High mortality and reduced fish welfare has a major influence on the reputation of Norwegian Atlantic salmon farming, and it represents economic losses for producers. To make a shift towards a more sustainable production, welfare need to improve and the mortalities must be reduced. S tudies have found high mortalities after sea transfer of salmon smolts, and a connection between such mortality and which freshwater farm the smolt group comes from has been suggested. This indicates that the conditions experienced in the freshwater farm will affect the performance and survival after transfer to seawater . The aim of this study was to identify qualitative and quantitative r isk factors in the freshwater farms for mortality after sea transfer for Atlantic salmon smolts , and describe how management and organisational factors affect this outcome.
A qualitative approach using individual interviews was applied to explore the aims. Participants for the interviews were recruited from fish farming and fish health companies. A total of 15 in-depth interviews was conducted online using Teams , 10 with operations managers at freshwater farms, and five with fish health personnel who had experience working with fish health in freshwater farms for Atlantic salmon. The participants represent nine different companies, with three companies providing fish health services, and six companies producing Atlantic salmon. A semi structured interview guide was used, with the following topics: Factors influencing smolt m ortalities, factors influencing fish welfare and husbandry practices. The transcribed interviews were analysed by Systematic Text Condensation, a systematic thematic cross-case analysis strategy.
The results showed that the risk factors for mortalities after sea transfer in Atlantic salmon are a combination of non-infectious factors and infectious diseases that are mediated by management practices and organisational factors in the freshwater farms. In addition, risk factors related to the transfer itself were identified. The participants reported that even if the infectious diseases are brought from the freshwate r farm and cause mortalities after sea transfer, non-infectious diseases and factors cause the majority of the smolt-related mortality after sea transfer. These risk factors relates to production and management practices including smoltification strategy, large diversity in smolt size within groups, production of large smolts, strategies for destruction and sorting, densities, handling, suboptimal feeding, and water quality management. The intensity of the production was also highlighted by the participants. The organisational factors identified in the interviews included formal structures such as being part of a large company, culture and knowledge such as motivation and competence, interactions such as communication and production planning, and factors related to the physical conditions of the farm.
By using a qualitative approach to investigate potential risk factors for smolt mortalities after sea transfer, this study aimed to identify the perceptions and experiences of relevant stakeholders in the production of smolts. Risk factors identified in this study will be used in a complementary quantitative study .