for food and habitat.

Commenting on this year’s Thames seal survey, ZSL conservation biologist Thea Cox said: “The outer Thames Estuary has long been known as an important habitat for adult harbour seals – now, our first survey specifically of pupping in the outer Thames Estuary will hopefully also show how vital this habitat is as a breeding habitat for these charismatic marine mammals.

“Last year, we estimated populations of 1,104 harbour seals and 2,406 grey seals across the Estuary – an increase of 14% and 19% respectively against 2016’s figures. These positive findings support the idea that today’s Thames is not the same polluted, biologically dead ‘open sewer’ it was in the 1950s, but is in fact thriving with wildlife once again. There’s still a lot of work to do, however, so launching our first-ever pupping count this year should yield further invaluable evidence to support the ongoing renaissance of London’s river as a living, breathing ecosystem.”

To find out more about ZSL’s ongoing work in the River Thames and to sign-up as a ‘citizen science’ conservation volunteer, go to:

To report your marine mammal sightings, visit

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