Understanding Smolt Survival Trends in Sockeye Salmon

Many populations of Sockeye Salmon Oncorhynchus nerka in the eastern North Pacific Ocean experienced significant productivity declines that began about 1990, but there is no consensus on the mechanisms responsible. To better understand Sockeye Salmon survival trends, we examined the 50-year time ser...

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Published in:Marine and Coastal Fisheries
Main Author: James R. Irvine
Format: Text
Language:English
Published: American Fisheries Society 2013
Subjects:
Online Access:https://doi.org/10.1080/19425120.2013.831002
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spelling ftbioone:10.1080/19425120.2013.831002 2024-06-02T08:13:18+00:00 Understanding Smolt Survival Trends in Sockeye Salmon James R. Irvine James R. Irvine world 2013-01-01 text/HTML https://doi.org/10.1080/19425120.2013.831002 en eng American Fisheries Society doi:10.1080/19425120.2013.831002 All rights reserved. https://doi.org/10.1080/19425120.2013.831002 Text 2013 ftbioone https://doi.org/10.1080/19425120.2013.831002 2024-05-07T00:51:43Z Many populations of Sockeye Salmon Oncorhynchus nerka in the eastern North Pacific Ocean experienced significant productivity declines that began about 1990, but there is no consensus on the mechanisms responsible. To better understand Sockeye Salmon survival trends, we examined the 50-year time series for two age-classes of Sockeye Salmon smolts from Chilko Lake in central British Columbia. Arranging survival time series for both age-classes by ocean entry year and combining them, weighted by a proxy model of sampling variance, reduced the sampling variance in the original age-1 smolt survivals sufficiently to indicate a linear trend of increasing survival from 1960 to 1990 that suddenly changed at or near 1991 to a lower and declining trend from 1992 to 2008. Neither density nor mean length influenced smolt survival. Returns in a given year were not good predictors of siblings returning in subsequent years. Time spent at sea increased linearly beginning around 1970. Although smolt survivals differed between ecosystem regimes, there was only the one clear pattern break about 1991. To improve our understanding of mechanisms, survival trends were compared with environmental indices that included catches and hatchery releases of potentially competing salmon from around the North Pacific Ocean. Smolt survivals were more similar to abundance indices of Sockeye Salmon, Chum Salmon O. keta, and Pink Salmon O. gorbuscha than to indices of global, regional, or local ocean climate. Our results are consistent with the hypothesis that salmon productivity in the North Pacific declined soon after 1990. We present a simple model to illustrate how increased competition at sea, related to the release of large numbers of hatchery salmon, in conjunction with changes in ocean productivity, may have played a significant role in improving Sockeye Salmon survivals while reducing their growth before 1991. After 1991, these factors may have acted to reduce survivals while the growth of survivors showed no effect. Text Pink salmon BioOne Online Journals Keta ENVELOPE(-19.455,-19.455,65.656,65.656) Pacific Sockeye ENVELOPE(-130.143,-130.143,54.160,54.160) Marine and Coastal Fisheries 5 1 303 328
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description Many populations of Sockeye Salmon Oncorhynchus nerka in the eastern North Pacific Ocean experienced significant productivity declines that began about 1990, but there is no consensus on the mechanisms responsible. To better understand Sockeye Salmon survival trends, we examined the 50-year time series for two age-classes of Sockeye Salmon smolts from Chilko Lake in central British Columbia. Arranging survival time series for both age-classes by ocean entry year and combining them, weighted by a proxy model of sampling variance, reduced the sampling variance in the original age-1 smolt survivals sufficiently to indicate a linear trend of increasing survival from 1960 to 1990 that suddenly changed at or near 1991 to a lower and declining trend from 1992 to 2008. Neither density nor mean length influenced smolt survival. Returns in a given year were not good predictors of siblings returning in subsequent years. Time spent at sea increased linearly beginning around 1970. Although smolt survivals differed between ecosystem regimes, there was only the one clear pattern break about 1991. To improve our understanding of mechanisms, survival trends were compared with environmental indices that included catches and hatchery releases of potentially competing salmon from around the North Pacific Ocean. Smolt survivals were more similar to abundance indices of Sockeye Salmon, Chum Salmon O. keta, and Pink Salmon O. gorbuscha than to indices of global, regional, or local ocean climate. Our results are consistent with the hypothesis that salmon productivity in the North Pacific declined soon after 1990. We present a simple model to illustrate how increased competition at sea, related to the release of large numbers of hatchery salmon, in conjunction with changes in ocean productivity, may have played a significant role in improving Sockeye Salmon survivals while reducing their growth before 1991. After 1991, these factors may have acted to reduce survivals while the growth of survivors showed no effect.
author2 James R. Irvine
format Text
author James R. Irvine
spellingShingle James R. Irvine
Understanding Smolt Survival Trends in Sockeye Salmon
author_facet James R. Irvine
author_sort James R. Irvine
title Understanding Smolt Survival Trends in Sockeye Salmon
title_short Understanding Smolt Survival Trends in Sockeye Salmon
title_full Understanding Smolt Survival Trends in Sockeye Salmon
title_fullStr Understanding Smolt Survival Trends in Sockeye Salmon
title_full_unstemmed Understanding Smolt Survival Trends in Sockeye Salmon
title_sort understanding smolt survival trends in sockeye salmon
publisher American Fisheries Society
publishDate 2013
url https://doi.org/10.1080/19425120.2013.831002
op_coverage world
long_lat ENVELOPE(-19.455,-19.455,65.656,65.656)
ENVELOPE(-130.143,-130.143,54.160,54.160)
geographic Keta
Pacific
Sockeye
geographic_facet Keta
Pacific
Sockeye
genre Pink salmon
genre_facet Pink salmon
op_source https://doi.org/10.1080/19425120.2013.831002
op_relation doi:10.1080/19425120.2013.831002
op_rights All rights reserved.
op_doi https://doi.org/10.1080/19425120.2013.831002
container_title Marine and Coastal Fisheries
container_volume 5
container_issue 1
container_start_page 303
op_container_end_page 328
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