Thames is back from the dead as seal pups thrive on its shores

THE river Thames in 1957, was so heavily polluted that it was declared “biologically dead”, leaving little hope for natural life in its waters.

But now, more than 60 years after the Natural History Museum’s proclamation, experts have counted more than 100 seal pups on the river’s shores.

Scientists from the Zoological Society of London (ZSL), an international conservation charity, were “thrilled” to discover 138 pups on the sandbanks and creeks of the river in the first comprehensive count of the offspring.

Using a light aircraft, they were able to capture images of harbour seals during pupping season. The count is evidence that the river’s ecosystem has come back from the brink after the museum said its low oxygen levels and polluted waters would mean nothing could survive in its murky tides.

The pioneering research took place in 2018, with the data released for the first time today. Scientists analysed hundreds of photos taken as part of a Uk-wide seal monitoring initiative.

Explaining the decision to base the count on photographs, ZSL said it was “much easier, and so more accurate, to count the seals in photos instead of the constantly moving, playful creatures”.

The figures are good news for the harbour seal population, which was decimated by outbreaks of Phocine Distemper Virus (PDV) in 1988 and 2002.

Anna Cucknell, who leads ZSL’S Thames conservation, said: “Incredibly, harbour seal pups can swim within hours of birth, which means they are well adapted to grow up in tidal estuaries like the Thames. By the time the tide comes in they can swim away on it. Grey seals, on the other hand, take longer to be comfortable in the water, so breed elsewhere and come to the Thames later to feed.”

Thames seal population estimates have been conducted annually by ZSL since 2013. The most recent results, from 2017, recorded 1,104 harbour seals and 2,406 grey seals.

Other species are also thriving in the river’s ecosystem, including over 100 species of fish, two types of shark, short-snouted seahorses and the critically endangered European eel.

But, experts warn that marine life remains threatened. Last year, the RSPCA told The Telegraph that it was the worst year for seals encountering “horrifying” plastic-related injuries.

And finally, for some good news: scientists have counted more than 100 seal pups on the shores of the River Thames. We are often told that the environment is on the brink of destruction, but how often do we hear of success stories, such as the transformation of the Thames?

In times past, the Thames functioned as a giant open sewer. During the Great Stink of 1858, Parliament was inoperable. At first they tried to escape the smell by covering the curtains in chloride and lime, but eventually MPS gave in and voted through reform in an unusually fast 18 days.

The Blitz, alas, destroyed some of the Victorian sewers; by the Fifties, the river had been declared biologically dead. Now, thanks to declining pollution, there are seals, porpoises and sharks living in it – and the smell is vastly improved, too.