FCRR
A Trophic Mass-Balance Model of Alaska's Prince William Sound Ecosystem for the Post-Spill Period 1994-1996, 2nd Edition
Editors
Publication
1999 | PDF
Edited by Okey, T., and Pauly, D.
ABSTRACT
Information about the ecological components of Alaska's Prince William Sound (PWS) has increased considerably since the 1989 Exxon Valdez oil spill (EVOS), but the structure and functional characteristics of the overall food web are still not well understood. A better understanding of the whole PWS food web and its dynamics was achieved by constructing a balanced trophic model using the Ecopath approach. This was the best available framework to summarize available ecosystem information in a trophic context, as it explicitly accounts for multi-species interactions. The PWS model is a cohesive synthesis of the overall biotic community with a focus on energy flow structure, and response to perturbations--both natural and anthropogenic. Flows of biomass among the various components of the food web were quantified using estimates provided by a collaborative group of over 35 experts on PWS ecosystem components.
The dynamic modelling routines Ecosim and Ecospace can be used to simulate the ecosystem-level effects of disturbances and management actions, and to provide insights into ecosystem-level changes and dynamics that may occur in Prince William Sound. The Ecopath model of PWS can be used to help guide future research programs in the region, to help assess impacts of the EVOS, and to help resource agencies and local communities achieve ecosystem-based conservation and management in the face of increasing human activities in the region. This approach can also be used to help distinguish the relative importance of physical forces and tropic forces in marine ecosystems.
An annotated list of Alutiik words was included in this volume to facilitate cross-cultural flows of ecosystem knowledge. This list might serve as one step in helping to promote a more community-based approach to management of the wild living resources of Prince William Sound.
TABLE OF CONTENTS
Abstract | VI |
Director's Foreword | VII |
List of Exhibits | X |
Preface to the 2nd Edition | XII |
INTRODUCTION (Thomas A. Okey) | 1 |
Prince William Sound | 2 |
The 1989 Exxon Valdez Oil Spill | 5 |
Other Anthropogenic Stressors | 5 |
Natural Disturbances and Cycles | 6 |
Defining the PWS Ecosystem | 7 |
Aspects of the Ecopath approach relevant to the PWS model (V. Christensen, D. Pauly, T.A. Okey) | 9 |
Surface areas of PWS depth zones and habitats (Tom Dean) | 11 |
MODEL INPUTS | 12 |
PRIMARY PRODUCERS | 12 |
ZOOPLANKTON | 15 |
BENTHIC INVERTEBRATES | 19 |
PLANKTIVOROUS 'FORAGE FISHES' | 25 |
LARGER FISHES | 31 |
BIRDS | 47 |
MAMMALS | 56 |
Detritus | 62 |
PWS Fisheries | 65 |
Constructing and Balancing the PWS Model (Thomas A. Okey) | 68 |
Verification of web structure | 73 |
Ecosim and Ecospace Methodology (Thomas A. Okey) | 74 |
RESULTS (Thomas A. Okey) | 75 |
Temporal simulations of perturbations | 79 |
Spatially explicit simulations | 83 |
Ecopath and Resource Management (Thomas A. Okey) | 85 |
Ecosystem Models as Caricatures (Jennifer L. Ruesink) | 87 |
An annotated list of Alutiiq words relevant to modeling the Prince William Sound ecosystem (Dave Preikshot and Jeff Leer) | 90 |
ACKNOWLEDGEMENTS | 104 |
LITERATURE CITED | 105 |
Appendices | 117 |
Appendix 1. List of contributors to PWS Ecopath model | 117 |
Appendix 2. Workshop Agendas | 122 |
Appendix 3. Monthly estimates for PWS zooplankton parameters | 127 |
Appendix 4. Derivation of diet compositions of forage fishes | 130 |
Appendix 5. Input diet compositions of PWS animals | 135 |
Appendix 6. Diagram of arrowtooth founder spatial distribution | 137 |

