Assessment of aquaculture impact on Lake Titicaca: Combining Bayesian modelling and C and N stable isotopes to support sustainable management of fish farming

Aquaculture provides over half of the world's fish for human consumption but raises significant environmental concerns. In response, improved farming technologies have been developed, including cages equipped with waste collectors designed to intercept faecal pellets and uneaten feed.In this study, we assessed the environmental effects of cage-based trout farming in Lake Titicaca, a high-altitude lake shared between Peru and Bolivia. By integrating physicochemical variables, eutrophication-related indicators, and C and N stable isotopes, we tested whether trout cages and waste collectors influence water quality and isotopic signatures of sediments. Treatment effects were quantified using multivariate Bayesian modelling, accounting for spatial and seasonal variability.Our results indicate that trout farming contributes to local nutrient enrichment and reduced water transparency, although their effects were modulated by spatial and seasonal heterogeneity. Waters without cages showed lowest N concentrations and highest transparency, whereas cages equipped with waste collectors were associated with increased nitrates in waters. Stable isotopes revealed marked spatial differences in sediment values, while treatment-related isotopic differences were negligible. Overall, our integrative approach demonstrates the effectiveness of combining statistical modelling with multiple ecological indicators to decouple aquaculture impacts from inherent environmental variability. This provides a scientifically rigorous framework for validating mitigation technologies in sensitive, high-altitude freshwater ecosystems. Our findings underscore that waste collectors necessitate stringent operational management—such as regular waste extraction—to prevent nutrient leaching, ensure functional efficiency, and foster sustainable aquaculture strategies.