Depth use of adult Atlantic salmon during the first and last phase of the marine migration
The Atlantic salmon has declined in numbers over the last decades. Given the species’ anadromous nature, management is a challenge, and information is lacking, especially from the marine migratory phase. Information about repeat spawners and their migratory behaviour may be of major importance in ma...
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ftunivtroemsoe:oai:munin.uit.no:10037/7950 2023-05-15T15:30:54+02:00 Depth use of adult Atlantic salmon during the first and last phase of the marine migration Kjellman, Mari 2015-05-15 https://hdl.handle.net/10037/7950 eng eng UiT Norges arktiske universitet UiT The Arctic University of Norway https://hdl.handle.net/10037/7950 URN:NBN:no-uit_munin_7536 openAccess Copyright 2015 The Author(s) VDP::Mathematics and natural science: 400::Zoology and botany: 480::Ecology: 488 VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Økologi: 488 Atlantic salmon Migration Marine migration Depth use Diving Diet Feeding BIO-3950 Master thesis Mastergradsoppgave 2015 ftunivtroemsoe 2021-06-25T17:54:23Z The Atlantic salmon has declined in numbers over the last decades. Given the species’ anadromous nature, management is a challenge, and information is lacking, especially from the marine migratory phase. Information about repeat spawners and their migratory behaviour may be of major importance in management questions, as these individuals have been found to contribute significantly to spawning populations. The aims of this study were to analyse depth use during the first and last phase of the marine migration and to investigate if the Atlantic salmon forage during the return migration. During the years 2008-2014, 630 post-spawned Atlantic salmon were tagged with depth-recording data storage tags in the river Alta. Of these, 41 salmon were recaptured. Usable data were retrieved from 29 salmon during outward migration and from 20 salmon during return migration. In addition, stomachs were collected from 939 returning salmon in the Alta fjord. The salmon spent most of the time in the upper five meters of the water column in the fjord and outer coast both during outward and inward migration. Number of depth recordings at 0-5 m decreased with time from seawater entry during outward migration from 96% during the first 24h after seawater entry, to 75% at the fourteenth day. During the inward migration, the proportion of recordings at this depth interval was smaller in the outer coast areas (50%) than in the inner and outer fjord (88 and 91% respectively). Diving intensity increased with time and distance from the estuary, both during outward and inward migration, and so did the proportion of diving salmon and the overall maximum diving depths. Large individual variations in depth use was observed, and the deepest recorded dives were 337m during outward migration and 97m deep during inward migration. The stomach analyses showed that a large proportion (59%) of the returning salmon had empty stomachs. A proportion of the salmon (14%) also had only small fractions of stomach contents. All feeding salmon had fed exclusively on fish, including herring, capelin and sand eel, but the contents were often highly digested, suggesting that the food intake had occurred some time ago. This suggests that other explanations than feeding have to be considered for diving behaviour during inward migration. The proximity to surface and diving behaviour observed in both outward migrating and inward migrating salmon is likely a combination of factors like orientation, predator avoidance, control of body temperature, or other unknown factors. Master Thesis Atlantic salmon University of Tromsø: Munin Open Research Archive Alta |
institution |
Open Polar |
collection |
University of Tromsø: Munin Open Research Archive |
op_collection_id |
ftunivtroemsoe |
language |
English |
topic |
VDP::Mathematics and natural science: 400::Zoology and botany: 480::Ecology: 488 VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Økologi: 488 Atlantic salmon Migration Marine migration Depth use Diving Diet Feeding BIO-3950 |
spellingShingle |
VDP::Mathematics and natural science: 400::Zoology and botany: 480::Ecology: 488 VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Økologi: 488 Atlantic salmon Migration Marine migration Depth use Diving Diet Feeding BIO-3950 Kjellman, Mari Depth use of adult Atlantic salmon during the first and last phase of the marine migration |
topic_facet |
VDP::Mathematics and natural science: 400::Zoology and botany: 480::Ecology: 488 VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Økologi: 488 Atlantic salmon Migration Marine migration Depth use Diving Diet Feeding BIO-3950 |
description |
The Atlantic salmon has declined in numbers over the last decades. Given the species’ anadromous nature, management is a challenge, and information is lacking, especially from the marine migratory phase. Information about repeat spawners and their migratory behaviour may be of major importance in management questions, as these individuals have been found to contribute significantly to spawning populations. The aims of this study were to analyse depth use during the first and last phase of the marine migration and to investigate if the Atlantic salmon forage during the return migration. During the years 2008-2014, 630 post-spawned Atlantic salmon were tagged with depth-recording data storage tags in the river Alta. Of these, 41 salmon were recaptured. Usable data were retrieved from 29 salmon during outward migration and from 20 salmon during return migration. In addition, stomachs were collected from 939 returning salmon in the Alta fjord. The salmon spent most of the time in the upper five meters of the water column in the fjord and outer coast both during outward and inward migration. Number of depth recordings at 0-5 m decreased with time from seawater entry during outward migration from 96% during the first 24h after seawater entry, to 75% at the fourteenth day. During the inward migration, the proportion of recordings at this depth interval was smaller in the outer coast areas (50%) than in the inner and outer fjord (88 and 91% respectively). Diving intensity increased with time and distance from the estuary, both during outward and inward migration, and so did the proportion of diving salmon and the overall maximum diving depths. Large individual variations in depth use was observed, and the deepest recorded dives were 337m during outward migration and 97m deep during inward migration. The stomach analyses showed that a large proportion (59%) of the returning salmon had empty stomachs. A proportion of the salmon (14%) also had only small fractions of stomach contents. All feeding salmon had fed exclusively on fish, including herring, capelin and sand eel, but the contents were often highly digested, suggesting that the food intake had occurred some time ago. This suggests that other explanations than feeding have to be considered for diving behaviour during inward migration. The proximity to surface and diving behaviour observed in both outward migrating and inward migrating salmon is likely a combination of factors like orientation, predator avoidance, control of body temperature, or other unknown factors. |
format |
Master Thesis |
author |
Kjellman, Mari |
author_facet |
Kjellman, Mari |
author_sort |
Kjellman, Mari |
title |
Depth use of adult Atlantic salmon during the first and last phase of the marine migration |
title_short |
Depth use of adult Atlantic salmon during the first and last phase of the marine migration |
title_full |
Depth use of adult Atlantic salmon during the first and last phase of the marine migration |
title_fullStr |
Depth use of adult Atlantic salmon during the first and last phase of the marine migration |
title_full_unstemmed |
Depth use of adult Atlantic salmon during the first and last phase of the marine migration |
title_sort |
depth use of adult atlantic salmon during the first and last phase of the marine migration |
publisher |
UiT Norges arktiske universitet |
publishDate |
2015 |
url |
https://hdl.handle.net/10037/7950 |
geographic |
Alta |
geographic_facet |
Alta |
genre |
Atlantic salmon |
genre_facet |
Atlantic salmon |
op_relation |
https://hdl.handle.net/10037/7950 URN:NBN:no-uit_munin_7536 |
op_rights |
openAccess Copyright 2015 The Author(s) |
_version_ |
1766361371918729216 |