Ocean warming cannot explain synchronous declines in North American Atlantic salmon populations
Ocean warming cannot explain synchronous declines in North American Atlantic salmon populations
Atlantic salmon Salmo salar populations have suffered global, synchronous declines over the past decades. These declines are coincident with improvements in river habitats and reductions in high seas fisheries, implying higher rates of natural marine mortality that have been widely linked to increasing ocean temperatures in the North Atlantic. The mechanisms linking temperature to marine mortality in Atlantic salmon, however, are unclear. During the period 1980−2010, populations of S. salar returning to the St. John River, New Brunswick, Canada, after spending either 1 or multiple winters at sea have shown similar patterns of decline, coincident with recent ocean warming in the North Atlantic Ocean. Here we used stable isotope data from historic scale collections to investigate the relationship between foraging location, experienced ocean temperature and population trends for S. salar returning to the St. John River. We show that salmon spending either 1 or multiple winters at sea before returning to the St. John River consistently fed in different regions of the North Atlantic and experienced different ocean warming trends. However, both cohorts show synchronous progressive population declines over the study period. We therefore suggest that ocean warming cannot be the principal cause of increased marine mortality for salmon returning to the St. John River. Both cohorts experience similar conditions during the initial post-smolt period, and increased post-smolt mortality could underpin population declines. Our results support concentrating management and conservation efforts to reduce mortality in the post-smolt phase of salmon lifecycles.
Archived scale tissue, Ocean migration, Ocean warming, Salmo salar, Sea surface temperature, Stable isotopes
203-213
Soto, David X.
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Trueman, Clive N.
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Samways, Kurt M.
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Dadswell, Michael J.
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Cunjak, Richard A.
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Soto, David X.
ed880b4a-57a6-4b70-b54d-9ef3ffec70cc
Trueman, Clive N.
d00d3bd6-a47b-4d47-89ae-841c3d506205
Samways, Kurt M.
393edef8-544a-4fb8-b73d-2ec6224c63f6
Dadswell, Michael J.
4db57011-e2db-4f57-bbb4-af0ce9c4d92f
Cunjak, Richard A.
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Soto, David X., Trueman, Clive N., Samways, Kurt M., Dadswell, Michael J. and Cunjak, Richard A.
(2018)
Ocean warming cannot explain synchronous declines in North American Atlantic salmon populations.
Marine Ecology Progress Series, 601, .
(doi:10.3354/meps12674).
Abstract
Atlantic salmon Salmo salar populations have suffered global, synchronous declines over the past decades. These declines are coincident with improvements in river habitats and reductions in high seas fisheries, implying higher rates of natural marine mortality that have been widely linked to increasing ocean temperatures in the North Atlantic. The mechanisms linking temperature to marine mortality in Atlantic salmon, however, are unclear. During the period 1980−2010, populations of S. salar returning to the St. John River, New Brunswick, Canada, after spending either 1 or multiple winters at sea have shown similar patterns of decline, coincident with recent ocean warming in the North Atlantic Ocean. Here we used stable isotope data from historic scale collections to investigate the relationship between foraging location, experienced ocean temperature and population trends for S. salar returning to the St. John River. We show that salmon spending either 1 or multiple winters at sea before returning to the St. John River consistently fed in different regions of the North Atlantic and experienced different ocean warming trends. However, both cohorts show synchronous progressive population declines over the study period. We therefore suggest that ocean warming cannot be the principal cause of increased marine mortality for salmon returning to the St. John River. Both cohorts experience similar conditions during the initial post-smolt period, and increased post-smolt mortality could underpin population declines. Our results support concentrating management and conservation efforts to reduce mortality in the post-smolt phase of salmon lifecycles.
Text
m601p203
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Accepted/In Press date: 25 June 2018
e-pub ahead of print date: 9 August 2018
Keywords:
Archived scale tissue, Ocean migration, Ocean warming, Salmo salar, Sea surface temperature, Stable isotopes
Identifiers
Local EPrints ID: 424452
URI: http://eprints.soton.ac.uk/id/eprint/424452
ISSN: 0171-8630
PURE UUID: 8e64e3b0-5951-4c3c-9a2c-123bbf9c7f3d
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Date deposited: 05 Oct 2018 11:37
Last modified: 16 Mar 2024 03:35
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Contributors
Author:
David X. Soto
Author:
Kurt M. Samways
Author:
Michael J. Dadswell
Author:
Richard A. Cunjak
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