Product Environmental Footprint (PEF) of a case study on gilthead seabream (Sparus aurata) juveniles fed side-streams from farmed blue mussel

Transparent and precise information on the environmental impacts of products is critical for informed decision-making. In the EU, gilthead seabream ( Sparus aurata ) is among the most profitable aquaculture species. The environmental impacts of aquaculture vary depending on input factors. Despite the importance of hatcheries and nurseries in aquaculture, there are currently several knowledge gaps related to footprints, particularly outside of salmonid life cycle assessments. This study analysed the environmental footprint of a case study on rearing juvenile gilthead seabreams, and the implications of utilising byproducts from blue mussel ( Mytilus galloprovincialis ) aquaculture as a fish feed ingredient following the LCA principles in the Product Environmental Footprint (PEF). Data were collected from a research facility where fish juveniles were fed diets with fishmeal partially or fully substituted with blue mussel meal at 100%, 50%, or 0% in a triplicate study design. The results showed that the use of electricity and the feed were the largest contributors to most impact categories. Electricity use was primarily driven by the indoor flow-through facility's high-water renewal and lighting requirements. The sensitivity analyses showed a high uncertainty related to the impacts from the blue mussel meal. The total environmental footprint of juveniles was significantly higher when compared to fully grown finfish from aquaculture per functional unit, mirroring the higher input requirements during early life stages. Blue mussel meal shows to be similar to fishmeal from a palatability and growth perspective, however, its use may increase environmental impacts. Nevertheless, as the aquaculture industry continues to expand to meet global food demands, utilising a current waste stream might be among few feasible options to cover nutrient demands of marine fish.