Pathways to sustainability or collapse in inland small-scale aquaculture systems: insights from a social–ecological systems model

Despite the promise of small-scale aquaculture for improving food security and alleviating poverty, its long-term sustainability remains poorly understood, particularly in contexts where economic and ecological processes reinforce each other. This paper develops a stylized social-ecological model that captures feedbacks between producer wealth, fish biomass, and nutrient dynamics in pond aquaculture. The model reveals how these intertwined feedbacks shape the long-term dynamics of the system and lead to monostability, bistability, or multistability. These regimes correspond to collapse, a high-yield but high-risk, and a sustainable equilibrium in fish production. Using bifurcation and stability analysis, we identify six dynamic scenarios: Clearwater, Overload, Flux, Knife-edge, Tipping pond and Decay, that represent qualitatively different long-term outcomes. Rather than predicting specific outcomes, the model gives a structural understanding of small-scale aquaculture dynamics and highlights the importance of local context and producers' heterogeneity in shaping the outcomes. It also provides a theoretical foundation for scenario-based management and empirical model development.