Killer whales 'decimating harbour seal population'

The catastrophic decline of the common seal population in Scottish waters could be blamed partly on killer whales, marine biologists believe.

Numbers of the common seal, also known as harbour seals, are continuing to fall in Orkney, Shetland and Caithness – areas where the whales' predatory behaviour is increasing. One theory is that killer whales are moving south from Iceland and the Arctic to escape the effects of climate change.

The common seal population has falled by up to 50 per cent in the Firth of Tay and 25 per cent in Strathclyde. There are now up to 35,000 common seals in Scottish waters, compared with 50,000 in 2001. By contrast, there are about 164,000 grey seals – 44,000 more than was previously thought.

The Scottish Government's Special Committee on Seals report for 2008 found that competition for food from the more stable grey seal population might also be a significant factor in the decline in harbour seal numbers.

Professor Ian Boyd, director of the sea mammal research unit at St Andrews University, said the presence of killer whales was having an increasingly harmful effect on the species.

But Mark Simmonds, the director of science at the Whale and Dolphin Conservation Society, said the decline was much dar likely to be linked to the legalised shooting of seals to protect fish farms.

A report by the BBC's Countryfile programme this month suggested that up to 5,000 seals were killed off the Scottish coast each year to protect the lucrative salmon industry, as well as by netsmen and anglers.