ZMT - Leibniz Zentrum für Marine Tropenforschung

Abstract/Summary:

This thesis examines the social-ecological dynamics of two Peruvian bay systems: Independencia Bay, located within a marine protected area and shaped by the cold, nutrient-rich upwelling of the Northern Humboldt Current Upwelling System, and the much larger Sechura Bay in northern Peru, located at the transition between Humboldt and tropical waters. Both systems are highly productive, have been socially and ecologically linked for decades, and rely on small-scale fisheries and scallop aquaculture. Using Ecopath with Ecosim (EwE) models, time-series analyses and a governance case study from the Guano Islands Marine Protected Area, this research explores how environmental and fisheries-related drivers, including El Niño events and marine heatwaves, shape trophic dynamics, ecosystem resilience and resource use, while addressing governance challenges in managing interconnected systems. The results show structural and functional differences between these bays. Sechura Bay has higher biodiversity, but appears to be more vulnerable to stressors such as hypoxia and warming events that disrupt trophic interactions and species availability. In contrast, Independencia Bay shows resilience, with stable upwelling supporting a rapid return to pre-disturbance conditions. Dynamic simulations suggest that localised marine heatwaves affecting Sechura Bay may have masked effects on the productivity of Independencia Bay. Furthermore, an increased frequency of future warming events - despite changes in biomass and production - does not appear to push Independencia Bay past an ecosystem tipping point over a 100-year simulation. More frequent events resulted in higher average catches, further suggesting that Independencia Bay is a well-adapted, resilient system. However, frequent increases in fishing effort without corresponding increases in biomass indicate gradual ecosystem degradation over time. Following such events, a redistribution of fishing effort towards more resilient species, such as rock crabs and mussels, emerges as a promising adaptive management strategy to support ecosystem recovery while maintaining stable catches. These models and simulations provide valuable insights for local adaptive management strategies, which should integrate social-ecological connectivity. The Guano Islands case study reveals fragmented management, limited stakeholder participation and institutional constraints that hinder effective conservation, highlighting the need to integrate social-ecological connectivity into governance frameworks. By combining trophic modelling, time series analysis and governance studies, this research contributes to the discussion on ecosystem-based adaptive management and provides insights into a transferable management framework that simulates climate and fisheries impacts in social-ecological systems. It highlights the importance of adaptation strategies tailored to local socio-ecological conditions, while taking into account large-scale drivers such as climate change.