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bioRxiv · 10.64898/2026.02.08.704719

Lessons from local ecological knowledge: cumulative stressors and governance constraints in Spanish clam fisheries

Baeta, M.·Benestan, L. M.·Solis, M. A.·Madrones, M.·Delgado, M.·Silva, L.·Rodilla Alama, M.·Falco Giaccaglia, S. L.·Ballesteros Vazquez, M.·Hampel, M.·Rico, C.
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Abstract

Spanish clam fisheries have contracted sharply over the past two decades, with repeated closures and declining landings affecting coastal livelihoods. Using local ecological knowledge (LEK), we examine how fishers, fishers guild leaders and regional managers interpret (i) ecological change and (ii) the institutional conditions shaping management outcomes in Spains main clam fisheries, focusing on wedge clam (Donax trunculus), striped venus clam (Chamelea gallina) and smooth clam (Callista chione). We conducted 94 semi-structured interviews (April 2024-August 2025) across the Spanish Mediterranean and the south Atlantic coast (Catalonia, Valencian Community, Balearic Islands, Murcia and Andalusia). Stakeholders characterised declines as a cumulative process driven by interacting stressors: climate variability and extremes, coastal habitat alteration, pollution, episodic disease events and fishing pressure intensified by illegal extraction and informal marketing. Governance assessments were predominantly negative, emphasising fragmented authority across administrative scales, delayed or reactive measures, uneven rules among gears exploiting shared stocks, limited user influence in decision-making, and chronic monitoring and enforcement gaps, especially for shore-based fisheries operating outside port-based control points. Overall, LEK closely aligns with scientific evidence on cumulative stressors, suggesting that persistent declines reflect less a lack of ecological understanding than institutional constraints that hinder timely, legitimate and enforceable responses. Policy priorities include climate-adaptive harvest rules linked to environmental indicators, co-produced monitoring, strengthened traceability and compliance, harmonised rules across gears and management units, and improved cross-sector coordination to reduce conflict and safeguard nearshore habitats. HighlightsO_LIStakeholders across Spain describe clam declines as the outcome of interacting ecological, climatic, and governance stressors rather than as the consequence of isolated drivers. C_LIO_LIPerceived drivers differ regionally: climate- and habitat-related pressures dominate the Mediterranean, while effort, illegal fishing, and market dynamics are more salient in the Gulf of Cadiz. C_LIO_LIMost interviewees view management and governance as ineffective, citing fragmented authority, uneven rules among gears and regions, and weak enforcement. C_LIO_LIInformal practices (off-auction sales and poaching) are repeatedly identified as mechanisms undermining legitimacy, traceability, and effort controls--particularly in nearshore wedge clam fisheries. C_LIO_LIPolicy pathways include harmonising cross-scale rules, strengthening monitoring and compliance, and institutionalising co-management that integrates LEK with science. C_LI

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Baeta, M., Benestan, L. M., Solis, M. A., Madrones, M., Delgado, M., Silva, L., Rodilla Alama, M., Falco Giaccaglia, S. L., Ballesteros Vazquez, M., Hampel, M., Rico, C.. 2026-02-09. Lessons from local ecological knowledge: cumulative stressors and governance constraints in Spanish clam fisheries. https://doi.org/10.64898/2026.02.08.704719

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