Shaun Fraser, Alice Newbould, Evie Herrington, Katie Cubbon. UHI Shetland.

Executive summary

This report details the results from the first dedicated Fair Isle sandeel survey. Sandeels play a key role in the marine food web and are particularly important in the context of Fair Isle’s seabird populations. Recent sandeel survey work in Shetland has been undertaken annually since 2023 but these surveys did not extend as far south as the traditional sandeel fishing grounds to the east and west of Fair Isle. Thus, given the lack of sandeel data for the Fair Isle area, and importance of sandeel to the wider ecosystem, there was strong local and scientific interest in conducting further research to assess the status of Fair Isle sandeel populations.

Data were collected by UHI Shetland staff during May 2025 on board the 12 m MV Atlantia II (LK 502) using a specialised survey trawl to sample sandeel. This survey gear and method was identical to that used in surveys carried out in the late 90s, which enabled direct comparison of catch rates with historic data. Additional environmental data were collected using baited remote underwater video (BRUV) systems which were deployed at the seabed and mid-water to record the benthic and pelagic environments. Sediment samples were taken using a Van Veen grab sampler.

Four species of sandeel were observed in the trawl catches from around Fair Isle: smooth sandeel (Gymnammodytes semisquamatus), Raitt’s sandeel (Ammodytes marinus), great sandeel (Hyperoplus lanceolatus), and a small catch of Corbin’s sandeel (Hyperoplus immaculatus). Analysis of sediment samples, BRUV footage, and catch data confirmed that sandeel were present in habitats characterised by circalittoral fine sand with the highest sandeel concentrations observed in the shallower areas of sandbanks to the west and east of Fair Isle.

The catch rate results show that smooth sandeel were the most prevalent and by far the most abundant species observed around Fair Isle. Compared to catch rate data from elsewhere in Shetland, Fair Isle sandeel were comprised of a higher proportion of smooth sandeel (90.15% compared to 72.21%); however, the total catch rate (all species combined) was overall very similar between survey areas (406.05 kg/hr in Shetland and 400.60 kg/hr for Fair Isle) and broadly within the range of monthly average catch rates in historic data from the late 90s.

Raitt’s sandeel dominate the historic catch data from Fair Isle and spawn earlier in the year than smooth sandeel. Thus, the potential shift to a smooth sandeel dominated ecosystem has profound implications for Fair Isle seabird populations that depend on the availability of small sandeel at specific times of year to provision chicks.

These results are discussed in the context of other available information and recommendations made including future sandeel research to support the management of the Fair Isle DR MPA.