Page last updated at 12:08 GMT, Thursday, 23 April 2009 13:08 UK

Killer whales seal decline link

Common seal
Common seals continue to be in decline

Killer whales could be partly responsible for the decline of Scotland's common seal population.

A report by the Special Committee on Seals found numbers continue to fall in the Northern Isles, where the whales' predatory behaviour is increasing.

The population is also in decline by as much as 50% in the Firth of Tay and has spread to Strathclyde.

The study found competition for food from more stable grey seal population could also be a significant factor.

The report revealed there are around 164,000 grey seals in Scotland, 44,000 more than previously thought. The study said this could be explained by improved research techniques, rather than a spurt in numbers.

Our proposals will significantly increase protection for seals but allow for limited seal management for fisheries and fish farms under licence

Richard Lochhead
Environment Secretary

It estimated there are a minimum of 20,000 common seals, or harbour seals.

This represents a decline of almost half in the Firth of Tay since 2000, between 40-50% in Orkney, and more than 40% in Shetland.

The latest figures also show common seal numbers in Strathclyde are down by around 25%.

Professor Ian Boyd, director of the Sea Mammal Research Unit (SMRU) at the University of St Andrews said: "We are getting mixed messages from our studies of seal populations.

"On the one hand, we still have healthy populations of grey seals even though the increases of the 1990s are not being sustained.

"On the other hand, the causes of the recent decline in the common seal population are not understood."

Formidable animal

A team of research scientists from Aberdeen University studied the behaviour and feeding habits of killer whales around Shetland over the last two summers.

Andrew Foote, who led the study, said it appeared the killer whales were travelling over from Iceland during the common seal pupping season, from May to July, to feed.

He said: "When we've been following the killer whales they seem as intent on grey seals as common seals, but grey seals are a more formidable animal and can it can take hours to kill them.

"Nearly all the seals killed were pups, so I think naivety plays a part as they're more vulnerable."

Grey seals
Scotland has more grey seals than previously thought

Mr Foote said the predatory behaviour by the killer whales could hamper the common seal population's recovery.

He said measures to minimise the impact of man-made impacts, such as reducing the number of shooting licenses could help boost their number.

Environment and Rural Affairs Secretary Richard Lochhead said the report could influence a review of legislation regarding seals, which is almost 40 years old.

He said: "Our proposals will significantly increase protection for seals but allow for limited seal management for fisheries and fish farms under licence.

"They recognise the need for increased protection in respect of declining common seal numbers but acknowledge the continuing need to defend fisheries and fish farms from seals."

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