Identification and economic valuation of fishery resources associated with subtidal macroalgal forests: a case study from Northern Portugal

An in-depth understanding of ecosystem services is essential for informing policy decisions and supporting the sustainable management of local resources. Subtidal marine forests, dominated by large brown seaweeds, are biodiversity-rich habitats that deliver key ecosystem services to society, including the provision of fishery resources. In this context, the present study identifies and economically values the fishery resources associated with these habitats, using Northern Portugal as the study region. To achieve this, we conducted in situ video (2 min 34 s ± 0 min 58 s) surveys along the regional coast to identify fishery resources associated with subtidal macroalgal forests and assess Marine Protected Area (MPA) effects. In parallel, analyses of official landing data (2021-2024) allowed us to estimate the economic value of marine forest-dependent resources exploited by small-scale fisheries (SSF). A total of 298 fish belonging to six families were recorded, with pouting (Trisopterus luscus) and sea bass (Dicentrarchus labrax) showing the highest abundances. The commercially valuable purple sea urchin (Paracentrotus lividus) was also identified, with significantly higher abundance inside the MPA. Landing data revealed that regional SSF captured 111-122 different fishery resources annually, generating 7.61±0.6 × 106€ yr-1. Among these, 44 species were identified as dependent on macroalgal forests. The economic value of this subset was estimated at 1.83±0.2 × 106€ per year, with the common octopus (Octopus vulgaris) alone contributing 1.00±0.2 × 106€ per year. Our results confirm that subtidal macroalgal forests in Northern Portugal not only support a characteristic assemblage of non-benthic ichthyofauna but also deliver key ecosystem services by sustaining fishery resources exploited by SSF. These findings highlight the socio-economic relevance of these foundational habitats and the need for effective conservation and management to ensure their long-term sustainability.