Historical exploitation and widespread decline of blue mussel (Mytilus edulis) bed habitat in Scotland

Historical records reveal that sustained anthropogenic exploitation drove widespread decline of blue mussel ( Mytilus edulis ) bed habitat in Scotland by the early 20 th century. We synthesised >200 archival records published between 1760-1970 and over a century of landings data to reconstruct the historical distribution, extent and status of Scottish mussel beds, and document the history and trajectory of the mussel and associated line fishing industries. Archival evidence enabled the mapping of 124 historical beds at a resolution of 5km 2 ; by the early 1900s, 51% were reported as nearly or entirely exhausted or destroyed. Only one source described localised recovery in the 1960s, years after exploitation ceased. Spatial extent data were available for 31% of the historical mussel beds and for three mussel fishing areas, representing ∼1,800 hectares and ∼5,600 hectares respectively. From at least the 16 th century, mussels were highly sought after and intensively harvested primarily for line-fishing bait. Across the 1800s, accelerated exploitation compounded by additional stressors, viz. pollution, trawling, trampling, predation and smothering, drove widespread degradation of mussel bed habitat and likely reduced ecosystem resilience, with lasting ecological and socio-economic consequences. Mussel landings exceeded 10,000 tonnes in the late 19 th century but significantly declined thereafter and ceased entirely by 2004- mirroring significant declines in line fishing landings. Reduced mussel bait availability, rising competition with trawlers and alternative job opportunities were key drivers. This unique empirical record provides valuable context for contemporary habitat restoration efforts by identifying historical locations and extents of a now much reduced and threatened habitat. • 124 historical Scottish blue mussel beds mapped from >200 archival records • Mussels were intensively exploited for line fishing bait across 19 th -20 th centuries • Over half of beds were destroyed or exhausted by the early 1900s • Mussel landings declined from ∼14,000 tonnes year -1 (1880) to 0 tonnes (2004) • Historical record provides context and guidance for habitat restoration