It has been a highway, a sewer and was declared biologically dead in the 1950s but the River Thames is now a nursery for 138 baby seals, according to the first comprehensive seal pup count.
Scientists from the Zoological Society of London analysed photographs taken from light aircraft to identify and count harbour seal pups, which rest on sandbanks and creeks in the Thames downstream from London during the summer, shortly after they are born.
“We were thrilled to count 138 pups born in a single season, said the conservation biologist Thea Cox. “The seals would not be able to pup here at all without a reliable food source, so this demonstrates that the Thames ecosystem is thriving and shows just how far we have come since the river was declared biologically dead in the 1950s.”
The Thames is home to both grey seals and harbour seals, although only the latter breed there. The seals can feed on more than 120 species of fish in the Thames, including salmon, two species of shark, short-snouted seahorses and the European eel, which is critically endangered. Other marine mammals spotted in the Thames include porpoises, dolphins and “Benny” the beluga whale.
Anna Cucknell of ZSL said: “The restored ‘Mother Thames’ – as we call her – is an essential nursery habitat. 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.”
ZSL has conducted Thames seal population estimates annually since 2013. The most recent results, from 2017, recorded 1,104 harbour seals and 2,406 grey seals across the estuary.
The surveys show that seal numbers are rising but it is not yet known if this is due to resident seals having pups or adults moving in from other areas.
The seal pup survey, which was undertaken in 2018, aims to help ZSL researchers better understand the causes of changes in the Thames seal population.
Article Source: The Guardian