Résumé
Selective breeding plays a key role in the sustainable development of aquaculture by improving productivity and efficiency. While breeding programs have initially focused on growth traits, their potential to mitigate the environmental footprint of fish farming remains poorly explored. Here, we present a case-study on the environmental consequences of selective breeding during five generations (15 years) for growth and fillet yield in gilthead sea bream Sparus aurata by integrating genetic gain projections into a full supply chain Life Cycle Assessment (LCA), extending from hatchery to final consumer. The potential impacts were calculated in terms of 1 tonne of fish produced at the farm level and were also expressed per tonne of flesh consumed. Performance data and genetic parameters from families in a seabream breeding program were used to estimate breeding values under different selection scenarios. Selection for growth significantly shortened the production cycle, while selection for fillet yield increased the proportion of edible product. Although environmental gains at the farm level were modest (<1 %), substantial reductions (up to 7 % in climate change impacts and cumulative energy demand) were observed when impacts were expressed per tonne of fillet consumed. Feed production and consumption remained the dominant source of environmental burden across all scenarios. By explicitly accounting for post-farm stagesprocessing, distribution, consumption, and waste management -our study demonstrates that genetic improvement, particularly for fillet yield, can meaningfully reduce the environmental footprint of aquaculture products delivered to the consumer. This case study underlines the importance of integrating full supply chain assessments into genetic selection strategies to drive sustainable breeding in aquaculture.