Table 3 Ontogenetic changes in δ¹³C values and Trophic Position (TP) of Gonatus fabricii. n – sample size, GAMM – generalized additive mixed effect model, n/a – not applicable. Significant p-values are in bold

Late XIX^th century

2

32

0.41 ‰

1 to 4

-0.01 ‰

4 to 15

n/a

-16.67 ± 0.36

4, 2.99

< 0.0001

99.1

1900s

9

73

0.33 ‰

1 to 4

-0.13 ‰

4 to 8

0.07–0.49 (0.28 ± 0.04)

-17.63 ± 0.16

4, 2.91

< 0.0001

90.9

1930s

7

91

0.39 ‰

1 to 4

-0.06 ‰

4 to 12

0.39–0.74 (0.55 ± 0.06)

-16.73 ± 0.16

4, 2.93

< 0.0001

92.5

1970s

9

101

0.35 ‰

1 to 4

-0.02 ‰

4 to 12

0.36–0.60 (0.50 ± 0.03)

-17.14 ± 0.11

3, 2.00

< 0.0001

91.7

2000s

10

123

0.34 ‰

1 to 4

-0.06 ‰

4 to 11

0.10–0.45 (0.26 ± 0.03)

-16.06 ± 0.17

4, 2.85

< 0.0001

89.1

2010s

10

153

0.30 ‰

1 to 4

-0.04 ‰

4 to 11²

0.27–0.64 (0.38 ± 0.03)

-16.52 ± 0.13

3, 1.97

< 0.0001

78.7

Contemporary

(2016, 2017, 2019)³

13

157

0.29 ‰

1 to 5

0.01 ‰

5 to 15

0.20–0.67 (0.56 ± 0.05)

-17.17 ± 0.12

3, 1.93

< 0.0001

80.7

TP

Late XIX^th century

2

32

0.30 TP

1 to 5

0.02 TP

5 to 15

n/a

4.44 ± 0.56

4, 2.87

< 0.0001

98.3

1900s

9

73

0.24 TP

1 to 5

0.06 TP

5 to 8

0.94–0.97 (0.95 ± 0.01)

4.42 ± 0.04

4, 2.93

< 0.0001

94.7

1930s

7

91

0.23 TP

2 to 7

0.02 TP

7 to 12

0.92–0.95 (0.93 ± 0.01)

4.62 ± 0.05

4, 2.96

< 0.0001

95.6

1970s

9

101

0.28 TP

3 to 6

0.05 TP

6 to 12

0.81–0.91 (0.89 ± 0.01)

4.16 ± 0.06

4, 2.98

< 0.0001

96.1

2000s

10

123

0.31 TP

2 to 6

0.04 TP

6 to 12

0.51–0.67 (0.61 ± 0.02)

4.08 ± 0.09

4, 2.97

< 0.0001

96.3

2010s

10

153

0.21 TP

1 to 6

0.05 TP

6 to 15

0.72–0.85 (0.79 ± 0.01)

3.93 ± 0.09

3, 1.00

< 0.0001

89.6

Contemporary

(2016, 2017, 2019)³

13

165

0.22 TP

2 to 7

0.04 TP

7 to 15

0.31–0.82 (0.69 ± 0.04)

4.38 ± 0.09

3, 1.00

< 0.0001

88.2