From Invaders to Resources: Evaluating Freshwater Invasive Species as Sustainable Sources for Aquaculture Feed

The increasing spread of invasive alien species (IAS) represents one of the major causes of biodiversity loss, making containment practices necessary. In this regard, the circular economy framework proposes to reuse the biomass from IAS in growing sectors such as aquaculture, in which more sustainable practices are required. This study evaluated the possibility of using biomass derived from two widespread freshwater IAS, Procambarus clarkii and Silurus glanis , as dietary ingredients for Oncorhynchus mykiss . Experimental diets were formulated by incorporating 20% of IAS-derived muscle powder into a commercial feed, and their effects were assessed through a 35-day feeding trial. Chemical analyses confirmed the nutritional suitability of the formulated diets and the absence of antibiotic residues. No mortality or significant differences in growth performance were observed among treatments. Blood biochemical parameters showed limited variations, remaining within physiological ranges, while oxidative stress biomarkers indicated only minor, diet-specific responses without evidence of oxidative damage. An increase in Hsp70 expression suggested adaptive physiological responses rather than pathological stress. Histological analyses of liver and gut tissues revealed no structural alterations across experimental groups. Overall, the results demonstrate that the inclusion of IAS-derived biomass at 20% is well tolerated by O. mykiss and does not impair fish health. These findings support the potential of invasive species valorization as a sustainable strategy for aquaculture feed production, contributing to both resource efficiency and ecosystem management.