THE ESTUARINE AND EARLY MARINE SURVIVAL OF ATLANTIC SALMON: ESTIMATION, CORRELATES AND ECOLOGICAL SIGNIFICANCE

This thesis focuses on the estuarine, coastal and marine mortality of Atlantic salmon. The overall objective is to better understand the factors affecting the survival of Atlantic salmon during their early marine phase. To meet this objective, we first review trends in marine survival, and examine t...

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Main Author: Halfyard, Edmund
Other Authors: Department of Biology, Doctor of Philosophy, Dr. Joseph Zydlewski, Dr. Hal Whitehead, Dr. Paul Bentzen, Dr. A. Jamie F. Gibson, Dr. Frederick G. Whoriskey, Dr. Daniel E. Ruzzante, Received, Yes
Language:English
Published: 2014
Subjects:
Online Access:http://hdl.handle.net/10222/53777
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spelling ftdalhouse:oai:DalSpace.library.dal.ca:10222/53777 2023-05-15T15:31:07+02:00 THE ESTUARINE AND EARLY MARINE SURVIVAL OF ATLANTIC SALMON: ESTIMATION, CORRELATES AND ECOLOGICAL SIGNIFICANCE Halfyard, Edmund Department of Biology Doctor of Philosophy Dr. Joseph Zydlewski Dr. Hal Whitehead Dr. Paul Bentzen Dr. A. Jamie F. Gibson Dr. Frederick G. Whoriskey, Dr. Daniel E. Ruzzante Received Yes 2014-08-14T16:37:10Z http://hdl.handle.net/10222/53777 en eng http://hdl.handle.net/10222/53777 Atlantic Salmon Survival Marine Mortality Acoustic Telemetry 2014 ftdalhouse 2021-12-29T18:10:07Z This thesis focuses on the estuarine, coastal and marine mortality of Atlantic salmon. The overall objective is to better understand the factors affecting the survival of Atlantic salmon during their early marine phase. To meet this objective, we first review trends in marine survival, and examine theoretical and empirical evidence to identify; (a) potentially important mortality sources, and (b) the timing of high mortality. It is clear that widespread shifts in the marine survival of salmon have occurred, however the timing, magnitude and effect of survival shifts is variable. Likely mortality mechanisms are similarly variable. This review highlights predation during the early marine phase as important for North American salmon; thus granting focus to the remaining research chapters. We next estimate the survival of postsmolts in selected estuaries and coastal habitats using acoustic telemetry. Simultaneously, we incorporate methods to address the major limitations to estimating survival using acoustic telemetry, including the use of mark-recapture modelling to address the effect of receiver detection performance, and a novel cluster-analysis modelling approach that attempts to quantify the complicating effects of predation. Our findings suggest that the early marine survival of Atlantic salmon, similar to marine mortality as a whole, is highly variable. Cumulative survival through the river, inner estuary, outer estuary and bay habitats ranged from 39·4% to 73·5% in Nova Scotia’s Southern Upland, whereas survival past the outer estuaries of inner Bay of Fundy rivers ranged from 24.3-54.0%. Survival rates followed two patterns: (1) constant rates of survival independent of habitat or (2) low survival most frequently associated with inner estuary habitats. We also examine the potential mortality mechanisms related to predation by examining patterns in the estuarine mortality of acoustically tagged salmon juveniles, using insights from mortality covariates, and the relationship between migratory behaviour and survival. Avian predation appears to be the dominant mortality vector in some estuaries of Nova Scotia’s Southern Upland, with the sudden disappearance of most (75–100%) smolts and post-smolts; which we interpret as evidence of avian predation along with evidence of size-selective survival. Alternatively, predatory striped bass appear to be a major source of mortality for some inner Bay of Fundy salmon populations, with evidence of a minimum of 7.3-27.3% of all tagged smolts being consumed by striped bass, based on migratory movement patterns. The survival estimates reported in this thesis permit the division of the marine phase into two periods; an early period encompassing estuarine and coastal habitats ( < 1 month), and the remaining time at sea. By comparing estimated survival during these two periods, it appears that estuarine survival cannot be solely responsible for observations of reduced marine survival since approx. 1990.The highest marine mortality must occur outside of estuaries and early coastal habitats. However, efforts directed at reducing estuarine and coastal mortality may be valuable for conservation planning, and may help reduce the risk of extirpation and, in some cases, may lead to viable populations. Other/Unknown Material Atlantic salmon Dalhousie University: DalSpace Institutional Repository Inner Bay ENVELOPE(-37.967,-37.967,-54.017,-54.017)
institution Open Polar
collection Dalhousie University: DalSpace Institutional Repository
op_collection_id ftdalhouse
