Engaging small-scale fishers in a circular bioeconomy: valorization of Rhizostoma pulmo (Macri, 1778) jellyfish bycatch for sustainable collagen production

Jellyfish bycatch poses challenges for small-scale fisheries by increasing costs and generating underutilized biomass. Yet this same biomass could represent a valuable resource, as jellyfish are an emerging source of collagen with a wide range of biotechnological applications. Within the COLMED project, a collaboration between researchers and fishers was established to explore the sustainable valorization of jellyfish bycatch for collagen extraction as part of a circular bioeconomy strategy. The aims were to: (1) assess fishers’ perceptions and willingness to engage in jellyfish valorization; (2) quantify bycatch occurrence and species composition; and (3) evaluate the structural and molecular integrity of collagen derived from bycatch specimens. Fishers’ perspectives were gathered through semi-structured interviews across four small-scale fishing guilds in Catalonia and the Valencian Community, in the Spanish Mediterranean. Results revealed strong engagement and positive attitudes toward jellyfish valorization, although institutional, technical, and training support were key bottlenecks. Thirteen months of monitoring yielded the first quantitative baseline of jellyfish bycatch in the study area, with Rhizostoma pulmo and Pelagia noctiluca as the most abundant species. Collagen extracted from R. pulmo, whether hand-net collected or obtained as bycatch, retained molecular integrity, confirmed by SDS-PAGE, FTIR, and XRD analyses, demonstrating characteristic type I collagen bands, preserved amide groups, and native triple-helical patterns. These results show that incidental capture does not compromise collagen quality and support the use of R. pulmo bycatch as a sustainable marine collagen source. Overall, this study presents a novel interdisciplinary framework linking fisheries sustainability, ocean literacy, and the circular bioeconomy. It underscores the broader potential of jellyfish bycatch valorization to strengthen small-scale fisheries resilience and advance the development of high-value marine bioresources.