The fish weight at slaughter influences energy and environmental performance of fish farming: The case of Nile tilapia production in cages

The goal of this study was to evaluate the energy and environmental performance over the life cycle of Nile tilapia production for harvesting in different weight. The reference flow was 1 t (megagram - Mg) of fished Nile tilapia with the following weight: 0.6 kg, 0.9 kg, 1.2 kg, 1.5 kg, 1.8 kg and 2.0 kg. The inventory was defined for the stages of feed production and fish production with the processes for fingerlings, followed by rearing of juvenile and fattening of adult in cage. In addition, the inventory covered the supply of the remaining material and energy inputs, transport, infrastructure and waste management. The assessed categories were area occupation, water consumption, energy demand, global warming, acidification and eutrophication. Even though the smallersized fish demanded more fingerlings to produce 1 t of Nile tilapia than the larger ones, the feed conversion of the smaller-sized fish was more favorable compared to that of the larger-sized fish. The energy and environmental burden of Nile tilapia showed a tendency to increase with larger-sized fish. The largest contribution of area occupation, water consumption, energy demand and global warming was from feed production, while that of acidification and eutrophication was from the rearing and fattening processes of fish production. The choice of feed ingredient suppliers from more efficient and clean sources at feed production and the control of feed loss at fish production are key strategies to improve the energy and environmental performance of the fished Nile tilapia. Therefore, the sustainability of pisciculture must consider feed production from more eco-efficient ingredients, higher efficiency in feed conversion, control of feed loss, and the use of production effluent.