Shetland Shellfish Stock Assessments 2024: A report prepared for the Shetland Shellfish Management Organisation (SSMO)

This report details the results of the latest shellfish stock assessments within the 6nm limit off Shetland alongside management recommendations for the Shetland Shellfish Management Organisation (SSMO). Data in this report originates from logsheet data supplied by fishermen, catch data from observer trips and age-at-length from market sampling.
Landings per unit effort (LPUE) is used as a proxy for estimating abundance across all species and for comparing interannual variation. Where length data is available (brown and velvet crabs), length-based assessments are used to investigate catch composition. When species can be aged in addition to length data (king scallops), a state-space assessment model (SAM) is applied, providing estimates of stock biomass and fishing mortality. Additional surveys are carried out to obtain fisheries-independent data.

Overall, the fisheries examined continue to demonstrate effective and sustainable management. Brown crab LPUE has increased despite reduced effort, though the west division remains below the limit reference point and should be closely monitored. The king scallop fishery shows a steady rise in LPUE, reaching the highest value in the time series, with initial SAM results supporting previous assessments and indicating increasing SSB and recruitment. Velvet crab LPUE has improved, now meeting target reference points for the first time in a decade. Lobster landings have declined since 2020, yet LPUE remains above average. Green crab LPUE remains steady, though reporting for this species is inconsistent. The queen scallop fishery, though lightly targeted, shows LPUE above the long-term mean. The common whelk fishery has recorded its highest LPUE since highlighting the need for ongoing monitoring, given its vulnerability to recruitment overfishing. Continued monitoring across all fisheries remains important, with particular emphasis on keeping LPUE within established harvest control rules and advancing assessment approaches such as SAM.