Ecosystem Change and the Decline of Marine Mammals in the Eastern Bering Sea : Testing the Ecosystem Shift and Commercial Whaling Hypotheses ...
Some species in the Bering Sea underwent large changes between the 1950s and the 1980s. Among the best documented are the declines of Steller sea lions and northern fur seals, and the possible increase and dominance of ground fish – pollock and large flatfish. A frequently proposed explanation is th...
| Main Authors: | , , , , , |
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| Format: | Text |
| Language: | English |
| Published: |
Fisheries Centre, University of British Columbia
2017
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| Subjects: | |
| Online Access: | https://dx.doi.org/10.14288/1.0348097 https://doi.library.ubc.ca/10.14288/1.0348097 |
| Summary: | Some species in the Bering Sea underwent large changes between the 1950s and the 1980s. Among the best documented are the declines of Steller sea lions and northern fur seals, and the possible increase and dominance of ground fish – pollock and large flatfish. A frequently proposed explanation is that human exploitation of top predators and/or a shift in the physical oceanography altered the structure of the eastern Bering Sea ecosystem. We employed two inter-related software packages (Ecopath and Ecosim) to describe quantitatively the eastern Bering Sea ecosystem during the 1950s, before large-scale commercial fisheries were underway, and during the 1980s, after many marine mammal populations had declined. We grouped the hundreds of species that make up the Bering Sea ecosystem into 25 functional groups. Our mass-balance ecosystem models showed that most of the top predators (trophic level IV) declined from the 1950s to the 1980s. They included Steller sea lions, seals, sperm whales, deep-water fish and ... |
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