New data shows drop in Scotland’s harbour seal numbers and sparks concern for grey seal population

New research from the University of St Andrews has shown that there is a marked drop in the status of Scotland’s harbour seal population, as well in summer grey seal abundance, according to surveys conducted by the Sea Mammal Research Unit (SMRU). The report, commissioned by NatureScot and released today,  marks the completion of the sixth Scottish census of seal abundance based on August haulout counts (2021-2025) resulting in a 30-year time-series.

The Scottish harbour seal population had appeared to be in recovery following dramatic declines in the early 2000s in the north and east. However, last year the Special Committee on Seals (SCOS) report revealed that abundance in the harbour seal stronghold of the west coast had dropped by ~20% between 2018 and 2023. The latest surveys in 2025, covering the Northern Isles, now add further cause for concern. The long-running decline in Orkney has continued with abundance now ~90% lower than in the late 1990s. Of most concern was Shetland where counts fell by  ~45% between 2019 and 2025, despite having appeared broadly stable for the past two decades. Overall, the Scottish harbour seal population declined by ~25% between the last two censuses, and is at the lowest level (~28,000) of the 30-year time-series.

Scottish harbour seals (Phoca vitulina) are genetically distinct from those in England and elsewhere in continental Europe, making the decline of this unique population particularly worrying in a wider conservation context.

Dr Debbie Russell, Deputy Director and SMRU’s lead seal population ecologist, said: “These latest counts are of huge concern. The declines amount to the loss of ~ 10,000 harbour seals in a five-year period; that level of decrease cannot be explained through reduced birth rates or survival of young alone. It points to the loss of adult animals which are generally expected to be relatively resilient to pressures”.

Grey seals abundance in Scotland is monitored through counts of pups as well as the August surveys. After increasing throughout the time-series, the number of pups born in Scotland appears to have levelled off to ~55,000 in 2023. Similarly, there had been an upward trend in August counts, but the most recent census indicated a decline of over a third compared to 2016-2019. This was largely driven by a very low count in Orkney; where numbers were 60% lower than the previous census.

Dr Russell added: “The implications of the decreased grey seal count are more nuanced. Compared to harbour seals, there is much more inherent variation in the grey seal counts so although we can be confident there has been a decrease, it is not possible to estimate the true magnitude yet. Furthermore, a decrease in grey seal abundance could be explained through temporary emigration to England and continental Europe. Nevertheless, it raises questions about the health of Scotland’s seas”.

The findings are underpinned by one of the most valuable marine mammal datasets in the world — a decades-long time series maintained by SMRU, which has systematically monitored seal populations using aerial surveys, photo-identification, and tagging studies since the 1980s. This long-term perspective is essential for detecting population trends and understanding underlying ecological changes.

NatureScot Marine Mobile Species Monitoring Advisor, Rona Sinclair, said: “These latest survey results for harbour seals are incredibly worrying and highlight the challenges facing our seas. They reinforce the importance of maintaining long-term monitoring, which provides robust, up-to-date evidence on seal population numbers, distribution and trends. NatureScot will continue to support comprehensive surveys and work closely with SMRU and other partners to better understand the causes of decline and factors holding back the recovery of Scotland’s harbour seal populations, so our conservation advice can be as strong and effective as possible.”

The causes of the harbour seal decline remain complex. SMRU is currently investigating several potential drivers in recent declines and lack of recovery, including disease, environmental change and reduced prey availability, possibly linked to climate change, and competition with and predation by grey seals. The scale of the declines raises urgent questions about the health and resilience of Scotland’s marine ecosystems.

 Dr Carol Sparling, SMRU Director, added: “These results should be a wake-up call. Scotland holds internationally important seal populations, and declines on these scales raise serious questions about the wider condition of our marine environment. If we are serious about meeting ambitious targets for nature recovery, we need to understand what these changes are telling us, and be prepared to act on this evidence. Long-term monitoring tells us where and how populations are changing, the challenge is to understand why, and to ensure that science informs effective decision making.”

The findings are expected to inform ongoing discussions around UK marine conservation strategies, including the management of Marine Protected Areas (MPAs) and the development of national action plans for marine biodiversity and conservation.

ENDS