Harbour seal census confirms east-west divide - NatureScot
A full census reveals Scotland’s harbour seals are doing well overall but there remains a striking divide between east and west coast populations.
NatureScot has published the results of the fifth full census of Scotland’s harbour seals over the last 25 years.
Between 2016 and 2019 almost the entire Scottish coastline was surveyed by helicopter by the Sea Mammal Research Unit (SMRU) at the University of St Andrews.
During the most recent survey in August 2019, 26,846 harbour seals and 25,412 grey seals were counted - the second highest total ever recorded for harbour seals and the highest for grey seals.
Estimates based on these surveys suggest total populations in Scotland of around 37,300 harbour seals and 106,300 grey seals.
The data show that for harbour seals, there remain striking differences in population trends between different regions.
Northern and eastern coasts have seen significant declines since the early 2000s, with the most dramatic changes occurring around Orkney, in Shetland, and in the Firth of Tay and Eden Estuary.
In contrast, numbers in the west have been either stable or increasing. The latest counts show that more than three-quarters (78%) of all harbour seals in Scotland are currently found in the west.
This is a significant shift since the 1990s when Orkney and Shetland were the most important regions in Scotland for harbour seals.
Ongoing studies, funded by the Scottish Government, are attempting to identify the reasons behind the large regional declines, with possible causes under investigation including predation by orcas and grey seals, competition with grey seals, algal toxins and diseases.
Morven Carruthers, NatureScot Marine Ecologist, said: “This latest full census confirms the geographic east-west divide in the populations of harbour seals that we have seen over the last 20 years.
Read the report: Morris, C.D., Duck, C.D., Thompson, D. 2021. Aerial surveys of seals in Scotland during the harbour seal moult, 2016-2019. NatureScot Research Report 1256.
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Posted On: 03/06/2021