Salmon Welfare Index Model (SWIM 1.0): a semantic model for overall welfare assessment of caged Atlantic salmon: review of the selected welfare indicators and model presentation

Abstract

A semantic model for overall welfare assessment of Atlantic salmon reared in sea cages is presented. The model, called SWIM 1.0, is designed to enable fish farmers to make a formal and standardized assessment of fish welfare using a set of selected welfare indicators. In order to cover all welfare relevant aspects from the animals’ point of view and to create a science‐based tool we first identified the known welfare needs of Atlantic salmon in sea cages and searched the literature for feasible welfare indicators. The framework of semantic modelling was used to perform a structured literature review and an evaluation of each indicator. The selected indicators were water temperature, salinity, oxygen saturation, water current, 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. Selection criteria for the indicators were that they should be practical and measureable on the farm, 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 model that calculates welfare indexes for salmon in sea cages. More importantly, the model identifies how each indicator contributes (negatively and positively) to the overall index and hence which welfare needs are compromised or fulfilled.

Review of the assessment of animal welfare with special emphasis on the "Welfare Quality<sup>®</sup> animal welfare assessment protocol for growing pigs"

“…This overall welfare assessment system was first tested on husbandry systems for pigs (Bracke et al, 2002) and adapted to poultry (de Mol et al, 2006), cattle (Ursinus et al, 2009) and recently to salmon (Stien et al, 2013). It was invented as a tool to actually make decisions concerning animal welfare (Bracke et al, 2002).…”

Approaches for delaying sexual maturation in salmon and their possible ecological and ethical implications

“…Sexual maturation, with heavy investments in gonadal development and gamete production, has several negative consequences for growth rate, welfare and product quality of domesticated Atlantic salmon (Stien et al, 2013). Maturation represents a welfare issue in fish farming since the domesticated salmon gradually loses tolerance to seawater due to compromised hypo-osmoregulation ability during maturation (shift from seawater adaptations to freshwater adaptations; hyper-osmoregulation) (Persson et al, 1998, Stien et al, 2013, this may cause dehydration, stress and possible negative effects on the immune system (Harris and Bird, 2000).…”

“…Maturation represents a welfare issue in fish farming since the domesticated salmon gradually loses tolerance to seawater due to compromised hypo-osmoregulation ability during maturation (shift from seawater adaptations to freshwater adaptations; hyper-osmoregulation) (Persson et al, 1998, Stien et al, 2013, this may cause dehydration, stress and possible negative effects on the immune system (Harris and Bird, 2000). When the wild salmon begins to mature, they immigrate to their native rivers, an escape that is not possible for domesticated salmon due to their confinement in cages in seawater facilities.…”

“…mainly focused on the metabolic and physiological state of the animal and its ability to maintain homeostasis. There are other definitions of welfare with other focuses such as the animal's subjective experience of its condition (feeling based) and/or on whether it as an individual or as a population can lead a natural life and maintain itself within its natural habitat and its changes (Bergqvist and Gunnarsson, 2013, Stien et al, 2013, Ashley, 2007, Lund et al, 2007. Animal welfare includes more than the absence of suffering as it also encompasses positive welfare (Boissy et al, 2007), implying that denying an animal all positive experiences and stimuli is also an ethical problem.…”

“…Open sores and damage to fins and forks due to aggressive interactions are detrimental to fish health and welfare (Bergqvist andGunnarsson, 2013, Ashley, 2007). Maturation in seawater is also problematic because the ability to hyper-osmoregulate is lost, which in turn leads to dehydration and death, unless the fish is moved to fresh water (Stien et al, 2013. While wild salmon migrate up their native rivers, domestic salmon is usually kept in sea pens until slaughtered, regardless of maturation state.…”