Bioenergetic and economic impacts of humpback whale depredation at salmon hatchery release sites
Dissertation (Ph.D.) University of Alaska Fairbanks, 2018 Since 2008, humpback whales have been documented depredating hatchery-produced juvenile salmon, a novel prey, at points of their release in Southeast Alaska. The objectives of this dissertation are to determine the spatial distribution, seaso...
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ftunivalaska:oai:scholarworks.alaska.edu:11122/9664 2023-05-15T16:35:49+02:00 Bioenergetic and economic impacts of humpback whale depredation at salmon hatchery release sites Chenoweth, Ellen M. Atkinson, Shannon McPhee, Megan Criddle, Keith Friedlaender, Ari Heintz, Ron Straley, Janice 2018-08 http://hdl.handle.net/11122/9664 en_US eng http://hdl.handle.net/11122/9664 Department of Fisheries Humpback whale Food Southeast Alaska Pacific salmon Predators Dissertation phd 2018 ftunivalaska 2023-02-23T21:37:19Z Dissertation (Ph.D.) University of Alaska Fairbanks, 2018 Since 2008, humpback whales have been documented depredating hatchery-produced juvenile salmon, a novel prey, at points of their release in Southeast Alaska. The objectives of this dissertation are to determine the spatial distribution, seasonal distribution, and frequency of humpback whale foraging at release sites, determine whether whale presence is affecting the economic productivity of hatchery operations, and compare the bioenergetic benefits for whales feeding on juvenile salmon at hatchery release sites relative to typical prey. Five hatchery release sites were monitored over six years during the spring release season for whale presence/absence, numbers, and behaviors. Linear models were used to determine that for coho salmon, cohorts with frequent humpback whale presence had lower marine survival than cohorts with less or no humpback whale presence, but this was not seen for chum or Chinook salmon. Over six years, these sites lost an estimated 23% of revenue from coho salmon totaling almost a million dollars per year in addition to increased rearing costs to mitigate whale predation. A process model was developed to compare the net energy gain for humpback whales foraging on krill, herring and juvenile salmon. Whales were found to feed profitably on krill and chum salmon where they occurred in dense enough distributions and on herring when large coordinated groups impeded the escape of prey. Coho salmon typically distributed too diffusely for humpback whales to recuperate the full energetic costs of engulfment, indicating that behaviors such as bubble net feeding may be essential for increasing prey aggregation to an energetically profitable level, or humpback whales may be feeding to mitigate energetic losses. As intraspecific competition increases due to recovery and or changes to prey resources, generalist humpback whales may expand feeding to exploit new and less profitable prey resources. Doctoral or Postdoctoral Thesis Humpback Whale Alaska University of Alaska: ScholarWorks@UA Fairbanks Pacific |
institution |
Open Polar |
collection |
University of Alaska: ScholarWorks@UA |
op_collection_id |
ftunivalaska |
language |
English |
topic |
Humpback whale Food Southeast Alaska Pacific salmon Predators |
spellingShingle |
Humpback whale Food Southeast Alaska Pacific salmon Predators Chenoweth, Ellen M. Bioenergetic and economic impacts of humpback whale depredation at salmon hatchery release sites |
topic_facet |
Humpback whale Food Southeast Alaska Pacific salmon Predators |
description |
Dissertation (Ph.D.) University of Alaska Fairbanks, 2018 Since 2008, humpback whales have been documented depredating hatchery-produced juvenile salmon, a novel prey, at points of their release in Southeast Alaska. The objectives of this dissertation are to determine the spatial distribution, seasonal distribution, and frequency of humpback whale foraging at release sites, determine whether whale presence is affecting the economic productivity of hatchery operations, and compare the bioenergetic benefits for whales feeding on juvenile salmon at hatchery release sites relative to typical prey. Five hatchery release sites were monitored over six years during the spring release season for whale presence/absence, numbers, and behaviors. Linear models were used to determine that for coho salmon, cohorts with frequent humpback whale presence had lower marine survival than cohorts with less or no humpback whale presence, but this was not seen for chum or Chinook salmon. Over six years, these sites lost an estimated 23% of revenue from coho salmon totaling almost a million dollars per year in addition to increased rearing costs to mitigate whale predation. A process model was developed to compare the net energy gain for humpback whales foraging on krill, herring and juvenile salmon. Whales were found to feed profitably on krill and chum salmon where they occurred in dense enough distributions and on herring when large coordinated groups impeded the escape of prey. Coho salmon typically distributed too diffusely for humpback whales to recuperate the full energetic costs of engulfment, indicating that behaviors such as bubble net feeding may be essential for increasing prey aggregation to an energetically profitable level, or humpback whales may be feeding to mitigate energetic losses. As intraspecific competition increases due to recovery and or changes to prey resources, generalist humpback whales may expand feeding to exploit new and less profitable prey resources. |
author2 |
Atkinson, Shannon McPhee, Megan Criddle, Keith Friedlaender, Ari Heintz, Ron Straley, Janice |
format |
Doctoral or Postdoctoral Thesis |
author |
Chenoweth, Ellen M. |
author_facet |
Chenoweth, Ellen M. |
author_sort |
Chenoweth, Ellen M. |
title |
Bioenergetic and economic impacts of humpback whale depredation at salmon hatchery release sites |
title_short |
Bioenergetic and economic impacts of humpback whale depredation at salmon hatchery release sites |
title_full |
Bioenergetic and economic impacts of humpback whale depredation at salmon hatchery release sites |
title_fullStr |
Bioenergetic and economic impacts of humpback whale depredation at salmon hatchery release sites |
title_full_unstemmed |
Bioenergetic and economic impacts of humpback whale depredation at salmon hatchery release sites |
title_sort |
bioenergetic and economic impacts of humpback whale depredation at salmon hatchery release sites |
publishDate |
2018 |
url |
http://hdl.handle.net/11122/9664 |
geographic |
Fairbanks Pacific |
geographic_facet |
Fairbanks Pacific |
genre |
Humpback Whale Alaska |
genre_facet |
Humpback Whale Alaska |
op_relation |
http://hdl.handle.net/11122/9664 Department of Fisheries |
_version_ |
1766026124823887872 |