Summary
The steadily growing aquaculture industry has been blamed for increasing environmental impacts at local and global levels. The greatest increase in production is expected for freshwater fish, such as carp and related species. Decisions on sustainable environmental management strategies in aquaculture should be based on quantitative analyses of their environmental impacts. In this study, Life Cycle Assessment (LCA) methodology was employed to compare the environmental impacts of conventional and organic common carp (Cyprinus carpio L.) raised in traditional pond aquaculture. Data collected in personal interviews with carp farmers in southern Germany was used for inventory analysis. Interviews with farmers showed that in practice, the key difference between organic and conventional production of carp lies in the sourcing of feed grains from certified organic versus conventional origin. The results of the impact analysis showed that conventional carp production has higher indicator values for climate change, ozone depletion as well as ionizing radiation (human health) and uses more water resources. Organic production led to higher acidification and an increase of over 100% in marine and terrestrial eutrophication compared to conventional production. Independent of the production system, feed and pond dredging (i.e., the effort of sludge removal from the pond using machinery) were the main contributors to many of the impact categories, apart from freshwater eutrophication, which was largely dependent on the carp farming stage. Therefore, the environmental superiority of one production method over the other depends on the impact category analyzed. A comparison with previously published LCAs of fish and meat products for the impact category of climate change shows that both, conventional and organic carp, have significantly lower indicator values than products from recirculating aquaculture systems or terrestrial animal products, such as beef. This finding, as well as the retention functions and ecosystem services provided by carp ponds, contribute to the environmental sustainability of both forms of carp aquaculture studied. Further efforts to increase the systems sustainability should target the key areas of feed type and amount, frequency and method of pond dredging as well as the nutrient retention rate of carp, affecting potential emissions during harvest. Moreover, carp products with organic certification, wanting to uphold their claim of superior environmental friendliness, should address the critical issues uncovered in this LCA. Continuing methodological development, which acknowledges aquaculture specific impacts, will further increase the applicability of LCAs for products from aquaculture.