Risk Assessment of Recirculation Systems in Salmonid Hatcheries

To be able to judge whether existing legislation is adequate in safeguarding fish welfare in hatcheries where water is recirculated, the Norwegian Food Safety Authority requested the Norwegian Scientific Committee for Food Safety (VKM) to conduct an assessment of the current situation and whether, or to which degree, a risk of injury, disease or other unnecessary suffering exists. The assessment is limited to salmon and rainbow trout in freshwater systems. Based on literature data and practical experiences from recirculating aquaculture systems (RAS), possible environmental effects on fish welfare were assessed. It is clear that there is a risk that the water quality in RAS can deteriorate and cause severely compromised welfare for the fish. On the other hand, a well-managed RAS can in fact stabilize, or even improve water quality, resulting in better welfare compared with some flow-through systems