Salmon welfare index model 2.0: an extended model for overall welfare assessment of caged Atlantic salmon, based on a review of selected welfare indicators and intended for fish health professionals

Abstract

Here, we present an extended version of a semantic model for overall welfare assessment of Atlantic salmon reared in sea cages. The model, called SWIM 2.0, is designed to enable fish health professionals to make a formal and standardized assessment of fish welfare using a set of reviewed welfare indicators. SWIM 2.0 supplements SWIM 1.0, which was designed for application by fish farmers. We searched the literature for documented welfare indicators that could be used by fish health professionals. The selected indicators are eyes, cardiac condition, abdominal organs, gills, opercula, skeletal muscles, vaccine-related pathology, aberrant fish, necropsy of the dead fish and active euthanasia. Selection criteria for the SWIM 2.0 indicators were that they should be practical and measureable on salmon farms by fish health professionals and that each indicator could be divided into levels from good to poor welfare backed up by relevant scientific literature. To estimate each indicator's relative impact on welfare, all the indicators were weighted based on their respective literature reviews and according to weighting factors defined as part of the semantic modelling framework. This was ultimately amalgamated into an overall SWIM 2.0 model that can be used to calculate welfare indexes for salmon in sea cages, taking into account the available fish health expertise. Using this model, an example calculation based on recordings and samplings done from an Atlantic salmon sea cage containing 106 000 fish yielded an overall welfare index of 0.81 of a maximum of 1.0.

Consistent melanophore spot patterns allow long‐term individual recognition of Atlantic salmon Salmo salar

“…As with the top of the head, the operculum also has the advantage that it is a well‐defined area that does not have scales that could affect the shape of the spots or that could be lost and leave darker areas that can be confused with spots. Salmo salar can occasionally develop shortened opercula over time due to genetic disposition or negative welfare (Pettersen et al., ), which would render identification with opercular spots impractical. In these rare cases, the fish should be withdrawn from the subsample, just as an individual that has lost its external tag would be.…”

Effects of repeated anaesthesia on gill and general health of Atlantic salmon, Salmo salar

“…Monitoring gill health is a priority when evaluating the effect on fish of non‐lethal monitoring that involves repeated removal from water and exposure to anaesthesia. This is due to the importance of the gills from multiple standpoints: they are the site of uptake for immersion anaesthesia (Hunn & Allen, ); their biological importance in regulatory functions (Evans et al ., ); the welfare of the fish (Pettersen et al ., ). Furthermore, the European aquaculture industry is facing increasing threat from gill‐related health issues, such as amoebic (AGD) (Oldham et al ., ), proliferative (PGD) (Durborow et al ., ) gill disease and damage due to phyto and zooplanktonic species (Hallegraeff et al ., ; Treasurer et al ., ).…”

“…Monitoring gill health is a priority when evaluating the effect on fish of non-lethal monitoring that involves repeated removal from water and exposure to anaesthesia. This is due to the importance of the gills from multiple standpoints: they are the site of uptake for immersion anaesthesia (Hunn & Allen, 1974); their biological importance in regulatory functions (Evans et al, 2005); the welfare of the fish (Pettersen et al, 2014). ), 25th and 75th percentiles ( ), range ( ) and outlier ( ) glucose concentrations of plasma from Salmo salar after single (n = 10) or repeat exposure (n = 30) to the anaesthetics MS-222 (80 mg l −1 ), metomidate (12.5 mg l −1 ) and AQUI-S (17 mg l −1 ).…”

From Land to Water: Taking Fish Welfare Seriously

“…The SWIM 1.0 welfare protocol takes into account a number of welfare-related inputs and outputs: water temperature, salinity, stocking density, lighting, disturbance, daily mortality rate, appetite, sea lice infestation ratio, condition factor, emaciation state, vertebral deformation, maturation stage, smoltification state, fin condition, and skin condition [31,32]. Complementarily, SWIM 2.0 adds the need to attend to eye condition, cardiac condition, abdominal organs, gills, opercula, skeletal muscles, vaccine-related pathology, aberrant fishes, necropsy, and active euthanasia [33]. These types of indicators-including the ones in the most recent protocols available [34]-are validated tools for making inferences about the health of an individual.…”