Prioritization of Fish Welfare Issues in European Salmonid Aquaculture Using the Delphi Method

The European aquacultural sector is undergoing immense growth, and, generally, many more aquatic animals are farmed than land animals. However, the welfare of aquatic animals like fish has received less attention. This study focuses on the two largest contributors to Europe's aquaculture – Atlantic salmon and rainbow trout – farmed in cages in Northern Europe. An extensive literature review was conducted on potential welfare issues. These issues were grouped into five provisions / welfare aims according to an animal welfare framework adapted to fish. To set priorities among the issues, a Delphi assessment was performed, for which experts had to rate each issue based on the severity, duration, and prevalence. The participants were also asked to propose interventions to tackle the main issues. The three main welfare issues identified were ineffective prevention of diseases, sea lice treatment issues, and poor conditions during husbandry practices. Examples of interventions to improve the three main issues are lowering the stocking density, better monitoring, and specifically to prevent diseases, including sea lice, also developing more effective vaccines. This study provides valuable insights into which fish welfare issues should be tackled more urgently in European salmonid aquaculture. Future research could assess interventions more in depth and conduct similar studies for other aquatic farm animals and regions.