Valorization of Fishery and Aquaculture Wastes in Madeira Archipelago: Addressing Challenges and Opportunities

Fish processing generates substantial quantities of by-products, creating important management and valorization challenges, particularly in insular regions. This study provides a first-order quantification of fishery and aquaculture wastes in the Madeira archipelago. The methodology combined a feed-based mass-balance model, targeted data collection, stakeholder analysis, and valorization assessment. Organic matter (OM) released from marine cage aquaculture was estimated at approximately 851.6 t yr−1 (dry weight), while fish by-products from processing activities in factories and retail stores generated approximately 938 t yr−1 (wet weight). These waste streams differ substantially in their physical characteristics and management pathways, with aquaculture producing diffuse environmental discharges and processing activities generating concentrated and potentially recoverable residues. Structured stakeholder interviews identified limited scale and insufficient raw materials, logistics and labor as the main factors affecting valorization initiatives. A comparative multi-criteria assessment further evaluated potential valorization strategies based on environmental performance and economic viability. Despite the generation of organic residues, the results suggest that effective valorization is constrained less by total waste generation than by biomass fragmentation, logistical limitations, and restricted economies of scale, emphasizing the need for integrated circular management approaches. A combined approach, integrating farm usage of decaying OM from cage systems and locally supported valorization strategies is required to transition towards a more resource-efficient production system.