Document Detail

Directional selection by fisheries and the timing of sockeye salmon (Oncorhynchus nerka) migrations.
MedLine Citation:
PMID:  17494392     Owner:  NLM     Status:  MEDLINE    
The timing of migration from feeding to breeding areas is a critical link between the growth and survival of adult animals, their reproduction, and the fitness of their progeny. Commercial fisheries often catch a large fraction of the migrants (e.g., salmon), and exploitation rates can vary systematically over the fishing season. We examined daily records of sockeye salmon (Oncorhynchus nerka) in the Egegik and Ugashik management districts in Bristol Bay, Alaska (USA), for evidence of such temporally selective fishing. In recent years, the early migrants have experienced lower fishing rates than later migrants, especially in the Egegik district, and the median migration date of the fish escaping the fisheries has been getting progressively earlier in both districts. Moreover, the overall runs (catch and escapement) in the Egegik district and, to a lesser extent the Ugashik district, have been getting earlier, as predicted in response to the selection on timing. The trends in timing were not correlated with sea surface temperature in the region of the North Pacific Ocean where the salmon tend to concentrate, but the trends in the two districts were correlated with each other, indicating that there may be some common environmental influence in addition to the effect of selection. Despite the selection, both groups of salmon have remained productive. We hypothesize that this resilience may result from representation of all component populations among the early and late migrants, so that the fisheries have not eliminated entire populations, and from density-dependent processes that may have helped maintain the productivity of these salmon populations.
Thomas P Quinn; Sayre Hodgson; Lucy Flynn; Ray Hilborn; Donald E Rogers
Publication Detail:
Type:  Historical Article; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Ecological applications : a publication of the Ecological Society of America     Volume:  17     ISSN:  1051-0761     ISO Abbreviation:  Ecol Appl     Publication Date:  2007 Apr 
Date Detail:
Created Date:  2007-05-14     Completed Date:  2007-07-30     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9889808     Medline TA:  Ecol Appl     Country:  United States    
Other Details:
Languages:  eng     Pagination:  731-9     Citation Subset:  IM    
Fisheries Research Institute, School of Aquatic and Fishery Sciences, Box 355020, University of Washington, Seattle, Washington 98195, USA.
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MeSH Terms
Animal Migration*
Fisheries / history*
History, 20th Century
History, 21st Century

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