St Andrews Researchers Monitoring Declining Harbour Seal Populations in Scotland

Researchers at the University of St Andrews Sea Mammal Research Unit (SMRU) have been monitoring harbour seal populations to understand the causes of their decline in population. Once a familiar sight along the Scottish coast, recent research reveals that the number of harbour seals in the UK has dropped by a quarter in just seven years.

Harbour seals (Phoca vitulina), also known as common seals, are one of two seal species found in the UK, with Scotland home to the largest population. While West Coast and Western Isles populations have remained stable or even grown, other regions have seen the opposite effect. Sealing numbers in the Tay Estuary have dropped by 95 per cent since 2000. The Orkney Islands have seen a 75 per cent decline. In the Shetland Islands, numbers are down by 30 per cent, raising considerable concerns amongst environmentalists about the future of the species in these regions.

One of SMRU’s key projects, the Harbour Seal Decline Project (HSDP), is focused on identifying the main factors behind population losses. By studying birth and survival rates and investigating potential threats such as declining fish stocks, pollution, and competition with the grey seal population, the team hopes to uncover why the populations are declining. Researchers hope to gather data to guide future conservation efforts using aerial surveys, photo identification, and ground counts.

As global temperatures rise, Marine Heat Waves (MHWs) — periods of unusually high ocean temperatures — are becoming more frequent in the North Atlantic. Climate models suggest these heat waves will continue to become more intense and prolonged in the coming decades, posing a major threat to marine ecosystems.

Although current research indicates that warmer waters may not directly affect harbour and grey seals, the long-term impact of MHWs is expected to disrupt their food supply. Key prey species like herring and sand eels are highly sensitive to temperature changes, meaning their population and distribution shifts could leave seals struggling to find enough to eat. Increased competition for food could put additional pressure on declining seal populations, making survival even more challenging. With climate change accelerating, understanding how MHWs affect marine ecosystems is more important than ever. Ongoing research will be key to assessing the long-term implications for seals and other aquatic life.

In a recent University report, Dr Debbie Russell, Deputy Director of SMRU, highlighted, “SMRU is conducting a programme of work to determine the cause of the South East England harbour seal declines, which will be critical to inform potential population recovery. The key potential causes of such declines include interactions with grey seals, increased human developments, toxins or disease, with multiple interacting factors being most likely.”

As the challenges facing harbour seals continue to grow, research and conservation must work together to address these issues fully. In congruence with the HSDP, the Scottish Government and various conservation organisations are ramping up efforts to protect marine habitats. Key initiatives include creating Marine Protected Areas (MPAs) and enforcing stricter commercial fishing regulations. These measures are designed to ease the pressure harbour seals face by ensuring healthier fish populations and minimal human disturbance.

The declining population of harbour seals serves as a reminder that climate change and human activity severely impact marine life. With the current threats posed by MHWs and other environmental stresses, continued conservation efforts are needed.

SMRU is currently asking the public to help them with their research by sending in images and videos of any seal observations to sealreports@st-andrews.ac.uk.

Image by Wikimedia Commons