Impacts of invasive algae from the perspective of fishers in the Lagoon of Venice, Northern Italy

Invasive alien species are generally considered a cause of biodiversity decline globally, and studying their evolution could provide valuable insights about their invasion mechanism and impacts to new habitats. The Lagoon of Venice (LV) is a significant gateway for invasive algae introduction into the Adriatic Sea. This work aims to address the pressing need to enhance research on the perceptions of local resource users, especially fishers, on invasive algae impacts on marine resources in the Mediterranean setting. The study conducted between February 2022 and April 2024 involved 31 people, most of whom had been engaged in fishing activities for up to over 60 years, who were interviewed during boat trips and algae collection. Interviewees reported knowledge components, complemented by scientific expertise, related to the invasion mechanisms of algae. Of the 26 identified algae recorded, eight taxa have not yet been reported with their scientific names in surveys on the impact of algae in the LV. Together with perceived reasons and related challenges, environmental impacts, solutions proposed by local fishing experts, and adaptations along with their positive uses are socio-economic impacts which are lacking in the LV scientific surveys. The findings reveal perceptions on the direct and indirect impacts of invasive macroalgae in the LV environment affecting its coastal ecosystem functions. Local fishers' knowledge (LFK) offers many ecologically relevant perspectives, which based on the long-lasting practice could complement scientific knowledge (SK) about the impacts of invasive algae and local stressors related to climate change. Hence, it is vital to integrate the broader knowledge of fishers and include them as equal stakeholders in conservation initiatives.