Seal count discovers over 700 in Thames Estuary Over 700 seals have been counted in the Thames Estuary after the first ever count by land, air and sea. Conservationists and volunteers spotted 708 grey and harbour seals in the Thames, in a survey stretching up the estuary to Tilbury. The count, which was conducted through the Zoological Society of London (ZSL), included around 500 harbour seals and 200 of the larger grey seals - although final numbers will need to be confirmed after further analysis. Intrepid conservationists used aircraft, boats and humble leg-power to track the animals. The aerial survey enabled researchers to count seals on the outer sandbanks of the estuary where colonies of up to 120 seals were recorded in remote and undisturbed spots away from people and boats. Boats were used for surveying areas of the Medway and Swale estuaries, while researchers on foot were able to investigate small creeks and rivers the vessels could not reach. The survey was timed to coincide with the annual seal moult, when harbour seals shuffle onto sandbanks to shed their coats and grow a new layer in time for the winter, making them easier to spot. It was the first comprehensive count following one from just boats by ZSL last year. ZSL also runs a scheme where members of the public can report sightings of seals and other marine mammals in the Thames. So far the public have claimed to have seen seals near Richmond, by the London Eye, by the Houses of Parliament and at Canary Wharf. ZSL's conservation scientist Joanna Barker said: "We knew there were a lot of seals in the Thames but 708 is pretty incredible." Now we know the numbers and where they are, it can help with conservation. The survey will produce the first complete count of harbour seals in the Thames and south east coast, Ms Baker added. The survey was good news for the Thames Estuary, which was declared biologically dead in the 1950s as a result of heavy pollution, but has recovered significantly since.