The dilemma of opportunity in developing a life cycle assessment of emerging aquaculture systems - a case study of a Eurasian perch (Perca fluviatilis) hatchery recirculating aquaculture system.

Abstract Eurasian perch (Perca fluviatilis) has been identified as an aquaculture species that can contribute to supply and supplement wild stocks for niche markets in European alpine regions. As a species earmarked for expansion it is important to benchmark the environmental impact associated with its production. The case study site presented a dilemma of opportunity (the dilemma of carrying out a study to inform production processes, at the beginning or development of a product/system or to wait until it is established and in steady state). This dilemma is often a limiting factor in the assessment of emerging systems or products and as a result this site was data deficient in a number of areas (energy use, growth rate and water use) which required the use of an ab initio approach to overcome these gaps. Data for growth, oxygen and heating were modelled for one kilogram of fish to the farmgate for 2018. The generated data was investigated for environmental impact using life cycle assessment (LCA). Impact categories included in the study were global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), freshwater and marine ecotoxicity potential (FAETP and MAETP), cumulative energy demand (CED), net primary production use (NPPU) and water use. The results indicated that there was high variability between the inputs, outputs and impacts associated with the production of perch to the farmgate. The highest variability was observed in live feed use and energy inputs between the batches. This was related to egg quality and the survival rates of the batches. The nursery stage of production was found to have the greatest environmental burden of all stages. EP was dominated by emissions from the stock. Electricity use and feed were the greatest contributors to GWP, AP and FAETP. Electricity and heating had the greatest share of CED and MAETP. Water use (using the AWARE methodology) was dominated by feed production, fish culture and electricity generation. The result of this analysis echoes that of similar studies in that the dominant contributors to the life cycle impacts of RAS products are electricity and feed. This study constitutes the first LCA of perch production in RAS. In addition to this, the study also outlines a framework and methodology, which can be used to overcome the dilemma of opportunity when assessing the environmental burden of an emerging aquaculture system or species. This approach allows operators to overcome data deficits, which may exist and implement impact strategies prior to the finalisation of the process or system.