Krill and the Antarctic: Finding the Balance

0,46

MB

98

stron

4890

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University of British Columbia

2004

rok

Table of Contents

Abstract. ii

Table of Contents . iii

List of Tables v

List of Figures vi

Acknowledgements . vii

1. The Southern Ocean: an overview of its history, geography, biology and management 1

1.1 Introduction. 1

1.2 The Southern Ocean – physical characteristics . 2

1.2.1 Bathymetry 3

1.2.2 Winds, currents and water masses 4

1.2.3 Temperature and sea-ice . 5

1.2.4 Nutrients. 5

1.3 The Southern Ocean – exploitation . 6

1.3.1 Pinnipeds 6

1.3.2 Penguins. 7

1.3.3 Whales 7

1.3.4 Fish. 8

1.3.5 Krill . 8

1.4 Management of the Southern Ocean 9

2. Potential impacts of krill fishing in the Southern Ocean . 13

2.1 Introduction. 13

2.2 Methods . 15

2.2.1 Study area 15

2.2.2 Model construction . 16

2.3 Results. 16

2.3.1 Role of krill in the ecosystem . 18

2.3.2 Krill fishery. 20

2.3.3 Krill variability 20

2.4 Discussion. 23

2.4.1 Ecosystem structure 23

2.4.2 Role of krill in the ecosystem . 25

2.4.3 Southern Ocean food chain, re-evaluated . 26

2.4.4 Krill fishery. 27

2.4.4.1 Effects of fishery 27

2.4.4.2 Bycatch 27

2.4.4.3 Issue of spatial overlap. 29

2.4.5 Krill variability 30

2.4.5.1 Factors affecting variability . 30

2.4.5.2 Consequences of variability. 32

2.5 Conclusions. 33

2.6 Summary. 33

3. The impact of sealing, whaling and fishing on the Southern Ocean: insights from four ecosystem

models 35

3.1 Introduction. 35

3.2 Methods and Results 36

3.2.1 Study area 36

3.2.2 Tools . 36

3.2.3 Models 1 and 2: the 1990s and 1960s. 37

3.2.4 Model 3: the pre-exploitation ecosystem 39

3.2.5 Model 4: the 1900s model. 39

3.2.6 Large whale recovery 41

3.3 Discussion. 42

3.3.1 Models 1 and 2: the 1990s and 1960s. 42

3.3.2 Model 3: the pre-exploitation ecosystem 43

3.3.3 Model 4: the 1900s model. 44

3.3.4 Large whale recovery 44

3.4 Conclusions. 45

3.5 Summary. 46

Literature Cited 47

Appendix A: Ecopath with Ecosim . 74

Appendix B: Sources for 1990s model input parameters 77

Appendix C: Additional model information. 82