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The return of these endearing mammals vindicates years of work on cleaning London’s iconic river once, in the ’50s, declared ‘dead,’ writes PETER FROST

This year walkers along the banks of the Thames in central London, or those travelling by boat up and down the river, have had a real wildlife bonus.

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Seals have been spotted near to a number of the capital’s most famous riverside locations.

Crowds queuing for the London Eye, crossing Westminster Bridge and walking across the Millennium Bridge as well as passengers on pleasure cruises and the river buses have all reported sightings either of large whiskered heads or of seals hauled up on the tiny beaches exposed at low tide.

Seals are prospering in the greater Thames estuary too — all the way to Kent and Essex coasts.

Upriver some have reached as far the Teddington Lock — the limit of the tidal section of London’s river.

This summer a major survey by the Zoological Society of London (ZSL) has reported that seal numbers are bouncing back from centuries of culling, persecution and river pollution. The research suggests hundreds of seals visited the Thames in 2014.

In the 1950’s the Thames was declared a dead river that supported no wildlife at all except perhaps a population of dockland rats.

Today you can still find rats — now wearing smart suits in the banking offices of Canary Wharf — but fish, even salmon, swim in the Thames and populations of two species of seal are visiting the capital to eat those fish.

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As late as 1970 seals were killed for meat and fur until the practice was outlawed. They are still hunted in many parts of the world.

The increase in seal numbers over last year is dramatic.

One species, the grey seal (Halichoerus grypus), is now a common visitor. That Latin name translates as hooked-nosed sea pig. The survey showed that there had been nearly twice as many hooked-noses in the London river as in 2013 — 449 in all.

The other species, the common or harbour seal (Phoca vitulina), had increased by a much smaller percentage but sightings were still a very healthy 679 on the river.

These increases for both species reflect other populations growing all around the English coast despite, or perhaps because of, winter storms and flooding.

Conservationist Joanna Barker, who worked on the ZSL survey, told us: “Grey seals in Suffolk, Norfolk and the Wash have been rapidly increasing and we are seeing more pupping areas. We think the same grey seals are travelling down to the Thames to feed or rest.”

Grey seals (below) are over three times bigger than the common or harbour seals and the effect of more of them in the river is not yet clear. Nobody knows yet how the smaller common seals will respond to the competition from the greys.

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The Thames survey was carried out late in August which is the seals’ moulting season when the animals bask on sunny sand banks while growing a new winter coat.

Environmental scientist conducting the survey observed the river from land, boats and aircraft to get the most accurate idea of the population of the seals and their range.

The area of the estuary stretches from Deal in Kent to Felixstowe in Suffolk and includes huge sand banks up to 30 miles off the coast.

One thing the scientists were particularly interested in was the effect of the many new offshore wind farms in these waters.

Satellite tracking showed that common seals (below) are taking advantage of turbine foundations to forage for fish and for shelter.

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Data from tagging common and grey seals on the British and Dutch coasts confirmed that common seals like to visit wind-farms.

News for seals is not so good north of the border, where numbers have suffered a considerable decline in recent years. Scientists are puzzled as to why this is happening.

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You can help with this important research. If you see any see mammals, seals, dolphins, porpoises or even whales — yes whales do sometimes visit the Thames — please visit: http://sites.zsl.org/inthethames/#Publicsightings

This article first appeared in the Morning Star 5 December 2014

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