Mussel culture carrying capacity: Learning from the past to face the future

At the northern boundary of the NE Atlantic upwelling system, seasonal wind patterns that facilitate the influx of nutrient-rich waters, combined with the presence of protected embayments known as the Galician Rías, have established this region as the third largest producer of mussels in the planet. Since the early 1970s, the need to ensure sustainable exploitation of this natural resource has prompted scientific and administrative efforts to identify environmental conditions that optimize mussel farming and to clarify the impacts of mussel cultivation on marine food web dynamics. This article synthesizes scientific advances from recent decades, including research on turnover times in the Galician Rías and diverse methodologies for defining ecosystem carrying capacity. Recent in situ analyses have revealed intense turbulent flows in and around mussel cultivation units, thereby challenging earlier carrying capacity models that assumed linear water flow through rafts and cultivation polygons. This finding highlights the importance of incorporating seasonal fluctuations in food availability, both within and beyond the turbulent zone, when evaluating the future sustainability of mussel aquaculture. Additionally, the strong dependence of regional productivity on wind regime seasonality requires that any modeling of mussel farming in the Galician Rías should consider potential hydrographic and hydrodynamic changes within the embayments, whether due to interannual ocean-atmosphere variability or global climate change. Such an integrated approach is essential for developing an action plan that ensures the long-term sustainability of mussel farming in the Galician Rías.