THE strength of seal populations in Scotland varies dramatically, depending on which part of the coastline they inhabit.
While stocks of harbour seals are thriving on the west coast and in the Western Isles, they have declined on the east coast, according to research commissioned by Scottish Natural Heritage (SNH).
A four-year survey, carried out by the Sea Mammal Research Unit (SMRU) at the University of St Andrews, counted 3,533 harbour seals around the Western Isles in 2017 – the highest number in the area since surveys began in 1992, the Press and Journal reported.
In many of the west coast areas surveyed, harbour seal numbers were either comparable or slightly higher than previous counts.
But on the east coast, the number of harbour seals counted in the Moray Firth was 831. And numbers in the Dornoch Firth reached a low of 39, while the population at Culbin and Findhorn increased to 526. Only 29 harbour seals were counted in the Firth of Tay and Eden Estuary.
The latest estimate of the size of the harbour seal population around Scotland is 26,565.
The reasons for the variations range from availability and quality of prey, competition from grey seals, predation by grey seals and killer whales, and exposure to toxins from harmful algae.
Morven Carruthers, SNH policy and advice officer, told the Press and Journal: ‘These latest findings provide further evidence of a geographic divide in the fortunes of harbour seals in Scotland.
‘While populations on the west coast are increasing in many areas, numbers on some parts of the east coast are historically low.’