Reviewing the Severity of Handling-Induced Injuries in the LAKSVEL Protocol for Salmon Welfare

Injuries from lice treatments are ranked as a major cause of mortality and poor welfare for Atlantic salmon in marine net pens. As a result, scoring schemes based on the external appearance of injuries and severity are now frequently used. One such recently developed scheme for farmed salmon is the LAKSVEL protocol, inspired by previous schemes such as the SWIM models and the FISHWELL scoring system. Here we review the injury-based welfare indicators (WIs) in the LAKSVEL protocol that can be associated with and induced by handling: Scale loss, Skin bleeding, Body wounds, Snout wounds, Eye injuries, Operculum damage, Gill status, and Fin damage. We used semantic modeling as a formalized procedure to attain information from the literature on how each of these injury-based WIs is likely to affect the injured fish in the days and weeks to come. Based on the reviews, we then followed the semantic modeling procedure to define weighting categories and score the welfare consequences of each WI and their levels. Results showed that injuries to eyes, gills, and snout are particularly harmful to the fish, followed by penetrating body wounds, operculum damage, and fin damage; but also injuries such as scale loss and skin bleeding can have severe consequences, especially if they indicate unseen internal injuries. It is our hope that the presented reviews and modeling of welfare consequences will be a valuable resource for fish farmers and fish health personnel in their decision-making processes and thereby contribute to improved fish welfare in the salmon aquaculture industry.