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Thousands of people have taken part in a survey on wildlife in the Thames.

The ZSL Thames Marine Mammal Sightings Survey, which launched in 2004, was designed to help conservationists develop a better understanding of how marine mammals use the Thames in order to help conserve them.

Highlights from the 10 year report just published include:

  • More sightings were reported around Canary Wharf than any other area along the Thames.

  • Many sightings were recorded in Central London, especially between the Houses of Parliament and the O2 Arena. Other sighting hotspots include Hammersmith, Southend-on-Sea and Cliffe

  • Seals were seen as far upstream as Hampton Court Palace, harbour porpoises and dolphins as far as Teddington Lock and whales as far as Gravesend

  • Harbour seals were the most commonly spotted marine mammal, with more than 1,000 animals reported over the 10 year period

  • Marine mammals were found year-round throughout the Thames Estuary

  • The majority of sightings lasted less than 2 minutes and were of marine mammals swimming

  • 2013 saw the greatest number of sightings submitted (239 sightings)

  • Most sightings were of individual animals, but occasionally large groups are seen: In September 2014 100 seals were spotted at Greenwich and in November 2014 30 pilot whales were spotted near Clacton-on-Sea

Joanna Barker, European Conservation Projects Manager at ZSL, said: “People are often surprised to hear that marine mammals are regularly spotted in Central London. As a top predator, their presence is a good sign that the Thames is getting cleaner and supporting many fish species. The presence of these animals is also a great example of how urban environments are important for wildlife.”

“We were pleased to see that harbour seals were some of the most commonly spotted mammals. Their numbers have dramatically declined in some parts of Scotland, so the fact that they are frequently sighted in the Thames Estuary confirms that the South East is an important area for their conservation.

“It’s fantastic that so many people have got involved in the project – we rely on sightings to understand the whereabouts and behaviour of marine mammals in Central London. The more Londoners get involved, the more accurate our understanding of wildlife in the Thames will be."

The survey is continuing and you can take part at

Pics: ZSL. Top left: Morden Wharf (D.Nolan); Top right Chiswick Pier (James Duncan); Below Teddington Lock (Emma Durnford).