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Last updated on April 17, 2014 at 1:21 EDT

Researchers Concerned Over Alarming Decline Of Harbor Seals

December 3, 2008

Scientists say harbor seals (common seals) are vanishing along coastlines across the northern hemisphere at an alarming rate.

Researchers from St Andrews University say numbers have halved in the hardest hit area, the Orkney Islands, since 2001 – falling almost 10% each year.

Professor Ian Boyd of the Sea Mammal Research Unit said there would soon be no harbor seals left in some areas if the mysterious decline continues.

Marine biologists currently have no explanation for the disappearances and have begun investigating possible causes, which include illegal hunting and disease.

Boyd said the change in numbers is well outside normal limits and the decline appears to be accelerating.

“We’re worried that over the next 10 years, there will be no harbor seals left in the core area for the animals in Europe.”

Classified as Phoca vitulina, the harbor seal inhabits cold and temperate waters throughout much of the northern hemisphere. The UK is home to 40% of the European population.

The seals are a familiar sight around the coasts of the UK, much more so than their more elusive cousin, the grey seal. But the latest report shows dramatic decreases in the numbers around most of Scotland.

Compared to figures six years ago, counts in 2007 showed drops of 56% in Orkney, 42% in Shetland and 30% in Strathclyde. And researchers have seen similarly worrying declines along the Scottish east coast, and along the North-East coast of England.

Boyd said science still doesn’t know the cause of the dramatic drops in population. It looks like the problems are likely to be complex and the decline in numbers is probably down to a combination of factors.

“It could be a change in the ecosystem. We know that the grey seal is moving into harbor seal territory and this might be having an effect on the harbor seal.

“But we don’t really know the nature of the competition between the two species. We do know that both feed on sand eels, which are also in decline.”

Experts say the decline in harbor seals mirrors a similar trend in North Sea marine life.

A recent study on the Isle of May, off Scotland’s east coast, by scientists from the UK Center for Ecology & Hydrology, showed that Puffin numbers have fallen 30% over the past five years.

The Fisheries Research Service in Aberdeen has also reported a decline in sand eels.

Observers say there is no evidence, so far, of any kind of parasite-mediated infection of harbor seals.

Professor Boyd said that while grey seal populations seem to be healthy, grey seals could be more robust than harbor seals, which seem to be more susceptible to disease.

An outbreak of phocine distemper virus (PDV) in 1988 killed around 18,000 harbor seals in European waters, over half the population in some areas.

By 2002, the population had recovered fully, when a second outbreak began, in which several thousand seals died. There is no cure or prevention for the disease.

In the UK, common seal numbers are monitored annually with funding from the Natural Environment Research Council, which published the results of the latest survey.

NERC advises the UK government on the size and status of the British seal population under the Conservation of Seals Act, 1970.

Some environmental groups are calling for the Scottish government to use powers under the proposed marine bill for Scotland to legally protect harbor seals, by abolishing the Act.

Under law, it is currently legal to shoot harbor seals that come near fisheries.

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