Mama’s Clams: Environmental Performance of an Extended Nursery Phase for Manila Clams—Sand-Nurseries as a Potential Strategy to Address Juvenile Scarcity

Between 2014 and 2023, Italian Manila clam ( Ruditapes philippinarum ) production declined by 36% due to climate change and predation by the invasive blue crab ( Callinectes sapidus ), which preys particularly on small clams. Traditionally, Manila clam farming starts with seed collection from natural recruitment or hatcheries, followed by pre-fattening in raceways and/or FLUPSY (Floating Upweller Systems) to size T3 (>3 mm). The fattening phase in lagoons up to the commercial size (>25 mm) follows. Rearing juveniles in controlled conditions may ensure stable supplies of high-quality seed, reduced mortality, and increase overall yields. Furthermore, a larger pre-seeding size (e.g., T10, >10 mm) is supposed to improve resistance to predators and environmental stress. This study uses an ex-ante Life Cycle Assessment (LCA) to evaluate the potential environmental impacts of a novel and unique “sand-nursery” method under development at an Italian company. The nutrient removal potential of juvenile clams was also assessed as an ecosystem service. At full capacity, the optimised system could produce 120 t of liveweight juveniles and remove 338 kg of nitrogen and 32 kg of phosphorus. Although it has inherent limitations, the ex-ante LCA results show that electricity consumption is the main contributor to environmental impacts, with a global warming potential of 1.11 kg CO 2 eq/kg T10 clam. Further research is needed to assess impacts across the full production cycle.