language English
topic Atlantic Salmon
Survival
Marine
Mortality
Acoustic Telemetry
spellingShingle Atlantic Salmon
Survival
Marine
Mortality
Acoustic Telemetry
Halfyard, Edmund
THE ESTUARINE AND EARLY MARINE SURVIVAL OF ATLANTIC SALMON: ESTIMATION, CORRELATES AND ECOLOGICAL SIGNIFICANCE
topic_facet Atlantic Salmon
Survival
Marine
Mortality
Acoustic Telemetry
description This thesis focuses on the estuarine, coastal and marine mortality of Atlantic salmon. The overall objective is to better understand the factors affecting the survival of Atlantic salmon during their early marine phase. To meet this objective, we first review trends in marine survival, and examine theoretical and empirical evidence to identify; (a) potentially important mortality sources, and (b) the timing of high mortality. It is clear that widespread shifts in the marine survival of salmon have occurred, however the timing, magnitude and effect of survival shifts is variable. Likely mortality mechanisms are similarly variable. This review highlights predation during the early marine phase as important for North American salmon; thus granting focus to the remaining research chapters. We next estimate the survival of postsmolts in selected estuaries and coastal habitats using acoustic telemetry. Simultaneously, we incorporate methods to address the major limitations to estimating survival using acoustic telemetry, including the use of mark-recapture modelling to address the effect of receiver detection performance, and a novel cluster-analysis modelling approach that attempts to quantify the complicating effects of predation. Our findings suggest that the early marine survival of Atlantic salmon, similar to marine mortality as a whole, is highly variable. Cumulative survival through the river, inner estuary, outer estuary and bay habitats ranged from 39·4% to 73·5% in Nova Scotia’s Southern Upland, whereas survival past the outer estuaries of inner Bay of Fundy rivers ranged from 24.3-54.0%. Survival rates followed two patterns: (1) constant rates of survival independent of habitat or (2) low survival most frequently associated with inner estuary habitats. We also examine the potential mortality mechanisms related to predation by examining patterns in the estuarine mortality of acoustically tagged salmon juveniles, using insights from mortality covariates, and the relationship between migratory behaviour and survival. Avian predation appears to be the dominant mortality vector in some estuaries of Nova Scotia’s Southern Upland, with the sudden disappearance of most (75–100%) smolts and post-smolts; which we interpret as evidence of avian predation along with evidence of size-selective survival. Alternatively, predatory striped bass appear to be a major source of mortality for some inner Bay of Fundy salmon populations, with evidence of a minimum of 7.3-27.3% of all tagged smolts being consumed by striped bass, based on migratory movement patterns. The survival estimates reported in this thesis permit the division of the marine phase into two periods; an early period encompassing estuarine and coastal habitats ( < 1 month), and the remaining time at sea. By comparing estimated survival during these two periods, it appears that estuarine survival cannot be solely responsible for observations of reduced marine survival since approx. 1990.The highest marine mortality must occur outside of estuaries and early coastal habitats. However, efforts directed at reducing estuarine and coastal mortality may be valuable for conservation planning, and may help reduce the risk of extirpation and, in some cases, may lead to viable populations.
author2 Department of Biology
Doctor of Philosophy
Dr. Joseph Zydlewski
Dr. Hal Whitehead
Dr. Paul Bentzen
Dr. A. Jamie F. Gibson
Dr. Frederick G. Whoriskey, Dr. Daniel E. Ruzzante
Received
Yes
author Halfyard, Edmund
author_facet Halfyard, Edmund
author_sort Halfyard, Edmund
title THE ESTUARINE AND EARLY MARINE SURVIVAL OF ATLANTIC SALMON: ESTIMATION, CORRELATES AND ECOLOGICAL SIGNIFICANCE
title_short THE ESTUARINE AND EARLY MARINE SURVIVAL OF ATLANTIC SALMON: ESTIMATION, CORRELATES AND ECOLOGICAL SIGNIFICANCE
title_full THE ESTUARINE AND EARLY MARINE SURVIVAL OF ATLANTIC SALMON: ESTIMATION, CORRELATES AND ECOLOGICAL SIGNIFICANCE
title_fullStr THE ESTUARINE AND EARLY MARINE SURVIVAL OF ATLANTIC SALMON: ESTIMATION, CORRELATES AND ECOLOGICAL SIGNIFICANCE
title_full_unstemmed THE ESTUARINE AND EARLY MARINE SURVIVAL OF ATLANTIC SALMON: ESTIMATION, CORRELATES AND ECOLOGICAL SIGNIFICANCE
title_sort estuarine and early marine survival of atlantic salmon: estimation, correlates and ecological significance
publishDate 2014
url http://hdl.handle.net/10222/53777
long_lat ENVELOPE(-37.967,-37.967,-54.017,-54.017)
geographic Inner Bay
geographic_facet Inner Bay
genre Atlantic salmon
genre_facet Atlantic salmon
op_relation http://hdl.handle.net/10222/53777
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