Threshold management strategies for exploited fish populations
Dissertation (Ph.D.) University of Alaska Fairbanks, 1994 Under a threshold management strategy, harvesting occurs at a constant rate but ceases when a population drops below a threshold. The threshold approach seeks to enhance long-term yield of a population and to maintain population renewability....
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ftunivalaska:oai:scholarworks.alaska.edu:11122/5187 2023-05-15T15:43:57+02:00 Threshold management strategies for exploited fish populations Zheng, Jie 1994-05 http://hdl.handle.net/11122/5187 en_US eng http://hdl.handle.net/11122/5187 Dissertation phd 1994 ftunivalaska 2023-02-23T21:36:23Z Dissertation (Ph.D.) University of Alaska Fairbanks, 1994 Under a threshold management strategy, harvesting occurs at a constant rate but ceases when a population drops below a threshold. The threshold approach seeks to enhance long-term yield of a population and to maintain population renewability. I evaluated threshold management strategies for selected herring and pollock stocks in Alaska. First, I examined stock-recruitment data from 19 major herring stocks worldwide to provide the basis for evaluating threshold management strategies. Seventy-three percent of these stocks exhibited statistically significant density-dependence. Most stocks have compensatory, dome-shaped stock-recruitment curves. Then, I simulated threshold management strategies for eastern Bering Sea (EBS) pollock and herring and Prince William Sound (PWS) herring using a single-species model. I further examined seven alternative threshold estimation methods. Cohort analysis, catch-at-age analysis, and catch and population sampling yielded estimates of population parameters. The objective function was a weighted function of increased average yield and decreased standard deviation of yield over a planning horizon. Compared to a non-threshold approach, threshold management strategies increase the long-term average yields, stabilize population abundances, shorten rebuilding times, and increase management flexibility. For a maximum yield criterion and Ricker stock-recruitment models, optimal fishing mortalities are slightly above fishing mortalities at maximum sustained yield (MSY), and optimal threshold levels range from 40% to 60% of pristine biomass for EBS pollock, from 40% to 50% for EBS herring and from 30% to 60% for PWS herring. With fishing mortality at MSY and the criterion of equal trade-off between yield and its variation, optimal thresholds range from 20% to 30% of pristine biomass for pollock. With the status quo exploitation rate of 20%, optimal thresholds range from 10% to 25% of pristine biomass for EBS herring, and from 5% to ... Doctoral or Postdoctoral Thesis Bering Sea Alaska University of Alaska: ScholarWorks@UA Bering Sea Fairbanks |
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Open Polar |
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University of Alaska: ScholarWorks@UA |
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ftunivalaska |
language |
English |
description |
Dissertation (Ph.D.) University of Alaska Fairbanks, 1994 Under a threshold management strategy, harvesting occurs at a constant rate but ceases when a population drops below a threshold. The threshold approach seeks to enhance long-term yield of a population and to maintain population renewability. I evaluated threshold management strategies for selected herring and pollock stocks in Alaska. First, I examined stock-recruitment data from 19 major herring stocks worldwide to provide the basis for evaluating threshold management strategies. Seventy-three percent of these stocks exhibited statistically significant density-dependence. Most stocks have compensatory, dome-shaped stock-recruitment curves. Then, I simulated threshold management strategies for eastern Bering Sea (EBS) pollock and herring and Prince William Sound (PWS) herring using a single-species model. I further examined seven alternative threshold estimation methods. Cohort analysis, catch-at-age analysis, and catch and population sampling yielded estimates of population parameters. The objective function was a weighted function of increased average yield and decreased standard deviation of yield over a planning horizon. Compared to a non-threshold approach, threshold management strategies increase the long-term average yields, stabilize population abundances, shorten rebuilding times, and increase management flexibility. For a maximum yield criterion and Ricker stock-recruitment models, optimal fishing mortalities are slightly above fishing mortalities at maximum sustained yield (MSY), and optimal threshold levels range from 40% to 60% of pristine biomass for EBS pollock, from 40% to 50% for EBS herring and from 30% to 60% for PWS herring. With fishing mortality at MSY and the criterion of equal trade-off between yield and its variation, optimal thresholds range from 20% to 30% of pristine biomass for pollock. With the status quo exploitation rate of 20%, optimal thresholds range from 10% to 25% of pristine biomass for EBS herring, and from 5% to ... |
format |
Doctoral or Postdoctoral Thesis |
author |
Zheng, Jie |
spellingShingle |
Zheng, Jie Threshold management strategies for exploited fish populations |
author_facet |
Zheng, Jie |
author_sort |
Zheng, Jie |
title |
Threshold management strategies for exploited fish populations |
title_short |
Threshold management strategies for exploited fish populations |
title_full |
Threshold management strategies for exploited fish populations |
title_fullStr |
Threshold management strategies for exploited fish populations |
title_full_unstemmed |
Threshold management strategies for exploited fish populations |
title_sort |
threshold management strategies for exploited fish populations |
publishDate |
1994 |
url |
http://hdl.handle.net/11122/5187 |
geographic |
Bering Sea Fairbanks |
geographic_facet |
Bering Sea Fairbanks |
genre |
Bering Sea Alaska |
genre_facet |
Bering Sea Alaska |
op_relation |
http://hdl.handle.net/11122/5187 |
_version_ |
1766378168482004992 |