Canary Wharf has been the top location on the Thames for spotting marine mammals, over the last decade, according to a new survey.

It may be the number of human eyes trained on the docks that accounts for the success or it may be the presence of Billingsgate fish market – either way, the presence of Sammy and friends has triggered more reported sightings than more desolate places closer to the sea.

Seals and porpoises have been seen around The O2, according to the Zoological Society Of London while a pod of 10 bottlenose dolphins was seen near Deptford in April 2006.

• Also online: Is this George or is it Sammy?

The survey, which has been running since 2004, coincides with an annual seal survey, tracking numbers in 1,500 square miles south east of England between Deal and Felixstowe from land, sea and air.

ZSL European conservation projects manager Joanna Barker said: “The presence [of marine mammals] is a good sign that the Thames is getting cleaner and supporting many fish species. It is also a great example of how urban environments are important for wildlife.

“Harbour seal 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.”

People can take part in the ongoing survey here

Sightings logged on the ZSL website