Table 1 Descriptive statistics of categorical explanatory variables versus mortality.

From: Factors associated with baseline mortality in Norwegian Atlantic salmon farming

Variable

Category

n

Monthly deaths per 1000 fish

Mean

Median

IQRa

Production zoneb

1

332

4.1

2.26

1.39–5.69

2

939

5.36

3.76

1.79–7.99

3

2884

5.71

4.02

1.80–8.44

4

2077

5.2

3.47

1.68–7.32

5

598

4.78

3.15

1.95–6.02

6

1870

4.61

2.83

1.54–6.06

7

498

3.6

2.15

1.19–4.39

8

1270

3.8

2.37

1.30–4.74

9

1136

3.66

2.29

1.20–4.59

10

692

3.73

2.38

1.29–4.71

11

540

5.08

3.37

1.79–7.10

12 and 13c

1444

5.03

3.63

1.97–6.57

Month of 1st stocking at sea

Mar

1158

5.48

3.56

1.77–8.07

Apr

2561

5.29

3.60

1.80–7.41

May

2173

4.7

3.07

1.63–6.22

Jun

690

5.0

3.24

1.76–7.23

Jul

1046

4.88

3.37

1.78–6.57

Aug

2362

4.43

2.85

1.45–5.97

Sep

2607

4.51

2.51

1.31–6.06

Oct

965

4.24

2.58

1.41–5.47

Nov

298

5.18

3.79

1.49–7.33

Dec, Jan and Febc

420

4.65

3.42

1.79–6.21

H2O2 or medicinal treatmentsd

Not treated

11,162

4.42

2.77

1.48–5.84

1 time per month

2189

5.94

4.35

2.15–8.61

≥ 2 times per monthc

929

6.63

4.97

2.21–10.0

Non-medicinal treatmentse

Not treated

13,039

4.48

2.81

1.50–5.97

1 time per month

920

7.72

6.68

3.72–10.8

≥ 2 times per monthc

321

9.2

8.66

4.58–13.3

  1. aIQR interquartile range.
  2. bProduction zones delimited in Fig. 6.
  3. cMerged category due to few number of observations for one of them.
  4. dBath treatments using H2O2 or medicinal compounds, such as azamethiphos and pyrethroids.
  5. eRemoval of sea lice usually by flushing or brushing, warm water or freshwater baths.
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