Environmental assessment of freshwater aquaculture in Ireland
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Aquaculture is the fastest growing food production activity in the world and has been for the last several decades. With over 60% of wild fish stocks at or below their maximum sustainable yield, it is expected that to relieve this pressure that fish and seafood products will be produced using alternative means, namely aquaculture. Aquaculture is an activity not without its impacts (like all food production activities). If aquaculture is to become the primary source of marine protein, there need to be increases in production efficiencies and identification of hotspots in these systems. European countries are required to have national strategic plans for the development of sustainable aquaculture under the Common Fisheries Policy. In Ireland, this has resulted in the National Strategic Plan for Sustainable Aquaculture Development, which aims to increase aquaculture production and diversify the sector with novel species. Against this proposed expansion, it is imperative to benchmark and characterise the environmental performance of the sector. A popular tool popular in capturing the environmental impacts of a process, system or product, is life cycle assessment (LCA). LCA is a technique, which accounts for the inputs, outputs and impacts associated with a production system. It was first applied to aquaculture production in the early 2000s. Studies have used impact categories such as global warming potential (GWP), eutrophication potential (EP) and acidification potential to name a few. One impact category, which has been under investigated with aquaculture LCAs, is biodiversity. The expansion and intensification of the aquaculture sector in Ireland is likely to result in an increase in the number of freshwater sites. These systems abstract water from rivers and lakes and discharge the nutrient enriched waters back to the rivers. There are currently no plans to use recirculating aquaculture systems (RAS) within the salmonid sector, as this would disallow the hallmark of Irish aquaculture, organic status. The Water Framework Directive (WFD) is European law that requires that all surface waters meet or maintain good ecological status. The WFD in essence aims to maintain high levels of biodiversity in freshwater systems. The aim of this body of work was to complete LCAs of the main and emerging freshwater aquaculture species in Ireland, while using the WFD as a common framework to develop biodiversity indicators for future aquaculture LCAs. The LCAs focused on sites which produced 66% of Atlantic salmon smolts (Salmo salar), 47% of rainbow trout (Oncorhynchus mykiss) and 100% of Eurasian perch (Perca fluviatilis), or 57% of average annual freshwater output. The results of the LCAs were in line with international studies, in that feed was the dominant contributor to environmental burden. Water use and GWP for trout were higher than was previously reported and energy use for smolts was lower. The perch LCA required an ab initio approach due to data deficits, but showed that the results were in line with other studies of species cultured in RAS. This was also the first LCA of perch culture carried out. The EP (as kg PO4 eq.) of the sector was investigated using three different approaches, regulatory, hydrobiological and nutritional. The results of these methods indicated that aquaculture was under utilising its regulatory EP. Comparisons between other land based food production activities were made (beef, dairy, sheep and tillage), on EP, value (€) and land use. The results indicated that tillage had the lowest EP per tonne, followed by aquaculture. A monitoring campaign conducted to assess the impact and recovery of water quality in terms of physical, chemical and biological parameters due to aquaculture discharges. The results of this monitoring indicated that in general there was a recovery in biological water quality within 1,000 m of the site. Increases in nutrient concentrations in several instance indicated there were other contributors to changes in water quality. The results of this monitoring were used to propose several indicators for biodiversity and its supporting mechanism for freshwater aquaculture. These indicators covered physical (hydromorphology), biological (ecological quality rating) and chemical (catchment nutrient budget) components. In conclusion, the results of the study provided the first results of LCA on aquaculture in Ireland and for an emerging aquaculture, species (perch). It contextualised the role that aquaculture has in sustainable food production against other land based systems. It demonstrated that in terms of EP and land use that it performs more efficiently than beef, sheep and tillage activities with a higher gross economic output. Indicators on biodiversity in LCA were also proposed using a pan-European framework (WFD) which can be used not only in aquaculture but also in other activities (wastewater and drinking water). Future recommendations are also made on how to develop sustainable aquaculture and food production plans using a catchment based LCA.
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