Fishers’ Local Ecological Knowledge of vulnerable marine ecosystems indicator species on the Portuguese continental shelf and upper slope

Cold-water corals and sponges form structurally complex habitats, classified as Vulnerable Marine Ecosystems (VMEs) that serve as refuge and feeding grounds for many marine species. Understanding their distribution is essential for effective management and conservation, yet knowledge gaps persist in many regions. This study aimed to co-develop a knowledge baseline on the diversity and distribution of VME-indicator species (VMEIs) by gathering Local Ecological Knowledge (LEK) from 70 professional fishers operating bottom-contacting gears (trawls, gill-/trammel nets, longlines) in three fishing harbours in Northern and Central mainland Portugal (Póvoa de Varzim, Matosinhos, Aveiro). Fishers identified benthic morphospecies from an image guide and provided information on their bathymetric distribution and abundance. Of the 53 morphospecies recognised, 33 are indicators of four VME habitat types, such as cold-water coral reefs, coral gardens, sponge aggregations, and seapen fields. These included framework-forming scleractinian corals (e.g. Dendrophyllia spp. Desmophyllum pertusum), octocorals including the precious coral (Corallium rubrum), ground-forming demosponges (e.g. Neochrammeniella bowerbankii, Axinella infundibuliformis), and field-forming seapens (e.g. Pennatula sp.). On average, gill-/trammel net fishers recognised more morphospecies than trawl fishers, likely due to differences in the benthic communities that occur on the types of seafloors where each fleet operates. Years of fishing experience and onboard role did not significantly influence LEK. This study highlights the potential of LEK to complement scientific assessments of VMEIs and support the development of management and conservation strategies. Engaging fishers in processes may enhance conservation efforts, inform restoration initiatives, and promote the sustainable management of deep-sea habitats and fish