For many Bexley residents, the Thames is seen as just the boundary of the borough – something to keep Essex out! But it is of course a valuable wildlife habitat too and not just for fish and birds. Seals are occasionally reported and are no doubt much more prevalent than we might realise.
Every year the Zoological Society of London undertakes a census of the seal population of the Thames. Here is a report on their August 2014 survey.
Their report of the survey and report can be found at their page: http://www.zsl.org//conservation/news/seal-numbers-increasing-in-the-thames?utm_medium=email&utm_source=ZSL+-+London+Zoo&utm_campaign=4656505_Conservation+Focus+September+2014&utm_content=SEALS&dm_i=7U7,2RSZD,1GY4UR,A35O0,1
Sightings of marine mammals can be logged at: http://sites.zsl.org/inthethames/#Public sightings
The Grey Seal is the larger of the two seals, up to 9 foot (2.7m) long. Head shape is also distinctive. http://www.mammal.org.uk/mawsespeciesguides/grey-seal
The Harbour Seal, better known to us old people as the Common Seal, is a rounder faced (and overall rounder animal) and much smaller at upto 6 foot (1.8m) long. http://www.mammal.org.uk/mawsespeciesguides/common-seal-0
This is a Harbour Seal filmed in Greenwich in February 2013 in a playful mood.
BBC film of Common (Harbour) Seals in the Thames.
The film of the 2013 survey when 708 seals were recorded.