Testing of the Salmon Welfare Index Model (SWIM 1.0) as a computational welfare assessment for sea-caged European sea bass

Figures & data

Table 1. Fish welfare markers, weighting categories and ranges of weighting scores used in semantic modelling (adapted from Stien et al. 2013).

Weighting category	The base of the welfare-related approach	Weighting scores (WS) intervals
Markers for poor welfare
Stress in short-term	Deterioration in homeostasis: sympathetic adrenal medullary (SAM) activation under catecholamine effects	−5 to −1
Stress in long-term	Disruption in homeostasis: hypothalamus-pituitary-interrenal (HPI) axis activation under adrenalin effects	−5 to −1
Health problems	Disease signs (i.e. haemorrhages, exophthalmos, etc.) and increased mortality	−5 to −1
Skin and fin damage	Possible pain	−5 to −1
The decrease in survival rate	Impairment in physiological status (i.e. deprivation of feed, suboptimal water quality)	−5 to −1
Behavioural changes	Disturbed behaviour (i.e. abnormality in swimming activity or apathy)	−5 to −1
Restiveness	Restiveness due to external factors such as ectoparasites	−5 to −1
Avoidance	Perceiving negative stimulus such as catching activity, treatment with a chemical	−5 to −1
Frustration	A shock status or deprivation	−5 to −1
Negative performance	Worsening in normal performance including reproduction effects	−5 to −1
Markers for good welfare
Demand	An effort to find the feed	1–5
Natural behaviour	Normal swimming, feeding activity	1–3
Positive performance	Healthy appearance, suitable condition factor	1–3
Preference	Adaptation to culture conditions	1–3

Table 2. Welfare indicators (WI), the levels for each indicator, and the corresponding indicator level score (IS), the calculated weighting factor (WF), and the relative weighting factor (RWF).

Welfare Indicator (WI)	Levels	IS	Weighing factor (WF)	RWF
Cage environment WI
1) Temperature (°C)	1. 18–26	1.00	16	0.17
	2. 26–28	0.50
	3. 28–30	0.25
	4. 28 or <18, long period	0.00
	5. Sharp decline under 12	Knockout
2) Oxygen saturation (%)	1. ≥75	1.00	17	0.18
	2. 65–75	0.50
	3. <65 short term (days)	0.00
	4. <65 long term (weeks)	Knockout
3) pH	1. 8.0–8.5	1.00	3	0.03
	2. 7.5–8.5	0.75
	3. <7.5–>8.5	0.00
4) Water current (cm/s)	1. 10–15	1.00	3	0.03
	2. <10	0.50
	3. >15	0.25
5) Stocking density (kg/m^3)	1. 10–15	1.00	8	0.09
	2. 15–20	0.75
	3. 20–22	0.50
	4. >22	0.00
6) Lighting	1. Normal (natural lighting)	1.00	4	0.04
	2. Abnormal (different from natural lighting)	0.00
7) Disturbances	1. None	1.00	11	0.12
	2. Light	0.75
	3. Moderate	0.50
	4. Severe	0.00
Fish group specific WI
1) Mortality (% monthly)	1. <1	1.00	21	0.22
	2. 1–2.5	0.75
	3. >2.5–5	0.50
	4. >5	0.00
2) Appetite	1. Good appetite (food demand is higher than expected)	1.00	11	0.12
	2. Normal	0.75
	3. Poor appetite	0.25
	4. No appetite	Knockout
Sum			94	1.00
Individual fish-specific WI
1) Emaciation	1. Not emaciated	1.00	16	0.18
	2. Emaciated	0.00
	3 Extremely emaciated (generally small, very thin fish of poor health)	Knockout
2) Vertebral deformity	1. No external signs of vertebral deformity (including operculum, skull shape, etc.)	1.00	10	0.11
	2.. Vertebral abnormality with normal weight	0.50
	3. Vertebral abnormality with low weight	0.00
3) Fin condition	1. Normal appearance of fins	1.00	13	0.14
	2. Less ruptured rays, rips in fin membranes, slight thickening of the rays	0.75
	3. Multiplexed ruptured rays, rips in fin the membranes, slight erosion on the edge of the fins	0.50
	4. Loss of any fin, bleeding in the fins	0.00
4) Gill condition	1. Normal appearance	1.00	20	0.21
	2. Short filaments	0.75
	3. The slight change in colour, filament morphology	0.50
	4. Disease signs	0.00
5) Skin condition	1. Normal healthy skin	1.00	15	0.17
	2. Scar tissue	0.80
	3. Scale loss (dislocated or missing scales)	0.60
	4. The superficial wound or ulcer < 1 cm^2	0.40
	5. The superficial wound or ulcer > 1 cm^2	0.20
	6. Penetrating and/or multiple wounds or ulcers possibly infected	0.00
	7. Large open wounds	Knockout
6) External parasite presence	1. No parasite	1.00	11	0.12
	2. Light parasite intensity in body surface	0.50
	3. Light parasite intensity on the gills	0.50
	4. Parasite presence in the mouth	0.25
	5. Heavy parasite invasion	0.00
7) Condition factor	1. >1.0	1.00	6	0.07
	2. 0.90–1.0	0.75
	3. 0.90–0.80	0.50
	4. <0.80	0.00
Sum			91	1.00

K: knockout levels (adapted from Stien et al. 2013).

Figure 1. Image of European sea bass with OWI of 1.0, showing normal individual-specific welfare indicators.

Figure 2. European sea bass examples with lower OWI values. (a) OWI of 0.88 (IWS for parasite presence = 0 due to the visible copepod parasites in the gills); (b) OWI of 0.93 (IWS for skin condition = 0.10 due to scale loss; (c) OWI of 0.88 (IWS for fin condition = 0 due to loss of pectoral fin).

Table 3. Indicator welfare scores (IWS) and overall welfare index (OWI) for cage specific indicators.

	Level detected		IWS
Sea cage environment	Farm A	Farm B	Farm A	Farm B
Water temperature (°C)	24–26	22–24	0.17	0.17
Oxygen Saturation (%)	75	70	0.18	0.01
pH	8.40	8.20	0.03	0.03
Water current (cm/s)	15 (surface) 10–12 (below 10 m depth)	8 5	0.03	0.015
Stocking density (kg/m^3)	12.88	12	0.09	0.09
Lighting	Normal	Normal	0.04	0.04
Disturbances	None	None	0.12	0.12
Mortality	<1%	1	0.22	0.165
Appetite	Good	Good	0.12	0.12
OWI			1.00	0.76

Table 4. Total overall welfare index (OWI) for E. sea bass from farm A and farm B.

Farm	Farm A	Farm B
Total OWI	1.0	0.81
Calculation	(91 × 1 + 94 × 1/91 + 94)	94 × 0.76 + 91 × 0.88/91 + 94)

Stien LH, Bracke MBM, Folkedal O, Nilsson J, Oppedal F, Torgersen T, Kittilsen S, Midtlyng PJ, Vindas MA, Øverli Ø, et al. 2013. 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. Rev Aquac. 5(1):33–57..

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