Panama Canal expansion and shifts in fishing practices: A social‐ecological network approach

Abstract Species introductions have spiked over the past two centuries due to globalization. These introductions impact ecosystems, but may also have long‐term implications for human communities. In one of the world's hubs for global shipping, the Panama Canal, a recent canal expansion has coincided with an increase in marine fishes entering the freshwater portion of the canal, Lake Gatun. These introductions may impact the lake's fishers who depend on that ecosystem for their livelihoods. Social‐ecological network (SEN) modelling presents a powerful tool to understand the combined impacts of these marine fish introductions on ecosystems and people. Using information from interviews with key stakeholders and available ecological data, this study constructs two SENs to analyse how the fish community composition and trophic links, as well as potential consequences on fishers' livelihoods and income from fishing, have changed after the canal expansion and the subsequent rise in marine fish species incursions. We found a less connected network after the expansion with a lower diversity of income sources for fishers, indicating decreased fisher, and thus network, resilience. Fishers in Lake Gatun widely reported sharp increases in populations of marine fishes coinciding with a decline in their catch of historically targeted species (e.g. the introduced freshwater Peacock Bass, Cichla cf. monoculus ). Network indices revealed differences in diversity of species targeted between small‐scale fishers and recreational fishing guides, and thus variable susceptibility to economic impacts from ecosystem changes as a result of marine fish incursions. Our results demonstrate the importance of income and target species diversification in small‐scale fishers' adaptive capacity to network‐wide impacts resulting from marine fish species moving into a freshwater lake ecosystem. This study framework highlights the value of local ecological knowledge in building a more holistic and nuanced understanding of the consequences of biological invasions. This study provides a first suggestion on how to adopt a SEN perspective for the analysis of species' invasion impact on aquatic ecosystems with the potential for application in policy‐making at the Panama Canal and in other case studies concerned with the pressing issue of species introductions. Read the free Plain Language Summary for this article on the Journal blog.