Ecosystem Change and the Decline of Marine Mammals in the

0,98

MB

Eastern Bering Sea - Testing the Ecosystem Shift and

100

stron

Commercial Whaling Hypotheses

4864

ID

University of British Columbia

1999

rok

Table of Contents

Summary.2

Table of Contents.3

Introduction.5

An Overview of Ecopath & Ecosim6

Eastern Bering Sea – Defining the System.7

Species Assemblages of the Eastern Bering Sea .9

Balancing the Ecosystem 10

Balancing the 1980s model. 11

Balancing the 1950s model. 11

Ecopath Model Results 15

Flow Charts & Trophic Levels 18

Niche Overlaps 22

Mixed Trophic Impacts 23

Fisheries 25

Characterizing the Bering Sea Ecosystem 26

Ecosim Model Results 30

Equilibrium Simulation Results 32

Dynamic Simulation Results 38

System Recovery Time . 46

Discussion of Simulation Results 47

Conclusions. 48

Acknowledgements 49

Literature Cited 50

Appendix 1 – Mass-Balance Model Details 66

ECOPATH - steady state mass-balance ecosystem model 66

ECOSIM - dynamic mass-balance approach for ecosystem simulation 67

Appendix 2 – Species Assemblage Details . 68

Mammals and Birds 68

1. Baleen Whales . 71

2. Sperm Whales 74

3. Toothed Whales . 75

4. Beaked Whales 77

5. Walruses and Bearded Seals. 77

6. Steller Sea Lions. 78

7. Seals. 78

8. Piscivorous Birds 81

Fish and Cephalopods . 81

9,10. Pollock 83

11. Deepwater Fish 83

12. Large Flatfish 83

13. Small Flatfish 84

14. Pelagics 84

15. Other Demersal Fish 85

16. Cephalopods 85

Benthics and Jellies 86

17. Benthic Particulate Feeders . 86

18. Infauna 86

19. Jellyfish . 87

20. Epifauna 87

Plankton 88

21. Large Zooplankton 88

22. Herbivorous Zooplankton . 88

23. Phytoplankton. 89

Other. 89

24. Discards and By-Catch. 89

25. Detritus . 90

Appendix 3 – Parameters for the 45-Box Ecopath Model 92

Appendix 4 – Diet Matrix Tables 93

Appendix 5 – Niche Overlap Tables 97