Critical review of common approaches to evaluate fin condition of farmed fish

Abstract

Fin condition is one of the most frequently used welfare parameters for farmed fish. However, several methods for actually evaluating and calculating fin conditions have been used in the past. What we would expect from a suitable welfare assessment method is a high reliability (i.e., correlation with other welfare factors) and a low variability between different fish sizes allowing to use the method in a fish farm more easily. For the present study, farm data from 6 different fish farms in Switzerland have been collected for more than 19 months and different methods for calculating the fin conditions have been used and compared. The selected fish farms raised 3 different fish species, so that also species-specific differences in fin characteristics could be evaluated. The results indicate that the area index (AI) method is the most promising assessment method for the investigated fish. Further fish farms and fish species should be included in similar investigations in the future to confirm the relevance of these results.