Harbour seal populations around the Scottish coast have increased over the last five years after a long period of decline, according to a new national survey.
But the latest counts show a clear east-west divide in fortune for the protected species.
Scotland-wide surveys of seal numbers are carried out in five-year cycles by the Sea Mammal Research Unit (SMRU) at the University of St Andrews for government nature adviser Scottish Natural Heritage (SNH).
The latest report contains the findings of counts in Shetland, the Moray Firth, the Firth of Tay and on Scotland’s southern coasts in August last year, completing a study that began in 2011.
Scotland’s seas and coasts are internationally important for harbour seals, hosting more than a third of the total European population.
The harbour seal, also known as the common seal, is one of two seal species resident in Scotland. The other is the grey seal.
From 2011 to 2015 a total of 25,399 harbour seals were recorded around the country.
This is significantly higher than the 20,430 counted in the last nationwide survey, but still fewer than the 29,514 in the previous poll.
Results from the SMRU surveys show there has been a significant drop in numbers of the animals spotted on eastern coasts.
The hardest-hit areas are in Orkney and the area around Dundee and St Andrews, where populations have crashed by more than 90 per cent in two decades.
Meanwhile there has been a population explosion on the west coast, where numbers have risen by around 70 per cent.
John Baxter, principle marine adviser with SNH, said: “It’s great to hear that harbour seal numbers on the west coast are doing so well but it’s of real concern that numbers on the east coast remain at historical lows.”
The cause of the declines is unclear, and grey seal populations are not following the same trend.
Experts believe a number of factors may be to blame, including climate change, predation, pollution and shooting by fish farmers.
Seals are protected by law and can only be killed under special licence.